LD - Lecture 1 Flashcards
(19 cards)
How are oceans formed? (3)
Continental drift - Seafloor spreading - Global Plate tectonics
Continental Drift evidence - fossils
Fossils found on different continents in certain patterns
Wegners Hypothesis
Continents are moving so must have been Pangaea
Continental Drift evidence mountains
Continuous mountain change on either side of Atlantic ripped apart
What are striations?
Scratches in bedrock carved by glaciers
Chatter marks?
When a glacier picks up a boulder and causes it to jump, ripping out chunks of bedrock
Ice sheet evidence?
Proof that ice sheets would have been land based and originally circled a pole before continental drift
Using sonar, what features did they discover? (3)
Trenches, Gyots, Mid Ocean Ridges
What did the development of sonar help prove?
Seafloor spreading
Who proposed seafloor spreading?
Harry Hess
Mechanism of seafloor spreading (3)
Seafloor split in large blocks, forced by up-welling molten magma, from convection within the mantle. As magma cools, contracts, drawing ocean floor downwards. (Divergent plate boundaries)
Magnetic anomaly stripes? (3)
Rising Magma assumes earths polarity, rock cools locking in magnetic alignment, ~every 0.5 million years magnetic pole reverses
Which boundary’s have more powerful earthquakes?
Convergent
What fully drives tectonic motion?
Subduction of heavy oceanic crust.
Where are divergent plate boundaries generally found?
Mid-ocean ridges
What does oceanic crust tend to made of?
Volcanic Basalt
What is a transform boundary? (2)
Lateral movement of plates, causes weak-moderate earthquakes.
Example of transform boundaries? (2)
San Andreas, Alpine fault
What are hotspots? (2)
Where mantle plumes far from plate boundaries, can create island chains. e.g Hawaii
