Tilted layers of thick sandstone (pink) and thin shale (dark) along the coast at Olympic National Park reveal the enormous forces that lifted and deformed the oceanic layers as the Juan de Fuca and North American plates converged. The island is in between tectonic plates, which creates a subduction zone beneath Tambora (Fig. These oceanographic features are the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries, along which lithospheric plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. The Cascadia subduction zone last ruptured over 300 years ago on January 26, 1700. This contortion attests to the great forces that squeezed and lifted the layers from the sea. Modified from “Oregon's Island in the Sky: Geology Road Guide to Marys Peak, by Robert J. Lillie, Wells Creek Publishers, 75 pp., 2017, www.amazon.com/dp/1540611965. Visits to coastal NPS sites in the Pacific Northwest can help us appreciate the landscapes that develop over time because of these large quakes, and learn how we are preparing our homes, communities, and infrastructure for the next “Big One.”. A forearc basin develops in the low area between the two mountain ranges. The initial magma formed as mantle rock melts beneath a subduction zone has low silica (basalt) composition. The Cascadia Subduction Zone, extending from northern California through western Oregon and Washington to southern British Columbia, is a type of convergent plate boundary. The Cascade Volcanoes extend in a north-south line from Mt. Create your own unique website with customizable templates. spreading. subduction. 1815 Explosion The vent was the source for most of the ash and pyroclastic flows expelled during the 1912 eruptions, and has since filled with a lava dome known as Novarupta. The grinding action also produces devastating earthquakes, including some that result in giant tsunami waves. Remove the Washington quarter and you can see what the landscape might look like, in the form of Crater Lake in Crater Lake National Park in Oregon. Their high-silica magmas produce not only andesite and rhyolite lava flows, but also lots of other volcanic materials such as ash and pumice. The two parallel mountain ranges influence many of the physical and cultural aspects of the Pacific Northwest. The ocean trench is a geologically complex site. Farther east, the continent began to rift apart in the Basin and Range Province. The eruption of Aniakchak Volcano about 3,500 years ago rivals the eruption and collapse of Mt. The three West Coast states are especially meaningful because they have geologic features that, when the quarters are stacked, represent the surface and subsurface of the chain of volcanoes that has been developing over the past 200 million years. What are the effects of plate tectonics in Indonesia? USGS photo. This causes a build up of pressure in a process knows as subduction. And very large parks in the Southern Alaska Subduction Zone display magnificent mountains, rock layers and active volcanoes that tell the story ongoing plate convergence along the North Pacific Coast. Layers of pillow basalt exposed at NPS sites in the Coastal Ranges are evidence that lava flows that formed in the Pacific Ocean were later scraped off the subducting plate and lifted upward as part of the accretionary wedge. Effects of the 1964 earthquake are quite spectacular in the park; the coastline dropped so much that in places it lies submerged beneath about 8 feet (2.5 meters) of water. The same forces that shift the land so dramatically also gradually build spectacular landscapes like the coastlines of the Pacific Northwest. Katmai National Park Crater Lake in Crater Lake National Park partially fills the large depression formed when a composite volcano erupted and collapsed in on itself 7,700 years ago. But thousands of eruptions over less than a million years have built Mount Rainier and other Cascade peaks to elevations of more than 10,000 feet (3,000 meters)! Likewise, individual volcanic eruptions may add only a thin layer to the surface. Mazama, Aniakchak spewed lava across its caldera floor for centuries after its collapse. When caught between the converging Juan de Fuca and North American plates, the pillows and other ocean layers can be lifted upward to more than a mile above sea level. This event is known as a phreatomagmatic event and as a result, extremely hot steam carried the pyroclastic flows up to 40km at speeds greater than 100km/h. The physical landscape was an important component of the practical and spiritual aspects of Native Americans’ lives. [12] These seismically active areas of subduction are known as Wadati–Benioff zones. Mount Rainier is a 14,000 foot (4,300 meter) volcano in the Cascade Range developed above the place where the subducting Juan de Fuca Plate reaches sufficient depth to release hot fluids into the overriding North American Plate. The 6-mile (10-kilometer) wide caldera is about 2,000 feet (600 meters) deep. Another, Wrangell-St. Elias National Park, is a vast region that extends across the accretionary wedge and volcanic arc, and is built of accreted terranes. The lava that flows from stratovolcanos is typically made of magma with high levels of silica which causes it to have a high