Grade 8: Plate Tectonics (with pictures)

Big Idea: Earth's crust consists of _________ and ____________ tectonic plates that move relative each other.

major, minor

crust

The thin and solid outermost layer of the Earth above the mantle

mantle

the layer of rock between the earth's crust and core

core

the center part of the Earth below the mantle

lithosphere

the solid, outer layer of the earth that consists of the crust and the rigid upper part of the mantle

asthenosphere

the soft layer of the mantle on which the lithosphere floats

mesosphere

The strong, lower part of the mantle between the asthenosphere and the outer core

tectonic plates

a block of lithosphere that consists of the crust and the rigid, outermost part of the mantle

plate tectonics theory and convection

The theory that describes the movement pieces of the Earth's continents are in constant motion, driven by convection currents in the mantle.

3 possible driving forces of plate tectonics

ridge push, convection, slab pull

continental drift

the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

sea-floor spreading

the process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies; occurs at mid-ocean ridges; magnetic reversals are evidence that new crust is being formed.

convergent boundary

boundary of two tectonic plates moving together (collide)

divergent boundary

the boundary between two tectonic plates that are moving away from each other (divide)

rift zone

an area of deep cracks that forms between two tectonic plates that are pulling away from each other (divergent)

transform boundary

the boundary between tectonic plates that are sliding past each other horizontally

Compression (plate boundary)

stress that occurs when forces act to squeeze an object or tectonic plage

Tension (plate boundary)

stress that occurs when forces act to stretch an object or tectonic plate

folding

the bending of rock layers due to stress

fault

a break in a body of rock along which one block slides relative to another

normal fault

a fault in which the head wall moves down relative to the foot wall caused by tension

reverse fault

A fault in which the head wall moves up relative to the foot wall caused by compression

strike-slip fault

opposing forces cause rock to break and slide past each other with little vertical movement

volcanic mountains

mountains that form when magma erupts onto Earth's surface.

tectonic boundary

area where two tectonic plates meet; this is where most earthquakes and volcanoes occur

magma

molten rock found deep within the Earth

hot spots

areas of hot magma that stays stationary while plates slide over them, often leaving a chain of volcanic eruptions; examples are the chain of Hawaiian islands and Yellowstone

magnetic reversals

when Earth's magnetic poles change places; this is found at mid-ocean ridges- as the liquid rock cools the magnetic minerals "lock in" the magnetic polarity; this provides evidence for sea-floor spreading and plate tectonics.

monocline fold

a fold with one side up

anticline fold

-bends upward (upside down U shape); outside edges down and center up; like a hill

syncline fold

-bends downward (U shape); outside edges up and center down.

uplift

the raising of Earth's crust to higher elevations

subsidence

the sinking of Earth's crust to lower elevations

3 main types of volcanoes

shield, stratovolcano, and cinder cone

earthquakes

Occur at the edges of tectonic plates; Elastic rebound is the direct cause of earthquakes.

convergent boundary-surface features and boundaries*

mountain ranges, volcanoes, ocean trenches, reverse faults, folding, earthquakes, island arcs

divergent boundary - surface features and hazards

mid-ocean ridges, rift zones, normal faulting, volcanoes, new rock

transform boundary - surface features and hazards

extreme faulting usually strike-slip, violent earthquakes, offset land features

continent-continent convergence

When two continents converge, their similar densities make it difficult to force either of them to sink. This causes folding and reverse faults. An example is the Indian Plate slamming into the Eurasian Plate creating the Himalayan Mountains (tallest mountains).

"Ring of Fire"

A major belt of volcanoes that rims the Pacific Ocean; this is caused by subduction of oceanic plates beneath lighter continental plates. Most of the Earth's volcanoes are located around the Pacific Ring of Fire because that the location of most of the Earth's subduction zones.