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. Scientists now classify the bumping and grinding between plates in three different ways. S. Ornes. Fifty years later, it continues to shape Alaska, its people, and the science of earthquakes. At spreading zones, molten rock rises, pushing two plates . Now, 50 years later, plate tectonics is no longer a clever hypothesis. The control tower at Anchorage International Airport collapsed, killing an air traffic controller. Free educator resources are available for this article. Houses pulled apart. The 1964 Alaska Earthquake and Tsunami lecture by George Plafker, USGS Geologist Emeritus. Californias sheared-up landscape and earthquake hazards reflect the movement of the Pacific Plate past the edge of North America along a transform plate boundary that extends from the Mexican border to north of San Francisco. Over 80 per cent of large earthquakes occur around the edges of the Pacific Ocean, an area known as the Ring of Fire; this where the Pacific plate is being subducted beneath the surrounding plates. Notice what happens as you move your left hand away and slide your right hand toward you. An expanded version (11 min) is also available: 1964 Quake: The Alaska Earthquake The .gov means its official. convergent plate boundaries divergent plate boundaries transform plate . Our mission is to regenerate the natural world through science, learning, and collaboration. Depending on how you count them, there are about 12 main tectonic plates, and numerous smaller ones. Richter scale Modified Mercalli scale the Centigrade scale the moment magnitude scale. Images above modified from Earth: Portrait of a Planet, by S. Marshak, 2001, W. W. Norton & Comp., New York. Thats a type of convergent plate boundary where one plate dives beneath another. Since neither plate is stronger than the other, they crumple and are pushed up. Articles with the HISTORY.com Editors byline have been written or edited by the HISTORY.com editors, including Amanda Onion, Missy Sullivan and Matt Mullen. briefly recounts the events of March 27, 1964 and explains the scientific and societal importance of the earthquake. Seiches, a sloshing of water back and forth in a small body of water, were observed as far away as Louisiana, where a number of fishing boats sank in a harbor. Tomales Bay. This is an earthquake. In bays and inlets, the quake also triggered underwater landslides. These maps, by Randall W. Jibson and John A. Michael, depict seismic landslide hazards in Anchorage and are an important tool for planning, zoning, and emergency-response preparation. A sudden unlocking could produce an earthquake every bit as big as the one that occurred in Alaska in 1964, when a similar subduction zone boundary snap occurred. As the plates move past each other, they sometimes get caught and pressure builds up. National Park Service Sites (shown in red) The earthquake had uplifted large sections of seafloor. Although the school was destroyed, the nearby water tower was undamaged. Remnants of the ancient volcanic mountain chain remain. At 5:36 p.m. on March 27, 1964Good Fridaythe earth trembled just as many Alaskans were sitting down to dinner. Feature labels. Thousands of earthquakes over millions of years have built this landscape not only along the major fault linethe San Andreas Faultbut also on other faults within the broad zone of shearing between the Pacific and North American plates. The earthquake lasted approximately 4.5 minutes and is the most powerful recorded earthquake in U.S. history. Local tsunamis also caused destruction in Kodiak, Whittier and Seward. The earthquake triggered a swell of devastating tsunamis, landslides and submarine. In the Turnagain Heights area of Anchorage, soil liquefaction (when the ground behaves like a liquid) triggered a landslide which moved parts of a suburban bluff 2,000 feet into the bay, taking up to 75 homes with it. Oral presentations, poster sessions, exhibits, field trips, business meetings and social gatherings all provide participants the opportunity to meet and share with their peers. Lucky for this team, 70 new seismographs (SIZE moh grafs) had recently been installed all over the world. The plate motion has plucked the rocks from their original position and moved them more than 300 miles north-northwestward to their current position at Point Reyes. Ned Rozells personal account of his meeting with George Plafker, one of three USGS Geologists who responded to the Alaska quake a few days after event. When this happens, some part of the surface is said to subside. Modified from Earth: Portrait of a Planet, by S. Marshak, 2001, W. W. Norton & Comp., New York. 