The structure of the earth

Convection Currents 

Convection currents are the circular currents of heat in the mantle.

Plates float on the mantle beneath the Earth's surface. Convection currents cause the plates to move. This means some plates are moving apart and some plates are moving together. 

Oceanic and Continental crusts

Oceanic Crust

• Newer - most less than 200 million years old
• Denser
• Can sink
• Can be renewed and destroyed

Continental Crust

• Older - most over 1500 million years oils
• Less dense
• Cannot sink
• Cannot be renewed or destroyed 

Location of plates and margins

Plate Margin: Destructive - subduction

Direction of plate movement: When continental plates move together, the oceanic plate sinks under the continental 

Example: Philippines Plate

Plate Margin: Destrucutive - collision 

Direction of Plate Movement: Plates of continental crust meet head on and 'buckle' 

Example: Indo Australian plate and Eurasian plate

Plate Margin: Constructive 

Direction of Plate Movement: Plates move apart 

Example: Antarctic Plate and Pacific plate 

Plate Margin: Conservative

Direction of Plate Movement: Plates slide past each other moving in the same direction

Example: San Andreas Fault

Where is each plate margin located? 

Destructive: An example of a destructive plate margin is the Juan de Fuca Plate. The Juan de Fuca plate sub ducts beneath the North American plate off the coast of east america (near the state of Washington) The Nazca plate located in the Pacific Ocean, sub ducts beneath the South American Plate forming a destructive plate margin along the coast of South America (Pacific ocean). Furthermore, where the South American plate meets the Caribbean Plate it sub ducts beneath it. This plate margin is found in Puerto Rico. The indo Australian Plate is colliding with the Eurasian Plate near Japan and the east China sea. 

Constructive: An example of a constructive plate is the Mid - Atlantic Ridge. This constructive margin surfaces at the volcanic island of Iceland. The Mid Atlantic ridge is formed where the North America Plate is moving away from the Eurasian Plate in the Atlantic sea. A constructive plate margin is splitting eastern Africa away from the African continent.Additionally, the Indo Australian Plate is moving away from the Antarctic Plate forming a constructive plate boundary south of Australia in the southern Ocean. 

Conservative: An example of a conservative plate margin is the San Andreas Fault, located on the west Coast of North America in the pacific ocean. The San Andreas Fault is where the North American Plate and the Pacific Plate are moving in the same direction, but at different speeds.