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112-464: The Columbia River Basalt Group (CRBG) 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 ,

224-489: A chain of volcanoes (the Cascade Volcanic Arc) above the subduction zone. Soil conditions for farming are generally good, especially downwind of volcanoes . This is largely because volcanic rocks are often rich in potassium -bearing minerals such as orthoclase , and erode relatively easily. Volcanic debris, especially lahars , also helps to spread mineral-rich volcanic material, and the storage of water in

336-484: 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

448-486: 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 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

560-449: A consequence of the initial hot-spot activity in ocean basins as well as on continents. It is possible to track the hot spot back to the flood basalts of a large igneous province; the table below correlates large igneous provinces with the track of a specific hot spot. Eruptions or emplacements of LIPs appear to have, in some cases, occurred simultaneously with oceanic anoxic events and extinction events . The most important examples are

672-602: A few strikingly large volcanoes, like Mount Hood and Mount St. Helens, that dominate the landscape. The Cascade volcanoes define the Pacific Northwest section of the Ring of Fire , an array of volcanoes that rim the Pacific Ocean. The Ring of Fire is also known for its frequent earthquakes. The volcanoes and earthquakes arise from a common source: subduction , where the dense Juan de Fuca Plate plunges beneath

784-620: A fur trader with the North West Company , seeking a viable route across the mountains, explored and crossed the northern Cascades between Fort Okanogan and Puget Sound. His report of the journey is vague about the route taken. He followed the lower Methow River into the mountains. He might have used Cascade Pass to reach the Skagit River . Ross was the first European-American to explore the Methow River area and likely

896-423: A high proportion of dykes relative to country rocks, particularly when the width of the linear field is less than 100 km. The dykes have a typical width of 20–100 m, although ultramafic dykes with widths greater than 1 km have been reported. Dykes are typically sub-vertical to vertical. When upward flowing (dyke-forming) magma encounters horizontal boundaries or weaknesses, such as between layers in

1008-517: A large proportion (>75%) of the total igneous volume has been emplaced. They are dominantly mafic, but also can have significant ultramafic and silicic components, and some are dominated by silicic magmatism." This definition places emphasis on the high magma emplacement rate characteristics of the LIP event and excludes seamounts, seamount groups, submarine ridges and anomalous seafloor crust. The definition has since been expanded and refined, and remains

1120-549: A number of the Columbia River Basalt Group flows, and outcrop across 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

1232-441: A sedimentary deposit, the magma can flow horizontally creating a sill. Some sill provinces have areal extents >1000 km. A series of related sills that were formed essentially contemporaneously (within several million years) from related dikes comprise a LIP if their area is sufficiently large. Examples include: Volcanic rifted margins are found on the boundary of large igneous provinces. Volcanic margins form when rifting

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1344-500: A solid convective mantle above a liquid core . The mantle's flow is driven by the descent of cold tectonic plates during subduction and the complementary ascent of mantle plumes of hot material from lower levels. The surface of the Earth reflects stretching, thickening and bending of the tectonic plates as they interact. Ocean-plate creation at upwellings, spreading and subduction are well accepted fundamentals of plate tectonics, with

1456-464: 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

1568-490: 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

1680-768: A traveler passes through the Cascade Range, the climate first gets colder, then warmer and drier east of the crest. Most of the Cascades' lower and middle elevations are covered in coniferous forest ; the higher altitudes have extensive meadows as well as alpine tundra and glaciers . The southern part of the Cascades are within the California Floristic Province , an area of high biodiversity . Silver fir predominates above 2500 ft, while there are moors , meadows , and mountain hemlock / subalpine fir groves from 4500 to 6000 ft on

1792-627: A volcanic province), and volcanic rifted margins . Mafic basalt sea floors and other geological products of 'normal' plate tectonics were not included in the definition. Most of these LIPs consist of basalt, but some contain large volumes of associated rhyolite (e.g. the Columbia River Basalt Group in the western United States); the rhyolite is typically very dry compared to island arc rhyolites, with much higher eruption temperatures (850 °C to 1000 °C) than normal rhyolites. Some LIPs are geographically intact, such as

