Each series of animations below contains text, graphics, animations, and videos to help teach Earth Science fundamentals. Please click the link or scroll down to view the available animations. After viewing the animations, also check out our videos page.
Animations
Plate Tectonics Earth Structure
Divergent and Convergent Plate Boundaries Multi-Station Seismic Network
Elastic Rebound in a Subduction Zone 3-Component Seismograph
Elastic Rebound in a Strike-slip Fault Seismograph
Earthquake Faults Refraction NEW!
Basin and Range NEW!
Earthquakes
Seismic Wave Behavior- Effect on Buildings
Elastic Rebound Model- Block and Sandpaper
Seismic Signatures COMING MAY 2010!
Interactive Animations
Teachable Moments (Disponible en Español)
Animations
Plate Tectonics
Divergent and Convergent Plate Boundaries
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.
Elastic Rebound in a Subduction Zone
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.
Elastic Rebound on a Strike-slip Fault
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.
Asperities
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.
Earthquake 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.
Basin and Range
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.
Earth Structure
Multi-station Seismic Network
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.
3-Component Seismograph
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.
Seismograph
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.
Seismic Tomography
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.
Refraction
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.
Earthquakes
Seismic Wave Behavior: Effect on Buildings
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.
Travel-time Curves
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.
Elastic Rebound Model - Block and Sandpaper
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.
