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193-470: Originally created by plate tectonics about 35 million years ago and subsequently altered by volcanism and erosion, the river's drainage basin was significantly modified by the Missoula Floods at the end of the most recent ice age . Humans began living in the watershed over 10,000 years ago. There were once many tribal villages along the lower river and in the area around its mouth on

386-474: A divided highway carrying OR 99E Business , at an interchange that straddles the 45th parallel (marked with a sign in the median). I-5 continues northeast from the interchange, passing the Keizer Station complex and the minor-league Volcanoes Stadium before leaving the suburban fringes of Keizer. The freeway continues north along OR 99E and the former Oregon Electric Railway , passing

579-559: A flood in 1861 . This and many other large flows preceded the Flood Control Act of 1936 and dam construction on the Willamette's major tributaries. The river below Willamette Falls, 26.5 miles (42.6 km) from the mouth, is affected by semidiurnal tides , and gauges have detected reverse flows (backwards river flows) below Ross Island at RM 15 (RK 24). The National Weather Service issues tide forecasts for

772-439: A consequence, a powerful source generating plate motion is the excess density of the oceanic lithosphere sinking in subduction zones. When the new crust forms at mid-ocean ridges, this oceanic lithosphere is initially less dense than the underlying asthenosphere, but it becomes denser with age as it conductively cools and thickens. The greater density of old lithosphere relative to the underlying asthenosphere allows it to sink into

965-450: A few tens of millions of years. Armed with the knowledge of a new heat source, scientists realized that Earth would be much older, and that its core was still sufficiently hot to be liquid. By 1915, after having published a first article in 1912, Alfred Wegener was making serious arguments for the idea of continental drift in the first edition of The Origin of Continents and Oceans . In that book (re-issued in four successive editions up to

1158-600: A formal complaint. The final section of Interstate 5 was dedicated on October 22, 1966, at the Cow Creek rest area. At the time, the freeway had 114 interchanges and 467 bridge structures; it cost an estimated $ 298 million to construct. The Salem–Portland section of I-5 was widened to six lanes in the late 1970s and early 1980s. Beginning in 1976, the State Highway Division (now ODOT) experimented with asphalt recycling from construction projects on

1351-579: A layer of basalt (sial) underlies the continental rocks. However, based on abnormalities in plumb line deflection by the Andes in Peru, Pierre Bouguer had deduced that less-dense mountains must have a downward projection into the denser layer underneath. The concept that mountains had "roots" was confirmed by George B. Airy a hundred years later, during study of Himalayan gravitation, and seismic studies detected corresponding density variations. Therefore, by

1544-488: A meandering course along Barbur Boulevard (part of OR 99W) across several hilltops. In the South Burlingame neighborhood, the freeway begins a fishhook-shaped turn through the " Terwilliger curves ", a notoriously dangerous section of I-5 that changes directions five times in one mile (1.6 km). The area averaged about 100 collisions and crashes per year between 1995 and 2005. I-5 continues north from

1737-400: A misnomer as there is no force "pushing" horizontally, indeed tensional features are dominant along ridges. It is more accurate to refer to this mechanism as "gravitational sliding", since the topography across the whole plate can vary considerably and spreading ridges are only the most prominent feature. Other mechanisms generating this gravitational secondary force include flexural bulging of

1930-421: A multi-use trail for cyclists and pedestrians, and a MAX Light Rail extension into Vancouver. The bridge replacement is expected to cost up to $ 2.45 billion, while the entire program—including reconstruction of several interchanges and transit improvements—is estimated to cost $ 5.5 billion to $ 7.5 billion and would begin construction in 2025. In 2017, ODOT began planning an expansion of I-5 through

2123-658: A national highway system in 1926. The Oregon section was divided between Junction City and Portland into US 99W and US 99E , with the latter taking the original route of the Pacific Highway. It was completed on December 1, 1961, with direct connections to Harbor Drive in Downtown Portland. The first modern rest area in Oregon was opened in 1962 between Eugene and Albany; within four years, eight more sets were completed. The first section of

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2316-468: A plan to improve fish passage and take other actions to help native fish recover in 2008. Since then, work has proceeded slowly, and the Corps of Engineers, citing engineering difficulties and cost, may not meet the original agreed-upon deadline of 2023 for a system of effective remedies. Other major dams in the Willamette watershed are owned by other interests; for example, several hydroelectric facilities on

2509-402: A power plant. The locks at Willamette Falls were completed in 1873. Elsewhere on the main stem, numerous minor flow-regulation structures force the river into a narrower and deeper channel to facilitate navigation and flood control . The dams on the Willamette's major tributaries are primarily large flood-control, water-storage, and power-generating dams. Thirteen of these dams were built from

2702-558: A secondary phenomenon of this basically vertically oriented mechanism. It finds its roots in the Undation Model of van Bemmelen . This can act on various scales, from the small scale of one island arc up to the larger scale of an entire ocean basin. Alfred Wegener , being a meteorologist , had proposed tidal forces and centrifugal forces as the main driving mechanisms behind continental drift ; however, these forces were considered far too small to cause continental motion as

2895-658: A seven-acre (2.8 ha) solar power array with 7,000 panels. North of the interchange, I-5 crosses the Willamette River on the Boone Bridge and enters the city of Wilsonville , at the edge of the Portland metropolitan area. The highway bisects downtown Wilsonville and its adjacent suburban neighborhoods, continuing north along the WES Commuter Rail line into Tualatin . On the south side of

3088-407: A solid crust and mantle and a liquid core, but there seemed to be no way that portions of the crust could move around. Many distinguished scientists of the time, such as Harold Jeffreys and Charles Schuchert , were outspoken critics of continental drift. Despite much opposition, the view of continental drift gained support and a lively debate started between "drifters" or "mobilists" (proponents of

3281-478: A static Earth without moving continents up until the major breakthroughs of the early sixties. Two- and three-dimensional imaging of Earth's interior ( seismic tomography ) shows a varying lateral density distribution throughout the mantle. Such density variations can be material (from rock chemistry), mineral (from variations in mineral structures), or thermal (through thermal expansion and contraction from heat energy). The manifestation of this varying lateral density

3474-519: A system of parks, trails, and wildlife refuges along the river. In 1998, the Willamette became one of 14 rivers designated an American Heritage River by U.S. President Bill Clinton . By 2007 the Greenway had grown to include more than 170 separate land parcels, including 10 state parks. Public uses of the river and land along its shores include camping, swimming, fishing, boating, hiking, bicycling, and wildlife viewing. In 2008, government agencies and

3667-465: A temporary lake, Lake Allison , that stretched from Lake Oswego to near Eugene. The ancestral Tualatin Valley, part of the Willamette basin, flooded as well; water depths ranged from 200 feet (61 m) at Lake Oswego to 100 feet (30 m) as far upstream (west) as Forest Grove . Flood deposits of silt and clay, ranging in thickness from 115 feet (35 m) in the north to about 15 feet (4.6 m) in

3860-438: Is mantle convection from buoyancy forces. How mantle convection directly and indirectly relates to plate motion is a matter of ongoing study and discussion in geodynamics. Somehow, this energy must be transferred to the lithosphere for tectonic plates to move. There are essentially two main types of mechanisms that are thought to exist related to the dynamics of the mantle that influence plate motion which are primary (through

4053-437: Is Portland, with more than 500,000 residents. Not all of these cities draw water in part or exclusively from the Willamette for their municipal water supply. Other cities in the watershed (but not on the main-stem river) with populations of 20,000 or more are Gresham, Hillsboro, Beaverton, Tigard, McMinnville, Tualatin, Woodburn , and Forest Grove. Sixty-four percent of the watershed is privately owned, while 36 percent

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4246-643: Is also designated as an important highway under the National Highway System . It is officially designated under Oregon's named route system as the Pacific Highway No. 1, a name shared with Oregon Route 99 (OR 99) and its split routes north of Junction City . OR 99 runs concurrent to I-5 through most of southern Oregon, splitting from the freeway to serve city centers and use other alternate routes, while OR 99W and OR 99E serve corridors on opposite sides of

4439-527: Is based on their modes of formation. Oceanic crust is formed at sea-floor spreading centers. Continental crust is formed through arc volcanism and accretion of terranes through plate tectonic processes. Oceanic crust is denser than continental crust because it has less silicon and more of the heavier elements than continental crust . As a result of this density difference, oceanic crust generally lies below sea level , while continental crust buoyantly projects above sea level. Average oceanic lithosphere

4632-461: Is called a plate boundary . Plate boundaries are where geological events occur, such as earthquakes and the creation of topographic features such as mountains , volcanoes , mid-ocean ridges , and oceanic trenches . The vast majority of the world's active volcanoes occur along plate boundaries, with the Pacific plate's Ring of Fire being the most active and widely known. Some volcanoes occur in

