Plate Tectonics

Plate tectonic activity is being observed presently on a historic timescale, especially in the form of volcanic eruptions and earthquakes, but, as with many large-scale Earth science phenomena, it is hard to appreciate the process within the short span of human history, particularly during the small part of history during which we've been keeping records and mapping tectonic activity. For this reason, an Earth history approach complements the traditional process-oriented approach of physical geology courses.

• Modern geography: Our oceans, continents, and mountains are all direct products of plate tectonics, and most other large features, such as big rivers, are indirect results.
• Earth hazards: Active volcanoes and earthquake-prone areas can be monitored in the present day, but an Earth history approach provides a longer baseline from which to make predictions. For example, if a glaciated volcano looms over a human community, we need to examine the deposits on and around the mountain to determine the paths taken by lahars (dangerous mud flows) during the last eruption, and avoid building there, as those paths are likely to carry lahars again when the volcano next erupts.
• Mineral resources: Many valuable minerals and useful rocks are the products of intrusive magmas, and their abundances and distributions are determined by past plate-tectonic activities.
• Outgassing: Even today, major volcanic eruptions disrupt weather for years at a time. Previous cold years are often visible in lake sediment records, as are volcanic ash layers. Over the long term, plate tectonics has been the major contributor of gases to the atmosphere and plays an important role in determining its composition.

One example of a course written around the plate tectonics theme is Processes and Concepts of Geology ( This site may be offline. ) at Wooster College, which emphasizes the development of the solid Earth.

Resources

Below are web resources specifically relevant to plate tectonics.

• 
  Annotated list of links to Plate Tectonics Visualizations
• ODSN Plate Tectonic Reconstruction Service. This is the Ocean Drilling Stratigraphic Network plate tectonic reconstruction service. In this section you can calculate plate tectonic reconstructions of any age back to 150 million years ago (or into the future!). Coordinates, such as age to be reconstructed, geographical boundaries, annotation interval, and gridline are entered by the site user, and a map is subsequently constructed. There is a reference section for information on how these maps are calculated and what data are used. An animation (330 kb) using 5 million year time steps is available too. If you are familiar with the features of this reconstruction system, there is also an Advanced Mapping System. There you can enter your own locations and plot them into paleogeographic maps. For users unfamiliar with geologic time, there is also a link to an on-line representation of a geological timescale. Links are also included to: a message board in which questions and comments can be posted, a tool to search the site, services offered by the Ocean Drilling Stratigraphic Network, and information on the Ocean Drilling Stratigraphic Network. ( This site may be offline. )
  
• Paleogeography Through Geologic Time. This website contains paleogeographic and plate tectonic reconstructions presented by Ron Blakey and Colorado Plateau Geosystems, Inc. Global images are available as mollewide (oval) globes, round globes, and rectangular maps in 27 time slices. More detailed regional maps are available for particular regions including Europe, North America, Colorado Plateau, and SW North America. (more info)
  
• Plate tectonics and the evolution of climate. Recent work has shown that climate, life, and tectonics interact in ways that are sometimes profound yet not obvious. Norman Sleep reviews two better understood terrestrial examples in this paper. First, the development of compressional orogens is strongly influenced by climate in that the extent of erosion determines whether high or low mountain ranges develop. Second, global geochemical processes are strongly influenced by tectonics and climate. For example, the build-up of oxygen in the Earth's atmosphere has been aided by deposit of organic-rich sediments in new ocean basins which prevented reaction of the oxygen with the reduced products of photosynthesis. The volume of the ocean depends on the extent to which water is subducted within the oceanic crust and sediments and on the extent which this water is returned to the surface at island arcs. Comparative planetology and further terrestrial studies are likely to yield additional examples of climatic, biological, and tectonic interaction. ( This site is likely no longer available. )