1904-554: A work in progress. Some new definitions of LIP include large granitic provinces such as those found in the Andes Mountains of South America and in western North America. Comprehensive taxonomies have been developed to focus technical discussions. Sub-categorization of LIPs into large volcanic provinces (LVP) and large plutonic provinces (LPP), and including rocks produced by normal plate tectonic processes, have been proposed, but these modifications are not generally accepted. LIP

2016-703: 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

2128-400: Is a common geochemical proxy used to detect massive volcanism in the geologic record, although its foolproofness has been called into question. Jameson Land Thulean Plateau Brazilian Highlands These LIPs are composed dominantly of felsic materials. Examples include: These LIPs are comprised dominantly of andesitic materials. Examples include: This subcategory includes most of

2240-462: Is accompanied by significant mantle melting, with volcanism occurring before and/or during continental breakup. Volcanic rifted margins are characterized by: a transitional crust composed of basaltic igneous rocks, including lava flows, sills, dikes, and gabbros , high volume basalt flows, seaward-dipping reflector sequences of basalt flows that were rotated during the early stages of breakup, limited passive-margin subsidence during and after breakup, and

2352-466: Is an arid plateau that was largely formed 17 to 14 million years ago by the many flows of the Columbia River Basalt Group . Together, these sequences of fluid volcanic rock form the 200,000-square-mile (520,000 km ) Columbia Plateau in eastern Washington, Oregon, and parts of western Idaho. The Columbia River Gorge is the only major break of the range in the United States. When

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2464-762: Is an interpretive site there now at "The End of The Oregon Trail". The road was constructed as a toll road – $ 5 per wagon – and was very successful. In addition, the Applegate Trail was created to allow settlers to avoid rafting down the Columbia River. The Trail used the path of the California Trail to north-central Nevada . From there, the Trail headed northwest into northern California, and continued northwest towards today's Ashland, Oregon . From there, settlers would head north along

2576-561: Is associated with subduction zones or mid-oceanic ridges, there are significant regions of long-lived, extensive volcanism, known as hotspots , which are only indirectly related to plate tectonics. The Hawaiian–Emperor seamount chain , located on the Pacific Plate , is one example, tracing millions of years of relative motion as the plate moves over the Hawaii hotspot . Numerous hotspots of varying size and age have been identified across

2688-754: 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

2800-710: Is great local relief . The southern part of the Canadian Cascades, particularly the Skagit Range , is geologically and topographically similar to the North Cascades, while the northern and northeastern parts are less glaciated and more plateau-like, resembling nearby areas of the Thompson Plateau . The range is near the Pacific Ocean and in the region's prevailing westerly winds , so it receives significant rain and snowfall, especially on

2912-592: Is known as the North Cascades in the United States but is formally named the Cascade Mountains north of the Canada–United States border , reaching to the northern extremity of the Cascades at Lytton Mountain . Overall, the North Cascades and Canadian Cascades are extremely rugged; even the lesser peaks are steep and glaciated, and valleys are quite low relative to peaks and ridges, so there

3024-1072: 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

3136-618: Is not now observable. The upper basalt layers of older LIPs may have been removed by erosion or deformed by tectonic plate collisions occurring after the layer is formed. This is especially likely for earlier periods such as the Paleozoic and Proterozoic . Giant dyke swarms having lengths over 300 km are a common record of severely eroded LIPs. Both radial and linear dyke swarm configurations exist. Radial swarms with an areal extent over 2,000 km and linear swarms extending over 1,000 km are known. The linear dyke swarms often have

3248-465: Is not uncommon for some places in the Cascades to have over 500 inches (1,300 cm) of annual snow accumulation, such as at Lake Helen , near Lassen Peak. Most of the High Cascades are therefore white with snow and ice year-round. The western slopes are densely covered with Douglas-fir ( Pseudotsuga menziesii ), western hemlock ( Tsuga heterophylla ) and red alder ( Alnus rubra ), while

3360-652: Is now frequently used to also describe voluminous areas of, not just mafic, but all types of igneous rocks. Further, the minimum threshold to be included as a LIP has been lowered to 50,000 km . The working taxonomy, focused heavily on geochemistry, is: Because large igneous provinces are created during short-lived igneous events resulting in relatively rapid and high-volume accumulations of volcanic and intrusive igneous rock, they warrant study. LIPs present possible links to mass extinctions and global environmental and climatic changes. Michael Rampino and Richard Stothers cite 11 distinct flood basalt episodes—occurring in

