From Continental Drift to Plate Tectonics

Continental Drift

Hypothesis proposing continents once formed Pangaea.

Plate Tectonics

Theory explaining lithosphere movement on asthenosphere.

Pangaea

Supercontinent that existed before continental drift.

Mesosaurus

Fossil evidence supporting continental connection.

Convergent Boundaries

Plates move toward each other, causing subduction.

Subduction

Process where denser oceanic lithosphere sinks.

Oceanic Trench

Deep trench formed by subducting oceanic lithosphere.

Volcanic Island Arc

Chain of islands formed by subducting oceanic plates.

Continental Volcanic Arc

Volcanic mountains formed by oceanic under continental plates.

Transform Boundaries

Plates slide past each other horizontally.

Seafloor Spreading

Process creating new oceanic crust at divergent boundaries.

Mid-Ocean Ridge

Underwater mountain range formed by seafloor spreading.

Asthenosphere

Semi-fluid layer allowing tectonic plate movement.

Lithosphere

Rigid outer layer of Earth, includes crust.

Divergent Boundaries

Plates move apart, allowing magma to rise.

Rift Valley

Valley formed at divergent plate boundaries.

Hydrothermal Vents

Underwater hot springs associated with mid-ocean ridges.

Seafloor Spreading Rate

Typically 2-5 cm per year.

Magnetic Anomalies

Variations in Earth's magnetic field on ocean floor.

Magnetic Reversals

Changes in Earth's magnetic field recorded in rocks.

Slab Pull

Force from subducting plates pulling on tectonic plates.

Ridge Push

Force from elevated mid-ocean ridges pushing plates.

Whole-Mantle Convection

Mantle circulation driving plate motion due to temperature.

Transform Faults

Faults with horizontal motion, no lithosphere creation.