The theory of plate tectonics version 2.2 download

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Written by Edward J. Tarbuck and Frederick K. Lutgens , Illinois Central College. Illustrated by Dennis Tasa. Here are some of the fascinating interactive explorations you and your students will encounter:. Low Speed Version takes approximately 2.

Two scientific advances in the midth Century resulted in information critical to acceptance of continental drift and plate tectonic theory. First, the topography of the ocean floor was mapped in great detail during and after World War II. It was discovered that the floors of the ocean basins are not flat. A continuous mountain chain circumscribes the globe near the centers of oceans and, in places, the ocean floor descends abruptly into deep-sea trenches.

Second, a network of seismographs was installed around the world in the early s, to detect nuclear tests during the Cold War. As a result geologists could more precisely locate earthquakes and map the speed of seismic waves passing through various regions of the Earth.

Continents fit together along the edges of their continental shelves. Mid-ocean ridges and deep-sea trenches develop at the boundaries of the moving plates. Volcanic islands and seamounts develop where a plate moves over a stationary hotspot. The new earthquake data revealed three startling observations. First, earthquakes are not scattered throughout the oceans, but instead are confined to narrow, rather continuous bands.

The narrow zones of earthquakes outline the boundaries of moving plates. Second, only shallow earthquakes less than 40 miles; 70 kilometers deep occur where plates diverge along mid-ocean ridges, while earthquakes at deep-sea trenches extend downward to as deep as miles kilometers where plates converge.

It provides a means by which continents can drift apart. The plates of crust and stiff mantle lithosphere move on the softer mantle layer beneath asthenosphere. Lillie, New York, W. Norton and Company, pp. Most earthquakes and volcanoes occur where the moving plates interact along their boundaries, and at hotspots. Earthquakes, mountain building and volcanic activity occur mostly at the boundaries of the moving plates. Only shallow earthquakes occur where plates diverge at mid-ocean ridges, whereas earthquakes extend to great depth where plates converge at subduction zones.

Below is a map of the tectonic plates of the earth. The Earth has a dozen or so major plates and several minor plates. Plate Tectonics and Our National Parks. Divergent Plate Boundaries. Convergent Plate Boundaries. Transform Plate Boundaries.

Oceanic Hotspots. Continental Hotspots.