PLATE TECTONICS,
a key to understanding fossils
Plate tectonics is the theory that all the continents of the earth were once united in a huge land
mass called Pangea.
Then the continents broke apart and began to drift on plates of the earth's lithosphere. People
have been posing this idea since the 4th century B.C.E., when Aristotle noticed that fossils of
marine animals could be found on the tops of mountains.
Many early scientists were puzzled when they found marine fossils on dry, and sometimes desert
land. Just how does a fossil of a 75-foot whale turn up on a hillside in Utah? Plate tectonics!
Over millions of years, the movement of these plates across the Earth's surface has caused
dramatic changes in appearance, climate, and habitation. There are trees in the Petrified Forest
National Park that were once forty feet under water! Plate tectonics is still happening today! The
continents still move approximately two centimeters every year.
One easy way to search for proof of plate tectonics is to look at a map. Notice that the western
shoreline of Africa and the eastern shoreline of South America fit together. These areas have
fossils in common even though in the present they are separated by thousands of miles of ocean.
Scientists also present evidence supporting plate tectonics by plotting the occurrence of
earthquakes and volcanoes. Most earthquakes happen along the boundaries of continental
plates.
The San Andreas Fault Zone in California is at the place where one plate slides along the edge
of another. The volcanic islands of Japan are created as one plate slides on top of another
(subducts).
Plate tectonics still occurs today and the earth is constantly being formed and changed. One
prediction for future plate movement is that the continents of North and South America, which
share a plate, will collide with the continental plate of Asia.
One early scientist, Albert Magnus, a 13th-century monk, discovered sea shells within rocks in
Paris, France. This evidence led Magnus to conclude that Paris was once engulfed by the sea.
Another such observation was made by Leonardo Da Vinci who discovered fish fossils in
Lombardy, Italy, and concluded that Italy was once also covered by water.
Modern scientists have concluded that much of the United States was once under water as well.
They believe that the tectonic plates have been drifting for millions of years.
Monkeyshines Fossil Trivia
How are fossils categorized?
Fossils are grouped by their age with reference to geological time scale. The fossil is identified by
biological classification, phylum (division in the animal kingdom), class, order, family, genus and
species.
Source: Monkeyshines on Health & Science, Jun2003 Fossils Issue, p4, 2p
Item: 3653963