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62-482: Rock Island Dam is constructed on Columbia River basalt similar to that which is exposed on the cliffs near the dam. These columnar basalts were formed from lava flows during the mid- to late- Miocene Epoch , some 14 to 16 million years ago. The rock is strong and durable and provides a very stable foundation for the structure. Columbia River stream flows at the Project averaged 73,700 cubic feet per second (2090 m³/s),

124-484: A common source, the Yellowstone hotspot . The ultimate cause of the volcanism is still up for debate, but the most widely accepted idea is that the mantle plume or upwelling (similar to that associated with present-day Hawaii) initiated the widespread and voluminous basaltic volcanism about 17 million years ago. As hot mantle plume materials rise and reach lower pressures, the hot materials melt and interact with

186-404: A decrease of 37% from 2000 and 63% of the 20 year average of 116,700 cubic feet per second (3305 m³/s). The Rock Island Hydro Project generated 1,900 gigawatt-hours of electricity in 2001 — 70% of its 2000 output. Over the past 10 years the Project has averaged 2,600 gigawatt-hours per year. During 2001, Rock Island's Second Powerhouse produced 1,800 gigawatt-hours of power, representing 95% of

248-535: A dramatic change in scenery while driving along Interstate 84 . In the western, temperate rainforest areas, forests are marked by bigleaf maples , Douglas fir , and western hemlock , all covered in epiphytes . In the transition zone (between Hood River and The Dalles), vegetation turns to Oregon white oak , ponderosa pine , and cottonwood . At the eastern end, the forests make way for expansive grasslands , with occasional pockets of lodgepole and ponderosa pine. Atmospheric pressure differentials east and west of

310-647: A maximum Pomona flow emplacement duration of several months based on the time required for rivers to be reestablished in their canyons following a basalt flow interruption. Three major tools are used to date the CRBG flows: Stratigraphy, radiometric dating, and magnetostratigraphy. These techniques have been key to correlating data from disparate basalt exposures and boring samples over five states. Major eruptive pulses of flood basalt lavas are laid down stratigraphically . The layers can be distinguished by physical characteristics and chemical composition. Each distinct layer

372-475: A period of some 50 years. There were three main construction periods, each taking place about 20 years apart as the need for low-cost hydroelectric power was paramount in the region. Development began in January 1930, and the dam, powerhouse, and first four operating units were turned over to Puget Sound Power & Light Company by Stone and Webster Engineering Corporation on February 1, 1933. Work on completion of

434-517: A stratum was deposited. This is possible because, as magnetic minerals precipitate in the melt (crystallize), they align themselves with Earth's current magnetic field. The Steens Basalt captured a highly detailed record of the Earth's magnetic reversal that occurred roughly 15 million years ago. Over a 10,000-year period, more than 130 flows solidified – roughly one flow every 75 years. As each flow cooled below about 500 °C (932 °F), it captured

496-490: A thickness of more than 1.8 km (5,900 ft). As the molten rock came to the surface, the Earth's crust gradually sank into the space left by the rising lava. This subsidence of the crust produced a large, slightly depressed lava plain now known as the Columbia Basin or Columbia River Plateau . The northwesterly advancing lava forced the ancient Columbia River into its present course. The lava, as it flowed over

558-704: Is 17.67±0.32 Ma with younger lava flows ranging to 15.50±0.40 Ma. Although the Imnaha Basalt overlies Lower Steens Basalt, it has been suggested that it is interfingered with Upper Steens Basalt. The next oldest of the flows, from 17 million to 15.6 million years ago, make up the Grande Ronde Basalt. Units (flow zones) within the Grande Ronde Basalt include the Meyer Ridge and the Sentinel Bluffs units. Geologists estimate that

620-824: Is believed the Yellowstone Hotspot created features like Smith Rock in Central Oregon and perhaps another flood basalt event known as Siletzia which underlies much of the Pacific Northwest coast with exposures in the Oregon Coast Range . There is additional confirmation that Yellowstone is associated with a deep hot spot. Using tomographic images based on seismic waves, relatively narrow, deeply seated, active convective plumes have been detected under Yellowstone and several other hot spots. These plumes are much more focused than