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. Channel Islands National Park includes five islands that are the tops of a mostly-submerged portion of the Transverse Ranges. Indeed, like ripples in a pond, a tsunami travels outward in all directions. Its like opening a sticky window or door. 1964 Alaskan Tsunami. Subduction zones occur when one or both of the tectonic plates are composed of oceanic crust. uplift A upward shift in some section of Earths surface due to tectonic activity along a fault. . Most earthquakes occur at the boundaries where the plates meet. Get a new perspective on earthquakes with this rich collection of multimedia resources. Magnitude type: M l 2; Event type: earthquake; Tectonic Setting of Southern Alaska . Farther east, the continent began to rift apart in the Basin and Range Province. Imagine that your left hand is the undeformed Pacific Plate, your right hand the intact North American Plate. to A.D. 2022, U.S. Drought: Weekly Report for April 25, 2023, U.S. Drought: Weekly Report for April 18, 2023, U.S. Drought: Weekly Report for April 11, 2023. The fastest plate race at 15 centimeters (6 inches) per year The slowest creep along at fewer than 2.5 centimeters a year. At still others, known as transform boundaries, plates slide past each other. As the plates grind together, they get stuck and pressure builds up. As the ground fractured, the trunk experienced extreme tension and eventually split. In Anchorage, roads buckled and sank. There are three types of plate boundaries, convergent, divergent, and transform. There are three types of tectonic plate boundaries: Another large-scale feature is a hotspot, where a plate rides over a rising plume of hot mantle, creating a line of volcanoes on top of the plate. Look at your fingernails and watch them grow. Plate Tectonics and Our National Parks (2020), Text and Illustrations by Robert J. Lillie, Emeritus Professor of Geosciences, Oregon State University [E-mail]. But Alaskas 1964 Great Quake led to a huge leap in their understanding. Underwater landslides along the Seward, Alaska, waterfront triggered the strong waves which hit here, 2 miles (3.2 kilometers) from Seward. The new magma (molten rock) rises and may erupt violently to form volcanoes, often building arcs of islands along the convergent boundary. It was so large that it caused the entire Earth to ring like a bell, observes seismologist Tom Brocher and his colleagues from the U.S. Geological Survey (USGS) in a recent publication. the earthquake and tsunami caused the deaths of over . In Alaska, the Pacific plate, relative to the North American plate, moves at a rate of ~5.5+ cm/yr (~2.2+ in/yr). California Academy of Sciences. Oreo cookies are a fun way to demonstrate the three types of plate boundaries and a hotspot. The foreground shows a ditch (or graben) that opened up roughly 12 feet (or around 3.7 meters) deep. Alaskas long southern coastline marks where the Pacific Plate, moving north, dives beneath the North American Plate. URL: https://pubs.usgs.gov/pp/0543i/ In fact, megathrust events are the largest type of earthquake on the planet, notes Peter Haeussler. Pacific Plate motion also creates volcanoes as rock melted by the sinking plate rises to the surface. Magnitude type: M l 2; Event type: earthquake; Tectonic Setting of Southern Alaska . Policies and Notices, U.S. Department of the Interior | The March 27, 1964, earthquake was accomp anied by crustal deformation-including warping, horizontal distortion, and faulting-over probably more than 110,000 square miles of land and sea bottom in south-central Alaska. USGS circular published one month after the earthquake by Arthur Grantz, George Plafker, and Reuben Kachadoorian detailing their scientific investigations of the quake. Retriangulation over roughly 25,000 square miles of the deformed region in and around Prince William Sound shows that vertical movements there were accompanied by horizontal distortion, involving systematic shifts of about 64 feet in a relative seaward direction. In places, the waves towered as high as a 20-story building. It was the first time we had physical proof of plate tectonics, concludes Mike West. Plates beneath the oceans are much thinner than those under continents. 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). The 1964 Alaska earthquake resulted from rupture along the thrust fault boundary bet- ween the downgoing Pacific Plate and the overriding North American Plate, causing widespread shaking and tectonic defor- mation. This material is also available as a free iBooks textbook and iTunes U course. They washed away everything in their immediate path buildings, docks and people. Transoceanic tsunami waves swept across the Pacific and reached as far away as Hawaii and Japan. Earthquakes are the result of sudden movement along faults within the Earth. 