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. Plate Tectonics and Our National Parks (2020), Text and Illustrations by Robert J. Lillie, Emeritus Professor of Geosciences, Oregon State University [E-mail]. 2023, A&E Television Networks, LLC. The Earthquake Trail at Point Reyes weaves back and forth across the fault line. This post is part of Exploring Earthquakes, a rich collection of resources co-presented by the California Academy of Sciences and KQED. The three main types of plate movements include: Divergent (Spreading):This is where two plates move away from each other. The 1964 earthquake was a defining moment in a territory that had just achieved statehood. The belt of seismic activity and major zones of tectonic deformation associated with the 1964 earthquake, to a large extent, lie between and parallel to the Aleutian Volcanic Arc and the Aleutian Trench, and are probably genetically related to the arc. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earths mantle to the surface, solidifying to create new oceanic crust. . On This Day: Great Alaska Earthquake and Tsunami, Aftershocks from the quake continued for three weeks, Transoceanic tsunami waves swept across the Pacific and reached as far away as Hawaii and Japan, The earthquake and ensuing tsunamis caused about $311 million in damages in 1964(about$2.3 billiontoday), Tsunami Warning Centers issue tsunami warnings in minutes, not hours, after a major earthquake occurs, National Tsunami Hazard Mitigation Program, Tsunami Forecast Model Animation: 1964 Alaska Earthquake, NCEI Great Alaska Earthquake Image Database, VIDEO: NCEI Ask a Scientist with Nic Arcos: Tsunamis. As convergent plates collide, the overriding or top plate gets slowly pushed up. Adding TravelTime as Impedance in ArcGIS Network Analyst? National Park Service sites in the San Francisco Bay Area reveal a sheared-up, ancient subduction zone landscape developed along the San Andreas Fault. The demolished towns of Valdez and Chenega were rebuilt on higher ground, but not everyone was prudent about rebuilding on earthquake-prone land. Excerpt from the TV show The Big Picture produced by the US Army in 1966 about the Alaska Earthquake and its tragic effects. plate boundary (in geology) The edge of a tectonic plate, or the place where two or more tectonic plates meet. Only time will tell if new building codes are strong enough to withstand the next massive Alaskan earthquake. The islands contain sedimentary layers and pillow lavas that formed on the ocean floor. Popular Geology - Earthquakes & Tsunamis</ | Alaska Division of The Alaska earthquake of March 27, 1964, magnitude approximately 8.3-8.4, began at 6:36 p.m. Its epicenter was in the northern part of the Prince William Sound area; focal depth was 20-50 km. In fact, West notes, four out of every five U.S. quakes occurs in this northernmost state. Their thickness ranges from 80 to 200 kilometers (50 to 124 miles). Talkeetna M1.4 | Alaska Earthquake Center Most earthquakes occur at the boundaries where the plates meet. (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. Aftershock distribution suggests movement on a segment of the megathrust, some 550600 miles long and 110180 miles wide, that underlies most of the major zone of uplift and the seaward part of the major zone of subsidence. Federal government websites often end in .gov or .mil. They occur where plates are subducting, spreading, slipping, or colliding. The tidal wave had diminished by the time it hit Hawaii and Japan, causing little damage. In the Caribbean Sea, the U. S. Virgin Islands lie along a transform plate boundary where the small Caribbean Plate moves eastward past the oceanic part of the North American Plate. There are three main types of plate boundaries: There are four types of boundaries between tectonic plates that are defined by the movement of the plates: divergent and convergent boundaries, transform fault boundaries, and plate boundary zones. All rights reserved. This can lead to the formation of huge, high mountain ranges such as the Himalayas. Remove unwanted regions from map data QGIS. Farther to the south, the Pacific Plate slides past the North American Plate. M 9.2 - 1964 Prince William Sound Earthquake, Alaska - USGS They were scouting for patterns. Geologic data indicate that the earthquake-related tectonic movements were but the most recent pulse in an episode of deformation that probably began in late Pleistocene time and has continued intermittently to the present. The damage was caused entirely by the shifting of ground along the fracture, USGS concluded. Local tsunamis also caused destruction in Kodiak, Whittier and Seward. magazine, are published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education. Find out what you can do right now to protect yourself in the event of an earthquake. ), rupture processes, elastic rebound, and resulting tsunami. Microplates are smaller fragments of tectonic plates that appear in plate boundary zones. In places like Hawaii and Yellowstone, a plate rides over a rising plume of hot mantle, causing earthquakes and a chain of volcanoes. Some of the plates have ocean water above