Plate Tectonics

Earth’s Layers The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

The Crust Outermost layer 5 – 100 km thick Made of Oxygen, Silicon, Aluminum

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

The Core Below the mantle and to the center of the Earth Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

Tectonic Plates

Plate Tectonics Greek – “tektonikos” of a builder Pieces of the lithosphere that move around Fit together like jigsaw puzzles. Float on top of mantle similar to ice cubes in a bowl of water.

Drifting Continents Theory Wegener suggested that a supercontinent he called Pangaea had existed in the past. It broke up starting 200 million years ago, and the pieces ``drifted'' to their present positions. He cited the fit of South America and Africa, ancient climate similarities, fossil evidence (such as the fern Glossopteris and mesosaurus), and similarity of rock structures.

Wegener ‘s hypothesis All continents were once together in a single landmass and have since drifted apart. In 1915, Wegener published a book called the “ Origin of Continents and Oceans.”

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” 300 Million years ago Split again – Laurasia & Godwin 180 million years ago

Evidence of Pangaea

Fossil or any trace of an ancient organism. Fossil preserve in rocks. Glossopteris ( fernlike plant ) lived 250 million years ago. Freshwater reptiles ( Mesosaurus and Lystrosaurus )

Evidence of Pangaea Climate, as continents move toward the poles, its climate is colder. As continents move toward the equator, its climate gets warmer. Fossils of tropical plants were found in the Arctic Ocean. ( Spitsbergen)

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. MOR lie under thousands of meters of water.

Sea Floor Spreading Mid- ocean ridges continually add new material ( CRUST ) to the ocean floor. Subduction is a process by which the ocean floor sinks beneath a deep ocean trench and back into the mantle again.

How Plates Move

Different Types of Boundaries

Divergent Boundary – Arabian and African Plates

Divergent Boundary – Iceland

Divergent Boundary - Oceanic

Divergent Boundary - Continental

Convergent Boundary – Indian and Eurasian Plates

Convergent Boundary – Oceanic & Continental &

Convergent Boundary – Oceanic & Oceanic &

Convergent Boundaries - Continental &

Transform Boundary – San Andreas Fault

Fault

Trench Puerto Rico Trench Depth 800 m. Length 8,000 m.

Rift Valley

Theory of Plate Tectonics Earth’s plates are in slow constant motion, driven by convection currents in the mantle.

Boundaries Divergent Boundaries Convergent Boundaries Transform Boundaries Plates shift or slip past each other Collision of plates Moving together Crust pulling apart Form Valleys VolcanoesEarthquakes

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