Plate Tectonics Wrap-Up

Fit of the Continents

Paleoclimate & Glaciers

Ancient climatic zones and large glaciated areas

match up.

Fossil Record

Glossopteris Fossils

These seeds are very large and do not float in water, so

how could they have survived transport

to all these different continents?

Ancient mountain chains match up.

Bathymetry

Magnetic Anomalies in Seafloor

Earthquakes

Volcanoes

Lithospheric Plates

• Fig 4.3

The Theory of Plate TectonicsThe continents are riding along on tectonic plates,

which move across the Earth’s surface driven by mantle convection (the very slow “boiling” of the mantle beneath the crust).

Three types of plate boundaries

• Divergent – plates are moving apart from one another. – Ex: Mid-Ocean Ridges

• Convergent – plates are colliding with one another. – Ex: Nazca plate and South American plate pushing up the

Andes. – Ex: Indian plate and Asian plate colliding to form the

Himalayas

• Transform – plates are sliding past one another– Ex: Pacific plate and North American plate moving past one

another along the San Andreas Fault

Divergent boundaries

Hot mantle material rises up and causes the crust to thin and move apart.

Mainly found in the middle of oceans • shallow, weak earthquakes• very few volcanoes• high topography on the sea floor• the youngest sea floor crust

Mid-Atlantic Rift in Iceland

Convergent boundaries•Deep trench on ocean side and then high elevations toward continent.•Shallow to deep earthquakes as you move toward continent.•Arc of volcanoes on the continent side.•No age relationship

Convergent boundariesOcean crust always moves below continental crust because ocean rocks (basalts) are more dense than continental rocks (granites).

Transform Boundaries

Lots of shallow earthquakes (some very strong) dispersed along the boundary.

San Andreas Fault