viscosity, and thus, not flow very far. What causes earthquakes? Produced under a Cooperative Agreement for earth science education between the National Park Service's Geologic Resources Division and the American Geosciences Institute. Solids and gases are also part of the mix. And, as at Mt. More than 40 volcanoes have erupted in Alaska since Russians first arrived in the mid 1700s – a great many of the volcanoes are in areas that are now National Park Service sites. Mazama, violently erupted 7,700 years ago. Novarupta Lava Dome Beginning about 30 million years ago, so much of the Farallon Plate was consumed by subduction that the Pacific and North American plates were in contact, forming the San Andreas transform plate boundary in western California. Mt. The unusually deep sea floor is not limited to the trench, but also extends farther south toward Puerto Rico. In doing so the magma is enriched in silica, because high-silica minerals commonly are the first ones to melt. Modified from “Parks and Plates: The Geology of our National Parks, Monuments and Seashores,” by Robert J. Lillie, New York, W. W. Norton and Company, 298 pp., 2005, www.amazon.com/dp/0134905172. Mazama, Aniakchak no longer holds a large lake because the caldera wall is breached. Imagine if Mt. When the edges of plates meet, four things can happen: slip. KEFJ—Kenai Fjords National Park, Alaska—[Geodiversity Atlas] [Park Home], CRLA—Crater Lake National Park, Oregon—[Geodiversity Atlas] [Park Home], LAVO—Lassen Volcanic National Park, California—[Geodiversity Atlas] [Park Home], MORA—Mount Rainier National Park, Washington—[Geodiversity Atlas] [Park Home], ANIA—Aniakchak National Monument and Preserve, Alaska—[Geodiversity Atlas] [Park Home], KATM—Katmai National Park, Alaska—[Geodiversity Atlas] [Park Home], LACL—Lake Clark National Park, Alaska—[Geodiversity Atlas] [Park Home]. Near the western edge of the continent, the Juan de Fuca Plate plunges downward and some of the layers of hard crust and ocean sediments are scraped off the top and squeezed upward as the Olympic Mountains and other coastal ranges. Photo courtesy of Robert J. Lillie. With continued uplift and erosion, most of the volcanic material would erode. An ancient volcano, Mt. Aniakchak National Monument and Preserve is on the Alaska Peninsula. They are part of the volcanic arc that extends northeastward from the Aleutian Islands, across the Alaska Peninsula and Aniakchak National Monument, Katmai and Lake Clark national parks, and then bends eastward to Wrangell-St. Elias National Park. Silica-rich ash melted and coated the hot engine turbines with glass, causing all four of them to shut down. Rainier National Park. Kenai Fjords National Park A variety of earthquakes shake the Pacific Northwest due to plate-tectonic activity. These mega-earthquakes occur every 200 to 600 years or so, and the last one was in the year 1700. Two parallel mountain ranges have been forming as a result of the Juan de Fuca Plate subducting beneath the edge of North America. Photo courtesy of Robert J. Lillie. State quarters can be used to demonstrate the current and ancient volcanic landscapes of the Pacific Northwest and California. Later, most of the settlers coming on the Oregon Trail continued past central Oregon and Washington to the lush farmland of the Willamette Valley and Puget Sound, the low-lying region between the two rising mountain ranges. Lake Clark National Park Photo courtesy of Robert J. Lillie. The eruption of Mt. Now suppose the subduction processes that form the volcanoes were to stop, shutting off the magma supply that feeds the volcanoes. Three others, Aniakchak National Monument, Katmai National Park, and Lake Clark National Park, are farther inland, along the active volcanic arc. Kenai Fjords National Park Most of the igneous rocks were manufactured in the ocean and are basalt. Other rocks seen in the high mountains at the center of the park were pushed more deeply into the Earth, where increasing temperature and pressure changed them into metamorphic rocks known as quartzite and slate. Shasta in California, and other Cascade Volcanoes. The Coast Range and Cascades are the two parallel mountain ranges that form the Cascadia Subduction Zone in the Pacific Northwest. The Puerto Rico Trench is also associated with the most negative gravity anomaly on earth, -380 milliGal, which indicates the presence of an active downward force. Mazama that formed Crater Lake. From 1999 to 2008, the United States Mint issued 25-cent coins representing each of the 50 states. A glance at a map of the western United States might suggest that the Sierra Nevada are a southward continuation of the Cascade Volcanoes. Earthquake activity around Sumatra has multiple sources including thrust earthquakes on the subduction fault, strike-slip earthquakes on the Sumatran fault, volcanic earthquakes and deeper earthquakes within the subducting lithosphere. Like Mt. Block diagram showing subduction of the Juan de Fuca Plate beneath the North American Plate along the Cascadia Trench, which is the western edge of the Cascadia subduction zone. The Cascadia Subduction Zone has two parallel mountain ranges separated by a low region near sea level. Modified from “Beauty from the