Each series of animations below contains text, graphics, animations, and videos to help teach Earth Science fundamentals.
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Subduction and Volcanoes COMING SOON!
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Teachable Moments (Disponible en Español)
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This simplified animation illustrates both the subduction-zone processes that lead to a "ghost forest" as well as the evidence that scientists collected to determine that the Pacific Northwest has had many great earthquakes and tsunamis in the past, and will again in the future. This is based on the work of Brian Atwater who published his findings in the book "The Orphan Tsunami of 1700" (USGS Professional Paper 1707).
How will 3 buildings, engineered equally, on different bedrock react to an earthquake?
Three buildings of different subsurface react differently to seismic waves. One important geologic factor that affects the level of ground shaking experienced from an earthquake is the presence of solid bedrock versus soft sediment. Soft soils amplify ground shaking. An example from the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake are included.
Tectonics & earthquakes of Alaska—More than just plate boundaries
Alaskan tectonics are dominated by the Pacific-North American plates. 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. This animation discusses the range of tectonic activity from megathrust earthquakes to accretion of geologic terranes.
GPS - Understanding Future Earthquakes in the Pacific Northwest
The Pacific Northwest subduction zone is a mirror-image setting to the pre March 11, 2011 earthquake off the Pacific coast of Tōhoku, Japan. By understanding the geologic processes off the Pacific Northwest coastline, we can prepare for a similar earthquake. This animation shows evidence for a major earthquake on January 26, 1700, and explains why another is forecast for the future.
Solomon Islands Regional Tectonics
The Solomon and Vanuatu Islands are subduction-related features caused by the subduction of the Indo-Australian Plate beneath the greater Pacific Plate. It is a seismically active area of frequent large earthquakes. This animation addresses both the subduction earthquakes, as well as a strike-slip component between the island chains. Basically the earthquakes are caused by the northeasterly movement of the Indo-Australian Plate as it dives beneath the Pacific Plate, but there are variations along the plate boundary.
Gulf of California tectonics
This animation depicts the evolution of the spreading ridge that marks the boundary between the Pacific and North American Tectonic Plates. The on-land part of this submarine spreading ridge extends into Baja California, Mexico and the Imperial Valley of California where it is transitioning from ridge-transform boundary to the continental boundary along the San Andreas fault zone.
A magnitude 8.7 earthquake occurred off the coast of Sumatra on April 11, 2012.
Why didn't it generate a tsunami as did the M9.0 earthquake in 2004? It turned out that it wasn’t a subduction- related earthquake, but was:
1) the largest strike-slip earthquake ever recorded
2) the largest intra-plate earthquake ever recorded,
3) the 10th largest earthquake of any kind ever recorded,
4) the most complex earthquake ever recorded.
What is a hotspot?
Two animations explore hotspot volcanism from both a plate-tectonic perspective and as a single-island history.
How do Earth's tectonic plates interact?
The static size of the Earth implies that crust must be destroyed at about the same rate it is being created. Plate Tectonics provides the mechanism used to recycle the Earth’s crust. Three boundary types are shown here. Video lecture discusses four basic plate boundaries.
Do subducting plates slide smoothly past one another?
Frictional stress builds up along a locked subduction-zone boundary. When that stress exceeds a critical value, a sudden failure occurs along the fault plane that can result in a "mega-thrust" earthquake releasing strain energy and radiating seismic waves. [See Divergent and Convergent Plate Boundaries for more-detailed depiction.
How is stress stored between tectonic plates?
Rock is deformed as it builds up strain in the plates at locked plate boundaries. Stress and strain increase along the contact until the friction is overcome and rock breaks. Video lecture showing demonstration of elastic rebound and brittle material using a yardstick.
Do faults break all at once, or in many short segments?
An asperity is an area on a fault that is stuck or locked. Scientists study areas along long fault zones that have not had earthquakes in a long time in order to determine where the next earthquake may occur; as long faults move, all areas of it will, at some point, become "unstuck" causing an earthquake relative the the size of the asperity that finally breaks.
What are the 4 basic classes of faults?
These animations of four faults are simplified examples of fault motion intended to show basic movement. Video lecture has classroom demonstration of faults and folds.
