Earth Structure Quick review • Earth is made up of four main layers; crust, mantle, outer core and inner core. • Crust- on the outside, very thin and hard. • Mantle- The largest part making up 2/3 of the earth. • Outer Core- Lies above the inner core and is thought to be composed of mostly molten metal. Liquid. • Inner Core- Hottest place on Earth. Solid iron. Thought to create magnetic field.
The Crust • What make up the earth’s crust? • What is the lithosphere? • Crust consists of many continental and oceanic plates that have slowly moved and changed positions on the globe throughout geologic time. • The rigid upper part of Earth’s mantle and crust. The location of our plates.
Plate Tectonics • What are plates? • What is plate tectonics? • The Earth is broken up into pieces of land which move slightly around the Earth. • Very slow- movement can take more than a year to move a few centimeters. • Pieces of the lithosphere that move around. • Each plate has a name • Fit together like jigsaw puzzles • Float on top of mantle similar to ice cubes in a bowl of water
Alfred Wegener • He proposed that in the distant past, the Earth’s continents were all joined as a single landmass. • After putting all of Earth’s puzzle pieces together he named the land mass Pangaea.
Plate tectonics • Plate Boundaries- • Fault- • The places where the edges of different plates meet • Plates- • Slide • Separate • Collide • Large fractures in rocks along which movement occurs.
How do Plates move? • Plate Movement • Sliding • Separating • Colliding • Plates slide along each other, earth quakes commonly occur from the built up pressure. • When plates move apart, new crust forms to fill the gap between plates. • Tremendous force causing large mountains to form.
Divergent Convergent Transform Three types of plate boundary
Divergent Boundaries • Spreading ridges • *As plates move apart new material is erupted to fill the gap
Iceland: An example of continental rifting • Iceland has a divergent plate boundary running through its middle
Convergent Boundaries • There are three styles of convergent plate boundaries • Continent-continent collision • Continent-oceanic crust collision • Ocean-ocean collision
Continent-Continent Collision • Forms mountains,e.g. European Alps, Himalayas
Continent-Oceanic Crust Collision • Called SUBDUCTION
Subduction • Oceanic lithosphere subducts underneath the continental lithosphere • Oceanic lithosphere heats and dehydrates as it subsides • The melt rises forming volcanism • E.g. The Andes
Ocean-Ocean Plate Collision • When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. • The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. • The worlds deepest parts of the ocean are found along trenches. • E.g. The Mariana Trench is 11 km deep!
Transform Boundaries • Where plates slide past each other Above: View of the San Andreas transform fault