682-739: Is known for its high concentration of waterfalls , with over 90 on the Oregon side of the gorge alone. Many are along the Historic Columbia River Highway , including the notable 620-foot-high (190 m) Multnomah Falls . Trails and day use sites are maintained by the Forest Service and many Oregon and Washington state parks . The Columbia River Gorge began forming as far back as the Miocene (roughly 17 to 12 million years ago), and continued to take shape through

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744-1073: Is made up of the Umatilla Member flows, the Wilbur Creek Member flows, the Asotin Member flows (13 million years ago), the Weissenfels Ridge Member flows, the Esquatzel Member flows, the Elephant Mountain Member flows (10.5 million years ago), the Bujford Member flows, the Ice Harbor Member flows (8.5 million years ago) and the Lower Monumental Member flows (6 million years ago). Camp & Ross (2004) observed that

806-584: Is the youngest, smallest and one of the best-preserved continental flood basalt provinces on Earth, covering over 210,000 km (81,000 sq mi) mainly eastern Oregon and Washington , western Idaho , and part of northern Nevada . The basalt group includes the Steens and Picture Gorge basalt formations. During the middle to late Miocene epoch , the Columbia River flood basalts engulfed about 163,700 km (63,200 sq mi) of

868-429: Is typically assigned a name usually based on area (valley, mountain, or region) where that formation is exposed and available for study. Stratigraphy provides a relative ordering (ordinal ranking) of the CRBG layers. Absolute dates, subject to a statistical uncertainty, are determined through radiometric dating using isotope ratios such as Ar/ Ar dating, which can be used to identify the date of solidifying basalt. In

930-635: The Cascade Range to the Pacific Ocean . Each river has carved out a gorge through the Cascades. The Columbia River Gorge marks the state line between Oregon and Washington, and its wide range of elevation and precipitation makes it an extremely diverse and dynamic place. Ranging from 4,000 feet (1,200 m) to sea level, and transitioning from 100 inches (2,500 mm) of precipitation to only 10 inches (250 mm) in 80 miles (130 km),

992-585: The Emeishan Traps ( Permian ), which cover more than 250,000 square kilometers in southwestern China ; and Siberian Traps (late Permian ) that cover 2 million km (800,000 sq mi) in Russia . Some time during a 10–15 million-year period, lava flow after lava flow poured out of multiple dikes which trace along an old fault line running from south-eastern Oregon through to western British Columbia. The many layers of lava eventually reached

1054-535: The Folsom and Marmes people, who crossed the Bering land bridge from Asia , were found in archaeological digs . Excavations near Celilo Falls , a few miles east of The Dalles , show humans have occupied this salmon -fishing site for more than 10,000 years. The gorge has provided a transportation corridor for thousands of years. Native Americans would travel through the gorge to trade at Celilo Falls, both along

1116-555: The Pacific Northwest , forming a large igneous province with an estimated volume of 174,300 km (41,800 cu mi). Eruptions were most vigorous 17–14 million years ago, when over 99 percent of the basalt was released. Less extensive eruptions continued 14–6 million years ago. Erosion resulting from the Missoula Floods has extensively exposed these lava flows, laying bare many layers of

1178-493: The Pleistocene (2 million to 700,000 years ago). During this period the Cascade Range was forming, which slowly moved the Columbia River's delta about 100 miles (160 km) north to its current location. Although the river slowly eroded the land over this period of time, the most drastic changes took place at the end of the last ice age when the Missoula Floods cut the steep, dramatic walls that exist today, flooding

1240-567: The Tualatin Mountains on the west side of Portland. Individual flows included large quantities of basalt. The McCoy Canyon flow of the Sentinel Bluffs Member released 4,278 km (1,026 cu mi) of basalt in layers of 10 to 60 m (33 to 197 ft) in thickness. The Umtanum flow has been estimated at 2,750 km (660 cu mi) in layers 50 m (160 ft) deep. The Pruitt Draw flow of

