Plat Tectonics Vocab

Continental Drift

Continental Drift is the theory - proposed by Alfred Wegener! - that today’s continents were once part of a single landmass, or supercontinent, called Pangaea. He proposed that Pangaea broke up into pieces that eventually “drifted” to the continents’ present locations. The continents drifted!

Plate Tectonics

Plate Tectonics is a theory that Earth's surface is made of giant tectonic plates that move due to temperature & pressure beneath them. 

Seafloor Spreading

Seafloor spreading is the process by which new sea floor forms as magma rises, pushes older rock in opposite directions, & creates a mid-ocean ridge. 

Fossil

Fossils are the preserved remnants or evidence of past living organisms. 

Superposition

Superposition is the geologic law that states that sedimentary layers are deposited in a time sequence, with the oldest on the bottom & the youngest on the top. So…in undisturbed rock layers, the oldest rocks are on the bottom.

Magnetic Reversal

Magnetic reversal is the change in the direction of the magnetic field of the Earth that has occurred from (long) time to time. *The last magnetic reversal was about 780,000 years ago!

Lithosphere

The lithosphere is the outermost physical layer of Earth composed of solid, rigid rock & which is divided into plates. 

*LITHOSPHERE = crust + uppermost mantle

Asthenosphere

The asthenosphere is the soft layer of the Earth within the upper mantle & directly below the lithosphere. This layer has a semi-solid consistency that reaches to about 200 kilometers (124 miles) below the surface. *You can call it a solid, just know it has some ‘squish’ & is slowly flowing.

Mid-Ocean Ridge

The mid-ocean ridge is a continuous range of undersea volcanic mountains that encircles the globe almost entirely underwater & stretches for nearly 65,000 kilometers (40,390 miles.) It formed & evolves as a result of spreading in Earth’s lithosphere at the divergent boundaries between tectonic plates. Most volcanic activity on the planet occurs along the mid-ocean ridge, & it is the place where the crust of the Earth is born.