3472-427: 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

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3584-756: The Baffin Island flood basalt about 60 million years ago. Basalts from the Ontong Java Plateau show similar isotopic and trace element signatures proposed for the early-Earth reservoir. Seven pairs of hotspots and LIPs located on opposite sides of the earth have been noted; analyses indicate this coincident antipodal location is highly unlikely to be random. The hotspot pairs include a large igneous province with continental volcanism opposite an oceanic hotspot. Oceanic impacts of large meteorites are expected to have high efficiency in converting energy into seismic waves. These waves would propagate around

3696-490: The Baker River is dammed to form Lake Shannon and Baker Lake . The Cascades harbor a largely-untapped potential for geothermal power . The U.S. Geological Survey Geothermal Research Program has been investigating this potential. Some of this energy is already being used in places like Klamath Falls, Oregon , where volcanic steam is used to heat public buildings. The highest recorded underground temperature found in

3808-785: The Cascade Volcanoes . The two most recent were Lassen Peak from 1914 to 1921 and a major eruption of Mount St. Helens in 1980 . Minor eruptions of Mount St. Helens have also occurred since, most recently from 2004 to 2008. The Cascade Range is a part of the American Cordillera , a nearly continuous chain of mountain ranges (cordillera) that form the western "backbone" of North, Central , and South America . The Cascades are home to many national parks and protected areas, including North Cascades National Park , Mount Rainier National Park , Crater Lake National Park , and Lassen Volcanic National Park . The northern half of

3920-626: The Cascades Rapids in the Columbia River Gorge, a feature on the river now submerged beneath the Bonneville Reservoir . Before long, the great white-capped mountains that loomed above the rapids were called the "mountains by the cascades" and later simply as the "Cascades". The earliest attested use of the name "Cascade Range" is in the writings of botanist David Douglas in 1825. In 1814, Alexander Ross ,

4032-779: The Deccan Traps (late Cretaceous period ), that cover an area of 500,000 km (190,000 sq mi) in west-central India ; 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

4144-514: The Deccan Traps of India were not antipodal to (and began erupting several Myr before) the Chicxulub impact in Mexico. In addition, no clear example of impact-induced volcanism, unrelated to melt sheets, has been confirmed at any known terrestrial crater. Aerally extensive dike swarms , sill provinces, and large layered ultramafic intrusions are indicators of LIPs, even when other evidence

4256-665: The Hudson's Bay Company (HBC) at Fort Vancouver near today's Portland, Oregon . From this base HBC trapping parties traveled throughout the Cascades in search of beaver and other fur-bearing animals. For example, using what became known as the Siskiyou Trail , Hudson's Bay Company trappers were the first non-natives to explore the southern Cascades in the 1820s and 1830s, establishing trails which passed near Crater Lake , Mount McLoughlin , Medicine Lake Volcano , Mount Shasta , and Lassen Peak. The course of political history in

4368-527: The Lushootseed name for Mount Rainier, and "Louwala-Clough", meaning "smoking mountain" for Mount St. Helens. In early 1792, British navigator George Vancouver explored Puget Sound and gave English names to the high mountains he saw. Mount Baker was named for Vancouver's third lieutenant, Joseph Baker , although the first European to see it was Manuel Quimper , who named it la gran montaña del Carmelo ("Great Mount Carmel ") in 1790. Mount Rainier

4480-707: The Missoula Floods has extensively exposed these lava flows, laying bare many layers of 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

4592-476: The North American Plate . As the oceanic slab sinks deep into the Earth's interior beneath the continental plate, high temperatures and pressures allow water molecules locked in the minerals of solid rock to escape. The water vapor rises into the pliable mantle above the subducting plate, causing some of the mantle to melt. This newly formed magma rises toward the Earth's surface to erupt, forming

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4704-790: The Pacific Crest Trail follows the range. The Cascades extend northward from Lassen Peak (also known as Mount Lassen) in northern California to the confluence of the Nicola and Thompson rivers in British Columbia . The Fraser River separates the Cascades from the Coast Mountains in Canada, as does the Willamette Valley from the upper portion of the Oregon Coast Range . The highest volcanoes of

