 What is the composition of Earth’s interior?  What are the key types of evidence that support the theory of plate tectonics?  Explain the details of the Plate tectonic theory.

 We talk about the layers of the earth by what they’re made of and how they behave.  What they’re made of:  Crust  Mantle  OuterCore  Inner Core

 Earth’s crust and upper most part of the mantle behave like rigid layers: we call this the lithosphere.  Below the lithosphere are rocks that move like silly putty- plastic like. We call this the asthenosphere.

 1912, Alfred Wegener proposed theory of Continental Drift  Recognized that the continents fit together like a puzzle.  Put them together and called them Pangea Pangea as visualized by Wegener

 Fossils of some plants and dinosaurs were found along opposite continents.  Mountain ranges lined up on opposite continents.  Rocks from opposite continents were the same age and the same marks from glaciers.  Coal, formed only in warm climates was found in Antarctica.

 Regardless of the overwhelming evidence, Wegner’s theory was not widely accepted by the scientific community.  This was because he couldn’t explain how it worked; he couldn’t define the mechanism.

 At the same time Wegener was doing his work, Arthur Holmes investigated another mechanism.: convection in the mantle- (hot stuff rises, cool stuff sinks)  Evidence came from the sea floor.

 New technology to explore the ocean floor allowed us to learn about the reactions crystals inside the rocks at the ocean floor have with earth’s magnetic field.

 The Earth’s magnetic field “flips” every few thousand years.  Iron crystals in newly formed rocks align themselves with the existing magnetic north pole like a compass.

 Matching magnetic stripes alternated on the sea floor.  These matching stripes allow us to date the sea floor rocks

 The age of the sea floor increases as you move away from the mid-ocean ridges  Mid-ocean ridge rocks are the youngest  Ocean trench rocks are the oldest

 The Earth's crust is covered by a series of rigid, lithospheric plates (the crust) that are attached to the asthenosphere.  Convection currents in the asthenosphere move the crustal plates in different directions.

 Sea floor spreading  The sea floor’s rock record of magnetic reversals  The age of sea floor rocks increases as you move away from the mid-ocean ridges  Pangea and Continental Drift  Fossils on opposite continents  Mountain ranges line up  Glacial striations match

 What is the composition of Earth’s interior?  What are the key types of evidence that support the theory of plate tectonics?  Explain the details of the Plate tectonic theory.

What are the processes involved at each of the type of plate boundaries? How can plate tectonics be evidenced by features found in VA?

 The Earth's crust is covered by a series of rigid, lithospheric plates (the crust) that are attached to the asthenosphere.  Convection currents in the asthenosphere move the crustal plates in different directions.

 Dense ocean plates made of basalt  Less dense continental plates made of granite.  The ocean floors are continuously moving, spreading from the mid- ocean ridges, sinking at the oceanic trenches, and melting back into the mantle.

 Where two plates come together.  Convergent = collide  Two ocean or continental plates colliding make folded mountains.  The Blue Ridge mountains were formed this way nearly a billion years ago.

 Occurs when a more dense oceanic plate meets a less dense continental plate.  The Ocean plate subducts (goes under) the Continental plate.  Forms volcanic mountains on land and oceanic trenches in the ocean.  The Appalachians mountains formed like this hundreds of millions years ago.

 When two plates come apart  Divergent = DIVIDE  Forms mid-ocean ridges and rift valleys.

 Normal- form at divergent boundaries  Reverse- form at convergent boundaries  Transform (strike-slip)- when 2 plates slide next to esach other

 What are the processes involved at each of the type of plate boundaries?  How can plate tectonics be evidenced by features found in VA?

 How do the distinctive zones of volcanism and seismic activity relate to plate tectonics?  How do the three types of volcanism vary from one another?

 The location of most volcanoes and earthquakes can aid us in outlining Earth’s crustal plates.  Most volcanoes and earthquakes occur at plate boundaries  This produces the famous “Ring of Fire”

 Volcanoes are created when superheated magma pushes through a weak point in Earth’s crust  Magma erupts from the volcano as lava.  There are 3 types  Shield Volcanoes  Cinder Cone Volcanoes  Composite Volcanoes

 Flat mountains  Largest of all types of volcanoes  Low silica content means the lava is very runny (basaltic lava)  Do NOT have explosive eruptions  Example: the Hawaiian Islands

 Steep cone-shaped mountain  Tend to be smallish mountains  Very high silica content means the lava is very thick (tephra)  Tend to have explosive but very short eruptions  Example: Paracutin in MexicoParacutin in Mexico

Paracutin- Cinder Cone

 Structure has features of flat shield volcanoes and cone shaped cinder cones  Forms very high mountains  Lava is a mixture of basaltic lava and tephra (granitic or andesitic lava)  Extremely explosive and dangerous eruptions  Example: Mount Rainier, Washington

Mt. Rainer- Composite Volcano

 Earthquakes are caused when convection currents in the mantle cause faults to rub against one another.  The pressure causes rocks to suddenly snap and break and may result in the ground shaking violently.  Earthquakes are measured using the Richter Scale.

 How do the distinctive zones of volcanism and seismic activity relate to plate tectonics?  How do the three types of volcanism vary from one another?