Continents have moved over Earth's surface throughout earth's history
Continents that once formed part of a single landmass.
Sound navigation and ranging. Uses sound waves to measure water depth.
Detects small changes in magnetic fields; measures magnetic field strength.
A narrow, elongated depression in the seafloor with steep sides.
Basaltic lava cools, iron-bearing minerals become oriented parallel to Earth's magnetic field.
Harry Hess' theory stating that molten rock wells from the mid-ocean ridge valley as the ocean floor moves away from the ridge.
Earth's crust and rigid upper mantle are broken into enormous slabs.
Plates move away from each other.
Plates move toward each other.
Plates slide past one another
Movement of warmer material toward the surface as cooler material sinks deep into the mantle.
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