Earth History
Category: Other
Updated: 19 Sep 2020
Contributors
Created bySam Goldsmith
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Events
1915-Continental Drift Theory Developed By Alfred Wegener-Fossils found in multiple different countries around the world with similarities
-Therefore meaning that the organisms must have moved with the movement of these 'plates'
-Also due to fossils also suggesting the environment they lived in. Wegener found that many of
these fossils often from warm environments where found in places like Antarctica suggesting
that the continent was once warm.
-Wegener came to the conclusion that all plates must have drifted across the world
-However Wegener had no evidence -Holmes' theory suggested that just like convection currents within the air
convection currents also occur within the mantle of the earth.
-This theory suggested the earths crust is then pushed by these moving
currents, causing seafloor to spread when the plates pull apart and mountains
to form when two plate meet through process' of subduction.1919-Holmes Develops Convection Theory (copy)After WWII more advanced use of sonar technology is used to map the ocean
floor .
The find volcanoes and trenches suggesting early evidence for seafloor
spreading and proccess' of subduction.1946 Military Use More Sonar1954-Worldwide Volcanoes and Earthquakes are recordedThis provides evidence that earthquakes occur along plate margins. Suggesting plates
may be moving.1960- Hess and Dietz Propose Sea Floor Spreading.This theory states that where two plates pull apart, molten basaltic rock (magma) rises
up and is rapidly cooled by the ocean, causing more seafloor to be created. Thus creating
ridges as mentioned earlier.
This also develops the theory that the plates are pushed away from each other resulting
in process' of the subduction on the other side, causing the oceanic plate to be pulled
under the continental plate via slap pull.1963- Theory of Palaeomagnetism is Developed.-The earth has a giant magnetic core.
-Every 200,000 years this magnetic core filps causing the North to be either at the
top or bottom of the planet
-Magnetic minerals (Iron,Cobalt, Nickel and Cadmium) show this by pointing to the
magnetic north
-As time goes on more seafloor is created where its magnetic minerals are pointing
south. This creates a striped pattern suggesting that the inside structure of the earth
is flipping but also more seafloor is being created.1965-Wilson Develops Plate Tectonic TheoryWilson Proposes that the entirety of Earths surface is made up of
multiple different plates and not just one large one.1983- GPS is Available to the Public-Military allow GPS for public use
-Satellites can monitor movement of plates
-This allows scientists to monitor plates and track
there movement
-Plate Tectonic theory is confirmed and the theory
that the crust is made of many different plates
is acceptedNow-Modern DevelopmentWith the increasingly improved accuracy of satellites
scientists are now able to monitor plate movement
down to 1cm. Providing even more evidence towards
tectonic theory and continental drift.Periods
1914-1918
Sonar Is DevelopedSonar Tech Developed by the navy allowing us
to see in the ocean floor in a new way.
It's not flat or feature less. This gives us very
early evidence of sea floor spreading as well
as slab pull and subduction.
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