Plate Tectonics & Boundaries

Key Terms 1.diverging 2.converging 3.transform 4.fault 5.tectonic plate Moving apart Moving together Sliding past A break or crack in the Earth’s crust a rigid layer of the Earth's lithosphere that is believed to drift slowly

Key Terms 6.Lithosphere 7.Asthenosphere 8.convection 9.subduction 10.topography Earth’s layer with crust and upper mantle Earth’s layer with slowly flowing mantle rock that allows tectonic plates to move Currents caused by rising hot matter, and sinking cooler matter process in which one edge of a crustal plate is forced downward into the mantle below another plate The shape and features of the surface of land

From studying maps, people noticed that the continents appeared as if they fit together like a giant jigsaw puzzle.

Because of this, a scientist named Alfred Wegener, hypothesized that the continents once formed a single landmass called a supercontinent. This was later called Pangaea.

Evidence #1: Similar Plant & Critter Fossils

Evidence #2: Rock Formations of nearly identical rocks and structures

Evidence #3: Similar climatic pasts

Beginning of the Theory Scientists (meteorologist) who proposed the Theory of Continental Drift, but did not know why the continents moved -- Alfred Wegener. Evidence he had: –Shape of continents –Similar plant and animal fossils –Similar rock formations –Similar climatic pasts with glacier evidence in warm areas and tropical evidence in cold areas

… but this was not enough evidence to convince the world of continental drift.

Beginning of the Theory The main reason other scientists did not agree with, or believe, this theory was because Wegener could not come up with a mechanism or reason why the continents could move. Wegener called the original land form Pangaea.

Sea Floor Mapping

Beginning of Evidence The scientist (geologist) Harry Hess discovered the mid-Atlantic ridge. Harry Hess had discovered that the sea floor is spreading and new earth is being generated at the crack. He also appreciated the fact that somewhere else in the world earth must also be being destroyed.

HARRY HESS Captain of the assault transport USS Cape Johnson

1-Heat from the light bulb heats the globs of wax, making them less dense. The heated wax rises. 2-Wax further away from the heat source cools and becomes more dense. The cooled wax sinks. 3-This process is known as convection.

Mantle Convection VERY HOT CORE heats magma, causing it to RISE COOLING caused by melting of crust causes mantle to SINK

VERY HOT CORE HOT MAGMA RISES (heated by core) Plate Diverging Boundaries

Diverging Plates - #1 Name: Rift Type of Crust: Ocean/Ocean Movement: Pulling Apart Geography: mountains and rift Locations: Mid-Ocean Atlantic Ridge

Diverging Plates #2 Name: Normal Fault Type of Crust: Continental/Continental Movement: Pulling Apart Geography: Valleys, Lakes Locations: Great Salt Lake, African Rift Valley, Death Valley

VERY HOT CORE COOLER, MELTING LAVA SINKS plate Converging Boundaries

Converging Plates #1 Name: Folded Fault Type of Crust: Continental / Continental Movement: Pushing Together Geography: Mountains, Hills, Folded Rock Location: Jura Mountains (Switzerland), Himalayans (Mt. Everest)

Converging Plates #2 Name: Subduction Fault Type of Crust: Ocean/Ocean Movement: Pushing together Geography: Trench, Volcanic Arc, Island Locations: Caribbean, Aleutian Islands

Converging Plates #3 Name: Subduction Fault Type of Crust: Ocean/Continental Movement: Pushing Together Geography: Mountain Ranges, Volcanoes, ocean trench Locations: Cascade Mountains (Mt. St. Helens), Ring of Fire, Pompeii

Transform Boundary Name: Transform or Strike-Slip Type of Crust –ANY Movement: Sliding Past Geography: Shifted land, cracks Locations: San Andreas Fault, Dead Sea

MAJOR PLATES