Plate boundaries, continental drift, and the tectonic processes that shape the Earth's crust.
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- What was Alfred Wegener's theory of continental drift?
- The idea that continents were once connected in a supercontinent (Pangaea) and have since drifted apart to their current positions
- What key evidence supported continental drift?
- Matching fossils across continents, continental coastlines fitting together, matching rock types and mountain ranges
- What is a lithospheric plate?
- A rigid slab of crust and upper mantle that moves over the asthenosphere
- What is the asthenosphere?
- The hot, partially melted layer of the mantle beneath the lithosphere that allows plates to move
- Name the three main types of plate boundaries
- Divergent, convergent, and transform boundaries
- What occurs at a divergent plate boundary?
- Plates move apart, new lithosphere is created, and magma rises to form new crust
- What occurs at a convergent plate boundary?
- Plates collide, one plate is pushed beneath another (subduction) or both plates buckle upward forming mountains
- What occurs at a transform plate boundary?
- Plates slide horizontally past each other, causing earthquakes but no creation or destruction of lithosphere
- What is seafloor spreading?
- The process where new oceanic crust forms at mid-ocean ridges as plates move apart
- Who proposed the seafloor spreading hypothesis?
- Harry Hess, in 1962
- What is a mid-ocean ridge?
- An underwater mountain chain where new oceanic crust forms due to seafloor spreading
- What causes magma to rise and create new crust at mid-ocean ridges?
- Decompression melting of mantle rock as the asthenosphere rises to fill the gap left by diverging plates
- What is subduction?
- The process where a denser oceanic plate is forced beneath another plate into the mantle
- What happens in a subduction zone?
- The descending plate heats up, releases fluids, causes melting, and triggers powerful earthquakes and volcanism
- What is the Wadati-Benioff zone?
- A zone of earthquakes that dips into the Earth along a subducting plate, marking the path of the descending slab