Columbia River Basalt Group
The Columbia River Basalt Group is a large igneous province that lies across parts of the Western United States. It is found in the U. S. states of Washington, Idaho and California. The Basalt group includes the Picture Gorge basalt formations. During the middle to late Miocene epoch, the Columbia River flood basalts engulfed about 163,700 km2 of the Pacific Northwest, forming a large igneous province with an estimated volume of 174,300 km3. 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 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, outcrop across the region.
Absolute dates, subject to a statistical uncertainty, are determined through radiometric dating using isotope ratios such as 40Ar/39Ar dating, which can be used to identify the date of solidifying basalt. In the CRBG deposits 40Ar, produced by 40K decay, only accumulates after the melt solidifies. Other flood basalts include Deccan Traps that cover an area of 500,000 km2 in west-central India and Siberian Traps that cover 2 million km2 in Russia; some time during a 10–15 million-year period, lava flow after lava flow poured out reaching a thickness of more than 1.8 km. As the molten rock came to the surface, the Earth's crust sank into the space left by the rising lava; this subsidence of the crust produced a large 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 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, 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 both composition and age, have been attributed to a common source, the Yellowstone hotspot; the ultimate cause of the volcanism is still up for debate, but the most accepted idea is that the mantle plume or upwelling 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 the materials in the upper mantle, creating magma. Once that magma breaches the surface, it flows as lava and solidifies into basalt. Prior to 17.5 million years ago, the Western Cascade Stratovolcanoes erupted with periodic regularity for over 20 million years 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, the Wanapum Basalt, 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. Major hot-spots have been tracked back to flood-basalt events. In this case 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. There is additional confirmation. Using tomographic images based on seismic waves narrow seated, active convective plumes have been detected under Yellowstone and several other hot spots.
These plumes are much more focused than the upwelling observed with large-scale plate-tectonics circulation. The hot spot hypothesis is not universally accepted; 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 km and 400 km, 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 uniform chemical properties through the bulk of individual flows, suggesting rapid placement. Ho and Cashman characterized the 500 km -long Ginkgo flow of the Columbia River Basalt Group, determining that it had been formed in 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 flow path from a Ginkgo flow feeder dike near Kahlotus, Washington to the flow terminus in the P
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of Canada, it flows northwest and south into the US state of Washington turns west to form most of the border between Washington and the state of Oregon before emptying into the Pacific Ocean. The river is 1,243 miles long, its largest tributary is the Snake River, its drainage basin is the size of France and extends into seven US states and a Canadian province. The fourth-largest river in the United States by volume, the Columbia has the greatest flow of any North American river entering the Pacific; the Columbia and its tributaries have been central to the region's culture and economy for thousands of years. They have been used for transportation since ancient times, linking the region's many cultural groups; the river system hosts many species of anadromous fish, which migrate between freshwater habitats and the saline waters of the Pacific Ocean. These fish—especially the salmon species—provided the core subsistence for native peoples.
In the late 18th century, a private American ship became the first non-indigenous vessel to enter the river. In the following decades, fur trading companies used the Columbia as a key transportation route. Overland explorers entered the Willamette Valley through the scenic but treacherous Columbia River Gorge, pioneers began to settle the valley in increasing numbers. Steamships along the river linked facilitated trade. Since the late 19th century and private sectors have developed the river. To aid ship and barge navigation, locks have been built along the lower Columbia and its tributaries, dredging has opened and enlarged shipping channels. Since the early 20th century, dams have been built across the river for power generation, navigation and flood control; the 14 hydroelectric dams on the Columbia's main stem and many more on its tributaries produce more than 44 percent of total US hydroelectric generation. Production of nuclear power has taken place at two sites along the river. Plutonium for nuclear weapons was produced for decades at the Hanford Site, now the most contaminated nuclear site in the US.
