Plate Tectonics Notes

The Earth’s crust is broken into many sections. These sections are called
Lithospheric plates. The Lithosphere is the lower portion of the crust.

The lithosphere sits on top of the asthenosphere. The asthenosphere is the
upper portion of the mantle. The asthenosphere has a plastic-like
consistency.

The movement of these lithospheric plates is what we call Plate Tectonics.
What was once called the theory of continental drift, (where it was thought
that only the continents moved) is now the theory of plate tectonics where
it includes the sea floor moving, too.

The theory of continental drift (or plate tectonics) was first proposed by a
German scientist named Alfred Wegener (pronounced Vay-Guh-Ner).

Wegener’s theory was supported by Harry Hess. Hess was the scientist
that discovered the sea floor was spreading.

Other evidence for continental drift or plate tectonics was the puzzle-like fit
of the continents, fossils found in climates where they couldn’t possibly
have lived, and matching rock and ice patterns in mountain ranges

When all the continents were connected it was called Pangaea; this meant
supercontinent.

The lithospheric plates move because of convection currents in the mantle.
This is what causes the plate tectonics. The plates move VERY slowly,
approximately 2 or 3cm per year.

The area around each plate is called the plate boundary. Plates move in
different directions, and this causes three types of plate boundaries. The
three types are Divergent, Convergent, and Transform.

Divergent-plates move away from each other. At these boundaries you will
find sea-floor spreading, mid-ocean ridges, some volcanoes, and small
earthquakes

Convergent-plates move towards each other. Here you will find mountain
ranges, volcanoes, subduction zones, major earthquakes, and deep ocean
trenches.

Transform-plates slide past each other. Here you will find major
earthquakes.