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Crescent Terrane
Siletzia is a massive formation of early to middle Eocene epoch marine basalts and interbedded sediments in the forearc of the Cascadia subduction zone, on the west coast of North America. It forms the basement rock under western Oregon and Washington and the southern tip of Vancouver Island. It is now fragmented into the Siletz and Crescent terranes. Siletzia corresponds geographically to the Coast Range Volcanic Province (or Coast Range basalts), but is distinguished from slightly younger basalts that erupted after Siletzia accreted to the continent and differ in chemical composition. The Siletzia basalts are tholeiitic, a characteristic of mantle-derived magma erupted from a spreading ridge between plates of oceanic crust. The younger basalts are alkalic or calc-alkaline, characteristic of magmas derived from a subduction zone. This change of composition reflects a change from marine to continental volcanism that becomes evident around 48 to 42 Ma (millions of ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siletzia
Siletzia is a massive formation of early to middle Eocene epoch marine basalts and interbedded sediments in the forearc of the Cascadia subduction zone, on the west coast of North America. It forms the basement rock under western Oregon and Washington and the southern tip of Vancouver Island. It is now fragmented into the Siletz and Crescent terranes. Siletzia corresponds geographically to the Coast Range Volcanic Province (or Coast Range basalts), but is distinguished from slightly younger basalts that erupted after Siletzia accreted to the continent and differ in chemical composition. The Siletzia basalts are tholeiitic, a characteristic of mantle-derived magma erupted from a spreading ridge between plates of oceanic crust. The younger basalts are alkalic or calc-alkaline, characteristic of magmas derived from a subduction zone. This change of composition reflects a change from marine to continental volcanism that becomes evident around 48 to 42 Ma (millions of y ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subduction Zone
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the heavier plate dives beneath the second plate and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries. Subduction is possible because the cold oceanic lithosphere is slightly denser than the underlying asthenosphere, the hot, ductile layer in the upper mantle underlying the cold, rigid lithosphere. Once initiated, stable subduction is driven mostly by the negative buoyancy of the dens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siletz River Volcanics
The Siletz River Volcanics, located in the Oregon Coast Range, United States, are a sequence of basaltic pillow lavas that make up part of Siletzia.Siletz River Volcanics at Fossilworks.org The basaltic pillow lavas originally came from es that existed during the . Description The |
Black Hills Formation (Washington)
The Spearfish Formation is a geologic formation, originally described from the Black Hills region of South Dakota, United States, but also recognised in North Dakota, Wyoming, Montana and Nebraska. It is a heterogeneous red bed formation, commonly with siltstone and gypsum low in the formation and sandstone and shale higher up. Other rock types include claystone, conglomerate, dolomite, and oil shale.Sabel, J. M. 1984. Sedimentology and depositional history of the Permo-Triassic Spearfish Formation, southwestern Black Hills, South Dakota. Pages 295-307 in Goolsby, J. and D. Morton, editors. The Permian and Pennsylvanian geology of Wyoming. Wyoming Geological Association, Casper, WY. Guidebook 35. It is typically regarded as Permian–Triassic in age, although its original description included Jurassic rocks. The Spearfish Formation is interpreted as representing shallow marine to coastal terrestrial deposition, like the modern Persian Gulf The Persian Gulf ( fa, خل ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crescent Formation
The Crescent Formation is a geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ... in Washington (state). It preserves fossils dating back to the Paleogene period. See also * List of fossiliferous stratigraphic units in Washington (state) * Paleontology in Washington (state) References * Paleogene geology of Washington (state) Ypresian Stage Wasatchian {{Paleogene-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metchosin Formation
The Metchosin Igneous Complex is an ophiolite sequence in southwestern British Columbia, Canada, located at the southern end of Vancouver Island. It is the northernmost expression of the Siletzia terrane and consists of three rock units, including a basaltic sequence, a sheeted dike complex and gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ... stocks. See also * Volcanism of Western Canada References Ophiolites Volcanism of British Columbia Southern Vancouver Island {{Canada-geology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Willapa Hills
