This Dynamic Earth

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This Dynamic Earth

This Dynamic Earth

By: Sydney Zarlengo

WegenerAlfred Wegener is the most well-known scientist who "came up" with Pagaea and the Continental Drift Theory. He really was just a meteorologist who put together the pieces of someone else's puzzle. Like, for example, how the continents look like they fit together, or how things like animals and plants on continents far away from each other matched. Many people didn't believe Wegener and it was still a controversial topic by the time he died. Finally, there has been more evidence, and the Continental Drift Theory was adopted and that led to the Plate Tectonics Theory.

Early BeliefsUp until the 1700s, most Europeams believed that the earth began with a large biblical flood. This belief is called catastrophism. A few others in times as early as 1596 thought of something somewhat like Pangaea, but weren't considered until Wegener in 1912. Also, most people thought the ocean floor was flat until bathymetric surveys and early sonar systems were used to discover that the floor is actually quite rugged.

MagnetsIn the 20th century, paleomagnetists, who study Earth's ancient magnetic field, noticed that all volcanic rock belonged into two groups based on metal properties. These are Normal Polarity (North) and Reversed Polarity (South). When magma cools, it's magnetic orientation matches that of the earth at the time it cools. When magnetometers were used underwater, it showed that the volcanic rock was extremely magnetic with magnetite, a very magnetic mineral. Then, in the 1950s, it was discovered that the two magnetic variations were always in rows every other. This was named magnetic striping.

TrenchesIn 1947, scientists discovered that the ocean floor had less sediment than they had thought. Scientists did more research and realized that if new crust is being made in one place and the earth is still the same size, crust is going away somewhere else. Then, they found trenches, which are huge canyon-like things underwater that take away crust. This process is also part of sea floor spreading, when oceanic crust descends into trenches. This explains the lack of sediment and how oceanic crust is younger than continental crust. Furthermore, scientists noticed that prominent earthquake zones are parallel to large trenches. These zones are called Benioff zones.

RidgesIn the 1950's, a huge underwater mountain chain called the Global Mid-Ocean Ridge. It is more than 50,000 km long and in some places over 800 km across. But why is it there? I'm 1961, it was theorized that mid-ocean ridges mark structurally weak zones where new crust is being created. This process is called sea floor spreading.

The Theory of Plate TectonicsThe Theory of Plate Tectonics has changed the was scientists see the earth forever. Even though scientists know a lot about the earth, there is still so much to learn. The Theory of Plate Tectonics states that the outermost layer of earth (the crust) is broken up into a bunch of plates all moving on magma and that these plates used to be together making all the land touch, called Pangaea.


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