The Theory of Plate Tectonics The lithosphere is

The Theory of Plate Tectonics

ØThe lithosphere is divided into separate sections called plates. ØThe plates carry continents and ocean crust or both.

A Theory of Plate Motion u J. Tuzo Wilson, a Canadian scientist, combined sea floor spreading, Earth’s plates and continental drift into a single theory. u Scientific theory is a well tested concept that explains a wide range of observations. u Plate tectonics is a theory that states the pieces of Earth’s lithosphere are in constant slow motion driven by convection currents in the mantle.

u Plate Tectonic Theory explains the formation, movement, and subduction of Earth’s plates. PLATE BOUNDARIES: u The edges of different pieces of the lithosphere meet at lines called plate boundaries. u Faults- breaks in Earth’s crust, form at boundaries.

u. There three types of plate boundaries: Transform, Divergent, and Convergent.

Transform Boundaries u. A place where two plates slip by each other, moving in opposite directions. u Earthquakes occur at these boundaries.

Divergent Boundaries u The place where two plates move apart or diverge. u When a divergent boundary occurs on land a Rift Valley, a deep valley, occurs.

Convergent Boundary u The place where two plates come together, or converge. u When two plates collide, the plate that is most dense will sink beneath the other.

The Continents Slow Dance u. The plates move from about one to ten centimeters a year. u. The North American and the Eurasian plates move about 2. 5 cm. a year.