Plate Tectonics. Earth’s Interior Earth is made of layers Crust Upper Mantle (asthenosphere ) Mantle Outer Core Inner Core Scientists discovered these.

Plate Tectonics

Earth’s Interior

Earth is made of layersCrustUpper Mantle (asthenosphere)MantleOuter CoreInner Core

Scientists discovered theselayers using seismic waves from Earthquakes.

Lithosphere- Crust

Lithosphere is the outermost layer of the Earth

The Lithosphere (crust) is broken into sections called Tectonic Plates, these are sections (plates) of lithosphere that move around on the upper mantle (asthenosphere)

Types of Crust:1. Oceanic Crust- Basaltic Materials, Heavy and Dense2. Continental Crust- Granitic Materials, light and less

dense than oceanic crust

The thickness of the crust ranges from 5-60km thick depending on what type of crust. http://www.youtube.com/watch?NR=1&feature=fvwp&v=uGcDed4xVD4

Mantle and Asthenosphere

Has an upper layer called the Asthenosphere which is responsible for the movement of plates

Composed of mostly silicon, oxygen, magnesium and iron

Texture is plastic like which has the characteristic of a solid but flows like a liquid when under pressure

Approx 2885 km thickHas large convection currentsthat drive the movement of the plates

Inner and Outer Core

Outer Core:Liquid rock composed of Iron, Sulfur and

NickelApprox 2270 km thick

Inner Core:Solid dense rock composed of Iron and NickelPressure from the upper layers cause it to be

solid

Types of Plate Boundaries

1. Divergent- new crust is generated and the plates pull AWAY from each other

2. Convergent- Crust is being destroyed or uplifted and the plates move TOWARDS each other

3. Transform- where crust is neither created or destroyed and the plates that slide horizontally past each other

Divergent Boundaries

There are two types of Divergent Boundaries where the crustal plates are pulling away from each other

1. Oceanic-Oceanic- Mid Ocean Ridgeso This is responsible for Sea floor spreading

where new crust is being made as magma rises and cools in the mid ocean ridges

Divergent Boundaries Continued

2. Continental- Continental Divergent When a divergent boundary cuts through a piece of

land, the feature called a Rift Valley is formed. Example is Iceland where the North American and

Eurasian Plates are pulling apart and the African Rift Valley

Volcanoes are created in Rift Valleys as magma plumes up from the separation of the plates

http://www.youtube.com/watch?v=w7Y2R4KBwvo

Iceland

Convergent Boundaries

Convergent Boundaries-Two plates move toward each other pushing

together

Subduction Zone- zone where one plate subsides (goes underneath) another plate Responsible for active volcanism and deep subduction

earthquakes

There are 3 types of Convergent plate boundaries1. Oceanic-Continental convergence- subduction2. Oceanic-Oceanic convergence- subduction3. Continental-Continental convergence- minimal or

ancient subduction and uplifting of large mountains

Oceanic to Continental Convergence

When an oceanic plate collides with a continental plate, there is a Subduction Zone A volcanic arc is created inland 100-300km from the

coast Trenches are formed off the coast of a subduction

zone Oceanic Crust subducts under continental crust

because it is more dense http://www.youtube.com/watch?v=NbDqJy28hBw

Oceanic-Oceanic Convergence

When two oceanic plates converge there is a battle between basaltic crusts until one subducts Volcanic Island arcs are created 100-300km away

from the plate boundary – Example: Japan, Aleutian Islands

Trenches are created off the plate boundaryCleveland Volcano Aleutian Islands, Alaska

Continental-Continental Convergence

When two continental plates collide both are very buoyant and want to stay above each other. They battle towards each other but neither one subducts under the other Builds large mountain

chains with very tall mountains

No volcanoes because there is not any

subduction causing melting of the plates and rising magma

INDIA ASIA

INDIA ASIA

The ancient Himalayas were

volcanoes because as India was pushing

towards Asia, there was an ocean

between them. This caused a subduction

of ocean crust resulting in volcanoes.

Transform Boundary

Transform boundaries are where two plates slide past each other Usually a part of a system of

divergent or convergent boundaries

Example is the San Andreas Fault in California

Responsible for frequent shallow earthquakes

Hot Spots

There are several other volcanoes that are not created near a plate boundary but instead in the middle of a plate

They are created when a mantle plume is super heated by the core and burns through the crust building a volcano

In the case of an oceanic hotspot, the plate continues to move and the volcano moves off the hotspot, and becomes inactive and just an island. A new volcano will begin to form on the ocean floor and as it peaks above the ocean surface it will become the new active volcanic island in the chain

In the case of a continental hotspot, the caldera moves off the hotspot and when there is a new volcanic explosion, a new caldera forms in the chain

Examples of Hot Spots

1. Hawaiian Islands- The active and newest island is the big island of Hawaii, and the oldest inactive island is Kauai. Since the inactive volcanoes are no longer adding to the size of the island, the island will erode away over millions of years until it becomes a seamount where is no longer above the ocean surface.

2. Yellowstone- this is in the middle of a continent causing large scale eruptions that form calderas or collapsed volcanoes. The continental crust is too thick to produce tall standing volcanoes from a hotspot.

Pangaea

Present