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What Was the Young Earth Like?
What Was the Young Earth Like?
The early Earth was not a pleasant place to be. How did it change to become a place that supports life?
As this video progresses, key ideas will be introduced to invoke discussion.
Think about the following questions as you watch the video
What challenges would humans have faced if they lived on the early Earth?
What are the four layers of the Earth?
What is Pangaea?
What are the two different types of crust?
What is the theory of plate tectonics?
: Imagine you're in a time machine and you've traveled back 4 and a half billion years and
: what you're doing is you're taking a stroll on the early Earth. Now what would it be like and would
: you be having fun? Well, the answer is I don't think you'd be having much fun. First you'd be
: walking on molten lava, not nice, secondly, you couldn't breathe because there's no oxygen you'd
: be asphyxiating, and thirdly you'd be ducking asteroids and meteorites that are crashing into
: the early Earth lots and lots of them, and fourth you'd probably be throwing up because of very high
: levels of radiation and if you stay there too long your hair would start falling out too.
: In fact, the early Earth got so hot it melted and that is really important because if it hadn't
: melted, today's Earth would be very different from the way it was. And because it melted it
: formed a series of layers, and they give it its structure today. Let's look at the four main
: layers and the first is at the center. It's the core, it's metallic nickel and iron,
: above all iron, sank to the center of the earth. Lighter stuff, lighter rocks float
: above the core and form a layer that's called the mantle. Now the mantle you can think of as
: a sort of hot sludge of rocks. These rocks are so hot, they're sort of semi molten,
: they're actually moving around in convection currents inside the mantle. And then at the very
: top you have a layer called the crust. Very light rocks such as basils and granites reach the top,
: they cool, they form this thin layer of the crust that's where we live. But the crust
: is pushed around by those convection currents from underneath. This looks weird to us simply
: because we don't live long enough to see that the Earth is in fact changing all the time
: Some scholars began to notice this as early as the 16th century when they studied the
: first world maps that were ever produced. Some of them noticed odd things like the fact that
: West Africa seems to fit well into Brazil. I mean, look at a modern map and you'll see the
: same thing. In the early 20th century, a German meteorologist called Alfred Wegener found lots
: of evidence to suggest that the continents had in fact once been connected. For example,
: he found very similar geological strata in West Africa and in Brazil and during World
: War I he wrote a book arguing that once all the continents on Earth had been united in a single
: super continent that he called Pangaea, after the Greek goddess Gia for the earth. Wegener
: came up with heaps of evidence to show that the continents seemed once to have
: been linked. What he couldn't do was explain how the continents moved around the earth.
: During World War II, sonar technologies were developed to track submarines and after World
: War II some geologists used that technology to try to map the ocean floor, and when they started
: doing this, they found something that really surprised them. Through many of the Earth's
: oceans they found huge chains of volcanoes. And what's happening is that lava is coming up from
: the mantle, it's rising up, its forming mountains, and it's pushing apart the old oceanic crust. In
: the center of the Atlantic Ocean for example, there's a huge chain of these mountains and what
: they're doing is they're pushing the Atlantic apart. They soon realized that elsewhere in the
: Earth crust was going back into the mantle which balanced what was happening in the Atlantic.
: Now to understand this, you need to think of two basic types of crust. There's continental crust,
: which is the land that we walk on, and then there's oceanic crust,
: the land beneath the oceans. Now once you've got that, think of two bits of crust colliding,
: continental and oceanic, what's going to happen is that the heavier oceanic
: crust is going to dive beneath the continental crust. Now think of this,
: it's grinding against the continental crust, it's creating huge friction, and lots of heat,
: and it melts part of the continental crust and punches up whole mountain chains. These are
: the basic ideas of the modern theory of plate tectonics. And the theory of plate tectonics
: is the fundamental idea of modern geology and earth sciences. It explains all the fundamental