9.2 – Plate Tectonics

Do Now What are the 3 different plate boundaries?

Do Now What are the 3 different plate boundaries? Divergent Convergent Transform Fault

Key Words Lithosphere Asthenosphere Rigid

Vocab Words Convergent Boundary Divergent Boundary Plate Tectonics Transform Fault Boundary

Earth’s Major Plates According to the plate tectonics theory, the uppermost mantle, along with the overlaying crust, behaves as a strong, rigid layer. This layer is known as the lithosphere. The lithosphere is divided into segments called plates, which move and continually change shape and size. The Pacific Plate is the largest plate, covering most of the Pacific Ocean. Several of the large plates include an entire continent plus a large area of the seafloor. Very different from Wegner’s continental drift hypothesis, which proposed that the continents moved through the ocean floor, not with it. The outer shell lies over a weaker region in the mantle known as the asthenosphere.

Lithosphere & Asthenosphere

Earth’s Major Plates The lithospheric plates move relative to each other at a very slow rate that averages about 5 centimeters per year – about as fast as your fingernails grow. This movement is driven by convection currents within Earth. Hot material found deep in the mantle moves slowly upward by convection. At the same time, cooler, denser slabs of oceanic lithosphere descend into the mantle, setting Earth’s rigid shell into motion.

Types of Plates All major interactions among individual plates occur along their boundaries. Divergent Occur when two plates move apart, creating new seafloor. Convergent Occur when two plates move together, towards each other, destroying lithosphere. Transform Fault Occur when two plates slide past each other, lithosphere is neither created or destroyed.

Types of Plates

Earth’s Tectonic Plates

Group Challenge Question Some people predict that California will sink into the ocean. Does this fit with the theory of plate tectonics? EXPLAIN