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. Coastal trees, here near the Port of Valdez, were snapped off. S. Ornes. The violent shaking led to water, sewer and gas line breaks and widespread telephone and electrical failures. Find History on Facebook (Opens in a new window), Find History on Twitter (Opens in a new window), Find History on YouTube (Opens in a new window), Find History on Instagram (Opens in a new window), Find History on TikTok (Opens in a new window), Education Images/Universal Images Group/Getty Images, Department of Homeland Security & Emergency Management, https://www.history.com/topics/natural-disasters-and-environment/1964-alaska-earthquake. Convergent (Colliding): This occurs when plates move towards each other and collide. When two tectonic plates slide past each other, the place where they meet is a transform or lateral fault. The large white star represents the zone where plates lock together for centuries then suddenly let go, causing the largest earthquakes. You'll learn why earthquakes happen, how they've shaped the Bay Area, and what you can do to prepare for the next one. Regional uplift and subsidence occurred mainly in two nearly parallel elongate zones, together about 600 miles long and as much as 250 miles wide, that lie along the continental margin. HISTORY.com works with a wide range of writers and editors to create accurate and informative content. There are three types of plate boundaries: spreading zones, transform faults, and subduction zones. This was the Big One. It was the first global seismic network, West tells Science News for Students. Photo courtesy of Robert J. Lillie. This photo shows a small snow slip in the center foreground. On the east, the North American Plate is subducting westward, forming volcanoes of the Lesser Antilles Island Arc. Tsunamis caused loss of life, extensive flooding, and damaged harbors along the North American Pacific Northwest coast. This is called subduction. For western California, each slipping card face would be a fault surface. 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. The transform plate boundary is a broad zone forming as the Pacific Plate slides northwestward past the North American Plate. When oceanic and continental plates meet, the denser oceanic plate moves under the less dense continental plate. According to the United States Geological Survey, The 1964 earthquake was giant because of the large area of the fault that slipped during the earthquake and the large amount of slip, or relative motion, between opposite sides of the earthquake fault.. About 200 million years ago, a large tectonic plate (called the Farallon Plate) started to subduct beneath the western edge of North America. Georges interpretation of this as a subduction zone was a real key, says Gary Fuis. Many transform boundaries are found on the sea floor, where they connect segments of diverging mid-ocean ridges. Big quake, little destruction. Science News for Students. It effortlessly toppled telephone poles, buckled railroad tracks, split roads in half, uprooted buildings, cars and docks and tore homes apart. Founded in 2003, Science News Explores is a free, award-winning online publication dedicated to providing age-appropriate science news to learners, parents and educators. Here, frozen ground holding the roots of this tree, in Anchorage, split apart during a landslide. Animations explain the magnitude (Just how big is 9.2? 1719 N Street, N.W., Washington, D.C. 20036, People and animals sometimes team up to hunt for food, Pokmon evolution looks more like metamorphosis, These beetles drink water using their butts. Its a bit like a rug wrinkling. thrust fault boundary The 1964 Alaska earthquake resulted from rupture along the thrust fault boundary bet- ween the downgoing Pacific Plate and the overriding North American Plate, causing widespread shaking and tectonic defor- mation. Scientists measured a wave runup of 220 feet in the Valdez Inlet. , Divergent boundaries where two plates are moving apart. Point Reyes National Seashore and Joshua Tree National Park have granitic magma-chamber rocks of the eroded arc, and Pinnacles National Park preserves volcanic rocks. These instruments detect and record earthquakes. Society for Science & the Public 20002023. The sequence begins shortly after the last earthquake. Plate Tectonics and Our National ParksSite Index, Plate TectonicsThe Unifying Theory of Geology, Tectonic Settings of NPS SitesMaster List. The second-largest earthquake in the U.S. was a magnitude-9.0 in 1700, which occurred at the Cascadia Subduction Zone, site of the leak. What kind of plate boundary causes mountains to form? By midnight, 131 people were dead. Produced under a Cooperative Agreement for earth science education between the National Park Service's Geologic Resources Division and the American Geosciences Institute. Along much of the boundary, the bulk of the motion occurs along the San Andreas Fault. The tsunamis created by the earthquake reached land within a few minutes of