1302-570: The Wanapum Basalt, and the Saddle Mountains Basalt. The various lava flows have been dated by radiometric dating—particularly through measurement of the ratios of isotopes of potassium to argon . The Columbia River flood basalt province comprises more than 300 individual basalt lava flows that have an average volume of 500 to 600 cubic kilometres (120 to 140 cu mi). The transition to flood volcanism in

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1364-646: The Yellowstone hotspot 's initial flood-basalt event occurred near Steens Mountain when the Imnaha and Steens eruptions began. As the North American Plate moved several centimeters per year westward, the eruptions progressed through the Snake River Plain across Idaho and into Wyoming . Consistent with the hot spot hypothesis, the lava flows are progressively younger as one proceeds east along this path. Previous to this eruptive period, it

1426-502: The 500 km (310 mi)-long Ginkgo flow of the Frenchman Springs Member, determining that it had been formed in roughly a week, based on the measured melting temperature along the flow from the origin to the most distant point of the flow, combined with hydraulics considerations. The Ginkgo basalt was examined over its 500 km (310 mi) flow path from a Ginkgo flow feeder dike near Kahlotus, Washington to

1488-403: The CRBG deposits Ar, which is produced by K decay, only accumulates after the melt solidifies. Magnetostratigraphy is also used to determine age. This technique uses the pattern of magnetic polarity zones of CRBG layers by comparison to the magnetic polarity timescale. The samples are analyzed to determine their characteristic remanent magnetization from the Earth's magnetic field at the time

1550-473: The Cascades create a wind tunnel effect in the deep cut of the gorge, generating 35-mile-per-hour (56 km/h) winds that make it a popular windsurfing and kiteboarding location. It also creates the right conditions for snow and ice storms during the winter months which also draw very cold east winds toward the mouth of the gorge on the west end. The gorge is a popular destination for hiking , biking , sightseeing , fishing , and water sports . The area

1612-509: The Columbia River Basalt Group (CRBG), similar to other large igneous provinces , was also marked by atmospheric loading through the mass exsolution and emission of volatiles, via the process of volcanic degassing. Comparative analysis of volatile concentrations in source feeder dikes to associated extruded flow units have been quantitatively measured to determine the magnitude of degassing exhibited in CRBG eruptions. Of

1674-452: The Ginkgo flow occurred in less than a week. The cooling/hydraulics analyses are supported by an independent indicator; if longer periods were required, external water from temporarily dammed rivers would intrude, resulting in both more dramatic cooling rates and increased volumes of pillow lava . Ho's analysis is consistent with the analysis by Reidel, Tolan, & Beeson (1994), who proposed

1736-548: The Grande Ronde Basalt comprises about 85 percent of the total flow volume. It is characterized by a number of dikes called the Chief Joseph Dike Swarm near Joseph , Enterprise , Troy and Walla Walla through which the lava upwelling occurred (estimates range to up to 20,000 such dikes). Many of the dikes were fissures 5 to 10 m (16 to 33 ft) wide and up to 10 miles (16 km) in length, allowing for huge quantities of magma upwelling. Much of

1798-647: The Grande Ronde basalts, but can be identified by different chemical characteristics. It flowed west to the Pacific, and can be found in the Columbia Gorge, along the upper Clackamas River, the hills south of Oregon City . and as far west as Yaquina Head near Newport, Oregon – a distance of 750 km (470 mi). The Saddle Mountains Basalt, seen prominently at the Saddle Mountains ,

1860-677: The Oregon High Lava Plains is a complementary system of propagating rhyolite eruptions, with the same point of origin. The two phenomena occurred concurrently, with the High Lava Plains propagating westward since ~10 Ma, while the Snake River Plains propagated eastward. Columbia River Gorge The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of

1922-495: The Oregon Plateau in sections up to 1 km (3,300 ft) thick. It contains the earliest identified eruption of the CRBG large igneous province. The type locality for the Steens basalt, which covers a large portion of the Oregon Plateau, is an approximately 1,000 m (3,300 ft) face of Steens Mountain showing multiple layers of basalt. The oldest of the flows considered part of the Columbia River Basalt Group,