Beast: Plate Tectonics and the Landscapes of the Pacific Northwest,” by Robert J. Lillie, Wells Creek Publishers, 92 pp., 2015, www.amazon.com/dp/1512211893. When two tectonic plates meet at a subduction zone, one bends and goes under the other towards the mantle, the hotter layer beneath the crust. Olympic National Park, Washington Katmai National Park and Preserve lies where the world’s largest volcanic event of the 20th Century occurred. Subduction in the Pacific Northwest creates incredible beauty in the form of coastlines, mountains, and valleys—iconic features of the many National Park Service sites in the region. The Sumatran Fault is a strike-slip fault which extends the entire length of Sumatra and coincides geographically with the volcanic arc. These hazards affect millions of people around the world, particularly around the edges of the Pacific Ocean, which mainly consist of subduction zones. When the plates suddenly let go, a massive earthquake will shake the entire Pacific Northwest, a series of tsunami waves will pound the Coast, and landslides will make it difficult to reach some of those in need. Redwood National and State Parks, California The importance of these short segments are that they limit the area that can be affected by one event, and magnitudes tend to be limited to 7.5 or less. Farther east the Juan de Fuca Plate descends deeper and deeper. Looking first at Washington, one sees Mt. Rainier National Park is an active composite volcano rising more than 14,000 feet above sea level. Subduction zones form where a plate with thinner (less-buoyant) oceanic crust descends beneath a plate with thicker (more-buoyant) continental crust. Crater Lake National Park has the 9th deepest lake in the world. Oceanic crust forms by eruptions along the Juan de Fuca Ridge. Granite rocks found in national parks in the Sierra Nevada are the cooled and eroded remnants of magma chambers that fed ancient subduction zone volcanoes in California. The rocks on top of the plate are metamorphosed due to the great temperatures and pressures at those depths. A transform boundary is where two tectonic plates slide past each other horizontally, thus creating stress when parts of these plates gets stuck at areas where they touch and the rest of the plates continue to move. Today As fluid basalt lava flows into the ocean it forms a pile of globular structures known as pillows. Plate Tectonics and Our National Parks (2020), Text and Illustrations by Robert J. Lillie, Emeritus Professor of Geosciences, Oregon State University [E-mail]. National Park Service sites are shown in red. Subduction zones are plate tectonic boundaries where two plates converge, and one plate is thrust beneath the other. They contain explosive volcanoes formed as fluids rise from the top of the subducting plate and generate magma as they melt their way to the surface. Sites in the Sierra Nevada Mountains reveal the eroded roots of an ancient volcanic range that formed when the subduction zone extended much farther south. A transform plate boundary developed where the Pacific Plate was in contact with the North American Plate and the volcanism ceased in central California. But parks in the Cascade Mountains – within the same subduction zone – are dramatically different. A series of explosions and ash clouds from the peak between 1914 and 1921 represents the last large volcanic eruption within the lower 48 states prior to Washington’s Mt. In 1912 the Katmai region erupted an estimated 7 cubic miles (30 cubic kilometers) of ash and pyroclastic material, roughly 50 times the amount that came out of Washington’s Mt. The reason for plate tectonics moving is due to the convection in the mantle, where hot material near the Earth's core rises and colder mantle rock sinks. National Park Service sites in the Cascades reveal colorful landscapes that result from a varity of volcanic processes. The caldera has partially filled with water – an approximately half-scale version of the better-known Crater Lake in Oregon. A subduction zone marks the collision between two tectonic plates which move slowly across the surface of Earth over millions of years. In the past, that was true. Storms coming in from the Pacific Ocean drop most of their moisture on the Coast Range and Cascades, leaving eastern Oregon and Washington high and dry. Ancient magma chamber rocks can be exposed if subduction stops and the volcanoes erode away. One of them, Kenai Fjords National Park, lies within the accretionary wedge of uplifting oceanic sedimentary strata and hard crust. Wrangell (left) and Mt. Where tectonic plates converge, the one with dense, thin oceanic crust subducts beneath the one with thick, more buoyant continental crust. But given enough time, the Coast Ranges lift up distances we can measure, while at the same time wind, rain, and the pounding of waves wear the landscape back down. Oceanic trenches are topographic depressions of the seafloor, relatively narrow in width, but very long. Photo courtesy of Robert J. Lillie. Layers of sand and mud, deposited on the ocean floor and later turned into the sedimentary rocks sandstone and shale, are seen above the pillows. 