1. Plate Tectonics

2. Earth’s Interior Earth is made of layers Crust
Upper Mantle (asthenosphere)
Mantle
Outer Core
Inner Core
Scientists discovered these
layers using seismic waves
from Earthquakes.

3. Crust- Lithosphere Outermost layer of the Earth
Broken into Tectonic Plates that move around on the upper mantle (asthenosphere)
Types of Crust:
Oceanic Crust- Basaltic Materials, Heavy and Dense
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. Oceanic crust is thinner and continental crust is thicker especially in mountainous regions.

4. 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 thick
Has large convection currents
that drive the movement of the
plates

5. Inner and Outer Core Outer Core:
Liquid rock composed of Iron, Sulfur and Nickel
Approx 2270 km thick
Inner Core:
Solid dense rock composed of Iron and Nickel
Pressure from the upper layers cause it to be solid

6. Types of Plate Boundaries
Divergent- new crust is generated and the plates pull AWAY from each other
Convergent- Crust is being destroyed or uplifted and the plates move TOWARDS each other
Transform- where crust is neither created or destroyed and the plates that slide horizontally past each other

7. Divergent Boundaries
There are two types of Divergent Boundaries where the crustal plates are pulling away from each other
Oceanic-Oceanic- Mid Ocean Ridges
This is responsible for Sea floor spreading where new crust is being made as magma rises and cools in the mid ocean ridges

8. Divergent Boundaries Continued
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
Iceland

9. 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 boundaries
Oceanic-Continental convergence- subduction
Oceanic-Oceanic convergence- subduction
Continental-Continental convergence- minimal or ancient subduction and uplifting of large mountains

10. Oceanic to Continental Convergence
When an oceanic plate collides with a continental plate, there is a Subduction Zone
A volcanic arc is created inland km from the coast
Trenches are formed off the coast of a subduction zone
Oceanic Crust subducts under continental crust because it is more dense

11. Oceanic-Oceanic Convergence
When two oceanic plates converge there is a battle between basaltic crusts until one subducts
Volcanic Island arcs are created km away from the plate boundary – Example: Japan, Aleutian Islands
Trenches are created off the plate boundary
Cleveland Volcano Aleutian Islands, Alaska

12. 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
ASIA
INDIA
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.
ASIA
INDIA

13. 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

14. 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

15. Examples of Hot Spots
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.
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.

16. Pangaea

17. Present