4825-533: Is called the geosynclinal theory . Generally, this was placed in the context of a contracting planet Earth due to heat loss in the course of a relatively short geological time. It was observed as early as 1596 that the opposite coasts of the Atlantic Ocean—or, more precisely, the edges of the continental shelves —have similar shapes and seem to have once fitted together. Since that time many theories were proposed to explain this apparent complementarity, but

5018-621: Is designated as Pacific Highway No. 1 . The Salem–Portland section was named the Baldock Freeway until 2022. The freeway also has three signed auxiliary routes that function as spurs and bypasses of major cities: I-105 in Eugene, I-205 in eastern Portland, I-405 in downtown Portland . Two additional auxiliary routes were planned in the early years of the Interstate system, but were shelved after local opposition . Interstate 5

5211-507: Is from Albany to Oregon City. At Willamette Falls , between West Linn and Oregon City, the river plunges about 40 feet (12 m). For the rest of its course, the river is extremely low-gradient and is affected by Pacific Ocean tidal effects from the Columbia. The main stem of the Willamette varies in width from about 330 to 660 feet (100 to 200 m). With an average flow at the mouth of about 37,400 cubic feet per second (1,060 m/s),

5404-492: Is in motion, presents a problem. The same holds for the African, Eurasian , and Antarctic plates. Gravitational sliding away from mantle doming: According to older theories, one of the driving mechanisms of the plates is the existence of large scale asthenosphere/mantle domes which cause the gravitational sliding of lithosphere plates away from them (see the paragraph on Mantle Mechanisms). This gravitational sliding represents

5597-408: Is invoked as the major driving force, through slab pull along subduction zones. Gravitational sliding away from a spreading ridge is one of the proposed driving forces, it proposes plate motion is driven by the higher elevation of plates at ocean ridges. As oceanic lithosphere is formed at spreading ridges from hot mantle material, it gradually cools and thickens with age (and thus adds distance from

5790-600: Is near Durham between junctions with I-205 and OR 217 , carrying an average of 164,000 vehicles daily in 2017. The least-traveled section of I-5 is located near Ashland and carries only around 16,600 vehicles daily. I-5 enters Oregon at the California state line in southern Jackson County . The highway travels northeast along a ridge in the Siskiyou Mountains , with a maximum grade of 6 percent, to Siskiyou Summit ; at 4,310 feet (1,310 m), it

5983-578: Is of indigenous origin, deriving from the French pronunciation of the name of a Clackamas Native American village. However, Native American languages in Oregon were very similar, so the name may also be derived from Kalapuya dialects. Around the year 1850, the Kalapuya numbered between 2,000 and 3,000 and were distributed among several groups. These figures are only speculative; there may have been as few as eight subgroups or as many as 16. In that time period,

Willamette River - Misplaced Pages Continue

6176-532: Is publicly owned. The U.S. Forest Service manages 30 percent of the watershed, the U.S. Bureau of Land Management 5 percent, and the State of Oregon 1 percent. Sixty-eight percent of the watershed is forested; agriculture, concentrated in the Willamette Valley, makes up 19 percent, and urban areas cover 5 percent. More than 81,000 miles (130,000 km) of roads criss-cross

6369-415: Is still advocated to explain the break-up of supercontinents during specific geological epochs. It has followers amongst the scientists involved in the theory of Earth expansion . Another theory is that the mantle flows neither in cells nor large plumes but rather as a series of channels just below Earth's crust, which then provide basal friction to the lithosphere. This theory, called "surge tectonics",

6562-481: Is the highest point on all of I-5 and one of the highest points on the Interstate system. The mountainous, 11-mile (18 km) section of the freeway runs along Siskiyou Pass and includes several runaway truck ramps and chain-up areas due to its heavy use by trucks and its foggy and snowy conditions in winter. North of the summit, the freeway intersects the Old Siskiyou Highway ( OR 273 ) and

6755-529: Is the second-longest freeway in Oregon, at 308 miles (496 km), and is the only Interstate to traverse the state from north to south. The highway connects several of the state's largest metropolitan areas, which lie in the Rogue and Willamette valleys, and passes through counties with approximately 81 percent of Oregon's population. As a component of the Interstate Highway System, I-5

6948-488: Is to consider the relative rate at which each plate is moving as well as the evidence related to the significance of each process to the overall driving force on the plate. One of the most significant correlations discovered to date is that lithospheric plates attached to downgoing (subducting) plates move much faster than other types of plates. The Pacific plate, for instance, is essentially surrounded by zones of subduction (the so-called Ring of Fire) and moves much faster than

7141-407: Is typically 100 km (62 mi) thick. Its thickness is a function of its age. As time passes, it cools by conducting heat from below, and releasing it raditively into space. The adjacent mantle below is cooled by this process and added to its base. Because it is formed at mid-ocean ridges and spreads outwards, its thickness is therefore a function of its distance from the mid-ocean ridge where it

7334-435: Is used. It asserts that super plumes rise from the deeper mantle and are the drivers or substitutes of the major convection cells. These ideas find their roots in the early 1930s in the works of Beloussov and van Bemmelen , which were initially opposed to plate tectonics and placed the mechanism in a fixed frame of vertical movements. Van Bemmelen later modified the concept in his "Undation Models" and used "Mantle Blisters" as

7527-567: The Appalachian Mountains of North America are very similar in structure and lithology . However, his ideas were not taken seriously by many geologists, who pointed out that there was no apparent mechanism for continental drift. Specifically, they did not see how continental rock could plow through the much denser rock that makes up oceanic crust. Wegener could not explain the force that drove continental drift, and his vindication did not come until after his death in 1930. As it

7720-829: The Broadway Bridge , which carries the Portland Streetcar's loop lines. Between the Boise and Eliot neighborhoods, the freeway intersects the terminating I-405 a short distance from the Fremont Bridge , which carries US 30 west into the Pearl District after it splits from I-5. The interchange, located between the Legacy Emanuel Medical Center and Albina railyard , has a set of three stub ramps that were built for

7913-818: The Clackamas River are owned by Portland General Electric . These include the River Mill Hydroelectric Project , the Oak Grove project, and the dam at Timothy Lake . The 50 or so crossings of the Willamette River include many historic structures, such as the Van Buren Street Bridge , a swing bridge . Built in 1913, it carries Oregon Route 34 (Corvallis–Lebanon Highway) over the river upstream of RM 131 (RK 211) in Corvallis. The machinery to operate

Willamette River - Misplaced Pages Continue

8106-568: The Coast Fork Willamette River , and Dorena on the Row River . Due to these tall dams, Chinook salmon and steelhead are blocked from roughly half of their historic habitat and spawning grounds on the Willamette's major tributaries. Unable to live and reproduce as they once did, they have been "brought to the brink of extinction". Endangered species listings and a subsequent lawsuit by Willamette Riverkeeper led to

8299-607: The Farallon Plate beneath the North American Plate , creating the forearc basin that would later become the Willamette Valley. The valley was initially part of the continental shelf , rather than a separate inland sea. Many layers of marine deposits formed in the forearc basin and cover the older Siletz River Volcanics. About 20 to 16 million years ago, uplift formed the Coast Range and separated

8492-694: The Hawthorne Bridge and under the Morrison Bridge , intersecting the latter to provide direct access to Downtown Portland. After passing under the Burnside Bridge , I-5 intersects the western terminus of I-84 , Oregon's lone east–west freeway and the main route through the Columbia River Gorge . After the interchange, US 30 joins I-5 in a short concurrency while the freeway travels around major landmarks in

8685-520: The Missoula Floods —a series of large outpourings originating at Glacial Lake Missoula in Montana—swept down the Columbia River and backfilled the Willamette watershed. Each flood produced "discharges that exceeded the annual discharge of all the present-day rivers of the world combined". Filling the Willamette basin to depths of 400 feet (120 m) in the Portland region, each flood created

8878-676: The Oregon State Capitol in Salem. Evidence suggests that massive quakes of 8 or more on the Richter scale have occurred historically in the Cascadia subduction zone off the Oregon coast, most recently in 1700 CE , and that others as strong as 9 on the Richter scale occur every 500 to 800 years. The basin's high population density, its nearness to this subduction zone, and its loose soils, which tend to amplify shaking, make

9071-622: The Pacific Crest Trail before it travels out of the Rogue River–Siskiyou National Forest . The highway descends from the mountains into the Rogue Valley and intersects the south end of OR 99 west of Emigrant Lake , adjacent to a railroad underpass. I-5 follows OR 99 and passes a rest area and welcome center before entering the city of Ashland . The freeway crosses OR 66 west of

9264-821: The Pacific Highway and various wagon roads . The freeway incorporated early bypasses and expressways built for US 99 in the 1950s, including a new freeway route from Portland to Salem, and additional bypasses were built using federal funds. The last segment of I-5, on the Marquam Bridge in Portland, was opened in October 1966 and the whole highway was dedicated later that month. The freeway remains parallel or concurrent to Oregon Route 99 (OR 99) and its spur routes, running along former segments of US 99 that were bypassed by I-5, from Ashland to Portland. Under Oregon's named route system , all of I-5