4816-688: The Pacific Northwest saw the spine of the Cascade Range being proposed as a boundary settlement during the Oregon Dispute of 1846. The United States rejected the proposal and insisted on the 49th parallel north , which cuts across the range just north of Mount Baker. Throughout the period of dispute and up to the creation of the Crown Colony of British Columbia in 1858, the Hudson's Bay Company's York Factory Express route, as well

4928-564: 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

5040-568: 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

5152-574: 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

5264-556: The crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics . The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes , which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems. In 1992, Coffin and Eldholm initially defined

5376-832: The railway roadbed and the Othello Tunnels , now decommissioned, are popular tourist recreation destinations for hiking and bicycling. The pass is used by the Coquihalla Highway , a government megaproject built as part of the Expo 86 spending boom of the 1980s, which is now the main route from the Coast to the British Columbia interior. Traffic formerly went via the Fraser Canyon , to the west, or via Allison Pass and Manning Park along Highway 3 to

5488-400: 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

5600-552: The Cascades began to rise 7 million years ago in the late Miocene , the Columbia River drained the relatively low Columbia Plateau. As the range grew, erosion from the Columbia River was able to keep pace, carving out the gorge and major pass seen today. The gorge also exposes uplifted and warped layers of basalt from the plateau. Before European exploration, First Nations tribes named many peaks, including "Wy'east" for Mount Hood , "Seekseekqua" for Mount Jefferson (Oregon) , "M'laiksini Yaina" for Mount McLoughlin , "Tahoma",

5712-414: The Cascades, known as the High Cascades, dominate their surroundings, often standing twice the height of the nearby mountains. They often have a visual height (height above nearby crestlines) of one mile or more. The highest peaks, such as the 14,411-foot (4,392 m) Mount Rainier, dominate their surroundings for 50 to 100 miles (80 to 161 km). The northern part of the range, north of Mount Rainier,

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5824-425: The Columbia River flood basalts engulfed about 163,700 km (63,200 sq mi) of 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

5936-427: 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

6048-726: The Deccan Traps ( Cretaceous–Paleogene extinction event ), the Karoo-Ferrar ( Pliensbachian-Toarcian extinction ), the Central Atlantic magmatic province ( Triassic-Jurassic extinction event ), and the Siberian Traps ( Permian-Triassic extinction event ). Several mechanisms are proposed to explain the association of LIPs with extinction events. The eruption of basaltic LIPs onto the earth's surface releases large volumes of sulfate gas, which forms sulfuric acid in

6160-468: 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 a maximum Pomona flow emplacement duration of several months based on

6272-472: 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

6384-399: 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 ,

6496-459: The LIP-triggered changes may be used as cases to understand current and future environmental changes. Plate tectonic theory explains topography using interactions between the tectonic plates, as influenced by viscous stresses created by flow within the underlying mantle . Since the mantle is extremely viscous, the mantle flow rate varies in pulses which are reflected in the lithosphere by small amplitude, long wavelength undulations. Understanding how

6608-525: 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. Large igneous province A large igneous province ( LIP ) is an extremely large accumulation of igneous rocks , including intrusive ( sills , dikes ) and extrusive ( lava flows, tephra deposits), arising when magma travels through

6720-431: 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,

6832-471: 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

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6944-448: 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

7056-445: 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

7168-536: 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

7280-454: 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

7392-447: The atmosphere; this absorbs heat and causes substantial cooling (e.g., the Laki eruption in Iceland, 1783). Oceanic LIPs can reduce oxygen in seawater by either direct oxidation reactions with metals in hydrothermal fluids or by causing algal blooms that consume large amounts of oxygen. Large igneous provinces are associated with a handful of ore deposit types including: Enrichment in mercury relative to total organic carbon (Hg/TOC)

7504-623: The basaltic Deccan Traps in India, while others have been fragmented and separated by plate movements, like the Central Atlantic magmatic province —parts of which are found in Brazil, eastern North America, and northwestern Africa. In 2008, Bryan and Ernst refined the definition to narrow it somewhat: "Large Igneous Provinces are magmatic provinces with areal extents > 1 × 10  km , igneous volumes > 1 × 10  km and maximum lifespans of ~50 Myr that have intraplate tectonic settings or geochemical affinities, and are characterised by igneous pulse(s) of short duration (~1–5 Myr), during which

