Collision of the Intermontane Islands
During the early Jurassic period, the Intermontane Islands and the Pacific Northwest drew closer together as the continent moved west and the Intermontane Microplate subducted. On the continent, subduction supported a new volcanic arc that again sent intruding granite-type rocks into the ancient continental sediments. Eventually, about 180 million years ago in the middle Jurassic, the last of the microplate subducted, and the Intermontane Islands collided with the Pacific Northwest.
The ass period was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions.
The Pacific Northwest (PNW), sometimes referred to as Cascadia, is a geographic region in western North America bounded by the Pacific Ocean to the west and (loosely) by the Cascade Mountain Range on the east. Though no official boundary exists, the most common conception includes the Canadian province of British Columbia (BC) and the U.S. states of Idaho, Oregon, and Washington. Broader conceptions reach north into Southeast Alaska and Yukon, south into northern California, and east to the Continental Divide to include Western Montana and parts of Wyoming. Narrower conceptions may be limited to the coastal areas west of the Cascade and Coast mountains. The variety of definitions can be attributed to partially overlapping commonalities of the region's history, culture, geography, society, and other factors.
Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock. Strictly speaking, granite is an igneous rock with between 20% and 60% quartz by volume, and at least 35% of the total feldspar consisting of alkali feldspar, although commonly the term "granite" is used to refer to a wider range of coarse-grained igneous rocks containing quartz and feldspar.
The Intermontane Islands were too big to sink beneath the continent. The subduction zone of the Intermontane Plate shut down, ending the volcanic arc. As the Intermontane Belt accreted to the edge of the continent, the subduction zone of the Insular Plate became the active subduction zone along the edge of the continent.
The Intermontane Belt is a physiogeological region in the Pacific Northwest of North America, stretching from northern Washington into British Columbia, Yukon, and Alaska. It comprises rolling hills, high plateaus and deeply cut valleys. The rocks in the belt have very little similarities with the North American continent.
A continent is one of several very large landmasses of the world. Generally identified by convention rather than any strict criteria, up to seven regions are commonly regarded as continents. Ordered from largest in area to smallest, they are: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.
Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to gravity into the mantle. Regions where this process occurs are known as subduction zones. Rates of subduction are typically in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries.
Obduction was originally defined by Coleman to mean the overthrusting of oceanic lithosphere onto continental lithosphere at a convergent plate boundary where continental lithosphere is being subducted beneath oceanic lithosphere.
The Coast Mountains are a major mountain range in the Pacific Coast Ranges of western North America, extending from southwestern Yukon through the Alaska Panhandle and virtually all of the Coast of British Columbia south to the Fraser River. The mountain range's name derives from its proximity to the sea coast, and it is often referred to as the Coast Range. The range includes volcanic and non-volcanic mountains and the extensive ice fields of the Pacific and Boundary Ranges, and the northern end of the volcanic system known as the Cascade Volcanoes. The Coast Mountains are part of a larger mountain system called the Pacific Coast Ranges or the Pacific Mountain System, which includes the Cascade Range, the Insular Mountains, the Olympic Mountains, the Oregon Coast Range, the California Coast Ranges, the Saint Elias Mountains and the Chugach Mountains. The Coast Mountains are also part of the American Cordillera—a Spanish term for an extensive chain of mountain ranges—that consists of an almost continuous sequence of mountain ranges that form the western backbone of North America, Central America, South America and Antarctica.
The Farallon Plate was an ancient oceanic plate that began subducting under the west coast of the North American Plate—then located in modern Utah—as Pangaea broke apart during the Jurassic period. It is named for the Farallon Islands, which are located just west of San Francisco, California.
The Cocos Plate is a young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it. The Cocos Plate was created approximately 23 million years ago when the Farallon Plate broke into two pieces, which also created the Nazca Plate. The Cocos Plate also broke into two pieces, creating the small Rivera Plate. The Cocos Plate is bounded by several different plates. To the northeast it is bounded by the North American Plate and the Caribbean Plate. To the west it is bounded by the Pacific Plate and to the south by the Nazca Plate.
A volcanic arc is a chain of volcanoes formed above a subducting plate,
positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally, volcanic arcs result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench. The oceanic plate is saturated with water, and volatiles such as water drastically lower the melting point of the mantle. As the oceanic plate is subducted, it is subjected to greater and greater pressures with increasing depth. This pressure squeezes water out of the plate and introduces it to the mantle. Here the mantle melts and forms magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.
The islands of Japan are primarily the result of several large ocean movements occurring over hundreds of millions of years from the mid-Silurian to the Pleistocene as a result of the subduction of the Philippine Sea Plate beneath the continental Amurian Plate and Okinawa Plate to the south, and subduction of the Pacific Plate under the Okhotsk Plate to the north.
Continental collision is a phenomenon of the plate tectonics of Earth that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produced, and two continents sutured together. Continental collision is known only to occur on Earth.
The Insular Islands were a giant chain of active volcanic islands somewhere in the Pacific Ocean during the Cretaceous period that rode on top a microplate called the Insular Plate, beginning around 130 million years ago. The Insular Islands were surrounded by two prehistoric oceans, the Panthalassa Ocean to the west and the Bridge River Ocean to the east. About 115 million years ago, these islands collided with the North American continent, fusing onto the North American Plate and closing the Bridge River Ocean during the Mid-Cretaceous time.
Volcanology of Canada includes lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes, and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds. It has a very complex volcanological history spanning from the Precambrian eon at least 3.11 billion years ago when this part of the North American continent began to form.
The geology of the Pacific Northwest includes the composition, structure, physical properties and the processes that shape the Pacific Northwest region of the United States and Canada. The geology of the region is responsible for some of area's scenic beauty as well as some of its hazards, such as volcanoes, earthquakes, and landslides.
The Coast Range Arc was a large volcanic arc system, extending from northern Washington through British Columbia and the Alaska Panhandle to southwestern Yukon. The Coast Range Arc lies along the western margin of the North American Plate in the Pacific Northwest of western North America. Although taking its name from the Coast Mountains, this term is a geologic grouping rather than a geographic one, and the Coast Range Arc extended south into the High Cascades of the Cascade Range, past the Fraser River which is the northward limit of the Cascade Range proper.
Located in the western Pacific Ocean near Indonesia, the Molucca Sea Plate has been classified by scientists as a fully subducted microplate that is part of the Molucca Sea Collision Complex. The Molucca Sea Plate represents the only known example of divergent double subduction (DDS), which describes the subduction on both sides of a single oceanic plate.
This is a list of articles related to plate tectonics and tectonic plates.
The Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines. It includes two subduction zones, the Manila Trench to the west and the Philippine Trench to the east, as well as the Philippine Fault System. Within the Belt, a number of crustal blocks or microplates which have been shorn off the adjoining major plates are undergoing massive deformation.
Halmahera Plate has recently (1990s) been postulated to be a microplate within the Molucca Sea Collision Zone of eastern Indonesia.
The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.