them. Notice what happens as you move your left hand away and slide your right hand toward you. Maximum indicated uplift in the Alaska and Aleutian Ranges to the north of the zone of subsidence was l feet. Earthquakes and tsunamis can happen along any coastline, at any time of the year, but Alaska is particularly prone to them because it sits on the convergence of two tectonic platesthe Pacific Plate and the North American Plate. Short video (4 min) by Stephen Wessells, USGS relating how the largest quake in U.S. history had profound and lasting impacts on our lives. Forty million years ago, a large tectonic plate, known as the Farallon Plate, was between the Pacific and North American plates. Natasha Ruppert at the Alaska Earthquake Center in Fairbanks is another seismologist. About 80% of earthquakes occur where plates are pushed together, called convergent boundaries. Transform boundaries - where plates slide passed each other. Global historical tsunami data, including more information about the Great Alaska Earthquake, are available via interactive maps and a variety of web services. Ahead of the wave. Science News for Students. Anchorage house pulled apart as the ground on which it had been anchored opened up, creating a fissure (or graben). This stretch of road had been built partly atop mud from a tidal estuary and other unsecure soils. Plate boundaries. And it moved parts of the Alaskan coast 15 meters (50 feet) toward the sea. The Alaska earthquake was a subduction zone (megathrust) earthquake, caused by an oceanic plate sinking under a continental plate. Alaska: Tectonics and Earthquakes - IRIS Consortium
Valdez was basically leveled. What caused the Alaska earthquake in 1964? They still had many questions to answer. The landscapes of our national parks, as well as geologic hazards such as earthquakes and volcanic eruptions, are due to the movement of the large plates of Earths outer shell. The California Academy of Sciences is a 501(c)(3) nonprofit organization. This material is also available as a free iBooks textbook and iTunes U course. 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. Compaction in the Rock Cycle: Understanding the Process Behind Sedimentary Rock Formation, Crystallization in the Water Cycle: A Fundamental Process in Water Distribution and Purification, Understanding Crystallization in the Rock Cycle: A Fundamental Process in Rock Formation, Extracting Lat/Lng from Shapefile using OGR2OGR/GDAL. W.R. Hansen/ USGS, 1964 Alaska quake files. fault (in geology) A fracture along which there is movement of part of Earths lithosphere. National Park Service sites along the transform plate boundary in California contain rocks formed during the earlier subduction that occurred in western North America. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely. By midnight, 131 people were dead. In fact, the locations of earthquakes and the kinds of ruptures they produce help scientists define the plate boundaries. The San Andreas Transform Plate Boundary developed within the past 40 million years as a large portion of the Farallon Plate was subducted and the Pacific Plate made contact with the North American Plate in the California region. Tectonic setting. It explains how the continents and oceans have been shaped, and why there are earthquakes, mountains, volcanoes and tsunamis. Photo courtesy of Robert J. Lillie. Quakes cause faraway sloshing. Science News for Students. The invention of new tools and faster data processing have drastically improved NOAAs ability to warn the public of tsunamis and to forecast their wave heights. As the plates collide, the oceanic plate is forced beneath the continental plate. Convergent Plate BoundariesSubduction Zones - National Park Service The collision of tectonic plates can result in earthquakes, volcanoes, the formation of mountains, and other geological events. This 3-panel image shows a simplified representation of a tsunami-generating earthquake cycle on the Alaska-Aleutian Megathrust. Movement in narrow zones along plate boundaries causes most earthquakes. by Carl W. Stover and Jerry L. Coffman, Seafloor topography map source: Global sea floor topography from satellite and ship depth soundings, 1997, by W. H. F. Smith and D. T. Sandwell, Science, v. 277, p. 1956-1962. 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. 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. (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). Fracking wastes and quakes. Science News for Students. Right image (en Espaol). 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. 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. April 30, 202323:15:06 AKDT (May 1, 202307:15:06 UTC)62.0155N148.8858W Depth 13.6 miles (22 km), This event has not been reviewed by a seismologist, 2156 Koyukuk Drive, PO Box 757320, Fairbanks, AK 99775. The earthquake had uplifted large sections of seafloor. 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. At still others, known as transform boundaries, plates slide past each other. The 1964 M9.2 Great Alaska Earthquake, which is still the second largest earthquake ever recorded worldwide, began under Prince William Sound.