7616-416: The core; roughly 15–20% have characteristics such as presence of a linear chain of sea mounts with increasing ages, LIPs at the point of origin of the track, low shear wave velocity indicating high temperatures below the current location of the track, and ratios of He to He which are judged consistent with a deep origin. Others such as the Pitcairn , Samoan and Tahitian hotspots appear to originate at

7728-414: The drier eastern slopes feature mostly ponderosa pine ( Pinus ponderosa ), with some western larch ( Larix occidentalis ), mountain hemlock ( Tsuga mertensiana ) and subalpine fir ( Abies lasiocarpa ) and subalpine larch ( Larix lyallii ) at higher elevations. Annual rainfall is as low as 9 inches (230 mm) on the eastern foothills due to a rain shadow effect. Beyond the eastern foothills

7840-439: The early 1840s, at first only marginally. Following the Oregon Treaty the inward flux of migration from the Oregon Trail intensified and the passes and back-valleys of what is now the state of Washington were explored and populated, and it was not long after that railways followed. Despite its being traversed by several major freeways and rail lines, and its lower flanks subjected to major logging in recent decades, large parts of

7952-433: 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

8064-596: The established Siskiyou Trail into the Willamette Valley . With the exception of the 1915 eruption of remote Lassen Peak in Northern California, the range was quiet for more than a century. Then, on May 18, 1980, the dramatic eruption of Mount St. Helens shattered the quiet and brought the world's attention to the range. Geologists were also concerned that the St. Helens eruption was a sign that long-dormant Cascade volcanoes might become active once more, as in

8176-595: 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

8288-466: The first to explore the Stehekin River and Bridge Creek region. Due to the difficulty of crossing the northern Cascades and the paucity of beaver, fur-trading companies made only a few explorations into the mountains north of the Columbia River after Ross. Exploration and settlement of the Cascades region by Europeans and Americans was accelerated by the establishment of a major trading post of

8400-445: 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 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

8512-421: The form of snow and ice is also important for agriculture. The snow-capped mountains, such as Mt. Hood and Mt. Bachelor , are used as ski resorts in the late winter, while in the summer they become popular hiking and mountaineering locations. Much of their meltwater eventually flows into reservoirs, where it is used for recreation, while its potential energy is captured to generate hydroelectric power before

8624-408: 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

8736-401: The interaction between mantle flow and lithosphere elevation influences formation of LIPs is important to gaining insights into past mantle dynamics. LIPs have played a major role in the cycles of continental breakup, continental formation, new crustal additions from the upper mantle , and supercontinent cycles . Earth has an outer shell made of discrete, moving tectonic plates floating on

8848-411: The large-scale plate tectonic circulation in which they are imbedded. Images reveal continuous but convoluted vertical paths with varying quantities of hotter material, even at depths where crystallographic transformations are predicted to occur. A major alternative to the plume model is a model in which ruptures are caused by plate-related stresses that fractured the lithosphere, allowing melt to reach

8960-722: 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

9072-457: The lower efficiency of kinetic energy conversion into seismic energy is not expected to create an antipodal hotspot. A second impact-related model of hotspot and LIP formation has been suggested in which minor hotspot volcanism was generated at large-body impact sites and flood basalt volcanism was triggered antipodally by focused seismic energy. This model has been challenged because impacts are generally considered seismically too inefficient, and

9184-497: 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

9296-554: 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,

9408-461: 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

9520-544: 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,

9632-493: The mountain range which contained these peaks. He referred to it simply as the "eastern snowy range". Earlier Spanish explorers called it Sierra Nevada , meaning "snowy mountains". In 1805, the Lewis and Clark Expedition passed through the Cascades on the Columbia River, which for many years was the only practical way to pass that part of the range. They were the first non-indigenous people to see Mount Adams , but they thought it

9744-774: The older Hudson's Bay Company Brigade Trail from the Canyon to the Interior, the Dewdney Trail, and older routes which connected east to the Similkameen and Okanagan valleys. The southern mainline of the Canadian Pacific Railway penetrated the range via the passes of the Coquihalla River , along one of the steepest and snowiest routes in the entire Pacific Cordillera . Near Hope, B.C. ,

