Where Are We Where Are We Going?Going?

Plate Tectonics and the Plate Tectonics and the Evidence Behind the TheoryEvidence Behind the Theory

Plate Tectonics and the Plate Tectonics and the Evidence Behind the TheoryEvidence Behind the Theory

As any good scientist would do, we'll begin by asking a few questions:– How did the mountains get there?– What caused the huge tsunami?– What causes some volcanoes to erupt

while others lay dormant?

These questions arise when we look around us and question what's going on.

What Happened Here?What Happened Here?

For example: Look at these pictures.

These pictures were taken near the San

Andreas Fault. What made the

rocks in the hillsides curve

like that?

And Here?And Here?

Continental DriftContinental Drift

This is caused by movement of the Earth's tectonic plates. The idea that the Earth has plates

of material that are actively moving around and changing the shape

of our planet was not articulated until 1912 by Alfred Wegener in what

is now known as the Theory of Continental

Drift.

•

Drifting???Drifting???

Wegener believed that these plates were once part of

one giant supercontinent, Pangaea, which broke apart and allowed the

continents to “drift.” Since then it has been

determined that the continents are not just

“drifting” but rather moving apart due to plate

tectonics. Wegener’s theory was, however,

instrumental in paving the way for the Theory of Plate

Tectonics.

•

Plate TectonicsPlate Tectonics

• The Theory of Plate Tectonics, as proposed by William Ewing and Harry Hess, states that the Earth’s outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another as they ride above the hotter, more mobile material below. (This Dynamic Earth, USGS, www.usgs.gov)

The Earth’s PlatesThe Earth’s Plates

What Evidence Do You Have?What Evidence Do You Have?

• •

In this lesson, we will look at the existing evidence for this theory. The evidence includes:– Fit of the Continents– Fossils– Rocks– Paleoclimatic Patterns– Paleomagnetic Patterns– Sea Floor Topography