Plate Tectonics Flashcards
What is the theory of plate tectonics?
The Earth’s lithosphere is broken into tectonic plates that move over the asthenosphere, driven by mantle convection, slab pull, and ridge push.
What is continental drift, and who proposed it?
- The theory that continents were once joined and have drifted apart over time.
- Proposed by Alfred Wegener (1912).
What is seafloor spreading, and how does it support plate tectonics?
- New oceanic crust forms at mid-ocean ridges as magma rises, pushing plates apart.
- Discovered by Harry Hess in the 1960s. Confirmed by paleomagnetic evidence showing symmetric magnetic striping on the ocean floor.
What are the 3 main forces driving plate movement?
- Mantle convection: Rising hot magma moves plates.
- Slab pull: Dense, sinking oceanic plates pull the rest of the plate down at subduction zones.
- Ridge push: New crust at mid-ocean ridges pushes older crust away.
What are the 2 major types of tectonic plates?
- Oceanic plates: Thin (5-10km), dense, basaltic (e.g., Pacific Plate).
- Continental plates: Thicker (30-70km), less dense, granitic (e.g., Eurasian Plate).
What are the three main types of plate boundaries?
- Divergent boundaries: Plates move apart (e.g., Mid-Atlantic Ridge).
- Convergent boundaries: Plates collide, causing subduction or mountain formation (e.g., Himalayas).
- Transform boundaries: Plates slide past each other (e.g., San Andreas Fault).
What 3 landforms are created at divergent boundaries?
- Mid-ocean ridges (e.g., Mid-Atlantic Ridge).
- Rift valleys (e.g., East African Rift).
- Volcanoes due to rising magma.
What happens at convergent boundaries? (Mention 3 things)
- Oceanic-continental: Oceanic plate subducts, forming volcanic arcs and deep-sea trenches (e.g., Andes).
- Oceanic-oceanic: Older plate subducts, forming island arcs (e.g., Japan).
- Continental-continental: No subduction, forming fold mountains (e.g., Himalayas).
What 2 hazards occur at transform boundaries?
- No magma movement, so no volcanoes.
- Frequent, shallow earthquakes (e.g., San Andreas Fault).
Where do most tectonic hazards occur?
Along plate boundaries, where plates collide, separate, or slide past each other.
What is the Pacific Ring of Fire? (Mention 2 things)
- A tectonically active zone around the Pacific Ocean.
- Contains 75% of the world’s volcanoes and 90% of earthquakes.
Why do some earthquakes occur away from plate boundaries?
Intraplate earthquakes occur due to ancient fault lines or mantle plumes (e.g., Hawaii).
Why are some areas more vulnerable to tectonic hazards? (Mention 4 things)
- Population density (more people at risk).
- Building quality (poor infrastructure increases damage).
- Emergency response (HICs recover faster than LICs).
- Geography (mountainous areas may worsen landslides).