9856-564: The order of 1 million cubic kilometers. In most cases, the majority of a basaltic LIP's volume is emplaced in less than 1 million years. One of the conundra of such LIPs' origins is to understand how enormous volumes of basaltic magma are formed and erupted over such short time scales, with effusion rates up to an order of magnitude greater than mid-ocean ridge basalts. The source of many or all LIPs are variously attributed to mantle plumes, to processes associated with plate tectonics or to meteorite impacts. Although most volcanic activity on Earth

9968-603: The past 250 million years—which created volcanic provinces and oceanic plateaus and coincided with mass extinctions. This theme has developed into a broad field of research, bridging geoscience disciplines such as biostratigraphy , volcanology , metamorphic petrology , and Earth System Modelling . The study of LIPs has economic implications. Some workers associate them with trapped hydrocarbons. They are associated with economic concentrations of copper–nickel and iron. They are also associated with formation of major mineral provinces including platinum group element deposits and, in

10080-597: The period from 1800 to 1857 when a total of eight erupted. None have erupted since St. Helens, but precautions are being taken nevertheless, such as the Cascades Volcano Observatory and Mount Rainier Volcano Lahar Warning System in Pierce County, Washington . The Cascade Range is made up of a band of thousands of very small, short-lived volcanoes that have built a platform of lava and volcanic debris. Rising above this volcanic platform are

10192-565: 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

10304-558: The presence of a lower crust with anomalously high seismic P-wave velocities in lower crustal bodies, indicative of lower temperature, dense media. The early volcanic activity of major hotspots, postulated to result from deep mantle plumes, is frequently accompanied by flood basalts. These flood basalt eruptions have resulted in large accumulations of basaltic lavas emplaced at a rate greatly exceeding that seen in contemporary volcanic processes. Continental rifting commonly follows flood basalt volcanism. Flood basalt provinces may also occur as

10416-411: The provinces included in the original LIP classifications. It is composed of continental flood basalts, oceanic flood basalts, and diffuse provinces. Cascade Mountains The Cascades are part of the Pacific Ocean 's Ring of Fire , the ring of volcanoes and associated mountains around the Pacific Ocean. All of the eruptions in the contiguous United States over the last 200 years have been from

10528-466: The range is 510 °F (266 °C) at 3,075 feet (937 m) below Newberry Volcano 's caldera floor. Forests of large, coniferous trees ( western red cedars , Douglas-firs, western hemlocks, firs , pines , spruces , and others) dominate most of the Cascade Range. Cool, wet winters and warm, dry summers (largely a result of oceanic influence) favor evergreen species, whereas mild temperatures and rich soils promote fast and prolonged growth. As

10640-495: The range remain intense and forbidding alpine wilderness. Much of the northern half of the Cascades, from Rainier north, have been preserved by U.S. national or British Columbia provincial parks (such as E.C. Manning Provincial Park ), or other forms of protected area. The Canadian side of the range has a history that includes the Fraser Canyon Gold Rush of 1858–60 and its famous Cariboo Road , as well as

10752-524: The route of fur brigades, followed the Okanogan River along the east edge of the Cascades and the Columbia River through the range. Passes across the range were not well known and little used. Naches Pass was used for driving cattle and horses to Fort Nisqually . Yakima Pass was also used by the Hudson's Bay Company. American settlement of the flanks of the Coast Range did not occur until

10864-407: The silicic LIPs, silver and gold deposits. Titanium and vanadium deposits are also found in association with LIPs. LIPs in the geological record have marked major changes in the hydrosphere and atmosphere , leading to major climate shifts and maybe mass extinctions of species. Some of these changes were related to rapid release of greenhouse gases from the lithosphere to the atmosphere. Thus

10976-691: The south, near the border. The Barlow Road was the first established land path for U.S. settlers through the Cascade Range in 1845, and formed the final overland link for the Oregon Trail (previously, settlers had to raft down the treacherous rapids of the Columbia River). The Road left the Columbia at what is now Hood River and passed along the south side of Mount Hood at what is now Government Camp , terminating in Oregon City. There

11088-465: The surface from shallow heterogeneous sources. The high volumes of molten material that form the LIPs is postulated to be caused by convection in the upper mantle, which is secondary to the convection driving tectonic plate motion. It has been proposed that geochemical evidence supports an early-formed reservoir that survived in the Earth's mantle for about 4.5 billion years. Molten material is postulated to have originated from this reservoir, contributing

