Lecture 5 - Why does the Earth Change? Plate Tectonics and Climate Change

What was the Continental Drift Hypothesis?

Proposed by Alfred Wegner in 1915 - World once was Pangea, continents drifted apart.

Previous idea about the continents

Land bridge theory

What is the continental drift called today?

Plate Tectonics

What was Pangea?

“All land”, one connected continent

5 lines of evidence for plate tectonics

1) Geographic Fit

2) Fossils span continents

3) Rock types identical at edges of continents

4) Glacial features in warmer places

5) Seafloor Spreading

Seafloor Spreading

Two plates diverge creating new land because of magma chambers between plates. Magnetic reversal over time is proof.

How do earthquakes and volcanoes relate to plate tectonics?

They are caused by shifting plates at plate boundaries

Divergent plates:

Spreading apart

Convergent plates:

Coming together

Transform plates:

Passing by each other

What tectonic plate does Maine sit on?

The North American plate

What is the pattern of climate over the past several million years

100,000 year cycles of warm, to, cold, to warm, back to cold, etc.

What 3 factors control long-term global temperature?

1) Insolation

2) Greenhouse Gases

3) Albedo

What are the 3 Milankovitch Cycles?

1) Earth’s Orbit around the sun (oval to round to oval to round)

2) Earth’s tilt (more tilted less tilted more tilted)

3) Earth’s wobble (more wobble to less wobble)

What is the Greenhouse Effect?

More greenhouse gasses=more retention of heat

What is Albedo?

How much heat is reflected or retained