Plate Tectonics
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Introduction
Plate tectonics is a relatively new theory that has revolutionized
the way geologists think about the Earth. According to the theory, the
surface of the Earth is broken into large plates. The size and position
of these plates change over time. The edges of these plates, where they
move against each other, are sites of intense geologic activity, such as
earthquakes, volcanoes, and mountain building. Plate tectonics is a
combination of two earlier ideas, continental drift and sea-floor
spreading. Continental drift is the movement of continents over the
Earth's surface and in their change in position relative to each other.
Sea-floor spreading is the creation of new oceanic crust at mid-ocean
ridges and movement of the crust away from the mid-ocean ridges.
The lesson starts with a description of the chemical and physical
layers of the Earth. Then the historical development of the plate
tectonic theory is described. The lesson concludes with descriptions of
the location and types of plate boundaries. This lesson is longer than
most . A concise classroom presentation might describe the layers of the
Earth, location of plate boundaries, and types of plate motion.