1). The Coast Range (accretionary wedge), Great Valley (forearc basin), and Sierra Nevada (volcanic arc) still reflect the subduction zone topography. The low region between the two parallel mountain ranges is the, 150 miles inland, the top of the subducting plate reaches depths where it’s hot enough to generate fluids, forming volcanoes in the. These quarters featured iconic images that have special meaning to each state. Individual earthquakes can offset or lift the land a fraction of an inch or a few inches (centimeters) at a time. Images above modified from “Oregon's Island in the Sky: Geology Road Guide to Marys Peak, by Robert J. Lillie, Wells Creek Publishers, 75 pp., 2017, www.amazon.com/dp/1540611965. As the Juan de Fuca Plate (lower cookie) subducts beneath the North American Plate (upper cookie), the layers are scraped off the ocean floor and pile up as the Coast Range. In this section, we will go deeper into explaining how these hot spots are the direct result of different types of plate tectonics and plate boundaries that make up the Earth's outer shell and thus explain the role of plate tectonics in causing damage to Indonesia. How do plate tectonics REALLY work?Please support us on Patreon at: http://www.patreon.com/minuteearthAnd subscribe! Stack the quarters with Washington on top, Oregon in the middle and California on the bottom. About 200 million years ago a large tectonic plate (called the Farallon Plate) started to subduct beneath the western edge of North America. The spectacular pillow lavas seen on the road up Hurricane Ridge indicate that lava formed on the sea floor and was later uplifted. The Cascades form above the line where the subducting plate extends to depths where it heats up, dehydrates and causes magma to form. On Dec. 15, 1989 a jet with 244 passengers and crew was en route from Amsterdam to Anchorage. Jennifer Natoli was a seasonal ranger at Redwood National and State Parks in California. The Pacific Northwest is an exciting place to observe geologic processes in action. Thus subduction-zone volcanoes—including those in the Cascades—can be explosive (think of the release of steam in a boiling pot of thick oatmeal). This affects not only plant and animal communities, but also human habitation and land use. The overlying volcanoes have since eroded away, exposing a vast expanse of the ancient magma chambers in the Sierra Nevada. The Cascades are the modern volcanic arc developing where the Juan de Fuca Plate subducts beneath the North American Plate. Lake Clark National Park and Preserve contains an active composite volcano with a profile and recent history reminiscent of Mt. St. Helens in 1980. The San Andreas Fault and Queen Charlotte Fault are transform plate boundaries developing where the Pacific Plate moves northward past the North American Plate. The park is a complex amalgamation of blocks of continental and oceanic crust that have slammed into North America. Mount Tambora is located on the island of Sumbawa, Indonesia (Fig. Among them are Mt. Layers of sandstone and shale deposited on the top of the Pacific Plate were later metamorphosed to quartzite and slate as the plate subducted beneath southern Alaska, and then shoved upward as part of the accretionary wedge. Subduction zones always have mountain ranges caused by plate subduction. Modified from “The Geology of our National Parks, Monuments and Seashores,” by Robert J. Lillie, New York, W. W. Norton and Company, 298 pp., 2005, www.amazon.com/dp/0134905172. The rising hot water causes overlying rock to melt, generating magma that at times erupts out on the surface as lava flows and other materials forming Mt. Rainier in Mt. If the seafloor rises or falls, giant sea waves (a tsunami) can form. The water rises and melts rock in its path. The trench is less deep where the component of subduction is larger. Elias National Park A point comes when the lighter plate can no longer take the intense pressure and suddenly snaps back up to the surface where it had been before. Modified from “The Geology of our National Parks, Monuments and Seashores,” by Robert J. Lillie, New York, W. W. Norton and Company, 298 pp., 2005, www.amazon.com/dp/0134905172. Over time, the San Andreas boundary has grown longer as the Farallon Plate split into two separate plates—the Juan de Fuca Plate on the north, and the Cocos Plate on the south. Katmai volcano did collapse, but unlike Mt. Some geological processes act so slowly that we may think of the Earth as rock-solid and unmoving. This can be demonstrated by stacking the three quarters with California on the bottom, overlain by Oregon and then Washington. But if the lava spills out from beneath the ocean, it encounters cold water and hardens quickly as a pile of pillows. This is what has happened in the Sierra Nevada of central and southern California, as represented by the granite-type rocks of Half Dome within Yosemite National Park shown on the California state quarter. The Coast Range (including the Olympic Mountains) consists of sedimentary rock layers and hard crust scraped off the ocean floor where the Juan de Fuca Plate begins to dive downward. Redoubt, on the eastern side of the park, had four explosive eruptions that resulted in large volumes of ash and mudflows. The original composite volcano was