11200-432: The surface topography. The convective circulation drives up-wellings and down-wellings in Earth's mantle that are reflected in local surface levels. Hot mantle materials rising up in a plume can spread out radially beneath the tectonic plate causing regions of uplift. These ascending plumes play an important role in LIP formation. When created, LIPs often have an areal extent of a few million square kilometers and volumes on

11312-458: The term "large igneous province" as representing a variety of mafic igneous provinces with areal extent greater than 100,000 km that represented "massive crustal emplacements of predominantly mafic (magnesium- and iron-rich) extrusive and intrusive rock, and originated via processes other than 'normal' seafloor spreading." That original definition included continental flood basalts , oceanic plateaus , large dike swarms (the eroded roots of

11424-522: 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

11536-472: The top of large, transient, hot lava domes (termed superswells) in the mantle. The remainder appear to originate in the upper mantle and have been suggested to result from the breakup of subducting lithosphere. Recent imaging of the region below known hotspots (for example, Yellowstone and Hawaii) using seismic-wave tomography has produced mounting evidence that supports relatively narrow, deep-origin, convective plumes that are limited in region compared to

11648-685: 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 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

11760-399: The upwelling of hot mantle materials and the sinking of the cooler ocean plates driving the mantle convection. In this model, tectonic plates diverge at mid-ocean ridges , where hot mantle rock flows upward to fill the space. Plate-tectonic processes account for the vast majority of Earth's volcanism . Beyond the effects of convectively driven motion, deep processes have other influences on

11872-450: The water is used to irrigate crops. Because of the abundance of powerful streams, many of the major westward-draining rivers of the Cascades have been dammed to provide hydroelectric power . One of these, Ross Dam on the Skagit River , retains a reservoir which spans the border southeast of Hope, British Columbia , extending 2 miles (3.2 km) into Canada. At the foot of the southeast flank of Mount Baker, at Concrete, Washington ,

11984-471: The west side. The treeline is at ~6000 feet. On the east side, subalpine forests of larch trees grade to pine and interior fir forests below 4200 ft, which grade to ponderosa below 2500 ft, which in turn grades to semidesert scrub near sea level. Above 7500 ft, the landscape is barren with either no plants or only moss and lichen . Black bears , coyotes , bobcats , cougars , beavers , deer , elk , moose , mountain goats and

12096-476: The western slopes due to orographic lift , with annual snow accumulations of up to 1,000 inches (2,500 cm) (= 83 feet (25 m)) in some areas. Mount Baker in Washington recorded a national record single-season snowfall in the winter of 1998–99 with 1,140 inches (2,900 cm) (= 95 feet (29 m)). Before that year, Mount Rainier held the American record for snow accumulation at Paradise in 1978. It

12208-399: The world and reconverge close to the antipodal position; small variations are expected as the seismic velocity varies depending upon the route characteristics along which the waves propagate. As the waves focus on the antipodal position, they put the crust at the focal point under significant stress and are proposed to rupture it, creating antipodal pairs. When the meteorite impacts a continent,

12320-415: The world. These hotspots move slowly with respect to one another but move an order of magnitude more quickly with respect to tectonic plates, providing evidence that they are not directly linked to tectonic plates. The origin of hotspots remains controversial. Hotspots that reach the Earth's surface may have three distinct origins. The deepest probably originate from the boundary between the lower mantle and

12432-457: Was Mount St. Helens. When they later saw Mount St. Helens they thought it was Mount Rainier. On their return trip, Lewis and Clark spotted a high but distant snowy pinnacle that they named for the sponsor of the expedition, U.S. President Thomas Jefferson . Lewis and Clark called the Cascade Range the "Western Mountains". The Lewis and Clark expedition, and the many settlers and traders that followed, met their last obstacle to their journey at

12544-564: Was named after Admiral Peter Rainier . Later in 1792, Vancouver had his lieutenant William Robert Broughton explore the lower Columbia River . He named Mount Hood after Lord Samuel Hood , an admiral of the Royal Navy . Mount St. Helens was sighted by Vancouver in May 1792, from near the mouth of the Columbia River. It was named for Alleyne FitzHerbert, 1st Baron St Helens , a British diplomat. Vancouver's expedition did not, however, name

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