9457-727: The Portland Aerial Tram and Gibbs Street Pedestrian Bridge . The freeway passes under the Ross Island Bridge (part of US 26 ) and reaches the southern terminus of I-405 , which it intersects in a large Y interchange situated over the light rail tracks of the MAX Orange Line and the Portland Streetcar . From the interchange, I-405 passes through the western part of Downtown Portland and Harbor Drive continues into downtown along

9650-701: The Portland Expo Center (where the MAX Yellow Line terminates) and St. Johns . The freeway continues north onto Hayden Island , where a single exit serves the entire island, and crosses over the Columbia River on the Interstate Bridge into Vancouver, Washington . The Interstate Bridge carries a daily average of 132,000 vehicles and consists of two bridges that lift vertically for river traffic. I-5 roughly follows

9843-624: The Powerland Heritage Park and Oregon Electric Railway Museum near Brooks . At the Woodburn Premium Outlets mall west of Woodburn , I-5 intersects the dual termini of OR 214 and OR 219 , which provide access to Silverton and Newberg , respectively. It reaches a junction with OR 551 north of Aurora State Airport and adjacent to the French Prairie rest area, which includes

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10036-631: The Rogue Valley Mall , providing access to Crater Lake and Mount McLoughlin northeast of the valley. The freeway continues northwest, passing Rogue Valley International–Medford Airport and the suburb of Central Point before turning west to follow the Rogue River . I-5 follows the Rogue River downstream through a narrow valley, where OR 99 and a railroad cross over and under the freeway several times, and passes Valley of

10229-516: The Rose Quarter to address congestion and safety issues on a 1.8-mile (2.9 km) section between I-84 and I-405. The agency's proposal—the addition of an auxiliary lane for merging and weaving traffic, as well as a freeway lid —would cost $ 450 million and was approved by the state legislature that year. The project attracted opposition and protests as it went through several years of environmental review and design revisions, during which

10422-829: The Rose Quarter , including the Oregon Convention Center , the Moda Center , and the Veterans Memorial Coliseum . At Northeast Holladay Street, the highway passes directly over the MAX Light Rail platforms of the Rose Quarter Transit Center just east of the Steel Bridge , which carries four MAX lines and OR 99W into Downtown Portland. I-5 veers northwest and briefly into a sunken section near

10615-685: The Sandy River did the explorers learn about their oversight. William Clark returned down the Columbia and entered the Willamette River in April 1806. Fur trappers originally working for the Pacific Fur Company (PFC)) and subsequently for the North West Company (NWC) were next to visit the Willamette River and various tributaries. The Siskiyou Trail (or California-Oregon Trail) originally developed by Indigenous people,

10808-851: The Siletz , the Nestucca , the Trask , and the Wilson to the west; the Nehalem and the Clatskanie to the northwest, and the Columbia River to the north. About 2.5 million people lived in the Willamette River basin as of 2010, about 65 percent of the population of Oregon. As of 2009, the basin contained 20 of the 25 most populous cities in Oregon. These cities include Springfield, Eugene, Corvallis, Albany, Salem, Keizer, Newberg, Oregon City, West Linn, Milwaukie, Lake Oswego, and Portland. The largest

11001-408: The Siskiyou Trail , an early trading route used by indigenous Oregonians and early trappers between the Willamette Valley and California. The trail was re-purposed as a settler's route in 1846, following the creation of the Applegate Trail by the territorial government. It was later incorporated into the early roads of the Willamette Valley, but remained secondary to waterborne transportation along

11194-413: The U.S. federal government . The main channel, which is the primary navigational conduit for Portland's harbor and riverside industrial areas, is 40 feet (12 m) deep and varies in width from 600 to 1,900 feet (180 to 580 m), although the river broadens to 2,000 feet (610 m) in some of its lower reaches. This channel enters the Columbia about 101 miles (163 km) from the Columbia's mouth on

11387-465: The University of Oregon campus, and continues north to Junction City , where it splits into OR 99W and OR 99E . The freeway then travels over the Whilamut Passage Bridge , a pair of concrete arch bridges that span 1,985 feet (605 m) across the Willamette River west of downtown Springfield. On the north side of the river near the Gateway Mall , it intersects I-105 , providing freeway access to downtown Eugene, and OR 126 . At

11580-428: The Willamette River . The state legislature also designated I-5 as the Purple Heart Trail and Korean War Veterans Memorial Highway in 2015. I-5 is maintained by the Oregon Department of Transportation (ODOT), who conduct an annual survey of traffic volume that is expressed in terms of annual average daily traffic (AADT), a measure of traffic volume for any average day of the year. The highway's busiest section

11773-426: The Willamette Town Center shopping mall and the Oregon State Fairgrounds , the freeway intersects the south end of OR 213 , a local highway that parallels I-5 to the east towards the Portland area . OR 99E splits from I-5 at an interchange with Portland Road, located west of the Chemeketa Community College campus in Hayesville . The freeway continues northwest into Keizer and intersects Salem Parkway,

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11966-401: The Willamette Valley and across the northern Siskiyou Mountains . The highway runs 308 miles (496 km) from the California state line near Ashland to the Washington state line in northern Portland, forming the central part of Interstate 5's route between Mexico and Canada. I-5 was designated in 1957 and replaced U.S. Route 99 (US 99) for most of its length, itself preceded by

12159-422: The chemical subdivision of these same layers into the mantle (comprising both the asthenosphere and the mantle portion of the lithosphere) and the crust: a given piece of mantle may be part of the lithosphere or the asthenosphere at different times depending on its temperature and pressure. The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates , which ride on

12352-488: The eastern United States , mainly the Upland South borderlands of Missouri, Iowa, and the Ohio Valley. Many of these emigrants followed the Oregon Trail , a 2,170-mile (3,490 km) trail across western North America that began at Independence, Missouri , and ended at various locations near the mouth of the Willamette River. Although people had been traveling to Oregon since 1836, large-scale migration did not begin until 1843, when nearly 1,000 pioneers headed westward. Over

12545-617: The fluid-like solid the asthenosphere . Plate motions range from 10 to 40 millimetres per year (0.4 to 1.6 in/year) at the Mid-Atlantic Ridge (about as fast as fingernails grow), to about 160 millimetres per year (6.3 in/year) for the Nazca plate (about as fast as hair grows). Tectonic lithosphere plates consist of lithospheric mantle overlain by one or two types of crustal material: oceanic crust (in older texts called sima from silicon and magnesium ) and continental crust ( sial from silicon and aluminium ). The distinction between oceanic crust and continental crust

12738-473: The lithosphere and asthenosphere . The division is based on differences in mechanical properties and in the method for the transfer of heat . The lithosphere is cooler and more rigid, while the asthenosphere is hotter and flows more easily. In terms of heat transfer, the lithosphere loses heat by conduction , whereas the asthenosphere also transfers heat by convection and has a nearly adiabatic temperature gradient. This division should not be confused with

12931-463: The main stem Willamette meanders generally north for 187 miles (301 km) to the Columbia River . The river's two most significant course deviations occur at Newberg , where it turns sharply east, and about 18 miles (29 km) downstream from Newberg, where it turns north again. Near its mouth north of downtown Portland , the river splits into two channels that flow around Sauvie Island . Used for navigation purposes, these channels are managed by

13124-470: The 1940s through the 1960s and are operated by the United States Army Corps of Engineers (USACE). Of those 13, 9 produce hydropower. Flood-control dams operated by the USACE are estimated to hold up to 27 percent of the Willamette's runoff. They are used to regulate river flows so as to cut peaks off floods and increase low flows in late summer and autumn, and to divert water into deeper, narrower channels to prevent flooding. A relatively small of amount of

13317-451: The 1960s, Oregon Governor Tom McCall led a push for stronger pollution controls on the Willamette. In this, he was encouraged by Robert (Bob) Straub —the state treasurer and future Oregon governor (1975)—who first proposed a Willamette Greenway program during his 1966 gubernatorial campaign against McCall. The Oregon State Legislature established the program in 1967. Through it, state and local governments cooperated in creating or improving

13510-403: The Cabin Creek canyon, but splits off again to serve the Pass Creek valley while I-5 remains in the Pleasant Valley. The two highways are rejoined at Anlauf and continue northeast along Pass Creek towards Cottage Grove in Lane County . The freeway runs through the eastern outskirts of Cottage Grove and continues north along the Coast Fork Willamette River into the Willamette Valley , trading

13703-403: The Cascade Range to 10 feet (3.0 m) at the mouth on the Columbia River. Watersheds bordering the Willamette River basin are those of the Little Deschutes River to the southeast, the Deschutes River to the east, and the Sandy River to the northeast; the North Umpqua and Umpqua rivers to the south; coastal rivers including (from south to north) the Siuslaw , the Alsea , the Yaquina ,

13896-470: The City of Portland and the State of Oregon to dramatically reduce combined sewer overflows (CSOs) led to Portland's Big Pipe Project . The project, part of a related series of Portland CSO projects completed in late 2011 at a cost of $ 1.44 billion, separates the city's sanitary sewer lines from storm-water inputs that sometimes overwhelmed the combined system during heavy rains. When that occurred, some of