These developments have altered river environments in the watershed through industrial pollution and barriers to fish migration. The Columbia begins its 1,243-mile journey in the southern Rocky Mountain Trench in British Columbia. Columbia Lake – 2,690 feet above sea level – and the adjoining Columbia Wetlands form the river's headwaters; the trench is a broad and long glacial valley between the Canadian Rockies and the Columbia Mountains in BC. For its first 200 miles, the Columbia flows northwest along the trench through Windermere Lake and the town of Invermere, a region known in British Columbia as the Columbia Valley northwest to Golden and into Kinbasket Lake. Rounding the northern end of the Selkirk Mountains, the river turns south through a region known as the Big Bend Country, passing through Revelstoke Lake and the Arrow Lakes. Revelstoke, the Big Bend, the Columbia Valley combined are referred to in BC parlance as the Columbia Country. Below the Arrow Lakes, the Columbia passes the cities of Castlegar, located at the Columbia's confluence with the Kootenay River, Trail, two major population centers of the West Kootenay region.
The Pend Oreille River joins the Columbia about 2 miles north of the US–Canada border. The Columbia enters eastern Washington flowing south and turning to the west at the Spokane River confluence, it marks the southern and eastern borders of the Colville Indian Reservation and the western border of the Spokane Indian Reservation. The river turns south after the Okanogan River confluence southeasterly near the confluence with the Wenatchee River in central Washington; this C‑shaped segment of the river is known as the "Big Bend". During the Missoula Floods 10,000 to 15,000 years ago, much of the floodwater took a more direct route south, forming the ancient river bed known as the Grand Coulee. After the floods, the river found its present course, the Grand Coulee was left dry; the construction of the Grand Coulee Dam in the mid-20th century impounded the river, forming Lake Roosevelt, from which water was pumped into the dry coulee, forming the reservoir of Banks Lake. The river flows past The Gorge Amphitheatre, a prominent concert venue in the Northwest through Priest Rapids Dam, through the Hanford Nuclear Reservation.
Within the reservation is Hanford Reach, the only US stretch of the river, free-flowing, unimpeded by dams and not a tidal estuary. The Snake River and Yakima River join the Columbia in the Tri‑Cities population center; the Columbia makes a sharp bend to the west at the Washington–Oregon border. The river defines that border for the final 309 miles of its journey; the Deschutes River joins the Columbia near The Dalles. Between The Dalles and Portland, the river cuts through the Cascade Range, forming the dramatic Columbia River Gorge. No other rivers except for the Klamath and Pit River breaches the Cascades—the other rivers that flow through the range originate in or near the mountains; the headwaters and upper course of the Pit River are on the Modoc Plateau. In contrast, the Columbia cuts through the range nearly a thousand miles from its source in the Rocky Mountains; the gorge is known
A forearc is the region between an oceanic trench and the associated volcanic arc. Forearc regions are found at convergent margins, include any accretionary wedge and forearc basin that may be present. Due to tectonic stresses as one tectonic plate rides over another, forearc regions are sources for great thrust earthquakes During subduction, an oceanic plate is thrust below another tectonic plate, which may be oceanic or continental. Water and other volatiles in the down-going plate cause flux melting in the upper mantle, creating magma that rises and penetrates the overriding plate, forming a volcanic arc; the weight of the down-going slab flexes the down-going plate creating an oceanic trench. The area between the trench and the arc is the forearc region, the area behind the arc is the back-arc region. Initial theories proposed that the oceanic trenches and magmatic arcs were the primary suppliers of the accretionary sedimentation wedges in the forearc regions. More recent discovery suggests that some of the accreted material in the forearc region is from a mantle source along with trench turbidites derived from continental material.
This theory holds due to evidence of pelagic sediments and continental crust being subducted in processes known as sediment subduction and subduction erosion respectively. Over geological time there is constant recycling of the forearc deposits due to erosion and sedimentary subduction; the constant circulation of material in the forearc region generates a mixture of igneous and sedimentary sequences. In general, there is an increase in metamorphic grade from trench to arc where highest grade is structurally uplifted compared to the younger deposits. Forearc regions are where ophiolites are emplaced should obduction occur, but such deposits are not continuous and can be removed by erosion; as tectonic plates converge, the closing of an ocean will result in the convergence of two landmasses, each of, either an island arc or continental margin. When these two bodies collide, the result is orogenesis, at which time the underthrusting oceanic crust slows down. In early stages of arc-continent collision, there is uplift and erosion of the accretionary prism and forearc basin.
