Flashcards in Plate Tectonics- content Deck (14)
An example for jigsaw fit
Africa and South America seem to fit together
An example for geological evidence
- rocks of the same age and type and displaying the same formations are found in SE Brazil and South Africa
- mountains in Canada and Scotland are similar
- glacial deposits are found in Antarctica, South America and India
An example of climatological evidence
Antarctica, North America, Svalbard and the UK all contain coal deposits of similar age that were formed in wet, tropical conditions
An example of biological evidence
What was the problem with Wegener's theories?
They were unable to explain how continental movement had occurred
What happened in the 1950s?
In the 1950s, nuclear submarines were used to map the ocean floors with better accuracy. They found the Mid Atlantic Ridge, an underwater mountain chain and deep ocean trenches which were seismically active.
What happened in 1962?
Harry Hess studied the age of the rocks on the Atlantic sea floor and found that the youngest were in the middle next to the ridge and the oldest further out near the USA and Caribbean, and so the floor must be spreading out from the centre.
What is the result of palaeomagnetism?
The result is a series of magnetic stripes. The striped pattern is mirrored across the Atlantic ridge so suggests that the ocean crust is spreading away from the boundary.
What was the new issue that the discovery of sea floor spreading brought up?
It implied that the Earth must be getting bigger, but it wasn't
How was the issue solved?
It was solved with the discovery of ocean trenches, where crust is being destroyed, such as that in the Pacific Ocean.
What are the physical formation evidence that supported sea floor spreading?
- mid oceanic ridges
- magnetic stripes
- oceanic trenches
- convection currents in the asthenosphere
How many major plates is the Earth split up into?
Seven major plates
What are the seven major plates?
1. Pacific Plate
2. North American Plate
3. South American Plate
4. Antarctic Plate
5. Eurasian plate
6. Indo-Australian plate
7. Nazca Plate