14089-546: The Clackamas' tribal population was roughly 1,800. The U.S. Census Bureau estimated that the Chinook population was nearly 5,000, though not all of the Chinook lived on the Willamette. The Chinook territory encompassed the lower Columbia River valley and significant stretches of the Pacific coast on both the north and the south side of the Columbia's mouth. At times, however, the Chinook territory extended even farther south in

14282-476: The Columbia River. Between the 1850s and the 1960s, channel-straightening and flood control projects, as well as agricultural and urban encroachment, cut the length of the river between the McKenzie River confluence and Harrisburg by 65 percent. Similarly, the river was shortened by 40 percent in the stretch between Harrisburg and Albany. Interstate 5 and three branches of Oregon Route 99 are

14475-552: The Columbia to Bachelor Island . Rockwell's survey was extremely detailed, including 17,782 hydrographic soundings. His work helped open the port of Portland to commerce. In the second half of the 19th century, the USACE dredged channels and built locks and levees in the Willamette's watershed. Although products such as lumber were often transported on an existing network of railroads in Oregon, these advances in navigation helped businesses deliver more goods to Portland, feeding

14668-579: The Columbia. Indigenous peoples lived throughout the upper reaches of the basin as well. Rich with sediments deposited by flooding and fed by prolific rainfall on the western side of the Cascades, the Willamette Valley is one of the most fertile agricultural regions in North America, and it was thus the destination of many 19th-century pioneers traveling west along the Oregon Trail . The river

14861-598: The Earth's rotation and the Moon as main driving forces for the plates. The vector of a plate's motion is a function of all the forces acting on the plate; however, therein lies the problem regarding the degree to which each process contributes to the overall motion of each tectonic plate. The diversity of geodynamic settings and the properties of each plate result from the impact of the various processes actively driving each individual plate. One method of dealing with this problem

15054-738: The East Bank Freeway in Portland, running 2.5 miles (4.0 km) from the Morrison Bridge to Shaver and Failing streets, opened to traffic on January 7, 1964. The Marquam Bridge , which connected the completed portions of I-5 to the East Bank Freeway, opened to southbound traffic on October 4, 1966, and northbound traffic two weeks later. Its design was criticized by the public and the Portland Art Commission, who described it as "so gross, so lacking in grace, so utterly inconsistent with any concept of aesthetics" in

15247-745: The Eugene area, and several others are exclusively for rail traffic. There are also ferries that convey cars, trucks, motorcycles, bicycles, and pedestrians across the river for a fare and provided river conditions permit. They are the Buena Vista Ferry between Marion County and Polk County south of Independence and Salem, the Wheatland Ferry between Marion County and Polk County north of Salem and Keizer, and Canby Ferry in Clackamas County north of Canby. Since 1900, more than 15 large dams and many smaller ones have been built in

15440-737: The HBC merged with the NWC. In 1825 a new Fort Vancouver headquarters was built on the north shore of the Columbia closer to the Willamette, and Fort George was closed. Alexander Roderick McLeod traveled up the Willamette in 1826 and 1827, to the Umpqua and the Rogue rivers. In 1829 Lucier established a land claim near the Champoeg trading post and started to settle, soon joined by Gervais (1831), Pierre Belleque (1833) and 77 French Canadian settlers by 1836. By 1843, approximately 100 newcomer families lived in

15633-804: The I-5 corridor to repave local roads. The Albany–Salem section was renamed the Atomic Veterans Memorial Highway by the Oregon Legislative Assembly in August 2017. In 2022, ODOT completed an emergency onramp at Mountain Avenue in Ashland to aid in evacuations in the event of a wildfire. The gravel ramp is controlled by a locked gate and was approved for construction following the 2020 Almeda fire , which started in

15826-516: The Middle and Coast forks and the McKenzie , Long Tom , Marys , Calapooia , Santiam , Luckiamute , Yamhill , Molalla , Tualatin , and Clackamas rivers. Beginning at 438 feet (134 m) above sea level, the main stem descends 428 feet (130 m) between source and mouth, or about 2.3 feet per mile (0.4 m per km). The gradient is slightly steeper from the source to Albany than it

16019-484: The Native Americans. Upper-river tribes caught steelhead and salmon, often by building weirs across tributary streams. Tribes of the northern Willamette Valley practiced a generally settled lifestyle. The Chinooks lived in great wooden lodges , practiced slavery , and had a well-defined caste system. People of the south were more nomadic, traveling from place to place with the seasons. They were known for

16212-634: The PFC. Free trappers Registre Bellaire, John Day and Alexander Carson hunted and traded furs during the winter of 1813-14 along the Willamette. About thirty NWC employees were stationed at the Champoeg post, now called the Willamette Trading Post , along with freemen housed in two huts and Kalapuya nearby. Nez Perce and Cayuse warned the NWC to stay out of the Willamette Valley hunting grounds. Skirmishes went on for several years over fishing and hunting grounds contended by several groups. By

16405-652: The Pacific Ocean. The smaller Multnomah Channel , a distributary , is 21 miles (34 km) long, about 600 feet (180 m) wide, and 40 feet (12 m) deep. It ends about 14.5 miles (23.3 km) farther downstream on the Columbia, near St. Helens in Columbia County . Proposals have been made for deepening the Multnomah Channel to 43 feet (13 m) in conjunction with roughly 103.5 miles (166.6 km) of tandem-maintained navigation on

16598-702: The Rogue State Park . It also passes the Oregon Vortex , a popular roadside attraction near Gold Hill . At the west end of the valley in Josephine County , the freeway reaches Grants Pass and intersects U.S. Route 199 (US 199), which connects to Crescent City, California , on the Pacific Coast. The freeway continues along the northeast edge of Grants Pass and becomes concurrent with OR 99 at an interchange north of

16791-668: The Terwilliger curves through South Portland , running uphill from OR 43 on the western bank of the Willamette River and downhill from Barbur Boulevard (now carrying OR 10 and OR 99W). The freeway dives northeasterly towards the South Waterfront district to avoid Marquam Hill , home of the Oregon Health & Science University campus. The lanes of OR 43 are split between Hood and Macadam avenues on west and east sides of I-5 as it crosses under

16984-539: The Willamette Falls Locks have been inactive. As commerce and industry flourished on the lower river, most of the original settlers acquired farms in the upper Willamette Valley. By the late 1850s, farmers had begun to grow crops on most of the available fertile land. The settlers increasingly encroached on Native American lands. Skirmishes between natives and settlers in the Umpqua and Rogue valleys to

17177-434: The Willamette River was divided into two stretches: the 27-mile (43 km) lower stretch from Portland to Oregon City—which allowed connection with the rest of the Columbia River system—and the upper reach, which encompassed most of the Willamette's length. Any boats whose owners found it absolutely necessary to get past the falls had to be portaged . This led to competition for business among steam portage companies. In 1873,

17370-480: The Willamette River waterfront. I-5 continues northeast over the Willamette River on the double-decked Marquam Bridge , with its northbound lanes on the upper deck and southbound lanes carried on the lower deck. The bridge is the busiest crossing in Oregon, with over 140,000 daily vehicles traveling across it, and runs parallel to the Tilikum Crossing transit bridge and Ross Island Bridge. The east end of

17563-531: The Willamette Valley especially vulnerable to damage from strong earthquakes. The Willamette River drains a region of 11,478 square miles (29,730 km), which is 12 percent of the total area of Oregon. Bounded by the Coast Range to the west and the Cascade Range to the east, the river basin is about 180 miles (290 km) long and 100 miles (160 km) wide. Elevations within the watershed range from 10,495 feet (3,199 m) at Mount Jefferson in

17756-685: The Willamette Valley were further divided into groups including the Kalapuyan-speaking Yamhill and Atfalati (Tualatin) (both Northern Kalapuya), Central Kalapuya like the Santiam , Muddy Creek (Chemapho), Long Tom (Chelamela), Calapooia (Tsankupi), Marys River (Chepenafa) and Luckiamute, and the Yoncalla or Southern Kalapuya, as well other tribes such as the Chuchsney-Tufti, Siuslaw and Molala . The name Willamette

17949-433: The Willamette Valley. The total native population was estimated at 15,000. The indigenous peoples of the Willamette River practiced a variety of life ways. Those on the lower river, slightly closer to the coast, often relied on fishing as their primary economic mainstay. Salmon was the most important fish to Willamette River tribes as well as to the Native Americans of the Columbia River, where white traders traded fish with

18142-646: The Willamette Valley. These included the Kalapuya , the Chinook , and the Clackamas . The territory of the Clackamas encompassed the northeastern portion of the basin, including the Clackamas River (with which their name is shared). Although it is unclear exactly when, the territory of the Chinook once extended across the northern part of the watershed, through the Columbia River valley. Indigenous peoples of