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1984-577: The Oregon shore. Until 1997, Amtrak's Pioneer also used the Union Pacific tracks. The Portland segment of the Empire Builder uses the BNSF tracks that pass through the gorge. The Columbia River Highway , built in the early 20th century, was the first major paved highway in the Pacific Northwest . Shipping was greatly simplified after Bonneville Dam and The Dalles Dam submerged

2046-650: The Project's total generation for the year. The 10 year average generation for the Project is 383 gigawatt-hours. Under the terms of the Rock Island Settlement Agreement, the District provides spill to improve the survival rate of juvenile salmon passing the Project. During the spring, 1,570,495 acre-feet (1.937177 × 10 m) of water was spilled during a 59-day period between April 20 and June 17. This resulted in 73,427 megawatt-hours of foregone generation valued at $ 13.4 million. In 1927,

2108-592: The Rock Island site came to the attention of the Stone and Webster Engineering Corporation, a Boston-based holding company that managed Puget Sound Power & Light Company. The site was recognized for its potential to provide power for the growing electrical load in the state. On December 13, 1928, an application was filed with the Federal Power Commission for a preliminary permit to investigate

2170-525: The Roza flow. Sulfuric acid , a by-product of emitted sulfur dioxide and atmospheric interactions, has been calculated to be 1.7Gt annually for the Roza flow and 17Gt in total. Analysis of glass inclusions within phenocrysts of the basaltic deposits have yielded emission volumes on the magnitude of 310 Mt of hydrochloric acid , and 1.78 Gt of hydrofluoric acid , additionally. Major hotspots have often been tracked back to flood-basalt events. In this case

2232-617: The Steens Basalt flow are considered to be atypical of other dike swarm trends associated with the CRBG. These swarms, characterized by a maintained trend of N20°E, trace the northward continuation of the Nevada shear zone and have been attributed to magmatic rise through this zone on a regional scale. Virtually coeval with the oldest of the flows, the Imnaha basalt flows welled up across northeastern Oregon. There were 26 major flows over

2294-448: The Steens basalt, includes flows geographically separated but roughly concurrent with the Imnaha flows. Older Imnaha basalt north of Steens Mountain overlies the chemically distinct lowermost flows of Steens basalt; hence some flows of the Imnaha are stratigraphically younger than the lowermost Steens basalt. One geomagnetic field reversal occurred during the Steens Basalt eruptions at approximately 16.7 Ma, as dated using Ar/ Ar ages and

2356-817: The Teepee Butte Member released about 2,350 km (560 cu mi) with layers of basalt up to 100 m (330 ft) thick. The Wanapum Basalt is made up of the Eckler Mountain Member (15.6 million years ago), the Frenchman Springs Member (15.5 million years ago), the Roza Member (14.9 million years ago) and the Priest Rapids Member (14.5 million years ago). They originated from vents between Pendleton, Oregon and Hanford, Washington . The Frenchman Springs Member flowed along similar paths as

2418-601: The United States. Up to 4,000 feet (1,200 m) deep, the canyon stretches for over eighty miles (130 km) as the river winds westward through the Cascade Range , forming the boundary between the state of Washington to the north and Oregon to the south. Extending roughly from the confluence of the Columbia with the Deschutes River (and the towns of Roosevelt, Washington , and Arlington, Oregon ) in

2480-584: The area, first filled the stream valleys, forming dams that in turn caused impoundments or lakes. In these ancient lake beds are found fossil leaf impressions, petrified wood , fossil insects, and bones of vertebrate animals. In the middle Miocene, 17 to 15 Ma, the Columbia Plateau and the Oregon Basin and Range of the Pacific Northwest were flooded with lava flows. Both flows are similar in composition and age, and have been attributed to

2542-623: The basalt flows at Wallula Gap , the lower Palouse River , the Columbia River Gorge and throughout the Channeled Scablands . The Columbia River Basalt Group is thought to be a potential link to the Chilcotin Group in south-central British Columbia , Canada . The Latah Formation sediments of Washington and Idaho are interbedded with a number of the Columbia River Basalt Group flows, and outcrop across

