Chapter 6.1 Flashcards
Who came up with the idea of “Continental drift”?
Alfred Wegener
What was Pangaea?
Pangaea was a supercontinent that existed 220 million years ago.
What did Wegener use to back up his theories?
The evidence of coastline fit, similar fossils, rocks and landforms created by glaciers in now widely separated continents, and the reconstructions of old climate zones.
Define “continental drift”
The idea that continents are continually moving and have significantly changed positions over millions of years
What is the “plate tectonic” theory?
The theory that the surface of the Earth is divided into a series of plates that are continually moving.
Define “continental shelf”
Underwater cliffs between the beach and ocean.
What are the two theories that are used to make up Plate tectonics?
Continental drift and sea-floor spreading.
Define “sea-floor spreading”
A theory that the middle of the ocean is spreading apart, forming new oceanic crust.
Who proposed the idea of “sea-floor spreading”?
Harry Hess
Define “magma”
Semi-liquid rock found beneath the Earth’s surface
How do convection currents work?
Rising magma creates a ridge crest and the rising magma pushes it to the side as more magma rises. The ridge splits and moves apart. As it gets further apart, tension between the surrounding rocks cause a rift zone and shallow earthquakes. As the mantle rock moves away from the ridge crest, it carries the seafloor with it. The rock cools, becomes more dense and eventually sinks back into the mantle
