EARTH’S MOVING SURFACE CHAPTER 4 LESSON 1 EARTH’S MOVING SURFACE

4.1 INFORMATION

PLATE TECTONICS 1 - Earth’s surface is broken into large, rigid pieces

PLATE TECTONICS 2 -The plates move with respect to each other

TECTONIC PLATES The pieces of Earth’s surface that move over Earth’s surface very slowly.

TECTONIC PLATES

TECTONIC PLATES Earth has 15 large tectonic plates, plus many smaller plates.

TECTONIC PLATES The motion of tectonic plates forms volcanoes and mountains and causes earthquakes.

CRUST Earth’s outermost layer

OCEANIC CRUST Crust under the oceans.

CONTINENTAL CRUST Crust under the continents.

LITHOSPHERE The crust and the uppermost part of the mantle

LITHOSPHERE

ASTHENOSPHERE The partially melted portion of the mantle below the lithosphere

ASTENOSPHERE The asthenosphere can bend more easily than the lithosphere because it is hotter than the lithosphere.

B. PLATE BOUNDARIES

RELATIVE MOTION Scientists describe the movement of a tectonic plate as relative motion

RELATIVE MOTION How it moves in relation to another plate.

RELATIVE MOTION The type of boundary between plates depends on the relative motion of the plates.

DIVERGENT BOUNDARY where two plates move away from each other.

DIVERGENT BOUNDARY As plates move apart, new crust forms between them.

DIVERGENT BOUNDARY

DIVERGENT BOUNDARY

CONVERGENT BOUNDARY where two plates move toward each other.

CONVERGENT BOUNDARY

CONVERGENT BOUNDARY

CONVERGENT BOUNDARY One plate can sometimes move under another plate.

SUBDUCTION when one tectonic plate moves under another tectonic plate

TRANSFORM BOUNDARY where two plates slide past each other.

3 TYPES OF BOUNDARIES

PLATE MOVEMENT Tectonic plates move so slowly that geologists could not measure their movement until the 20th century.

PLATE MOVEMENT New technology has determined that North America and Europe are separating from each other at an average rate of just 2.5 cm/y.

GPS The network of satellites that can be used to accurately measure the position of any point on Earth’s surface.

GPS Scientists can measure the speed and direction of plate movement by tracking

GPS About 200 million years ago, North America and Europe were part of a large continent called Pangaea

GPS when the plates moved apart, the Atlantic Ocean formed between the continents.

WHY PLATES MOVE

DENSITY The amount of matter per unit of volume

DENSITY Density = mass / volume How heavy it is divided by how much space it takes up

DENSITY When a fluid is heated, its molecules spread out and it becomes less dense.

DENSITY When fluids heat unevenly, the warmer, less- dense fluid rises, and the cooler, denser fluid sinks.

CONVECTION the circulation within fluids caused by differences in density and thermal energy.

CONVECTION Convection in the mantle can drag plates over Earth’s surface.

CONVECTION

SUBDUCTION Plates can also move as a result of subduction.

SUBDUCTION When two plates collide, one can subduct or sink into the hotter, less-dense mantle.

SUBDUCTION The sinking part of a plate pulls the rest of the plate along.