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Sometimes the extraction of groundwater leaves a hole that cannot support the ground above. When a continental plate meets an oceanic plate, the thinner, denser, and more flexible oceanic plate sinks beneath the thicker, more rigid continental plate. 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. Deployment of tools like deep ocean pressure sensors (Deep-ocean Assessment and Reporting of Tsunamis or DART) are designed to ensure early detection of tsunamis and acquire data critical to real-time forecasts. Explains Fuis: This was some of the first clear evidence that plate tectonics was right.. U.S. Geological Survey Professional Paper 1527, Youre now subscribed to NightLife updates. 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. Exhibits along the trail include the reconstruction of a fence that was offset 16 feet (5 meters) during the 1906 earthquake. United States Government Printing Office, Washington: 1993. Earthquakes at divergent plate boundaries occur as new crust is created and other crust is pushed apart. 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 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. It was the first time we had physical proof of plate tectonics, concludes West. What type of plate boundary causes earthquakes in Alaska? Underwater landslides along the Seward, Alaska, waterfront triggered the strong waves which hit here, 2 miles (3.2 kilometers) from Seward. The earthquakes that occur along these zones, called spreading centers, are relatively small. In general, the deepest and the most powerful earthquakes occur at plate collision (or subduction) zones at convergent plate boundaries. An official website of the United States government. Convergent boundaries , where two plates are moving toward each other, are of three types, depending on the type of crust present on either side of the boundary oceanic or continental . In Mexico, a combinatiion of divergent and transform plate boundary motion is opening the Gulf of California, causing the Baja Peninsula to separate from the rest of Mexico. 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 1964 Alaska Earthquake and Tsunami lecture by George Plafker, USGS Geologist Emeritus. The U.S. Army Corps of Engineers spent about $110 million dollars repairing infrastructure, rebuilding communities, and clearing debris. In some cases, however, a convergent plate boundary can result in one tectonic plate diving underneath another. URL: https://pubs.usgs.gov/pp/0543i/
The earthquake triggered a swell of devastating tsunamis, landslides and submarine slumps which caused massive property damage and loss of life. The fissure shown here is about 1.5 inches wide. uplift A upward shift in some section of Earths surface due to tectonic activity along a fault. IRIS webpage dedicated to George Plafker, a USGS field geologist noted for his studies of subduction-zone and backarc thrust earthquakes. Afterward, the roots daily bathing for hours each day in salt water killed these trees. As you slide your hands laterally past one another, a broad zone of shearing develops as several card faces slip. Why do earthquakes usually occur at plate boundaries? As bad as the tremors were, the worst was yet to come. SSAs 2014 Annual Meeting will provide a stimulating exchange of research on a wide range of topics with colleagues from all over the world. The Aleutian Trench (or Aleutian Trough) is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands.The trench extends for 3,400 kilometres (2,100 mi) from a triple junction in the west with the Ulakhan Fault and the northern end of the Kuril-Kamchatka Trench, to a junction with the northern end of the Queen Charlotte . This vehicle illustrates the force of the tsunami waves that had struck this truck, which had been 32 feet (9.8 meters) above sea level at the time of the quake. They washed away everything in their immediate path buildings, docks and people. First posted September 10, 2012 Revised August 8, 2013, For additional information:
Read personal accounts of the earthquake and submit your own story. Summary of the earthquakes cause and effects from the Alaska Earthquake Information Center. In that one quake, it was the first time you could actually see plate motion in action. Subduction zones usually have a deep trench along the top. Where do earthquakes happen besides plate boundaries? But its interesting to note that this region is so heavily populated because of the same tectonic forces that sometimes shake it up with such violent consequences during earthquakes. Document ID 19990116704 Document Type Other The lithosphere is relatively rigid and is broken into slowly moving tectonic plates.
