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Then suddenly, it pops open. mantle The thick layer of the Earth beneath the crust. 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. Earthquakes - General Interest Publication - USGS It was the largest U.S. earthquake ever recorded, and a turning point in earth science. The San Andreas Fault and Queen Charlotte Fault are transform plate boundaries developing where the Pacific Plate moves northward past the North American Plate. 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. Photo courtesy of Robert J. Lillie. In places, the waves towered as high as a 20-story building. Society for Science & the Public 20002023. Downtown Anchorage had the most property damage mainly due to immense landslides, one of which dropped the business district nine feet. As the ground fractured, the trunk experienced extreme tension and eventually split. tsunami One or many long, high sea waves caused by an earthquake, submarine landslide or other disturbance. The broad zone of shearing at a transform plate boundary includes masses of rock displaced tens to hundreds of miles, shallow earthquakes, and a landscape consisting of long ridges separated by narrow valleys. They were scouting for patterns. in that one quake, it was the first time that you could actually see plate motion in action. She now estimates that it takes at least 500 years of plate motion to set the stage for such big earthquakes. Farther to the south, the Pacific Plate slides past the North American Plate. Like many of the rocks that are caught up in the zone of transform motion between the Pacific and North American plates, the rocks at Channel Islands National Park were deformed as part of the accretionary wedge during earlier subduction of the Farallon Plate. This uplift attained a measured maximum on land of 38 feet in a northwest-trending narrow belt less than 10 miles wide that is exposed on Montague Island in southwestern Prince William Sound. Photo courtesy of the National Parks Conservation Association. The earthquake hit at 3:11 pm approximately 100 miles (160 km) off the coast of Chile . 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. Comparable horizontal movements are presumed to have affected those parts of the major zones of uplift and subsidence for which retriangulation data are unavailable. At this boundary, the Pacific Plate slides beneath the North American Plate, causing the majority of Alaskas earthquakes, including the 1964 earthquake. Adding TravelTime as Impedance in ArcGIS Network Analyst? Interplate earthquake - Wikipedia Point Reyes National Seashore, California. Why do earthquakes usually occur at plate boundaries? That will give you an idea of how fast the plates move relative to one anotherabout a fraction of an inch to a few inches per year! When two tectonic plates slide past each other, the place where they meet is a transform or lateral fault. It extends across the two zones from the chain of active volcanoes in the Aleutian Range and Wrangell Mountains probably to the Aleutian Trench axis. The plates move towards one another and this movement can cause earthquakes. Plate Tectonics and Our National ParksSite Index, Plate TectonicsThe Unifying Theory of Geology, Tectonic Settings of NPS SitesMaster List. Since neither plate is stronger than the other, they crumple and are pushed up. This Story map combines an interactive map with historic photos of the earthquake. What Can the Ocean Floor Tell Us About Tsunamis? 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. 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. But Alaskas 1964 Great Quake led to a huge leap in their understanding.