Plate Tectonics

Crust

• The crust is formed from continental and oceanic crust

• The crust covers the whole Earth

Convection currents

• The crust moves on convection currents formed from heat in the core.

convection currents

Pangea

• pangea into the future

Tectonic plates

• Earth is separated into 12 major tectonic plates. You are here

Plate Boundaries

• Where plates come together they form boundaries.

• There are three types of boundaries.1)Divergent2)Convergent3)Transform

Divergent Plate boundaries

• These boundaries exist where plates are spreading apart.

• As plates spread magma wells up from the mantle.

• New crust is formed.• Lots of volcanic activity and earthquakes.

Divergent plate boundary

Mid Atlantic Ridge

Mid Atlantic Ridge

Iceland

• Iceland sits right on the mid-atlantic ridge. • They live on a volcanic island.

As the plates continue to spreadwhat is going to happen?

Convergent Plate boundary

• At convergent boundaries plates are moving together.

• One plate moves under the other one. This is called subduction.

• The oceanic plate will subduct under the continental plate because it is less dense.

subduction

Formation of mountains

• Mountains• Formed at continental-continental plate

boundaries.

Pacific Northwest•Along Washington and Oregon coast.

This is why we have a lot of mountains volcanoes, and earthquakes

When the plate sticks, pressure builds up until it releases. This is an earthquake.

Subducting crust melts and rises to the surface

CO

Transform boundaries

• Large jagged edges are slipping past each other in a transform boundary.

• When the edges stick energy builds up, when it suddenly releases that is an earthquake.

Three types

• Shield• Cinder cone• Composite

Volcanoes

• Formed at divergent or convergent boundaries.

• Magma rises to the surface.• Carbon dioxide builds up pressure.• Pressure releases CO2, ash, lava, pyroclastic

clouds.

Shield Volcanoes

• Largest in the world

• Formed at divergent boundaries

• Slow moving magma builds walls gradually

• Hawaii

Mauna Loa, Hawaii largest volcano in the world

Cinder cone

• Smallest volcanoes• Formed from ash and

not lava• Usually less than 300-

400 feet tall• When they erupt they

force out gases, ash, and lava in tiny bits.

Composite volcano

Composite Volcanoes• pyroclastic flow• “pyro” means fire, “clastic”

means rock, so it is a cloud of rock, gas and fire.

• These flows can travel hundreds of miles an hour

• Most volcanoes on the ring of fire are composite volcanoes, a mix between cinder cones and shields.

• Most destructive eruptions

Lahar flow

• Lahars are caused by melting snow, ash, and mud.

• The mix makes the water have a consistency of wet concrete.

• Lahars can travel up to 70 mph.

Mt. St. Helen

• eruption of mt st helen

Hot spots

• The Earth’s crust is thin• In the middle of plates, magma might well up

and melt some of the rock.• These spots are called hot spots

Hawaii

• Hawaii is in the middle of the Pacific plate, not on a boundary

Yellowstone National Park

yellowstone supervolcano

man falls into volcano

Earthquakes

• When the crust shifts suddenly energy is released.

• The focus is the place in the Earth where the energy is first released.

• The epicenter is the point on Earth’s surface that is directly above the focus.

Faults

• Breaks in the crust of the Earth.• Can form where plates meet and away from

the edge of a plate.• Faults

How energy travels

• When rock breaks within Earth’s lithosphere it releases energy that is carried by seismic waves.

• Primary waves (p-waves)Underground, travel fast through the Earth,

similar to sound waves.

Seismic waves

• Secondary wavesUnderground, travel more slowly than p-waves. Can only travel through solids.• Surface wavesTravel along the surface in a rolling motion.

How do we know the structure of the Earth? refraction

Measuring Earthquakes

• Magnitude: measurement of energy released at the source.

• Intensity: amount of shaking and damage.• Richter Scale: Used to compare the sizes of

earthquakes.• Seismograph: detects earthquakes and

measures their magnitudes.

Richter scale

Earthquake video

• Tsunami• How earthquakes form• What caused Japan's tsunami?• scientist and lava lake