In the stages of collision, the forearc region may be sutured and shortened which can form syn-collisional folds and thrust belts. The forearc region includes any forearc basin, outer-arc high, accretionary prism and the trench itself; the accretionary prism is located at the slope of the trench break where there is decreased slope angle. Between the break and the magmatic arc, a sedimentary basin filled with erosive material from the volcanic arc and substrate can accumulate into a forearc basin which overlays the oldest thrust slices in the wedge of the forearc region. In general, the forearc topography is trying to achieve an equilibrium between buoyancy and tectonic forces caused by subduction. Upward motion of the forearc is related to buoyancy forces and the downward motion is associated with the tectonic forcing which causes the oceanic lithosphere to descend; the relationship between surface slope and subduction thrust plays a huge role in the variation of forearc structure and deformation.
A subduction wedge can be classified as either stable with little deformation or unstable with pervasive internal deformation. Some common deformation in forearc sediments are synsedimentary deformation and olistostromes, such as that seen in the Magnitogorsk forearc region. There are two models which characterize a forearc basin formation and deformation and are dependent on sediment deposition and subsidence; the first model is associated with a forearc basin formed with little to no sediment supply. Conversely, the second model is associated with sediment supply. Topographic depressions which are accertionary and nonaccretionary in nature will depend on the supply of oceanic plate sediments, continentally derived clastic material and orthogonal convergence rates; the accretionary flux determines the rate at which the sedimentation wedges grow within the forearc. The age of the oceanic crust along with the convergent velocity controls the coupling across the converging interface of the continental and oceanic crust.
The strength of this coupling controls the deformation associated with the event and can be seen in the forearc region deformation signatures. The intense interaction between the overriding and underthrusting plates in the forearc regions have shown to evolve strong coupling mechanisms which result in megathrust earthquakes such as the Tohoku-oki earthquake which occurred off the Pacific coast of Northeast Japan; these mega thrust earthquakes may be correlated with low values of heat flow associated with forearc regions. Geothermal data shows a heat flow of ~ 30 -- 40 mW/m2, which indicates strong mantle. One good example is the Mariana forearc. In this setting there is an erosive margin and forearc slope which consists of 2 km high and 30 km diameter serpentine- mud volcanoes; the erosive properties of these volcanoes are consistent with the metamorphic grades expected for this region in the forearc. There is evidence from geothermal data and models which show the slab-mantle interface, levels of friction and the cool oceanic lithosphere at the trench.
Other good examples are: Central Andean Forearc Banda Forearc Savu-Wetar Forearc Luzon arc-forearc Tohoku Forearc Between Western Cordillera and Peru-Chile Trench Back-arc region Einsele, Gerhard Sedimentary B
Central Oregon Coast Range
The Central Oregon Coast Range is the middle section of the Oregon Coast Range, in the Pacific Coast Ranges physiographic region, located in the west-central portion of the state of Oregon, United States between the Salmon River and the Umpqua River and the Willamette Valley and the Pacific Ocean. This 90-mile long mountain range contains mountains as high as 4,097 feet for Marys Peak. Portions of the range are inside the Siuslaw National Forest and three wilderness areas exist as well: Drift Creek Wilderness, Cummins Creek Wilderness and Rock Creek Wilderness; the underlying rock of the Central Coast Range are the igneous rocks from the Siletz River Volcanics of the Paleocene age. It is estimated; these formations consist of pillow basalt, large lava flows, tuff-breccia, sills. This part of the mountains are 50 to 60 million years old, it is theorized that the source of these lava flows came from oceanic islands that formed over a tectonic hotspot. The entire Oregon Coast Range overlies a convergent tectonic margin that interacts with the Juan de Fuca Plate, being sub-ducted beneath the North America tectonic plate.