18335-493: The Willamette basin. The highest flow recorded at this station was 420,000 cubic feet per second (11,893 m/s) on February 9, 1996, during the Willamette Valley Flood of 1996 , and the minimum was 4,200 cubic feet per second (120 m/s) on July 10, 1978. The highest recorded flow of 635,000 cubic feet per second (18,000 m/s) for the Willamette at a different gauge in Portland occurred during

18528-542: The Willamette ranks 19th in volume among rivers in the United States and contributes 12 to 15 percent of the total flow of the Columbia River. The Willamette's flow varies considerably season to season, averaging about 8,200 cubic feet per second (230 m/s) in August to more than 79,000 cubic feet per second (2,200 m/s) in December. The U.S. Geological Survey (USGS) operates five stream gauges along

18721-404: The Willamette's drainage basin, 13 of which are operated by the U.S. Army Corps of Engineers (USACE). The dams are used primarily to produce hydroelectricity , to maintain reservoirs for recreation, and to prevent flooding. The river and its tributaries support 60 fish species, including many species of salmon and trout ; this is despite the dams, other alterations, and pollution (especially on

18914-447: The Willamette, continued on until the falls portage (present-day Oregon City ) and finished their journey at a flattening of both banks, the later site of Champoeg . A first trading post was established. By early 1813, William Wallace and John C. Halsey established a second outpost, Wallace House , farther south, north of present-day Salem. By the end of the War of 1812 , the NWC acquired

19107-541: The actual motions of the Pacific plate and other plates associated with the East Pacific Rise do not correlate mainly with either slab pull or slab push, but rather with a mantle convection upwelling whose horizontal spreading along the bases of the various plates drives them along via viscosity-related traction forces. The driving forces of plate motion continue to be active subjects of on-going research within geophysics and tectonophysics . The development of

19300-423: The area and destroyed 2,500 homes. The states of Oregon and Washington began planning of a replacement for the twin spans of the Interstate Bridge in the late 1990s to address regional congestion and disruptions due to the lift span. The Columbia River Crossing program was established in 2004 to design a replacement, which was to be 17 lanes wide over Hayden Island and cost up to $ 3.5 billion. The program

19493-478: The assumption of a solid Earth made these various proposals difficult to accept. The discovery of radioactivity and its associated heating properties in 1895 prompted a re-examination of the apparent age of Earth . This had previously been estimated by its cooling rate under the assumption that Earth's surface radiated like a black body . Those calculations had implied that, even if it started at red heat , Earth would have dropped to its present temperature in

19686-399: The asthenosphere. This theory was launched by Arthur Holmes and some forerunners in the 1930s and was immediately recognized as the solution for the acceptance of the theory as originally discussed in the papers of Alfred Wegener in the early years of the 20th century. However, despite its acceptance, it was long debated in the scientific community because the leading theory still envisaged

19879-530: The basalt with up to 1,000 feet (300 m) of silt in the Portland and Tualatin basins. During the Pleistocene , beginning roughly 2.5 million years ago, volcanic activity in the Cascades combined with a cool, moist climate to produce further heavy sedimentation across the basin, and braided rivers created alluvial fans spreading down from the east. Between about 15,500 and 13,000 years ago,

20072-476: The base of the lithosphere. Slab pull is therefore most widely thought to be the greatest force acting on the plates. In this understanding, plate motion is mostly driven by the weight of cold, dense plates sinking into the mantle at trenches. Recent models indicate that trench suction plays an important role as well. However, the fact that the North American plate is nowhere being subducted, although it

20265-625: The basin from the Pacific Ocean. Basalts of the Columbia River Basalt Group , from eruptions primarily in eastern Oregon , flowed across large parts of the northern half of the basin about 15 million years ago. They covered the Tualatin Mountains (West Hills), most of the Tualatin Valley , and the slopes of hills farther south, with up to 1,000 feet (300 m) of lava . Later deposits covered

20458-495: The bathymetry of the deep ocean floors and the nature of the oceanic crust such as magnetic properties and, more generally, with the development of marine geology which gave evidence for the association of seafloor spreading along the mid-oceanic ridges and magnetic field reversals , published between 1959 and 1963 by Heezen, Dietz, Hess, Mason, Vine & Matthews, and Morley. Simultaneous advances in early seismic imaging techniques in and around Wadati–Benioff zones along

20651-534: The bridge, adjacent to the Oregon Museum of Science and Industry , has a southbound stub ramp that was built to serve the cancelled Mount Hood Freeway . I-5 descends from the bridge and runs north along the Willamette River, following the eastern bank of the river and the Eastbank Esplanade bicycle and pedestrian trail a few blocks west of OR 99E. The freeway crosses over the east end of

20844-578: The cancelled Rose City Freeway and were re-purposed to serve the hospital. Through most of North Portland , I-5 runs in a trench that is crossed by several local streets and pedestrian overpasses, connecting Interstate Avenue to the west and Albina Avenue to the east. Interstate Avenue, a part of OR 99W, also carries the MAX Yellow Line through the Overlook , Arbor Lodge , and Kenton neighborhoods. At an interchange with Going Street,

21037-499: The city's municipal airport and follows Bear Creek around the north side of downtown Ashland. I-5 and OR 99 run parallel each other on opposite sides of Bear Creek through Talent and Phoenix to Medford , at the center of the Rogue Valley and its winery region . The freeway runs through downtown Medford on a 3,229-foot (984 m) elevated viaduct with no exits to the city center. It then intersects OR 62 at

21230-489: The city's first officially recognized public swimming beach, Poet's Beach . There are more than 20 major dams on the Willamette's tributaries, as well as a complex series of levees and channels to control the river's flow. The only dam on the Willamette's main stem is the Willamette Falls Dam, a low weir -type structure at Willamette Falls that diverts water into the headraces of the adjacent mills and

21423-412: The city's growing economy. Trade goods from the Columbia basin north of Portland could also be transported southward on the Willamette due to the deeper channels made at the Willamette's mouth. By the early 20th century, major river-control projects had begun to take place. Levees were constructed along the river in most urban areas, and Portland built concrete walls to protect its downtown sector. In

21616-590: The city, I-5 intersects the south end of I-205 , a bypass of Portland serving Oregon City and eastern Portland. The freeway crosses over the Tualatin River into Durham , where it passes the Bridgeport Village shopping center, before entering Tigard and an intersection with OR 217 , a major freeway that connects to Beaverton . I-5 then enters Multnomah County and the city of Portland, where it travels around Mount Sylvania and through

21809-655: The city. I-5 splits from the Rogue River and continues north along a zig-zag course across several passes and valleys in the Southern Oregon Coast Range . At Wolf Creek , it passes a historic inn and tavern that is listed on the National Register of Historic Places . The freeway crosses into Douglas County near Stage Road Pass east of Glendale and turns northeast to follow the Cow Creek valley before resuming its northern course through

22002-416: The concept of continental drift , an idea developed during the first decades of the 20th century. Plate tectonics came to be accepted by geoscientists after seafloor spreading was validated in the mid-to-late 1960s. The processes that result in plates and shape Earth's crust are called tectonics . Tectonic plates also occur in other planets and moons. Earth's lithosphere, the rigid outer shell of

22195-413: The concept was of continents plowing through oceanic crust. Therefore, Wegener later changed his position and asserted that convection currents are the main driving force of plate tectonics in the last edition of his book in 1929. However, in the plate tectonics context (accepted since the seafloor spreading proposals of Heezen, Hess, Dietz, Morley, Vine, and Matthews (see below) during the early 1960s),

22388-495: The construction of the Willamette Falls Locks bypassed the falls and allowed easy navigation between the upper and lower river. Each lock chamber measured 210 feet (64 m) long and 40 feet (12 m) wide, and the canal was originally operated manually before it switched to electrical power. Usage of the locks peaked in the 1940s, and by the early 21st century, the lock system was little used. Since 2011,

22581-540: The controlled burning of woodlands to create meadows for hunting and plant gathering (especially camas ). The Willamette River first appeared in written records in 1792, when it was observed by British Lieutenant William Robert Broughton of the Vancouver Expedition , led by George Vancouver . The 1805-1806 Lewis and Clark Expedition originally missed the mouth of the Willamette. On their return journey, only after receiving directions from natives along

22774-415: The deep mantle at subduction zones, providing most of the driving force for plate movement. The weakness of the asthenosphere allows the tectonic plates to move easily towards a subduction zone. For much of the first quarter of the 20th century, the leading theory of the driving force behind tectonic plate motions envisaged large scale convection currents in the upper mantle, which can be transmitted through

22967-534: The discussions treated in this section) or proposed as minor modulations within the overall plate tectonics model. In 1973, George W. Moore of the USGS and R. C. Bostrom presented evidence for a general westward drift of Earth's lithosphere with respect to the mantle, based on the steepness of the subduction zones (shallow dipping towards the east, steeply dipping towards the west). They concluded that tidal forces (the tidal lag or "friction") caused by Earth's rotation and

