CONTINENTAL DRIFT

I can explain the hypothesis of continental drift.

EGG MODEL

- What does the egg represent?

- What do the pieces of eggshell represent?

WHAT ARE TECTONIC PLATES? - pieces of the lithosphere that move around on top of the asthenosphere

* The plates fit together like puzzle pieces. * Plates can be different shapes and sizes.

Notice the different shapes and sizes of the plates.

TYPES OF CRUST Oceanic Crust - Earth’s crust located under the ocean - more dense - thinner crust

Continental Crust - Earth’s dry land and mountains - less dense - thicker crust

Notice the different types of crust for the plates.

WEGENER’S CONTINENTAL DRIFT HYPOTHESIS - early 1900s - states that the continents once formed a single landmass (or supercontinent), broke up, and drifted to their current locations - named the super continent “Pangaea” -explained why fossils and rock types were found on continents that are now on different sides of oceans

PANGAEA – GREEK FOR “ALL EARTH”

EVIDENCE TO SUPPORT WEGENER’S CONTINENTAL DRIFT

1.) Fossil records 2.) Landforms

3.) Sea-floor spreading

FOSSIL RECORDS

LANDFORMS

SEA-FLOOR SPREADING (HARRY HESS)o Mid-ocean ridge – underwater mountain chainso Sea-floor spreading – the process by which new oceanic lithosphere forms as magma rises toward the surface and hardenso Sea-floor spreading takes place at the mid-ocean ridgeso As new crust forms, the old crust gets pushed away from the mid-ocean ridge.

SEA-FLOOR SPREADING

GLOMAR CHALLENGER

- a drilling ship built in 1968 - drilled samples of oceanic crust This feat has been compared to using a sharp-ended wire to dig a hole into a sidewalk from the top of the Empire State Building.

MAGNETIC REVERSALS

How are the matching stripes evidence of sea-floor spreading?

I CAN… CAN YOU?

I can explain the hypothesis of continental drift.

Can you?