Plate Tectonics Mrs Morgan Structure of the Earth

Plate Tectonics Mrs. Morgan

Structure of the Earth • The Earth is made up of 3 main layers: – Core – Mantle – Crust Mantle Outer core Inner core

Earth’s Layers This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The Crust • This is where we live! • The Earth’s crust is made of: Continental Crust Oceanic Crust - thick (10 -70 km) - buoyant (less dense than oceanic crust) - mostly old - thin (~7 km) - dense (sinks under continental crust) - young

The Mantle • Layer of Earth between the crust and the core • Contains most of the Earth’s mass • Has more magnesium and less aluminum and silicon than the crust • Is denser than the crust

What are tectonic plates made of? • Plates are made of rigid lithosphere. The lithosphere is made up of the crust and the upper part of the mantle.

What is the Lithosphere? • The crust and part of the upper mantle = lithosphere – 100 km thick –Less dense than the material below it so it “floats”

What is the Asthenoshere? • The plastic layer below the lithosphere = asthenosphere • The plates of the lithosphere float on the asthenosphere

Tectonic Plates

Plate Tectonics • • • Greek – “tektonikos” of a builder 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

Continental Drift Alfred Wegener 1900’s Continents were once a single land mass that drifted apart. Fossils of the same plants and animals are found on different continents Called this supercontinent Pangea, Greek for “all Earth” 245 Million years ago Split again – Laurasia & Gondwana 180 million years ago http: //members. enchantedlearning. com/subjects/astronomy/planets/earth/Continents. shtml

Evidence of Pangea

Sea Floor Spreading

Sea Floor Spreading • Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins • Magma rises to the surface and solidifies and new crust forms • Older Crust is pushed farther away from the ridge

How Plates Move http: //pubs. usgs. gov/gip/dynamic/unanswered. html

Plate Movement • “Plates” of lithosphere are moved around by the underlying hot mantle convection cells

Different Types of Boundaries http: //pubs. usgs. gov/gip/dynamic/understanding. html

Three types of plate boundary • Divergent • Convergent • Transform

Divergent Boundary – Arabian and African Plates Arabian Plate Red Sea African Plate

Divergent Boundary – Iceland http: //pubs. usgs. gov/gip/dynamic/understanding. html

Divergent Boundary - Oceanic http: //www. geology. com

Divergent Boundary - Continental http: //www. geology. com

Convergent Boundary – Indian and Eurasian Plates Eurasian Plate Indian Plate

Convergent Boundary – Oceanic & Continental http: //pubs. usgs. gov/gip/dynamic/understanding. html & http: //www. geology. com

Convergent Boundary – Oceanic & Oceanic NOTE – PLATES ARE REVERSED http: //pubs. usgs. gov/gip/dynamic/understanding. html & http: //www. geology. com

Convergent Boundaries - Continental http: //pubs. usgs. gov/gip/dynamic/understanding. html & http: //www. geology. com

Transform Boundary – San Andreas Fault www. geology. com

Review • • • Name the 3 main layers of the Earth What is a tectonic plate? What was Pangea? What is Sea-Floor spreading? Name three different types of plate boundaries and one location on Earth for each one