what type of plate boundary caused the 1964 alaska earthquake what type of plate boundary caused the 1964 alaska earthquake

Also just like a rug, the land spreads out as it flattens. 2023, A&E Television Networks, LLC. the first to be generally understood by earth scientists as having occurred on a subduction zone interface: the slip was along the gently dipping boundary, or "megathrust fault," between the denser downgoing oceanic plate and the lighter overriding continental plate. Focal-mechanism studies, when considered in conjunction with the pattern of deformation and seismicity, suggest that it was a complex thrust fault (megathrust) dipping at a gentle angle beneath the continental margin from the vicinity of the Aleutian Trench. Chemists have unlocked the secrets of long-lasting Roman concrete, Sea life may suffer as plastic bits alter metals in water, A new solar-powered gel purifies water in a flash, Magnetic fields melt and re-form new shape-shifting devices, Explainer: Telling a tsunami from a seiche, The Great Alaska Earthquake and Tsunami of March 27, 1964, Energy companies triggered quakes, study says, Heres how to increase clean energy without harming wildlife, Native Amazonians make rich soils and ancient people may have too, A powerful laser can control the paths that lightning takes, Creating less new stuff could greatly help Earths climate, Using Science News Explores in the Classroom. That motion was huge, West says. To view this site, enable JavaScript by changing your browser options and try again. U.S. Geological Survey Includes extensive archival footage of the earthquake and aftermath. Finally, the transform boundary, that the San Andreas . Quakes cause faraway sloshing. Science News for Students. In bays and inlets, the quake also triggered underwater landslides. As the plates move past each other, they sometimes get caught and pressure builds up. Evidence for progressive coastal submergence in the deformed region for several centuries preceding the earthquake, in combin1ation with transverse horizontal shortening indicated by the retriangulation data, suggests pre-earthquake strain directed at a gentle angle downward beneath the arc. Subduction of the Farallon Plate beneath the entire West Coast created a line of volcanoes from Alaska to Central America. S. Perkins. Plafker spent most of the summer in Alaska researching and documenting the earthquake. These films were shot by amateur and professional cameramen in the hours and days following the earthquake at locations such as Anchorage, Kodiak, Seward, Valdez, Chenega, Afognak. Most seismic activity occurs at three types of plate boundariesdivergent, convergent, and transform. Reports of residual water sloshing (seiches) came in from the U.S. Gulf Coast and as far away as Australia. Is earthquake a result of plate tectonics? Through very complete mapping of vertical deformation and faulting and the application of tectonics, he was first to propose in 1965 that the source of the 1964 Alaska earthquake was a low-angle thrust fault. The 1964 earthquake was a defining moment in a territory that had just achieved statehood. Alaskan tectonics are dominated by the Pacific-North American plates. Register to access: Already Registered? Divergent boundaries - where two plates are moving apart. This led to the establishment of the Pacific Tsunami Warning Center (originally called the West Coast/Alaska Tsunami Warning Center) to alert people when a widespread tsunami is possible. Sometimes a sub-surface cave becomes too weak to support the ground above it. You push and push. Point Reyes National Seashore, Golden Gate National Recreation Area, and Pinnacles National Park present landscapes affected by the main line of movement, the San Andreas Fault. As bad as the tremors were, the worst was yet to come. Transform plate boundaries produce enormous and deadly earthquakes. Shallow earthquakes and little volcanism occur where one plate slides laterally past another. The magnitude 7.8 San Francisco Earthquake struck the morning of April 18, 1906. Southeast of Florida, the Caribbean Plate is sliding east-northeast about 0.8 inches (2 centimeters) per year relative to the North American Plate. These quakes at transform faults are shallow focus. UA is committed to providing accessible websites. You'll learn why earthquakes happen, how they've shaped the Bay Area, and what you can do to prepare for the next one. Farther east, the continent began to rift apart in the Basin and Range Province. The southern edge of our state is an active tectonic plate boundary where the Pacific plate