the ground shaking and engulfed some areas as much as 170 feet above sea level. If a segment of the San Andreas Fault is locked for a century, then a large earthquake might result in 200 inches (2 inches/year x 100 years) of movement along the fault in less than a minute. The delta slump triggered a local tsunami which destroyed almost anything left standing and ruptured the Union Oil Companys oil tanks, igniting a massive fire. Learn about the Great Alaska Earthquake of 1964 in this video adapted from the Valdez Museum & Historical Archive. This pattern has since been seen at other subduction zones. At still others, known as transform boundaries, plates slide past each other. Ground subsidence due to the earthquake created a huge, deep ditch (a graben) that ran through the yard and under this house in Anchorage. 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. Warping resulted in permanent tilt of larger lake basins and temporary reductions in discharge of some major rivers. divergent boundaries The edges of two neighboring tectonic plates that are spreading away from each other. Chile earthquake of 1960, the largest earthquake recorded in the 20th century. Point Reyes National Seashore and Golden Gate National Recreation Area are the only two NPS sites that are right on the San Andreas Fault. These quakes at transform faults are shallow focus. Often it is the older and colder plate that is denser and subducts beneath the younger and warmer plate. The duration of strain accumulation in the epicentral region, as interpreted from the time interval during which the coastal submergence occurred, probably is 9301,360 years. seismograph (also known as aseismometer) An instrument that detects and measures tremors (known as seismic waves) as they pass through Earth. commemorates the Alaska Earthquake and examines the advances in knowledge and technology that have helped improve earthquake preparation and response in Alaska and around the world. All Rights Reserved. (For example, the 2011 magnitude-9.0 earthquake off the eastern coast of Japan that unleashed a huge tsunami also was a megathrust earthquake.) tsunami One or many long, high sea waves caused by an earthquake, submarine landslide or other disturbance. (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). Transform plate boundaries produce enormous and deadly earthquakes. Slight uplift inland from the major zones of deformation presumably was related to elastic strain changes resulting from the overthrusting; however, the data are insufficient to permit conclusions regarding its cause. Here, that 11-foot (3.4 meter) drop or subsidence took a line of parked cars with it. Sometimes the extraction of groundwater leaves a hole that cannot support the ground above. Active volcanoes of the Lesser Antilles Island Arc form as the North American Plate subducts beneath the Caribbean Plate. In 1964, plate tectonics still was just an emerging if unproven concept. The earthquake was so powerful it registered in all U.S. states except Connecticut, Rhode Island and Delaware. The Pacific Plate slides north-northwestward past the North American Plate along the San Andreas Transform Plate Boundary. The Virgin Islands are in a broad zone where the landscape is being sheared up as the Carribean Plate slides eastward past the oceanic part of the North American Plate. Scientists also confirmed that earthquake-related tsunamis arent always localized and can happen thousands of miles from the epicenter. This causes the crust to crack and form faults where earthquakes occur. If one plate is trying to move past the other, they will be locked until sufficient stress builds up to cause the plates to slip relative to each other. United States Government Printing Office, Washington: 1993. Along convergent boundaries, neighboring plates either collide head-on or a denser ocean plate dives beneath a lighter continental plate. lithosphereThe upper layer of Earth, which includes its thin brittle crust and upper mantle. They were lifted out of the ocean as part of the accretionary wedge of an ancient subduction zone. Tectonic plates constantly push against each other. Explains Fuis: This was some of the first clear evidence that plate tectonics was right.. Shallow earthquakes and little volcanism occur where one plate slides laterally past another. This is an earthquake. We strive for accuracy and fairness. What boundary was the 1964 Alaska earthquake? President Lyndon Johnson declared the entire state of Alaska a major disaster area a day after the earthquake. Two earthquake faults exposed on Montague Island are subsidiary northwest-dipping reverse faults along which the northwest blocks were relatively displaced a maximum of 26 feet, and both blocks were upthrown relative to sea level. Uplift that averages 6 feet over broad areas occurred mainly along the coast of