This reference provides an introduction to the geoid, the equipotential surface of the Earth's gravity field which best fits global mean sea level. There is a narrative of early attempts to describe the geoid, and schematic diagrams showing the geoid and its relationship to Earth's crust, local mean sea level, orthometric heights, and local dynamic ocean topography. Full description.

In this activity, students learn about the different types of seismic waves in an environment they can control. Using an interactive, online wave generator, they will study P waves, S waves, Love waves, and Rayleigh waves, and examine a combination of P and S waves that crudely simulates the wave motion experienced during an earthquake. A tutorial is provided to show how the wave generator is used. ... Full description.

These animations show students the nature of particle motion in longitudinal and transverse waves, and how they combine to form the more complex motions seen in water waves and Rayleigh surface waves, a type seen in earthquakes. The animations are accompanied by written explanations. Full description.

These animations show how various types of waves are propagated during an earthquake. Users can see how P-waves travel at the surface, how they are reflected and refracted as they travel further from their source, and how multiple reflections can combine to create a surface wave. There is also an animation showing how S-waves were amplified by reflections from the Moho during the 1989 Loma Prieta ... Full description.

This animation shows how P-waves (primary, or compressional, waves) travel through a Slinky toy. It is accompanied by a brief written explanation that describes some of the properties of P-waves and how they are generated in a real Slinky. Full description.

This tutorial instructs students on how to create simulations of P- and S-waves by using simple materials; a Slinky toy and a length of rope. Full description.

This animation shows how S-waves (secondary, or shear, waves) travel through a Slinky toy. It is accompanied by a brief written explanation that describes some of the properties of S-waves and how they are generated in a real Slinky. Full description.

By examining GPS time series plots from stations on opposing sides of the San Andreas Fault, students will determine the relative movement between the two stations. They can then apply this to calculate the time it will take for Los Angeles to reach San Francisco. Background information and necessary equations are provided. There is also a link provided to print out the time series. Full description.

This portal offers access to data on recent earthquakes and volcanic activity in the Pacific Northwest, particularly Washington and Oregon. Materials presented here include catalogs and data from previous earthquakes, including historic events, information on earthquake hazards and research activities of the PNSN, and links to news articles, frequently asked questions, and educational materials. Full description.

The Geomagnetic and Solar Activity Forecast Service is a service of the British Geological Survey. It provides data for daily local, global and solar geomagenetic activity. Data includes information projected up to 27 days ahead using a linear prediction method, up to 3 days ahead using a non-linear prediction method and smoothed monthly solar and geomagnetic activity for the next solar cycle using ... Full description.