This introduction to plate tectonics covers plates and boundaries, subduction zones, colliding continents, plumes, and earthquakes. There is also more advanced material on buoyancy, floating continents, and rates of isostasy; sedimentation, continental growth, rifts and creation of continental margins, passive and active margins, and island arcs and back-arc basins; continental collision, folding ... Full description.

This bulletin discusses the magnitude 7.9 earthquake that shook the islands of Tonga in May 2006. Topics include the tectonic setting of the islands, at the boundary of the Pacific and Australian plates, the frequent seismic activity at this location, how earthquakes are produced at subduction zones, and how they can reveal information about the Earth's interior. There is also information about the ... Full description.

Recordings on this site present 164 aftershocks as they were heard at one seismic recording station. They occurred after an earthquake with a magnitude of 6.2 beneath and near New Zealand. All events are heard in rapid sequence, without the true time intervals between them. The main shock was at a depth of 30 kilometers, 10 kilometers below the interface between the subducting Pacific Plate and the ... Full description.

This map of world seismicity illustrates earthquake data for the years 1991 through 1996. It is intended to provide a sense of the depth distribution of earthquakes. Plate boundaries are shown, along with diffuse regions of seismicity, such as in central Asia, and earthquake locations are color-coded to indicate the depths at which they occurred. In addition to the map, selected cross-sections of ... Full description.

Early evidence showing striking similarities between regions on opposite sides of vast oceans suggested that in Earth's distant past what are now separate continents may once have been connected. However, this evidence said nothing about how the continents could have moved to their present positions. This video shows how seafloor spreading creates new oceanic crust and how the crust is destroyed by ... Full description.

This demonstration models the manner in which the convection currents in the mantle of the Earth cause movement of the plates. Convection currents in the mantle were thought, for many years, to be solely responsible for plate tectonic movements, with the movement taking rocks down at destructive margins and new rocks forming when plates spread. It is now thought likely that there are three possible ... Full description.

On the Pacific Northwest an oceanic tectonic plate (Juan de Fuca) is being pulled and driven (subducted) beneath the North American continental plate. Earthquakes generated along that fault may produce local tsunamis. Local tsunamis are those generated by earthquakes near the coast. This site provides links to external webpages describing the physics behind a tsunami. Resources featured in the links ... Full description.

This resource provides general information about volcanoes. It illustrates the growth of a volcano, using Paricutin and Mt. St. Helens as examples of an active volcano and a lava dome. The terms extinct and dormant are also discussed. This site provides an explanation of why and how volcanoes form, zones of subduction, mid-ocean ridges, and hot spots. Deadly dangers associated with eruptions are discussed ... Full description.

This link takes you to the download page for Tanya Atwater's plate tectonics animations. Users must register before using the site, but it is free of charge. The site contains a series of QuickTime movies illustrates the movement and tectonic history of the Pacific-North America plate from 85 million years ago to present. The movies show the tectonic evolution of California, evolution of the San Andreas ... Full description.

This resource offers, among other things, a collection of journal entries from scientists reporting on their personal experiences of the volcanoes of Costa Rica. Reference sections include an introduction to volcanoes and Central America, the anatomy of subduction zones, the source of volatiles, sampling volatiles, recycling elements, and isotope geochemistry (geochemical tracers). There is a short ... Full description.