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Plate
Tectonics is a set ofrelated concepts that describe how the Earth works. Plate
tectonics explains what happens when two continents run into each other, how
and why parts of the Earth's surface are ripping apart, and why volcanoes
and earthquakes occur where they do. The correlation of phenomena in space
or in time often provides the first clue to a scientist that the features
may be related by a causal mechanism as well.If the causal relationship can
be discovered, then we advance our understanding of how the world works. The
spatial relationship between the coastlines of Africa and South America was
one that Alfred Wegener observed, and used in support of his Continental Drift
hypothesis (Wegener, 1915 (German), 1966 (English translation)).He reconstructed
the shapes of the coastlines, moving South America and Africa adjacent to
each other, along with North America and Europe-indeed he connected 
all
the continents into a single "supercontinent" that he named Pangea.
Although Wegener uncovered a largenumber of intriguing spatial correlations-between
fossil groups on the southern hemisphere continents, between the structure
and geology of mountain ranges in Europe and North America, across glaciated
regions of India, Australia and Africa-his lack of a causal mechanism caused
his extraordinary proposal to be rejected by the scientific community.
Twenty
five years after Wegener's death, scientists-equipped with new instrumentation
originally designed for military use in World War II-began a much more thorough
examination of the Earth's geological and geophysical features. The new instruments
(SONAR, gravimeters, magnetometers, mass spectrometers) revealed even more
unusual spatial correlations, and began to hint at their causal connections.
In this section students will examine a series of data sets that show unusual spatial relationships. Many of these data are the same as those used by the original scientists who developed the ideas of plate tectonics. By mapping the position of geologic features of different types we can draw a number of conclusions about the relationships between geologic phenomena, and explore the processes that contribute to the dynamic behavior of the Earth's surface.
The assignments described here allow students to make their own maps of geological and geophysical features, to examine spatial correlations, and to draw inferences about the nature of plate tectonics. Students have the ability to assemble data just as scientists do, to formulate hypotheses, test them, and draw their own conclusions. While it is the rare student who may derive a truly new discovery from these data sets, it is the process of discovery-of learning from first-hand observation and critical thinking-that helps students gain a deeper understanding of Earth processes.
Discovery Topics > Plate Tectonics <