23160-466: The driving force for horizontal movements, invoking gravitational forces away from the regional crustal doming. The theories find resonance in the modern theories which envisage hot spots or mantle plumes which remain fixed and are overridden by oceanic and continental lithosphere plates over time and leave their traces in the geological record (though these phenomena are not invoked as real driving mechanisms, but rather as modulators). The mechanism

23353-532: The estimated cost grew to $ 715 million by 2020. In June 2020, several elected officials from the city and county governments announced that they would not support the proposal, following a local nonprofit advocacy group from the Albina neighborhood that did the same. A new design with larger freeway lids and potential for development, estimated to cost $ 1.25 billion, was adopted by ODOT in September 2021;

23546-473: The final one in 1936), he noted how the east coast of South America and the west coast of Africa looked as if they were once attached. Wegener was not the first to note this ( Abraham Ortelius , Antonio Snider-Pellegrini , Eduard Suess , Roberto Mantovani and Frank Bursley Taylor preceded him just to mention a few), but he was the first to marshal significant fossil and paleo-topographical and climatological evidence to support this simple observation (and

23739-444: The following decades, many large dams were built on Cascade Range tributaries of the Willamette. The Army Corps of Engineers operates 13 such dams, which affect flows from about 40 percent of the basin. Most of them do not have fish ladders. With development in and near the river came increased pollution. By the late 1930s, efforts to stem the pollution led to formation of a state sanitary board to oversee modest cleanup efforts. In

23932-695: The forces acting upon it by the Moon are a driving force for plate tectonics. As Earth spins eastward beneath the Moon, the Moon's gravity ever so slightly pulls Earth's surface layer back westward, just as proposed by Alfred Wegener (see above). Since 1990 this theory is mainly advocated by Doglioni and co-workers ( Doglioni 1990 ), such as in a more recent 2006 study, where scientists reviewed and advocated these ideas. It has been suggested in Lovett (2006) that this observation may also explain why Venus and Mars have no plate tectonics, as Venus has no moon and Mars' moons are too small to have significant tidal effects on

24125-473: The founding of the town in 1829. McLoughlin attempted to persuade the HBC (which still held sway over the area) to allow American settlers to live on the land, and provided significant help to American colonization of the area, all against the HBC's orders. Oregon City prospered because of the lumber and grist mills that were run by the water power of Willamette Falls, but the falls formed an impassable barrier to river navigation. Linn City (originally Robins Nest)

24318-573: The freeway runs along the west bank of the South Umpqua River opposite from the city's downtown and passes through several residential neighborhoods near the regional airport . At Harvard Avenue, I-5 begins a concurrency with OR 138 that continues for 12 miles (19 km) to Sutherlin , running parallel to OR 99 as the highways cross the North Umpqua River . OR 99 rejoins I-5 between Oakland and Yoncalla in

24511-563: The freeway turns northwest and crosses over the Columbia Slough , reaching Delta Park on the site of the former city of Vanport . The area also includes the Portland International Raceway and Portland Meadows horse racing track, along with several sports fields. At the north end of Delta Park, I-5 intersects the north end of OR 99E and the east end of OR 120 , a short local route connecting to

24704-735: The freeway's northbound lanes gain the city's lone high-occupancy vehicle (HOV) lane, which runs for 3.5 miles (5.6 km) to the north end of Delta Park . I-5 continues north and passes Peninsula Park and the Cascade campus of the Portland Community College in the Piedmont neighborhood before reaching an interchange with Lombard Street, which carries the US ;30 Bypass . From the Lombard Street interchange,

24897-588: The geographical latitudinal and longitudinal grid of Earth itself. These systematic relations studies in the second half of the nineteenth century and the first half of the twentieth century underline exactly the opposite: that the plates had not moved in time, that the deformation grid was fixed with respect to Earth's equator and axis, and that gravitational driving forces were generally acting vertically and caused only local horizontal movements (the so-called pre-plate tectonic, "fixist theories"). Later studies (discussed below on this page), therefore, invoked many of

25090-624: The government to a part of the Coast Reservation that later became the Grande Ronde Reservation . Between 1879 and 1885, the Willamette River was charted by Cleveland S. Rockwell , a topographical engineer and cartographer for the United States Coast and Geodetic Survey . Rockwell surveyed the lower Willamette from the foot of Ross Island through Portland to the Columbia River and then downstream on

25283-423: The highway, breaking ground on a link between Siskiyou Summit and Medford on November 28, 1913. These early sections were built using compacted dirt, which turned into mud in inclement weather and rendered them impassible. The state government enacted its own revenue sources for highway construction at the end of the decade, including the first state gas tax to be levied in the United States. The Pacific Highway

25476-718: The interiors of plates, and these have been variously attributed to internal plate deformation and to mantle plumes. Tectonic plates may include continental crust or oceanic crust, or both. For example, the African plate includes the continent and parts of the floor of the Atlantic and Indian Oceans. Some pieces of oceanic crust, known as ophiolites , failed to be subducted under continental crust at destructive plate boundaries; instead these oceanic crustal fragments were pushed upward and were preserved within continental crust. Three types of plate boundaries exist, characterized by

25669-412: The large scale convection cells) or secondary. The secondary mechanisms view plate motion driven by friction between the convection currents in the asthenosphere and the more rigid overlying lithosphere. This is due to the inflow of mantle material related to the downward pull on plates in subduction zones at ocean trenches. Slab pull may occur in a geodynamic setting where basal tractions continue to act on

25862-654: The largest of these originally weighed about 160 short tons (150 t). The northern part of the watershed is underlain by a network of faults capable of producing earthquakes at any time, and many small quakes have been recorded in the basin since the mid-19th century. In 1993, the Scotts Mills earthquake —the largest recent earthquake in the valley, measuring 5.6 on the Richter scale —was centered near Scotts Mills , about 34 miles (55 km) south of Portland. It caused $ 30 million in damage, including harm to

26055-834: The largest water storage capacity, at 477,700 acre-feet (589,200,000 m). The other 11 dams are Big Cliff on the North Santiam River; Green Peter and Foster on the Santiam River ; Cougar on the South Fork McKenzie River ; Blue River on the Blue River ; Fern Ridge on the Long Tom River ; Hills Creek and Dexter on the Middle Fork Willamette River; Fall Creek on Fall Creek ; Cottage Grove on

26248-421: The lithosphere before it dives underneath an adjacent plate, producing a clear topographical feature that can offset, or at least affect, the influence of topographical ocean ridges. Mantle plumes and hot spots are also postulated to impinge on the underside of tectonic plates. Slab pull : Scientific opinion is that the asthenosphere is insufficiently competent or rigid to directly cause motion by friction along

26441-403: The lower mantle, there is a slight westward component in the motions of all the plates. They demonstrated though that the westward drift, seen only for the past 30 Ma, is attributed to the increased dominance of the steadily growing and accelerating Pacific plate. The debate is still open, and a recent paper by Hofmeister et al. (2022) revived the idea advocating again the interaction between

26634-405: The many geographical, geological, and biological continuities between continents. In 1912, the meteorologist Alfred Wegener described what he called continental drift, an idea that culminated fifty years later in the modern theory of plate tectonics. Wegener expanded his theory in his 1915 book The Origin of Continents and Oceans . Starting from the idea (also expressed by his forerunners) that

26827-429: The matching of the rock formations along these edges. Confirmation of their previous contiguous nature also came from the fossil plants Glossopteris and Gangamopteris , and the therapsid or mammal-like reptile Lystrosaurus , all widely distributed over South America, Africa, Antarctica, India, and Australia. The evidence for such an erstwhile joining of these continents was patent to field geologists working in

27020-452: The mid-1950s, the question remained unresolved as to whether mountain roots were clenched in surrounding basalt or were floating on it like an iceberg. Interstate 5 in Oregon Interstate 5 ( I-5 ) in the U.S. state of Oregon is a major Interstate Highway that traverses the state from north to south. It travels to the west of the Cascade Mountains , connecting Portland to Salem , Eugene , Medford , and other major cities in

27213-512: The motion picture of the Atlantic region", processes that anticipated seafloor spreading and subduction . One of the first pieces of geophysical evidence that was used to support the movement of lithospheric plates came from paleomagnetism . This is based on the fact that rocks of different ages show a variable magnetic field direction, evidenced by studies since the mid–nineteenth century. The magnetic north and south poles reverse through time, and, especially important in paleotectonic studies,

27406-438: The motion. At a subduction zone the relatively cold, dense oceanic crust sinks down into the mantle, forming the downward convecting limb of a mantle cell , which is the strongest driver of plate motion. The relative importance and interaction of other proposed factors such as active convection, upwelling inside the mantle, and tidal drag of the Moon is still the subject of debate. The outer layers of Earth are divided into

27599-440: The mountainous terrain of southern Oregon for rolling hills and farms. At Goshen , I-5 intersects OR 58 and passes the Lane Community College campus before entering Eugene . I-5 continues north into Eugene, running along the city's eastern border with Springfield , and intersects OR 225 at Coryell Pass. OR 99 then splits from the freeway travels west along OR 126 Business into downtown Eugene, serving