Geologists call plate tectonics a unifying theory. Thats because it explains practically everything about Earths crust. As the mid-ocean ridge separating the Farallon and Pacific Plates entered the subduction zone, the Farallon Plate separated into the Juan de Fuca and Cocos Plates. This pattern has since been seen at other subduction zones. You can now see under the house to the yard beyond (center right of photo). Like a jigsaw puzzle, Earths lithosphere is divided into interlocking pieces, called plates. Downtown Anchorage had the most property damage mainly due to immense landslides, one of which dropped the business district nine feet. The Ring of Fire is the most seismically and volcanically active zone in the world. For western California, each slipping card face would be a fault surface. Most seismic activity occurs at three types of plate boundariesdivergent, convergent, and transform. The plate boundary is a broad zone of deformation with a width of about 60 miles (100 kilometers). A transform plate boundary developed where the Pacific Plate was in contact with the North American Plate and the volcanism ceased in central California. The 1964 Alaska earthquake, the strongest earthquake ever recorded in North America, struck Alaskas Prince William Sound, about 74 miles southeast of Anchorage. 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. What Can the Ocean Floor Tell Us About Tsunamis? 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. Thousands of strong aftershocks continued for weeks after the earthquake, some measuring greater than magnitude 6.2. Modified from Earth: Portrait of a Planet, by S. Marshak, 2001, W. W. Norton & Comp., New York. Tsunamis trek traced in the sky. Science News for Students. Earthquake history, photos, videos, and more from the Alaska Division of Homeland Security & Emergency Management. It effortlessly toppled telephone poles, buckled railroad tracks, split roads in half, uprooted buildings, cars and docks and tore homes apart. Parks in the Sierra Nevada, including Yosemite, Kings Canyon, and Sequoia national parks, contain granite-type rocks that cooled within magma chambers beneath ancient subduction zone volcanoes. The town of Valdez was originally built on sand and gravel. 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. After wreaking havoc on southeastern Alaskan coastal towns that had already endured local tsunamis, the tectonic tsunami made its way to British Columbia where it ravaged small villages along the coastline near Vancouver. Off the coast of Alaska lies the Aleutian subduction zone-a 2,500 mile long convergent plate boundary where the Pacific Plate subducts under the North American Plate at a rate of 6-7 cm/yr. When the earthquake hit, the ground underlying the road shimmied, fissured and then split apart. The sequence begins shortly after the last earthquake. One of many trees damaged by quake impacts. There, in California, that motion causes earthquakes along the infamous San Andreas Fault. They tend to subtly creep along. USGS published the results of investigations of the Alaska earthquake of March 27, 1964 in a series of six Professional Papers. It was the first time we had physical proof of plate tectonics, concludes Mike West.
But Plafker saw it first, there in Alaska. Though this hazardous event developed the moniker of the Great Alaska Earthquake, it was actually the ensuing tsunamis that did the greatest damage and took the most lives. Listing total number of features into an ArcGIS Online feature pop-up, Convergent boundaries: where two plates are colliding. Is earthquake a result of plate tectonics? Tsunamis caused loss of life, extensive flooding, and damaged harbors along the North American Pacific Northwest coast. CHISChannel Islands National Park, California [, CABRCabrillo National Monument, California[, GOGAGolden Gate National Recreation Area, California[, PINNPinnacles National Monument, California[, POREPoint Reyes National Seashore, California[, SAMOSanta Monica Mountains National Recreation Area, California[, BUISBuck Island Reef National Monument, U.S. Virgin Islands[, VIISVirgin Islands National Park, U.S. Virgin Islands[.
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