This is the Cascadia subduction zone. It is part of a large forearc basin that extends for much of the entire Coast Range on a north-south alignment. Parts of the upper portions of the range contain continental margin deposits from the early Eocene to Paleocene age. Portions of this include marine fossils in the geologic record. Sandstone and shale are present in the sections of the mountains, with thickness up to 7,875 ft. In the southern part of the range the bedrock is overlaid by Eocene age turbidite sediments and river sediment; the active tectonic forces have created many folds in the range. Additionally, erosion is a major landscape-shaping force for the range. Both heavy rainfall and the resulting landslides have worked to shape the mountains. Much of the landscape is dominated by steep slopes and drainages that are cut into the hillsides from the erosion. Unlike many areas in North America, the mountain range did not see glaciations during the Pleistocene age; the Oregon Coast Range is home to over 50 mammals, 100 species of birds, nearly 30 reptiles or amphibians that spent a significant portion of their life cycle in the mountains.
Birds living in the Central Coast Range include a variety of larger bird species. These include winter wrens, chestnut-backed chickadees, red-breasted nuthatches, varied thrushes, several swallow species, red crossbills, evening grosbeaks, brown creepers, olive-sided flycatchers, Hammond's flycatchers, gray jays, western wood-pewees, western tanagers; some of the larger species in the range include the red-breasted sapsucker, common ravens, peregrine falcons, the pileated woodpecker, turkey vultures, wood duck, common nighthawks, the red-tailed hawk. Birds in lower numbers include Vaux's swifts, the endangered spotted owl, bald eagles, the downy woodpecker, hairy woodpeckers, the pine siskin, the hermit warbler, Pacific-slope flycatchers, golden-crowned kinglets, ruffed grouse. One of the more common avian wildlife is the American dipper, which live near rivers and streams; these birds build nests from six to nine inches in diameter out of moss. The central coast range is home to some larger animals such as deer, elk and bear.
Bear are black bear while deer are black-tailed deer species. Some additional mammals are mountain beaver, mink, river otter, mountain lion, the common raccoon, common porcupine, brush rabbit, skunk; the coast range is inhabited by eleven different species of bats, they account for nearly 20% of all the mammal species in the range. Species of bats include the Yuma myotis, silver-haired bat, big brown bat, hoary bat, the long-eared myotis. Other mammals living in the central range include beavers, creeping voles, long-tailed voles, vagrant shrews, deer mice, Pacific jumping mice, western pocket gopher, marsh shrew, shrew-mole, coast-mole, northern flying squirrel, Townsend's chipmunk among others. Amphibians include, but are not limited to, rough-skinned newts, northwestern salamanders, western red-backed salamander, Coastal tailed frog, Coastal giant salamander, red-legged frog, southern torrent salamander, Ensatina. Additional species include northwestern garter snake, northern alligator lizard, Pacific tree frog, western pond turtles, gopher snake, ringneck snake, western fence lizards.
Fish species in the Central Coast Range include chinook salmon, cutthroat trout, the threatened species coho salmon. A large section of the range is covered by the Siuslaw National Forest. Most of the range is forested and within the western hemlock vegetation zone with the overstory of the forest dominated by red alder, western hemlock, western cedar, bigleaf maple, Douglas-fir trees. In these forested sections, trees include Sitka spruce, western redcedar, Douglas-fir, western hemlock; the understory of the forest areas contain vine maple, Oregon grape, salmonberry and sword fern to name a few. Other plants that grow in the region are Pacific madrone, Pacific silver fir, bracken fern, thimble-berry, Pacific dogwood, bitter cherry, some rose species, cascara. Additionally, various grass and moss species are some of the other plant life growing in the mountain range. Arthropods include various spiders, collembolans, a variety of centipedes; the range begins around the Salmon River with the Northern Oregon Coast Range to the north.