subducts (i.e., dives beneath) the North American plate along the great Alaska-Aleutian Megathrust. Landslide and slumping effects in the Turnagain Heights area, Anchorage, Alaska, caused by the March 28, 1964, earthquake. The compressed and uplifted region includes the Santa Monica Mountains north of Los Angeles as well as the Channel Islands south of Santa Barbara. Sunday: 11 am 5 pm When this happens, some part of the surface is said to subside. Channel Islands National Park, Santa Monica Mountains National Recreation Area and Joshua Tree National Park are within the Transverse Ranges, a block of crust that rotated as a result of the shearing motion. It is relatively cold and brittle. Here, frozen ground holding the roots of this tree, in Anchorage, split apart during a landslide. tsunami One or many long, high sea waves caused by an earthquake, submarine landslide or other disturbance. Active volcanoes of the Lesser Antilles Island Arc form as the North American Plate subducts beneath the Caribbean Plate. 1). All rights reserved. The landscapes of Channel Islands National Park, Pinnacles National Park, Point Reyes National Seashore and many other NPS sites in California are products of such a broad zone of deformation, where the Pacific Plate moves north-northwestward past the rest of North America. Virgin Islands National Park in the U. S. Virgin Islands is located on another transform plate boundary, where the Caribbean Plate is sliding past the oceanic part of the North American Plate. At spreading zones, molten rock rises, pushing two plates . There are three main types of plate boundaries: Convergent boundaries: where two plates are colliding. Plafker had confirmed that the earthquake occurred in a subduction zone. As you slide your hands laterally past one another, a broad zone of shearing develops as several card faces slip. Enter your e-mail address above. UAF is an AA/EO employer and educational institution and prohibits illegal discrimination against any individual: If you have difficulty accessing the information on this website due to a disability, please contact the web administrator by email at uaf-aec@alaska.edu or by phone at 907-474-7320. Sometimes the molten rock rises to the surface, through the continent, forming a line of volcanoes. National Park Service sites in the San Francisco Bay Area reveal a sheared-up, ancient subduction zone landscape developed along the San Andreas Fault. Plafker named this event a megathrust earthquake. The tidal wave had diminished by the time it hit Hawaii and Japan, causing little damage. Indeed, like ripples in a pond, a tsunami travels outward in all directions. A plate boundary is a three-dimensional surface or zone across which there is a significant change in the velocity (speed or direction) of motion of one lithospheric plate relative to the adjacent lithospheric plate. Produced under a Cooperative Agreement for earth science education between the National Park Service's Geologic Resources Division and the American Geosciences Institute. The powerful tremors lasted for nearly five minutes and were felt over a large area of Alaska and in parts of the western Yukon Territory and British Columbia. Why do earthquakes usually occur at plate boundaries? These plates constantly move. Get a new perspective on earthquakes with this rich collection of multimedia resources. . Richter scale Modified Mercalli scale the Centigrade scale the moment magnitude scale. The earthquake rupture started approximately 25 km beneath the surface, with its epicenter about 6 miles (10 km) east of the mouth of College Fiord, 56 miles (90 km) west of Valdez and 75 miles (120 km) east of Anchorage. Federal government websites often end in .gov or .mil. HISTORY.com works with a wide range of writers and editors to create accurate and informative content. This post is part of Exploring Earthquakes, a rich collection of resources co-presented by the California Academy of Sciences and KQED. July 6, 2011. The largest tsunami wave of the 1964 Alaska Earthquake measured over 200 feet in height and was recorded at Shoup Bay near the Valdez inlet. These strike-slip faults and their associated structures are defined by linkage of mid-ocean spreading centers and subduction zones, and are exposed onshore as they traverse the continental crust between mid-ocean ridges and other plate boundary segments (Figure 2). Department of Homeland Security & Emergency Management.The 1964 Great Alaskan Earthquake and TsunamisA Modern Perspective and Enduring Legacies. Thousands of strong aftershocks continued for weeks after the