What happens when the crust is stretched?
Over most of the last 30 million years, movement of hot mantle beneath the region caused the surface to dome up and then partially collapse under its own weight, as it pulled apart. Currently, there is very little actual stretching going on, and the small amount is concentrated on the Western and Eastern edges of the Basin and Range.
GPS - Measuring Plate Motion
Highly accurate measurements made by the GPS system allow scientists to record millimeter-scale slip on faults that cannot ordinarily be measured. This record of land movement provides a critical key to understanding plate tectonics, plate-boundary interaction, volcano deformation, and more. Scientists have placed
hundreds of GPS stations across the Western U.S., in an attempt to learn more about the events building up to earthquakes along the San Andreas Fault system and the Cascadia Subduction Zone. On a narrower scale, they are also used to monitor deformation of active volcanoes.
A hypothetical cross section is studied by going back to the beginning to study its progressive geologic history. Why study rock relations? The earthquake potential of an area can be determined by studying the geologic history of the rock strata, both locally and regionally. Faults and folds record a probable earthquake history, so by studying the age of the rocks and their deformation we interpret past earthquakes and gain an understanding about the potential for future earthquakes.
Same earthquake, different stations; why do the seismograms look different?
One seismic station can give information about how far away the earthquake occurred, but yields little other information. The cartoonish amplified ground motions show the compressive P wave, the shearing S wave, and the rolling surface wave motions recorded by many stations with their characteristic seismograms. See also Travel-time curves.
How do we capture the motion of an earthquake?
Modern seismometers include 3 elements to determine the simultaneous movement in 3 directions: up-down, north-south,and east-west. Following an earthquake, the ground responds to P, S, and surface waves by moving in all directions. Each direction of movement gives information about the earthquake.
How do seismographs work?
Animations of a drum-style vertical seismograph stations that record vertical and horizontal motion. Although the drum-roll seismographs are used only for museum-type venues, they illustrate the basic principles of operation.
How do earthquakes reveal secrets of Earth's interior?
Seismic tomography is an imaging technique that uses seismic waves generated by earthquakes and explosions to create computer-generated, three-dimensional images of Earth's interior. Human CAT scans are often used as an analogy. Here we simplify things and make an Earth of uniform density with a slow zone that we image as a magma chamber.
Why do seismic waves travel a curving path through the Earth?
Seismic waves through the Earth follow the same laws of refraction and reflection as any other wave at interfaces. When they encounter boundaries between different media, the wave will react according to Snell’s law, and the angle of refraction across the boundary will depend on the velocity of the second media relative to the first. The
angle of reflection will be equal to the angle of incidence. Various material properties (i.e., elastic moduli) control the speed and attenuation of seismic waves. Before we answer the question posed in the title, we will step through animations increasing in complexity to introduce the concept of refraction.
How do P & S waves give evidence for a liquid outer core?
Most of the knowledge we have about Earth’s deep interior comes from the fact that seismic waves penetrate the Earth and are recorded on the other side. Simple P- and S-waves traverse the mantle by similar paths, but their behavior at the core-mantle boundary affect different “shadow zones” after ~103°. This set of
animations not only explores the two major seismic shadow zones, but also addresses the paths of some of the common phases of P and S waves caused by reflections and refractions of seismic waves caused by changes within the Earth.
Can an earthquake be compared to a drop of water on a pond?
This set of animations was inspired by a visualization of ground motion resulting from the February 21, 2008 M 6.0 earthquake that occurred near Wells, NV sending a ripple of ground motion to hundreds of seismic stations. To understand how seismic waves migrate away from an earthquake, we combined the animation at
lower right with the image of a faucet to illustrate the classic Earth science functional analogy; “Seismic waves radiate outward from an earthquake’s epicenter like ripples on water”. And then employed Dr. Geophysics to explain the Earth-science concepts in a nutshell.
Tsunamis Generated by Megathrust Earthquakes
Subduction-zone mega-thrust earthquakes, the most powerful earthquakes in the world, can produce tsunamis through a variety of structures that are missed by simple models including: fault boundary rupture, deformation of overlying plate, splay faults, and landslides during earthquakes. From a hazards viewpoint, it is critical to remember that tsunamis are multiple waves that often arrive on shore for many hours after the initial wave.