27792-433: The mountains. After descending from Canyon Creek Pass and following Canyon Creek, I-5 reaches Canyonville and passes the Seven Feathers Casino Resort . The freeway follows the South Umpqua River through Myrtle Creek and the Cow Creek Reservation , with OR 99 splitting to serve Winston . I-5 intersects OR 42 east of Winston in Green and continues north into the outskirts of Roseburg . Within Roseburg,

27985-417: The name was removed from state records following the discovery of his membership in the Ku Klux Klan . Early proposals by engineers put the southern section of I-5 further east through Klamath Falls and the flatter Klamath Basin , but the Siskiyou Pass route was favored by local politicians. Most of the highway in the Pacific Northwest was incorporated into U.S. Route 99 (US 99), created as part of

28178-415: The next 25 years, some 500,000 settlers traveled the Oregon Trail, to reach the Willamette Valley. Starting in the 1830s, Oregon City developed near Willamette Falls. It was incorporated in 1844, becoming the first city west of the Rocky Mountains to have that distinction. John McLoughlin , the Hudson's Bay Company (HBC) superintendent of the Columbia District , was one of the major contributors to

28371-479: The non-profit Willamette Riverkeeper organization designated the full length of the river as the Willamette River Water Trail. Four years later, the National Park Service added the Willamette water trail—expanded to 217 miles (349 km) to include some of the major tributaries—to its list of National Water Trails . The water trail system is meant to protect and restore waterways in the United States and enhance recreation on and near them. A 1991 agreement between

28564-432: The north end of Eugene, intersects Beltline Road in a partial cloverleaf interchange with direct ramps to the western freeway, which carries OR 569 around Eugene. The freeway leaves Eugene after crossing the McKenzie River at Armitage Park south of Coburg . I-5 continues north along OR 99E through rural Linn County , intersecting OR 228 near Brownsville and OR 34 west of Lebanon , before

28757-418: The north pole, and each continent, in fact, shows its own "polar wander path". During the late 1950s, it was successfully shown on two occasions that these data could show the validity of continental drift: by Keith Runcorn in a paper in 1956, and by Warren Carey in a symposium held in March 1956. The second piece of evidence in support of continental drift came during the late 1950s and early 60s from data on

28950-407: The oceanic crust is suggested to be in motion with the continents which caused the proposals related to Earth rotation to be reconsidered. In more recent literature, these driving forces are: Forces that are small and generally negligible are: For these mechanisms to be overall valid, systematic relationships should exist all over the globe between the orientation and kinematics of deformation and

29143-437: The oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. Along convergent plate boundaries , the process of subduction carries the edge of one plate down under the other plate and into the mantle . This process reduces the total surface area (crust) of the Earth. The lost surface is balanced by the formation of new oceanic crust along divergent margins by seafloor spreading, keeping

29336-589: The planet including the crust and upper mantle , is fractured into seven or eight major plates (depending on how they are defined) and many minor plates or "platelets". Where the plates meet, their relative motion determines the type of plate boundary (or fault ): convergent , divergent , or transform . The relative movement of the plates typically ranges from zero to 10 cm annually. Faults tend to be geologically active, experiencing earthquakes , volcanic activity , mountain-building , and oceanic trench formation. Tectonic plates are composed of

29529-407: The planet. In a paper by it was suggested that, on the other hand, it can easily be observed that many plates are moving north and eastward, and that the dominantly westward motion of the Pacific Ocean basins derives simply from the eastward bias of the Pacific spreading center (which is not a predicted manifestation of such lunar forces). In the same paper the authors admit, however, that relative to

29722-399: The plate as it dives into the mantle (although perhaps to a greater extent acting on both the under and upper side of the slab). Furthermore, slabs that are broken off and sink into the mantle can cause viscous mantle forces driving plates through slab suction. In the theory of plume tectonics followed by numerous researchers during the 1990s, a modified concept of mantle convection currents

29915-426: The plates of the Atlantic basin, which are attached (perhaps one could say 'welded') to adjacent continents instead of subducting plates. It is thus thought that forces associated with the downgoing plate (slab pull and slab suction) are the driving forces which determine the motion of plates, except for those plates which are not being subducted. This view however has been contradicted by a recent study which found that

30108-408: The present continents once formed a single land mass (later called Pangaea ), Wegener suggested that these separated and drifted apart, likening them to "icebergs" of low density sial floating on a sea of denser sima . Supporting evidence for the idea came from the dove-tailing outlines of South America's east coast and Africa's west coast Antonio Snider-Pellegrini had drawn on his maps, and from

30301-474: The raw sewage in the system flowed into the river instead of into the city's wastewater treatment plant. The Big Pipe project and related work reduces CSO volume on the lower river by about 94 percent. In June 2014, Dean Hall became the first person to swim the entire length of the Willamette River. He swam 184 miles (296 km) from Eugene to the river mouth in 25 days. In 2017, Human Access Project partnered with Portland Parks & Recreation to open

30494-459: The relationships recognized during this pre-plate tectonics period to support their theories (see reviews of these various mechanisms related to Earth rotation the work of van Dijk and collaborators). Of the many forces discussed above, tidal force is still highly debated and defended as a possible principal driving force of plate tectonics. The other forces are only used in global geodynamic models not using plate tectonics concepts (therefore beyond

30687-428: The relative position of the magnetic north pole varies through time. Initially, during the first half of the twentieth century, the latter phenomenon was explained by introducing what was called "polar wander" (see apparent polar wander ) (i.e., it was assumed that the north pole location had been shifting through time). An alternative explanation, though, was that the continents had moved (shifted and rotated) relative to

30880-399: The ridge). Cool oceanic lithosphere is significantly denser than the hot mantle material from which it is derived and so with increasing thickness it gradually subsides into the mantle to compensate the greater load. The result is a slight lateral incline with increased distance from the ridge axis. This force is regarded as a secondary force and is often referred to as " ridge push ". This is

31073-419: The river and railroads built in the late 19th century. The rising popularity of automobiles at the turn of the century spurred the construction of new highways and the formation of automobile clubs and good roads associations. The Pacific Highway Association was formed in 1910 to bolster an ongoing campaign to build a highway along the West Coast, from Tijuana to Vancouver , British Columbia. The highway

31266-399: The river at the Morrison Bridge . The Willamette River basin was created primarily by plate tectonics and volcanism and was altered by erosion and sedimentation, including deposits from enormous glacial floods as recent as 13,000 years ago. The oldest rocks beneath the Willamette Valley are the Siletz River Volcanics . About 35 million years ago, these rocks were subducted by

31459-483: The river in Portland. The 3,700-foot (1,100 m) bridge is the only cantilevered deck truss in Oregon. Plate tectonics Plate tectonics (from Latin tectonicus , from Ancient Greek τεκτονικός ( tektonikós )  'pertaining to building') is the scientific theory that Earth 's lithosphere comprises a number of large tectonic plates , which have been slowly moving since 3–4 billion years ago. The model builds on

31652-425: The river's lower reaches). Part of the Willamette Floodplain was established as a National Natural Landmark in 1987, and the river was named as one of 14 American Heritage Rivers in 1998. The upper tributaries of the Willamette originate in the mountains south and southeast of Eugene, Oregon . Formed by the confluence of the Middle Fork Willamette River and the Coast Fork Willamette River near Springfield ,

31845-403: The river, at Harrisburg, Corvallis, Albany, Salem, and Portland. The average discharge at the lowermost gauge, near the Morrison Bridge in Portland, was 33,220 cubic feet per second (941 m/s) between 1972 and 2013. Located at river mile (RM) 12.8 or river kilometer (RK) 20.6, the gauge measures the flow from an area of 11,200 square miles (29,000 km), roughly 97 percent of

32038-441: The south, settled from this muddy water to form today's valley floor. The floods carried Montana icebergs well into the basin, where they melted and dropped glacial erratics onto the land surface. These rocks, composed of granite and other materials common to central Montana but not to the Willamette Valley, include more than 40 boulders, each at least 3 feet (0.9 m) in diameter. Before being partly chipped away and removed,

32231-436: The southern hemisphere. The South African Alex du Toit put together a mass of such information in his 1937 publication Our Wandering Continents , and went further than Wegener in recognising the strong links between the Gondwana fragments. Wegener's work was initially not widely accepted, in part due to a lack of detailed evidence but mostly because of the lack of a reasonable physically supported mechanism. Earth might have

32424-440: The southern outskirts of Salem . The freeway travels around McNary Field and intersects OR 22 at Mission Street, near the Corban University campus southeast of downtown Salem. I-5 and OR 99E continue north through suburban Salem, passing the Oregon State Penitentiary and Oregon State Hospital campus, which is located two miles (3.2 km) east of the Oregon State Capitol and Willamette University . Between