earthquake, some measuring greater than magnitude 6.2. Sometimes the valleys are partially filled with water, as at Point Reyes National Seashore, where Tomales Bay and Olema Valley follow the main trace of the San Andreas Fault. S. Ornes. One was figuring out why some parts of Alaska had risen as much as 11.5 meters (38 feet), while the ground at other sites had dropped, or subsided. An animation about tsunami-generating megathrust earthquakes using examples from Japan (2011), Chile (2010), and Alaska (1964) to describe structures that generate deadly tsunamis including: megathrust plate-boundary displacement, deformation of the overriding plate by splay faulting and/or folding, and earthquake-generated landslides. (For example, the 2011 magnitude-9.0 earthquake off the eastern coast of Japan that unleashed a huge tsunami also was a megathrust earthquake.) IRIS webpage dedicated to George Plafker, a USGS field geologist noted for his studies of subduction-zone and backarc thrust earthquakes. Imagine that your left hand is the undeformed Pacific Plate, your right hand the intact North American Plate. Trenchward velocities are found also for some sites in the Anchorage area. Now, 50 years later, plate tectonics is no longer a clever hypothesis. The quake also led to significant scientific breakthroughs in subduction earthquakes and how to minimize their destruction. Remnants of the ancient volcanic mountain chain remain. plate boundary (in geology) The edge of a tectonic plate, or the place where two or more tectonic plates meet. This is known as subduction. The Alaska earthquake was a subduction zone (megathrust) earthquake, caused by an oceanic plate sinking under a continental plate. When the plates finally give and slip due to the increased pressure, energy is released as seismic waves, causing the ground to shake. The megathrust boundary between the plates results in both the 4,000-km-long Aleutian Trench and in the arc of active volcanoes that lie subparallel to the trench. In places like Hawaii and Yellowstone, a plate rides over a rising plume of hot mantle, causing earthquakes and a chain of volcanoes. The islands contain sedimentary layers and pillow lavas that formed on the ocean floor. Do earthquakes occur at divergent plate boundaries? Historically, the Alaska subduction zone is known for its large earthquakes, where the Pacific and North American plates scrape against each other violently as one slides suddenly over the other in the subduction zone. Subduction causes deep ocean trenches to form, such as the one along the west coast of South America. The sedimentary and metamorphic rocks across the fault line are similar to those found in Redwood National and State Parks on the North Coast of California. These tectonic plates move gradually, bumping and grinding against each other. The publication, as well as. Maximum indicated uplift in the Alaska and Aleutian Ranges to the north of the zone of subsidence was l feet. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. It is also the second largest earthquake ever recorded, next to the M9.5 earthquake in Chile in 1960. Microplates are smaller fragments of tectonic plates that appear in plate boundary zones. Big quake, little destruction. Science News for Students. Pacific Plate motion also creates volcanoes as rock melted by the sinking plate rises to the surface. Transform boundaries - where plates slide passed each other. earthquake A sudden and sometimes violent shaking of the ground, sometimes causing great destruction, as a result of movements within Earths crust or of volcanic action. The plates move towards one another and this movement can cause earthquakes. For example, rocks found today in Point Reyes National Seashore north of San Francisco were originally part of the line of granite rocks formed beneath ancient subduction zone volcanoes. Plate Tectonics and Our National ParksSite Index, Plate TectonicsThe Unifying Theory of Geology, Tectonic Settings of NPS SitesMaster List. Although the school was destroyed, the nearby water tower was undamaged. fault (in geology) A fracture along which there is movement of part of Earths lithosphere. A convergent plate boundary is a location where two tectonic plates are moving toward each other, often causing one plate to slide below the other (in a process known as subduction). 345 Middlefield Road, MS 977 The tsunami, which caused massive property damage in Washington, Oregon and California, also claimed four lives in Oregon and 12 in California. The 1964 Great Alaska Quake caused several downtown areas of Anchorage to collapse.