Continental Drift Basics
What is continental drift?
The hypothesis that Earth's continents have moved over geologic time and were once joined in a single landmass.
What is evidence from rock formations?
Matching rock layers on widely separated continents (e.g., Appalachians and Greenland) supporting past connection.
What is seafloor spreading?
The process where new ocean crust forms at ocean ridges and moves away from the ridge.
What is paleomagnetism?
The study of Earth's past magnetic field as recorded by minerals in solidified lava
What are tectonic plates?
Huge pieces of crust and rigid upper mantle that fit together around Earth.
What is Pangaea?
The supercontinent proposed to have existed about 200 million years ago when all continents were joined.
What is fossil evidence?
Similar fossils of plants and animals found on widely separated continents indicating past contact.
What is an ocean ridge (or mid-ocean ridge)?
Underwater mountain chain where magma rises and new oceanic crust forms.
What is a magnetometer?
A device towed behind ships that detects small changes in magnetic fields of ocean-floor rocks
What is plate tectonics?
The theory that explains how plates move and shape Earth's surface.
Who is Alfred Wegener?
The German meteorologist who proposed the continental drift hypothesis in 1912.
What is Glossopteris?
A fossil plant found on multiple continents used as climatic evidence for continental drift.
What is sonar mapping?
Technology used to measure water depth and map ocean-floor topography.
What is a magnetic reversal?
When Earth's magnetic field changes direction due to changes in outer core flow.
What is a divergent boundary?
Place where two plates move apart; often forms rift valleys on continents
Why was Wegener's hypothesis rejected?
The early scientific community's dismissal of Wegener's idea because there was no convincing mechanism for movement.
What is climatic evidence?
Data such as coal beds and glacial deposits that show past climates different from present locations.
What is the age of oceanic crust?
The observation that seafloor rock ages increase with distance from an ocean ridge.
What is magnetic symmetry?
The pattern of alternating magnetic stripes on each side of ocean ridges that mirror one another.
What is subduction?
Process where the denser plate sinks below the less-dense plate at a boundary.
Who is Abraham Ortelius?
A 16th-century cartographer who noticed matching continental coastlines across the Atlantic.
What is coal in Antarctica?
Evidence that Antarctica was once closer to the equator because this forms from ancient swamp plants.
What are ocean trenches (or the Mariana Trench)?
Deep, narrow depressions on the seafloor where crust is often destroyed (the deepest example is over 11 km deep)
What is magnetite?
Iron-bearing mineral in lava that aligns with Earth's magnetic field as it crystallizes.
What is slab pull?
Tectonic process where the weight of a subducting plate pulls the trailing lithosphere into a subduction zone.