Plate Tectonics Review 2-5-21

The lithosphere plates were converging ( coming together) and the plate on the left subducted ( more dense oceanic crust) under the less dense continental crust.

Two plates sliding past each other ( causing earthquakes)

What do seismic waves tell us?

Seismic waves tell us that the Earth's interior consists of a series of concentric shells, with a thin outer crust, a mantle, a liquid outer core, and a solid inner core. A  seismograph, is a device that geologists use to measure and record seismic waves. By studying these recordings, scientists can map the earth's interior, and they can measure or locate earthquakes and other ground motions.

The liquid outer core of the Earth is locates above the Earth's solid inner core and below the crust and the mantle

Magma ( liquid rock) rise up from the mantle from convection currents and can cause the volcano to erupt.

Draw this picture

A few large regional earthquakes (greater than magnitude 6) are considered to be related to a subsequent eruption or to some type of unrest at a nearby volcano. ... Enough "eruptible" magma within the volcanic system. Significant pressure within the magma storage region

Seafloor spreading is a geologic process in which tectonic plates—large slabs of Earth's lithosphere—split apart from each other. Seafloor spreading and other tectonic activity processes are the result of mantle convection. Mantle convection is the slow, churning motion of Earth's mantle, new oceanic crust is created

Mid-Ocean Ridges

Used to think the ocean floor was flat. Harry Hess used sonar to discover there were mountain ranges, canyons, and deep trenches. Long system of mid-ocean ridges extends around the world.

Expanding Seafloor

Ocean floor is made from cooling lava. Lava comes from the MANTLE at the ridge and cools. As more lava erupts, the crust moves away from the ridge. This is called SEAFLOOR SPREADING

What about the Old Ocean Floor?

Old ocean floor moves edges of continents Trenches push ocean floor back to mantle RECYCLED! SUBDUCTION: crust pushing down into the mantle

Continental Drift

Hess's idea of sea floor spreading proved Alfred Wegener's idea of CONTINENTAL DRIFT. 1960 - THEORY OF PLATE TECTONICS The Earth's LITHOSPHERE or CRUST is divided into tectonic plates.