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2604-563: The dam, powerhouse expansion and installation of six additional units by Chelan County PUD began in July 1951 and was completed on April 30, 1953. Construction of the Second Powerhouse, with its eight turbine generators located on the west bank of the river, began on August 4, 1974. The Second Powerhouse was placed in commercial operation on August 31, 1979. Columbia River Basalt Group The Columbia River Basalt Group (CRBG)

2666-540: The east down to the eastern reaches of the Portland metropolitan area , the water gap furnishes the only navigable route through the Cascades and the only water connection between the Columbia Plateau and the Pacific Ocean . It is thus that the routes of Interstate 84 , U.S. Route 30 , Washington State Route 14 , and railroad tracks on both sides run through the gorge. A popular recreational destination,

2728-434: The emission of sulphur for the Roza flow is calculated to be on the order of 12Gt (12,000 million tonnes) at a rate of 1.2Gt (1,200 million tonnes) annually, in the form of sulphur dioxide (SO2). However, other research through petrologic analysis has yielded SO2 mass degassing values at 0.12% - 0.28% of the total erupted mass of the magma, translating to lower emission estimates in the range of 9.2Gt of sulfur dioxide for

2790-499: The existing industries in towns along the river to relocate. The designation was initially opposed by residents fearing government encroachment, due to restrictions in the plan for items such as building paint colors, and was also opposed by conservationists who feared additional development in the region. In 2004, the gorge became the namesake of the Columbia Gorge American Viticultural Area ,

2852-535: The exposed 2,000-foot (610 m) walls of Joseph Canyon along Oregon Route 3 . The Grande Ronde basalt flows flooded down the ancestral Columbia River channel to the west of the Cascade Mountains . It can be found exposed along the Clackamas River and at Silver Falls State Park where the falls plunge over multiple layers of the Grande Ronde basalt. Evidence of eight flows can be found in

2914-674: The flow terminus in the Pacific Ocean at Yaquina Head , Oregon . The basalt had an upper melting temperature of 1 095 ± 5 °C and a lower temperature to 1 085 ± 5 °C; this indicates that the maximum temperature drop along the Ginkgo flow was 20 °C. The lava must have spread quickly to achieve this uniformity. Analyses indicate that the flow must remain laminar , as turbulent flow would cool more quickly. This could be accomplished by sheet flow, which can travel at velocities of 1 to 8 metres per second (2.2 to 17.9 mph) without turbulence and minimal cooling, suggesting that

2976-410: The geomagnetic polarity timescale. Steens Mountain and related sections of Oregon Plateau flood basalts at Catlow Peak and Poker Jim Ridge 70 to 90 km (43 to 56 mi) to the southeast and west of Steens Mountain, provide the most detailed magnetic field reversal data (reversed-to-normal polarity transition) yet reported in volcanic rocks. The observed trend in feeder dike swarms associated with

3038-585: The gorge holds federally protected status as the Columbia River Gorge National Scenic Area and is managed by the Columbia River Gorge Commission and the U.S. Forest Service . The Columbia River, Klamath River in northern California , Pit River in northern California, and Fraser River in southern British Columbia are the only four rivers connecting the watersheds on the east side of

3100-651: The gorge provides the setting for a diverse collection of ecosystems , from the temperate rain forest on the western end—with an average annual precipitation of 75 to 100 inches (1,900 to 2,500 mm)—to the eastern grasslands with average annual precipitation between 10 and 15 inches (250 and 380 mm), to a transitional dry woodland between Hood River and The Dalles . Isolated micro-habitats have allowed for many species of endemic plants and animals to prosper, including at least 13 endemic wildflowers. The gorge transitions between temperate rainforest to dry grasslands in only 80 miles (130 km), hosting

3162-505: The gorge's major rapids such as Celilo Falls, a major salmon fishing site for local Native Americans until the site's submergence in 1957. In November 1986, Congress made the gorge the second U.S. National Scenic Area and established the Columbia River Gorge Commission as part of an interstate compact . The experimental designation came in lieu of being recognized as a national park , which would require

