Earths Structure Goal: Be able to identify the structure of the earth’s interior

Structure of the Earth Core Asthenosphere Lithosphere

Core About 1800 miles below your seat Around 6700 deg. F Dense ball of Iron and Nickel Made of the Inner and Outer cores Inner is solid Outer is molten

Asthenosphere Plastic Flows Fluid Convection currents drive movement

Lithosphere About 19miles below your seat Rigid upper mantle and crust Seafloors Basaltic: Very Dense, Sinks Granitic Continents: Lighter, Floating Broken into plates

Tectonic Boundaries Identify Boundary Types Contrast 3 types of Convergent Boundaries

History and Evidence Alfred Wagner: Theory of Plate Tectonics: movement over time. “Continental Drift” Evidence “Puzzle Pieces” Fossils Climate Change Sea Floor Magnetism

Boundary Types Diverging (moving apart) Converging (coming together) Transform ( Sliding)

Boundaries

Where are they?

Diverging Boundary Magma is pushing plates apart Small, shallow earthquakes occur here Mild, mafic volcanism Most have mid-ocean ridges- these ridges are not straight, but have many fracture zones On land it is called a rift valley Examples: Mid-Atlantic Ridge, African Rift Valleys, Iceland

Earth’s Polarity: Evidence of tectonics It reverses about once every 200,000 years on average The last time Earth's magnetic field flipped was 780,000 years ago

Transform Boundary (Sliding) Plates sliding past one another No volcanism Medium sized, shallow earthquakes Fault = a fracture in the earth where movement occurs Examples: San Andreas Fault

Converging Boundaries Three types: Continent/Continent (Collision) Ocean/Ocean (Subduction) Ocean/Continent (Subduction)

Continent to Continent Collision Boundary Continents crumple and make large mountains Regional Metamorphism Large, strong earthquakes Examples: Himalayas, Urals, Appalachians

Ocean/Ocean Subduction Boundary One plate sinks (subducts) forming trench and volcanic island arc Deep, strong earthquakes Lithosphere recycled at trench Example: Mariana trench. The trench has a maximum depth of 35,798 ft below sea level.

Ocean to Continent Subduction Boundary More dense oceanic plate gets subducted under the continental plate Continent crumples and scrapes sediment off of oceanic plate Trenches and volcanic Mt. chains occur at these boundaries Examples: Andes and Cascades

Hot Spots: Evidence of Tectonics The one place where volcanoes occur that aren’t on a plate boundary Magma welling up through the Lithosphere as the plate slides over it Examples: Hawaii, Yellowstone