32617-452: The southwest of the Willamette River led the Oregon state government to remove the natives by military force. They were first led off their traditional lands to the Willamette Valley, but soon were marched to the Coast Indian Reservation . In 1855, Joel Palmer , an Oregon legislator, negotiated a treaty with the Willamette Valley tribes, who, although unhappy with the treaty, ceded their lands to non-natives. The natives were then relocated by

32810-420: The swing span was removed in the 1950s. The Oregon City Bridge , built in 1922, replaced a suspension span constructed at the site in 1888. It carries Oregon Route 43 over the river at about RM 26 (RK 42) between Oregon City and West Linn . The Ross Island Bridge carries U.S. Route 26 ( Mount Hood Highway ) over the river at RM 14 (RK 23). It is one of 10 highway bridges crossing

33003-402: The theory of plate tectonics was the scientific and cultural change which occurred during a period of 50 years of scientific debate. The event of the acceptance itself was a paradigm shift and can therefore be classified as a scientific revolution, now described as the Plate Tectonics Revolution . Around the start of the twentieth century, various theorists unsuccessfully attempted to explain

33196-502: The theory) and "fixists" (opponents). During the 1920s, 1930s and 1940s, the former reached important milestones proposing that convection currents might have driven the plate movements, and that spreading may have occurred below the sea within the oceanic crust. Concepts close to the elements of plate tectonics were proposed by geophysicists and geologists (both fixists and mobilists) like Vening-Meinesz, Holmes, and Umbgrove. In 1941, Otto Ampferer described, in his publication "Thoughts on

33389-476: The total surface area constant in a tectonic "conveyor belt". Tectonic plates are relatively rigid and float across the ductile asthenosphere beneath. Lateral density variations in the mantle result in convection currents, the slow creeping motion of Earth's solid mantle. At a seafloor spreading ridge , plates move away from the ridge, which is a topographic high, and the newly formed crust cools as it moves away, increasing its density and contributing to

33582-429: The trenches bounding many continental margins, together with many other geophysical (e.g., gravimetric) and geological observations, showed how the oceanic crust could disappear into the mantle, providing the mechanism to balance the extension of the ocean basins with shortening along its margins. All this evidence, both from the ocean floor and from the continental margins, made it clear around 1965 that continental drift

33775-415: The two highways reach Albany . The freeway skirts the east side of the city, where it intersects US 20 , and begins a concurrency with OR 99E. I-5 and OR 99E then intersect the south and north ends of OR 164 near Millersburg and the Ankeny National Wildlife Refuge . The freeway continues northeast and passes the Enchanted Forest amusement park and several wineries before reaching

33968-527: The two major highways that follow the river for its entire length. Communities along the main stem include Springfield and Eugene in Lane County ; Harrisburg in Linn County ; Corvallis in Benton County ; Albany in Linn and Benton counties; Independence in Polk County ; Salem in Marion County ; Newberg in Yamhill County ; Oregon City , West Linn , Milwaukie , and Lake Oswego in Clackamas County ; and Portland in Multnomah and Washington counties. Significant tributaries from source to mouth include

34161-450: The vicinity of the Willamette on a section referred to as French Prairie . By 1841, members of the United States Exploring Expedition came through the Siskiyou Trail. They noted extensive salmon fishing by natives at Willamette Falls, much like that at Celilo Falls on the Columbia River. In the middle part of the 19th century the Willamette Valley's fertile soils, pleasant climate, and abundant water attracted thousands of settlers from

34354-410: The water stored in the reservoirs is used for irrigation . Cougar Dam on the South Fork McKenzie River and Detroit Dam on the North Santiam River are the two tallest dams in the Willamette River basin. Detroit Dam is 463 feet (141 m) high and stores 455,000 acre-feet (561,000,000 m) of water. Lookout Point Dam on the Middle Fork Willamette River , forming Lookout Point Lake , has

34547-426: The watershed. In 1987, the U.S. Secretary of the Interior designated 713 acres (289 ha) of the watershed in Benton County as a National Natural Landmark . This area is the Willamette Floodplain , the largest remaining unplowed native grassland in the North Pacific geologic province, which encompasses most of the Pacific Northwest coast. For at least 10,000 years, a variety of indigenous peoples populated

34740-467: The way the plates move relative to each other. They are associated with different types of surface phenomena. The different types of plate boundaries are: Tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere . Dissipation of heat from the mantle is the original source of the energy required to drive plate tectonics through convection or large scale upwelling and doming. As

34933-438: The winter of 1818-19, Thomas McKay led a hunting brigade farther south towards the sources of the Willamette River and reached the upper Umpqua River . More violent skirmishes were fought. Most brigade members returned to Fort George (formerly called Fort Astoria ). Louis LaBonté, Joseph Gervais , Étienne Lucier , Louis Kanota, and Louis Pichette (dit DuPré) remained in the Willamette Valley as free trappers. Meanwhile, in 1821

35126-415: Was an important transportation route in the 19th century, although Willamette Falls , just upstream from Portland, was a major barrier to boat traffic. In the 21st century, major highways follow the river, and roads cross the main stem on approximately 30 different bridges. More than half a dozen bridges not open to motorized vehicles provide separate crossings for bicycles and pedestrians, mostly in

35319-431: Was cancelled in 2013 due to opposition within the Washington state legislature; $ 200 million had been spent during planning, which included federal funds that would need to be reimbursed unless a new proposal was submitted. A new program, named the Interstate Bridge Replacement, began in 2019 and is expected to publish an environmental impact statement in 2023. The updated design would include an eight-lane toll bridge,

35512-495: Was completed in 1922 and was the first highway to be completely paved from border to border within a state west of the Mississippi River . The Oregon state legislature authorized the construction of controlled-access "throughways" (now called freeways) in 1947 and the Pacific Highway was designated as a future corridor the following year. A six-cent gas tax increase was approved by the legislature in 1949 and would be used to improve sections of US 99 to freeway standards. It

35705-400: Was established across the Willamette from Oregon City. After Portland was incorporated in 1851, quickly growing into Oregon's largest city, Oregon City gradually lost its importance as the economic and political center of the Willamette Valley. Beginning in the 1850s, steamboats began to ply the Willamette, despite the fact that they could not pass Willamette Falls. As a result, navigation on

35898-531: Was feasible. The theory of plate tectonics was defined in a series of papers between 1965 and 1967. The theory revolutionized the Earth sciences, explaining a diverse range of geological phenomena and their implications in other studies such as paleogeography and paleobiology . In the late 19th and early 20th centuries, geologists assumed that Earth's major features were fixed, and that most geologic features such as basin development and mountain ranges could be explained by vertical crustal movement, described in what

36091-599: Was formed. For a typical distance that oceanic lithosphere must travel before being subducted, the thickness varies from about 6 km (4 mi) thick at mid-ocean ridges to greater than 100 km (62 mi) at subduction zones. For shorter or longer distances, the subduction zone, and therefore also the mean, thickness becomes smaller or larger, respectively. Continental lithosphere is typically about 200 km (120 mi) thick, though this varies considerably between basins, mountain ranges, and stable cratonic interiors of continents. The location where two plates meet

36284-420: Was incorporated into a state highway plan adopted by the Oregon State Highway Commission in 1914, a year after the state legislature had established the commission and a state highway department . The first sections of the 345-mile (555 km) Pacific Highway were initially built by counties through bond issues and other revenue streams. Jackson County was the first to begin construction on its section of

36477-432: Was later augmented by federal funding under the Interstate Highways program. The State Highway Commission studied and approved the routing of I-5 around several cities in the late 1950s, including an elevated bypass of Medford. Although not generally referred as such, the portion of I-5 south of Portland near Tigard to Salem was formerly named the Robert Hugh Baldock Freeway after a former Oregon highway engineer. In 2022,

36670-424: Was observed early that although granite existed on continents, seafloor seemed to be composed of denser basalt , the prevailing concept during the first half of the twentieth century was that there were two types of crust, named "sial" (continental type crust) and "sima" (oceanic type crust). Furthermore, it was supposed that a static shell of strata was present under the continents. It therefore looked apparent that

36863-443: Was popularized during the 1980s and 1990s. Recent research, based on three-dimensional computer modelling, suggests that plate geometry is governed by a feedback between mantle convection patterns and the strength of the lithosphere. Forces related to gravity are invoked as secondary phenomena within the framework of a more general driving mechanism such as the various forms of mantle dynamics described above. In modern views, gravity

37056-444: Was supported in this by researchers such as Alex du Toit ). Furthermore, when the rock strata of the margins of separate continents are very similar it suggests that these rocks were formed in the same way, implying that they were joined initially. For instance, parts of Scotland and Ireland contain rocks very similar to those found in Newfoundland and New Brunswick . Furthermore, the Caledonian Mountains of Europe and parts of

37249-409: Was used to reach farther south. This trail, over 600 miles (970 km) long, stretched from the mouth of the Willamette River near present-day Portland south through the Willamette Valley, crossing the Siskiyou Mountains , and south through the Sacramento Valley to San Francisco . In 1812, William Henry and Alfred Seton paddled up from Fort Astoria (PFC) on the Columbia River into the mouth of

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