Chapter 4: Plate Tectonics PowerPoint Review

Section 4.1 Earth’s Interior

Can you name Earth’s layers? The crust The mantle The outer core The inner core

The Crust Crust - a layer of rock that forms Earth’s outer skin This includes both dry land and ocean floor 2 Types of Crust continental crust -the crust that forms the continents (granite) oceanic crust-the crust beneath the ocean (basalt)

The mantle is made of three parts: Lithosphere - uppermost part of the mantle (rigid, hard layer) Asthenosphere - some what soft and can bend like plastic Lower mantle - solid layer beneath the asthenosphere

The Core Outer Core Molten metal made of iron and nickel The movement of the outer core creates Earth’s magnetic field. Inner Core A dense ball of solid material made of iron and nickel

Travel to Earth’s Interior…Impossible Heat Temperature increases 1° C for every 40 meters traveled Pressure Pressure increases as you move deeper into Earth’s interior

How Do We Know What’s Inside? Evidence from rock samples Drilling samples Volcanic eruptions blast rock to the surface Evidence from seismic waves Geologists study how they travel through Earth

Layers of the Earth

Section 4.2 Convection in the Mantle

There are three types of heat transfer: radiation, conduction and convection.

Radiation Radiation- the transfer of energy through space No direct contact with the heat source Sunlight

Conduction Conduction- heat transfer within a material or between materials that are touching A metal spoon heats up in a pot of boiling water

Convection Convection - heat transfer by movement within a fluid

Let’s take a look at heat transfer.

Section 4.3 Drifting Continents

Alfred Wegener Wegener’s hypothesis was that all the continents were once joined in a single landmass and have since drifted apart. Wegener’s evidence to support continental drift included the puzzle-like fit of the continents, similar mountain ranges, glacial deposits, coal belts, Glossopteris fossils as well as fossils from Mesosaurus and Lystrosaurus.

A Theory Rejected Since Wegener couldn’t explain the force that would move massive continents, his theory wasn’t accepted by the scientific community until after his death.

Section 4.4 Sea-Floor Spreading Old Sea-Floor New Sea-Floor

Mid-Ocean Ridge Mid-ocean ridge - an undersea mountain chain that is part of a long system of mountains that winds beneath Earth’s oceans. The ocean floor is mapped using sonar.

Evidence of Sea-Floor Spreading Molten material Magnetic stripes Drilling samples

How Subduction Happens Convection currents pull the ocean floor apart at mid-ocean ridges Magma rises and cools creating new sea-floor. Gravity pulls old, dense sea-floor down beneath the trench. Old sea-floor is recycled back into the mantle. Takes 200 million years!

Let’s see it in action.

Section 4.5 The Theory of Plate Tectonics

Plate Boundaries There are three kinds of plate boundaries: spreading boundaries, colliding boundaries, and sliding boundaries.

Most common type of boundary Spreading Boundaries AKA: divergent boundary Two plates move apart Ocean: mid-ocean ridge Land: rift valley Most common type of boundary

Colliding Boundary AKA: convergent boundary Occurs where two plates collide Three Types oceanic/oceanic oceanic/continental continental/continental

The Himalayas

Sliding Boundary AKA: transform boundary Occurs where two plates move past each other in opposite directions Crust is neither created nor destroyed San Andreas Fault

The End.