Earth Science and M.E.A.P The benchmarks and you!

EG. Geosphere Benchmark 2 Use the plate tectonics theory to explain features of the earth’s surface and geological phenomena, and describe evidence for the plate tectonics theory.

Crust Mantle: upper part is able to flow very slowly Core: interior at high temperature and pressure Key concepts Earth Composition

starryskies.com/.../Earth/ under_the_surface.html

Evidence of “continental drift”—. Physical fit of continents Fossil evidence Measurements of movement Rock layer sequences Glacial evidence Key concepts Alfred Wegener

What is the theory of continental drift? the idea that the continents were once all joined together in one super-continent called Pangaea and slowly moved to their current positions

What evidence supports the theory of continental drift?

Shoreline Fit of the Continents

Fossil Evidence The fossils from the exact same animals are found on continents separated by vast oceans.

Matching Rock Layers

Glacier Evidence Glaciers scars are found on continents which are today too warm for glaciers.

How fast are the plates moving?

Bell Ringer Why are the continents moving?

During WWI scientists used sound waves to detect submarines and discovered underwater systems of ridges and valleys like those found on the continents.

Seafloor spreading is Hess’s theory that new seafloor is formed when magma is forced upward toward the surface at a mid-ocean ridge.

Seafloor Spreading The oceans are widening along the mid-ocean ridges.

Volcanoes located along ocean ridges erupt, creating new ocean floor.

Evidence for spreading In 1968, scientists aboard the research ship Glomar Challenger began gathering information about the rocks on the seafloor. They found that the youngest rocks are located at the mid- ocean ridges.

Plates —continental crust, oceanic crust Features —faults, trenches, mid-ocean ridges, folded mountains, hot spots, volcanoes Related actions —earthquakes, volcanic activity, seafloor spreading, mountain building, convection in mantle. Key concepts

The earth’s lithosphere is broken into huge sections called plates that are in constant motion.

What are the plates made of? Ocean plates are made of basalt. Continental plates are made of granite.

Divergent Plate Boundaries Two land or ocean plates move apart in opposite directions. Magma flows to the surface between them creating new crust.

Mid-Atlantic Ridge = Divergent Boundary

Iceland – a continent directly over the Mid-Atlantic Ridge

Subduction Zones An ocean plate and a continental plate hit head-on. The ocean plate subducts under the continent forming a trench. The subducting plate melts. Magma rises to the surface creating a string of volcanic mountains parallel to the shoreline.

Andes Mountains Subduction zones form chains of volcanic mountains along the shoreline.

Collision Zones Two continents hit head-on, crinkling up the land into a high mountain chain.

India’s Collision with Asia Himalayas

The Himalayas Are Born…

Island Arcs Two ocean plates hit head-on. One ocean plate is forced to subduct under the other forming an ocean trench. The subducting plate melts. Magma rises to the surface forming a string of volcanic islands parallel to the trench.

The Aleutian Islands

Forces —tension, compression shearing Key concepts Ask a Geologist Ask an earth scientist

How does tectonic activity affect the earth’s crust? Builds mountains Creates deep ocean trenches Causes earthquakes Create volcanoes

Ocean Trenches

Volcanoes

Most volcanoes occur at plate boundaries…

Recent patterns of earthquake and volcanic activities; maps showing the direction of movement of major plates and associated earthquake and volcanic activity Compressional boundaries: folded mountains, thrust faults, trenches, lines of volcanoes (e.g. Pacific “ring of fire”) Tensional boundaries: mid-ocean ridges, rift valleys Shearing boundaries: lateral movement producing faults (e.g. San Andreas Fault). Real-world contexts:

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