Earthquake Early Warning
An earthquake warning system uses existing seismic networks to detect moderate to large earthquakes. Computers, communications technology, and alarms are devised to notify the public while an earthquake is in progress.
1964 Great Alaska Earthquake
The 1964 Great Alaska Earthquake occurred on Good Friday, March 27th. It and rocked the state with strong ground shaking for 4.5 minutes. Liquefaction in and around Anchorage tore the land apart. At magnitude 9.2, it was the second largest quake ever recorded by seismometers. Only 9 people died from the earthquake, but 130 died from the subsequent tsunami; 10 as far away as Crescent City, CA. This animation shows the underlying causes of that subduction-zone mega-thrust earthquake, and tells how research done on the ground deformation shortly after the earthquake by George Pflaker, US Geological Survey, and colleagues contributed to confirmation of early theories of plate tectonics.
Earthquake Focal Mechanisms
Focal mechanisms are released after an earthquake to show what type of Earth movement produced the earthquake. These are typically shown using a so-called "beachball" diagram. They refer to the orientation of the fault plane that slipped and the slip vector, and are also called fault-plane solutions.
Understanding Moment Magnitude
The "moment magnitude" scale has replaced the Richter scale for large earthquakes. Scientists have developed far-more sensitive seismometers that, with faster computers, have enabled them to record & interpret a broader spectrum of seismic signals than was possible in the 1930's, when the Richter magnitude was developed. Find out what scientists learn from seismograms.
Animations about the New Madrid Seismic Zone & earthquakes of 1811–1812
This animation set commemorates the 200th anniversary of the most destructive earthquakes on the North American continent east of the Rockies that began suddenly on December 16th, 1811. Three >7.5 magnitude earthquakes, and countless aftershocks, caused damage over an area of 600,000 km2, and was felt over an area of 5 million km2.
Explore our suite of animations and interactive rollovers to learn about:
1) Eye-witness response to the events (from journals and newspaper accounts), including depicting how a river can run backwards as reported by witnesses. Scroll to see how growing U.S. populations would be affected if it occurred at any time after that.
2) Geology and geologic evolution of the region that is simplified and consolidated into easy to digest bits. From 500 million years ago to what we see now.
3) How seismologists analyze the subsurface and study evidence for past earthquakes to understand the tectonic history of a region.
How many different ways can an earthquake shake us?
An earthquake generates seismic waves that 1) penetrate the Earth as body waves (P & S) or 2) travel as surface waves (Love and Rayleigh). Each wave has a characteristic speed and style of motion. Here we exaggerate the motion by bouncing a building to show what sensitive instruments record as seismic waves arrive at the station.
Where do travel-time graphs come from?
A travel time curve is a graph of the time that it takes for seismic waves to travel from the epicenter of an earthquake seismograph stations varying distances away. The velocity of seismic waves through different materials yield information about Earth’s deep interior.
How can you model earthquakes in the classroom?
This block-and-sandpaper model can be used to teach the concept of elastic rebound and how energy is stored and released. Earthquakes can provide a useful context for teaching or reviewing many basic physics concepts, such as sliding and static friction, forms of energy and conversion from one form to another, and the elastic properties of materials.
Seismograph stations don't just record earthquakes; they record anything that shakes the instrument. These animations show the growth of seismograms from a variety of ground-shaking events. When the ground is jarred energy is released in the form of seismic waves that radiate from the source source in all directions. The
different types of energy waves shake the ground in different ways and travel through the earth at different velocities. Seismologists are trained to distinguish between events. The animations in this set were done in collaboration with the US Geological Survey and the Mount St. Helens Institute in recognition of the 30th Anniversary of the
1980 Mount St. Helens eruption.
Precursory seismicity, deformation of the crater floor and the lava dome, and, to a lesser extent, gas emissions provided telltale evidence of forthcoming eruptions, which is why we selected these three methods for our first volcano monitoring animations. The animations in this set were done in collaboration with the
US Geological Survey & Mount St. Helens Institute in recognition of the 30th Anniversary of the 1980 Mount St. Helens eruption.