The Willapa Hills is a geologic, physiographic, and geographic region in southwest Washington. When described as a physiographical province, the Willapa Hills are bounded by the Pacific Ocean to the west, the Columbia River to the south, the Olympic Mountains to the north, and the Cascade Range to the east. Some definitions place the Puget Lowland physiographic province east of the Willapa Hills. Included within the province are the Black Hills, the Doty Hills, and a number of broad river valleys, some of which open up into broad estuaries on the Pacific such as Grays Harbor and Willapa Bay. Other definitions do not include the Black Hills. The USGS GNIS defines the Willapa Hills as bounded by the Columbia River to the south and the Chehalis River to the north, without giving specific east and west bounds. The Willapa Hills are one of the Pacific Coast Ranges, which continue north as the Olympic Mountains and south, across the Columbia River, as the Oregon Coast Range. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Hills (Washington)
The Black Hills are a small range of hills in Thurston and Grays Harbor counties of Washington. They are widely considered a subset of the Willapa Hills, however, the line parent of the Black Hills is Rock Peak, in the Olympic Mountains. Capitol Peak is the highest peak in the range. The Black Hills takes its name from the Black River. A former variant name was "Black Mountains". The Capitol State Forest has roughly the same boundaries as the Black Hills. The high school A.G. West Black Hills, Tumwater, Washington Tumwater is a town in Thurston County, Washington, United States. The population was 25,350 at the 2020 census. It is situated near where the Deschutes River enters Budd Inlet, the southernmost point of Puget Sound; it also borders the state c ..., is named for the hills, as is the local soccer club the Blackhills Football Club. Capital Medical Center on the west side of Olympia was named Black Hills Community Hospital from its opening in 1985 until 1991.< ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olympic Mountains
The Olympic Mountains are a mountain range on the Olympic Peninsula of the Pacific Northwest of the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus is the highest at ; however, the eastern slopes rise out of Puget Sound from sea level and the western slopes are separated from the Pacific Ocean by the low-lying wide Pacific Ocean coastal plain. The western slopes are the wettest place in the 48 contiguous states. Most of the mountains are protected within the bounds of Olympic National Park and adjoining segments of the Olympic National Forest. The mountains are located in western Washington in the United States, spread out across four counties: Clallam, Grays Harbor, Jefferson and Mason. Physiographically, they are a section of the larger Pacific Border province, which is in turn a part of the larger Pacific Mountain System. Geography The Olympics have the form of a cluster of steep-sided peaks surrounded by heavily ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in the southwestern United States. Depending on differing definitions between Canada and the U.S., its northern terminus is located either in northern British Columbia's Terminal Range south of the Liard River and east of the Trench, or in the northeastern foothills of the Brooks Range/ British Mountains that face the Beaufort Sea coasts between the Canning River and the Firth River across the Alaska-Yukon border. Its southernmost point is near the Albuquerque area adjacent to the Rio Grande rift and north of the Sandia–Manzano Mountain Range. Being the easternmost portion of the North American Cordillera, the Rockies are distinct from the tectonically younger Cascade Range and Sierra Nevada, which both lie farther to its west. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laramide Orogeny
The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was deep-seated, thick-skinned deformation, with evidence of this orogeny found from Canada to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. The Laramide orogeny is sometimes confused with the Sevier orogeny, which partially overlapped in time and space. The orogeny is commonly attributed to events off the west coast of North America, where the Kula Plate, Kula and Farallon Plates were sliding under the North American plate. Most hypothes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectonic Plates
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of ''continental drift'', an idea developed during the first decades of the 20th century. Plate tectonics came to be generally accepted by geoscientists after seafloor spreading was validated in the mid to late 1960s. Earth's lithosphere, which is the rigid outermost shell of the planet (the crust and upper mantle), is broken into seven or eight major plates (depending on how they are defined) and many minor plates or "platelets". Where the plates meet, their relative motion determines the type of plate boundary: '' convergent'', '' divergent'', or ''transform''. Earthquakes, volcanic activity, mountain-building, and oceanic tren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