about 7,000 feet (2,000 meters) high, but lost about 2,500 feet (750 meters) of its height. Drum (right). Subduction (Tectonic) Process of plate tectonics where one lithospheric plate is pushed below another into the asthenosphere. The Coast Ranges, including the Olympic Mountains, are made of oceanic sediments and hard rocks that were caught in the vise between the converging plates, uplifted, and added to the edge of the continent. Poking through the mass of some of the highest mountains in North America are very young volcanoes formed by the ongoing Pacific Plate subduction. In the U.S., major subduction … Visitors to Olympic National Park, Oregon Caves National Monument, or Redwood National and State Parks can look down and imagine the top of the Juan de Fuca Plate about 10 miles (16 kilometers) beneath their feet. The line of active volcanoes, from Mt. Increased temperature and pressure at that depth cause the rocks to metamorphose and dehydrate (”sweat”). Mt. Parks in the Cascadia Subduction Zone dramatically display the two distinct mountain ranges – the Coast Range just above where the Juan de Fuca Plate begins to subduct, and the volcanic Cascade Range farther inland, where the top of the plate is deeper. The next is volcanic activity as a plate is subducted the pressure and … The mountains of Sumatra form a long, straight line which although are fertile and highly populated valleys, predominantly sit on the fault and damaging earthquakes cause severe damage. 20 Million Years Ago The average time between large earthquakes is about 535 years, but has been as little as 200 years, and more than 1,000 years. subscript a number following an element symbol that is written smaller and lower This beauty is part of the reason that residents and visitors have learned to tolerate, and develop ways to mitigate, the effects of earthquakes, tsunamis and volcanic eruptions—beasts that are consequences of the same tectonic forces that create the region’s beauty. The Seattle fault last ruptured about 1,100 years ago in AD 900–950. Without warning the plane flew right through the eruption cloud at 25,000 feet (7,500 meters) altitude. The rising water melts rock in its path, forming a volcanic arc on the overrriding plate. Modified from "Beauty and the Beast: Plate Tectonics and the Landscapes of the Pacific Northwest", by Robert J. Lillie, Wells Creek Publishers, 92 pp., www.amazon.com/dp.1512211893. A visit to Olympic National Park is an opportunity to witness features of an accretionary wedge as they develop. Finally, we used our last graham crackers to make a subduction zone – what happens when a more dense oceanic plate is thrust under a less dense continental plate. The flow of the mantle causes tectonic plates to move in different directions. Gases may be trapped in them under high pressure. National Park Service sites in the Coastal Ranges of Washington, Oregon and northern California contain rugged mountains of rocks that were manufactured in the ocean, then scraped off the plate and lifted out of the sea. The Caribbean and North American tectonic plates are scraping … The Cascadia subduction zone. Mount Rainier National Park showcases a 14,411-foot (4,393-meter) composite volcano. The volcanoes are forming above the region where the top of the subducting Juan de Fuca Plate reaches about 50 miles (80 kilometers) depth. Redoubt, an active volcano in Lake Clark National Park, illustrates how a volcano can pose an unexpected hazard in our modern age – and why monitoring volcanic activity is so important (see photo below). The collapse caldera from the Katmai eruption is about 3 miles (5 kilometers) across and 2,000 feet (600 meters) deep. After a terrifying free-fall that lasted 8 minutes, the pilots finally managed to restart the engines at only 6,000 feet (2,000 meters). The forearc basin is the Willamette Valley in Oregon and Puget Sound in Washington. Earthquakes, also known as temblors, occur along areas of weakness in the subterranean rocks that make up the Earth’s crust. USGS photo. In subduction zones, where older and colder oceanic crust descends beneath another tectonic plate, deep-focus earthquakes may occur at much greater depths (ranging from 300 up to 700 kilometers). Crater Lake partially fills the caldera of a volcano that erupted and collapsed in on Itself 7,700 years ago. Most of the sedimentary rocks formed from layers of sand and mud deposited in the ocean. The Krakatoa eruption was an example of convergent plates, where the volcano erupted due to the subduction of the Indo-Australian tectonic plate as it moved northwards towards Asia. Illustrations above modified from “Beauty from the Beast: Plate Tectonics and the Landscapes of the Pacific Northwest,” by Robert J. Lillie, Wells Creek Publishers, 92 pp., 2015, www.amazon.com/dp/1512211893. subduction zone the region where two plates collide and one plate sinks below the other Usually an oceanic plate sinks below a continental plate and down into the asthenosphere at a convergent boundary. The largest (locked zone earthquakes) occur where the Juan de Fuca and North American plates are stuck together, as they have been for the past three centuries.
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