the Gulf of Alaska, on the adjacent Continental Shelf, and probably on the continental slope. The 1964 Alaska Earthquake taught coastal citizens to run for higher ground at the first sign of strong tremors. convergent boundaries The edges of two neighboring tectonic plates that are colliding into one another. When the plates finally give and slip due to the increased pressure, energy is released as seismic waves, causing the ground to shake. Afterwards, geologists realized subduction zonesareas where two tectonic plates (huge slabs of rock made of the earths crust and upper mantle) meet and one bends under the otherplayed a major role in creating the immense Alaskan quake. But if you see something that doesn't look right, click here to contact us! Typically, a convergent plate boundarysuch as the one between the Indian Plate and the Eurasian Plateforms towering mountain ranges, like the Himalaya, as Earths crust is crumpled and pushed upward. It was the first time we had physical proof of plate tectonics, concludes West. The movement releases stored-up 'elastic strain' energy in the form of seismic waves, which propagate through the Earth and cause the ground surface to shake. Map showing ground motion and shaking intensity based on instrumental measurements of shaking along with information about local geology and the earthquakes location and magnitude. The fissure shown here is about 1.5 inches wide. A massive tidal wave crushed the small, coastal village of Chenega four minutes after the tremors subsidedthe town lost a third of its population. Alaskans are familiar with earthquakes. And as the Pacific Plate dives, it slopes downward. There, in California, that motion causes earthquakes along the infamous San Andreas Fault. The earthquake hit at 3:11 pm approximately 100 miles (160 km) off the coast of Chile . Alaskan tectonics are dominated by the Pacific-North American plates. (2) Intermediate depth seismicity (below 20 miles) occurs in the so-called Benioff Zone, where the subducting Pacific Plate descends towards the mantle beneath the North American Plate. The earthquake lasted approximately 4.5 minutes and is the most powerful recorded earthquake in U.S. history. aftershock One or more smaller earthquakes that often follow a major earthquake. The Alaska earthquake was a subduction zone (megathrust) earthquake, caused by an oceanic plate sinking under a continental plate. U.S. Geological Survey Of the 139 deaths attributed to this event, 124 were directly caused by the tsunamis. Parks near the coast, including Point Reyes National Seashore, Golden Gate National Recreation Area, and Pinnacles National Park, contain volcanic and plutonic rocks that were plucked from the edge of the North American Plate and transported tens to hundreds of miles northwestward as part of the Pacific Plate. You push and push. Forty million years ago, a large tectonic plate, known as the Farallon Plate, was between the Pacific and North American plates. Which type of boundaries can produce earthquakes? In addition to local tsunamis caused by underground landslides, the earthquake triggered an enormous tectonic tidal wave. Plafker had confirmed that the earthquake occurred in a subduction zone. The San Andreas Fault is one of the best examples of lateral plate motion. UA is committed to providing accessible websites. E. Wayman. 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. Like modern subduction zones, the region had an accretionary wedge (Coast Range), a forearc basin (Great Valley), and a volcanic arc (Sierra Nevada). Pillow basalt, formed as lava poured out on the ocean floor, was later scraped off the top of the subducting plate and thrust onto the edge of the continent. What Can the Ocean Floor Tell Us About Tsunamis? Most seismic activity occurs at three types of plate boundariesdivergent, convergent, and transform. 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. Scientists learned that at the point where the North American Plate overrode the Pacific Plate, it descended into a subduction zone. The Sierra Nevada are the eroded remnants of the volcanic arc developed when the Farallon Plate subducted beneath the continent. Thrust earthquakes (as opposed to strike slip) are far more likely to generate tsunamis, but small tsunamis have occurred in a few cases from large (i.e., > M8) strike-slip earthquakes. Valdez was basically leveled. 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. The pinnacles are the eroded remnants of hardened volcanic brecciaslurries of mud and rock from explosive eruptions. It includes many lesser faults in addition to the San Andreas Fault. Produced under a Cooperative Agreement for earth science education between the National Park Service's Geologic Resources Division and the American Geosciences Institute.
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