Page 56 - Laboratory Manual in Physical Geology

On which tectonic plate do you live?

ALASKA

CANADA

NORTH AMERICAN PLATE

PACIFIC
OCEAN
Chicago
New York
UNITED STATES
PACIFIC PLATE Los Angeles
Los Angeles
Los Angeles
ATLANTIC
OCEAN
MEXICO
AFRICAN
CARIBBEAN PLATE
Sacramento PLATE
North COCOS
San Francisco American PLATE SOUTH
Plate AMERICAN PLATE
Fresno
Plate boundaries (indicated by red lines) are linear
zones of movement between the plates, identified by
their topography and abundant earthquakes.

Pacific For greater detail, earthquake data, and other
Plate Los Angeles regions, refer to the U.S. Geological Survey‘s,
Los Angeles
Los Angeles
Earthquake Hazards Program real-time map:
http://earthquake.usgs.gov/earthquakes/map/
San Diego
Tijuana

FIGURE 2.1 Lithospheric plates associated with North America. The plate boundaries are identified as linear zones of abundant

earthquakes; whereas the plates tend to have few concentrated zones of earthquake activity.
where magma rises up between plates that are spread- The Theory of Plate Tectonics has become a unifying
ing apart. The magma cools to form new rock on the theory of geology in the way that the Theory of Evolution
edges of both plates. Plates are destroyed along conver- unifies all elements of biology. It explains such things as
gent boundaries , where the edge of one plate subducts the origin and distribution of earthquakes and volcanoes,
(descend beneath the edge of another plate) back into how the main features of oceans and continents form, how

the mantle ( FIGURE 2.2 ). When the ocean edge of one continents seem to drift about, patterns in the distribution

plate s ubducts beneath the ocean edge of another, an of fossil and living organisms, and the origin and distribu-
island arc forms (like the Aleutian Islands of Alaska). tion of Earth materials and hazards. It ties together all of
When the ocean edge of one plate subducts beneath the the sub-disciplines of geology.
continental edge of another plate, then a mountainous
volcanic arc forms on the continent’s edge (as in the Calculating Rates—The Math You Need
Andes and Cascades Mountains). When the continental Several of the activities in this laboratory require you
edges of two plates converge, the crust of both plates to calculate rates. You can review and learn more about
crumples into large folds and merge to form a tall calculating rates (including practice problems) at this
mountain belt (like the Alpine-Himalayan Mountain site featuring The Math You Need, When
Belt) that is eventually destroyed by weathering and You Need It math tutorials for students
erosion of the mountains). Plates slide past one another in introductory geoscience courses:

along transform boundaries , where plates are neither http://serc.carleton.edu/mathyouneed/
created nor destroyed ( FIGURE 2.2 ). rates/index.html

Plate Tectonics and the Origin of Magma ■ 41