Oregon Route 18 is the general divide between th
Snow hydrology is a scientific study in the field of hydrology which focuses on the composition and movement of snow and ice. Studies of snow hydrology predate the Anno Domini era, although major breakthroughs were not made until the mid eighteenth century. Snowfall and melt are important hydrological processes in watersheds at high altitudes or latitudes. In many western states in United States, snow melt accounts for a large percentage of the spring runoff that serves as water supply to reservoirs, urban populations and agricultural activities. A large portion of snow hydrology groups are pursuing new methods for incorporating snow hydrology into distributed models over complex terrain through theoretical developments, model development and testing with field and remote sensing data sets. Snow hydrology is quite complex and involves both mass and energy balance calculations over a time-varying snow pack, influenced by spatial location in the watershed, interaction with vegetation and redistribution by winds.
Some researchers seek to capture snow dynamics at a point and over a domain as the spatial pattern of snow cover area is observable from remote sensing. Snow and ice accounts for around 75% of the earth’s entire freshwater volume but lacks the capability of reliable applications. In comparison, the water supplied from rivers and freshwater lakes carries a consistent annual source of water; these natural bodies of water are formed through springs and mountainous snow runoff. According to estimates, snow represents about 5% of the precipitation that reaches the Earth’s surface. Due to the large amount of water held within these sources, snow hydrology has been a growing study in the field of river tides and seasonal flow rates. Despite common belief, snow fall is not the main cause for the destruction of organic matter in cold climates; the most damaging aspect is cold temperature winds. Studies have shown the insulating properties of snow defend the plants and small animals in the environment from these frigid winds.
“The snow itself is the habitat for various micro-organisms like snow worms and algae.” Without consistent annual snowfall, many plants would be destroyed due to frost damage. Both Ice worms and green algae are unique organisms that can live in snowy habitats. Though most of the knowledge in the field of snow hydrology has been discovered in the last two centuries, there is evidence that some understanding existed as early as 500-428BC in the Greek states; some of the earliest evidence that supports an ancient technical understanding of snow movement was produced by the Greeks. Anaxagoras, an ancient Greek notes: "the water in the Nile comes from the snow in Ethiopia, which freezes in the winter and melts in the summer"; the upper class Greeks in these city states were shown to have basic understanding of the cooling properties that snow exhibited. Upper class citizens would have hay lined pits dug beneath their homes and bring snow down from the mountains to fill them. Perishable food items could be stored in these pits for months at a time.
The Christian Bible contains numerous passages in its text that express a basic understanding of the hydrological cycle. Each of the following verses shows fundamental ideas behind the hydrological processes. One of the earliest modern records of the snow hydrology practice, was introduced by the geologist, Antonio Vallisnieri around the time of the 17th century, his work Theorized, “That rivers arising from springs in the Italian Alps came from rain and snowmelt seeping into underground channels."The first American research labs were introduced during the 1940s in order to solve the many problems associated with snow movement in the World War II era. These three labs were: Central sierra Snow Laboratory Upper Columbia Snow Laboratory Willamette Basin Snow Laboratory Currently there are hundreds of snow hydrology labs and sensing devices placed throughout the world; as of 2004, every continent was under observation with the exception of Antarctica. Since several sensing devices have been established in the Arctic Circle, allowing for constant observation.
Using these in part with satellite imaging systems has produced an accurate depiction of underlying landmass, unknown in the past. Snow hydrologists focus on movement and composition of snow and ice, within the field of hydrology; the knowledge gained from this career is most used in weather forecasting and ecological/ agricultural jobs, which require knowledge about the effects of snow migration. They retrieve the information they need through depth and composition readings, as well as various remote sensing techniques. Workers in this field can work for government agencies, research firms and public information services; the study of snow and glacial movement, though now dependent on remote sensing devices, still requires in field techniques to determine the validity of the data. These tools and techniques range from simple, such as a depth spike, to complex, such as the core sampling machines used to check for variations in ice composition. Three common types of terrestrial measurements are: Snow Depth-This is a measurement from the snow surface to the ground in meters.
It is does over a large time span using immobile graduated stakes. Snow Water Equivalency- A measuring tool which represents the vertical depth of water that would accumulate in an area, if all the snow and ice were melted in that given area. Snow Density- This is the value found by dividing the water equivalency measurement by the snow depth reading. Remote sensing technology is a recent tool in the field of snow hydrology, developed in response to a growing outl