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3224-662: The lava flowed north into Washington as well as down the Columbia River channel to the Pacific Ocean ; the tremendous flows created the Columbia River Plateau . The weight of this flow (and the emptying of the underlying magma chamber) caused central Washington to sink, creating the broad Columbia Basin in Washington. The type locality for the formation is the canyon of the Grande Ronde River . Grande Ronde basalt flows and dikes can also be seen in

3286-499: The magnetic field's orientation-normal, reversed, or in one of several intermediate positions. Most of the flows froze with a single magnetic orientation. However, several of the flows, which freeze from both the upper and lower surfaces, progressively toward the center, captured substantial variations in magnetic field direction as they froze. The observed change in direction was reported as 50⁰ over 15 days. The Steens Basalt flows covered about 50,000 km (19,000 sq mi) of

3348-555: The materials in the upper mantle , creating magma . Once that magma breaches the surface, it flows as lava and then solidifies into basalt. Prior to 17.5 million years ago, the Western Cascade stratovolcanoes erupted with periodic regularity for over 20 million years, even as they do today. An abrupt transition to shield volcanic flooding took place in the mid-Miocene. The flows can be divided into four major categories: The Steens Basalt, Grande Ronde Basalt,

3410-494: The more than 300 individual flows associated with the CRBG, the Roza flow contains some of the most chemically well preserved basalts for volatile analysis. Contained within the Wanapum formation, Roza is one of the most extensive members of the CRBG with an area of 40,300 square kilometres and a volume of 1,300 cubic kilometres. With magmatic volatile values assumed at 1 - 1.5 percent by weight concentration for source feeder dikes,

3472-567: The period, one roughly every 15,000 years. Although estimates are that this amounts to about 10% of the total flows, they have been buried under more recent flows, and are visible in few locations. They can be seen along the lower benches of the Imnaha River and Snake River in Wallowa county. The Imnaha lavas have been dated using the K–Ar technique, and show a broad range of dates. The oldest

3534-455: The plume at 650 and 400 km (400 and 250 mi), which may correspond to phase changes or may reflect still-to-be-understood viscosity effects. Additional data collection and further modeling will be required to achieve a consensus on the actual mechanism. The Columbia River Basalt Group flows exhibit essentially uniform chemical properties through the bulk of individual flows, suggesting rapid placement. Ho and Cashman (1997) characterized

3596-489: The region. Absolute dates, subject to a statistical uncertainty, are determined through radiometric dating using isotope ratios such as Ar/ Ar dating, which can be used to identify the date of solidifying basalt. In the CRBG deposits Ar, which is produced by K decay, only accumulates after the melt solidifies. Other flood basalts include the Deccan Traps (late Cretaceous period ), that cover an area of 500,000 km (190,000 sq mi) in west-central India ;

3658-412: The river and over Lolo Pass on the north side of Mount Hood . In 1805, the route was used by the Lewis and Clark Expedition to reach the Pacific. Early European and American settlers subsequently established steamboat lines and railroads through the gorge. Today, the BNSF Railway runs freights along the Washington side of the river, while its rival, the Union Pacific Railroad , runs freights along

3720-479: The river as high up as Crown Point . This quick erosion left many layers of volcanic rock exposed. The Columbia River Gorge is home to a number of plant species that are endemic or found mostly in the gorge and surrounding areas, including Heterotheca villosa , Lomatium columbianum , Lomatium klickitatense , Lomatium suksdorfii , Penstemon barrettiae , and Primula poetica . The gorge has supported human habitation for over 13,000 years. Evidence of

3782-457: The site. This was followed by an application for license submitted in June 1929 by the Washington Electric Company, a subsidiary construction corporation of Puget Sound Power & Light (now part of Puget Sound Energy ). The license was authorized on October 16, 1929, and on January 14, 1930, at the beginning of the Great Depression , construction started on the first dam to span the Columbia River. The development of Rock Island Dam occurred over

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3844-399: The upwelling observed with large-scale plate-tectonics circulation. The hot spot hypothesis is not universally accepted as it has not resolved several questions. The Yellowstone hot spot volcanism track shows a large apparent bow in the hot-spot track that does not correspond to changes in plate motion if the northern CRBG floods are considered. Further, the Yellowstone images show necking of

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