Earth's Interior and Continental Drift

• Earth's interior is composed of the inner core, outer core, mantle, and crust.

Heat Transfer

• Radiation is the transfer of heat through empty space.
• Conduction transfers heat through direct contact.
• Convection transfers heat through a moving fluid.

Theory of Continental Drift (Alfred Wegener)

• Continents were once joined together as a supercontinent, Pangaea.
• Continents split apart and gradually moved to their current locations.
• The theory was initially rejected due to the lack of an explanation for the mechanism of continental movement.

Evidence to Support Continental Drift

• Landforms: Matching mountain ranges are found on different continents, such as South America and Africa.
• Fossils: The Mesosaurus, a freshwater reptile, had fossils discovered in South America and Africa, indicating land connection as it could not have swum between the continents.
• The Glossopteris, a plant with large seeds, had fossils discovered in South America, Africa, and other continents; the seeds were too large to be blown across oceans and too fragile to float that far.
• Climate: Fossils of tropical Magnolia trees have been found in Greenland, suggesting a different climate in the past.

Mapping the Ocean Floor

• Sonar was used to map the ocean floor and discovered the Mid-Ocean Ridge.
• Seafloor spreading creates the Mid-Ocean Ridge.
• Magma erupts through cracks along the ridge, cools, and hardens, forming new rock.
• The new rock pushes older rock away on either side of the ridge.
• Testing of rock samples obtained by drilling confirms that the distance from the ridge correlates with the age of the rocks; i.e. rocks get increasingly older.
• Seafloor spreading occurs along the crack/center of the ridge.
• At the opposite edge of a plate, the seafloor sinks under another plate, forming a trench through subduction.
• The older, denser plate subducts because it is cooler.

Theory of Plate Tectonics

• The Earth's lithosphere consists of pieces (plates) slowly moving, driven by convection currents in the asthenosphere.

Types of Plate Boundaries

• Transform boundaries: Plates slip past each other in opposite directions.
• Divergent boundaries: Plates move apart from each other.
• Divergent boundaries cause seafloor spreading, which forms mid-ocean ridges.
• Divergent boundaries form rift valleys on land.
• Convergent boundaries: Plates come together.
• Two oceanic plates colliding result in subduction and trench formation.
• Two continental plates colliding create mountains.
• One oceanic and one continental plate colliding causes subduction and trench formation.