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| Sunday, 19 September 2004 |
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Junior Observer |  |
| News Business Features Editorial
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The Continental jigsaw puzzle Get a map of the world and take a good look at the five continents. Don't many of them seem to fit like the pieces of a giant jigsaw puzzle? Isn't it possible then, that once, long, long ago, the entire landmass on Planet Earth was one large chunk of land?
What are these clues? One is the discovery of the remains of a certain kind of animal which does not live today in both Africa and South America. Now, how can they be found in almost the same regions of two different continents which are oceans apart? (see the jigsaw map). Surely these animals couldn't have walked across the ocean? Or did they fly? It does not become such a puzzle if we imagine the continents to have been joined. Then the animals could have moved freely from one place to another. In the 1960s scientists found strong evidence to prove that the continents are moving. While exploring the ocean floor they discovered something really strange. A long chain of underwater mountains in the middle of the Atlantic Ocean! This underwater mountain chain or mid-ocean ridge which is two kilometres below the ocean's surface is 65,000 kilometres long. The ridge in the Atlantic Ocean is really two mountains side by side with a long valley between the mountain chains.
What happens to the magma that comes out onto the ocean floor? It hardens and forms a new crust which piles up to make mountains. Then it moves away on both sides of the valley, allowing more magma to come up. It is this movement of the crust that make the continents to shift. However, when the crust moves, all the earth's crust does not move at once. It slowly moves in sections that are known as 'plates'. Each of these plates includes the crust and part of the mantle. Most plates are large and may be the size of a whole continent or an ocean. The plates move at different times and speeds and in different directions too.The mid-ocean ride is the boundary between two plates that bump into each other. Find out... * What is happening at the mid-ocean ridge? * What are plates? * Part of the mid-ocean ridge runs through the Red Sea. What may be happening to the Red Sea? * Why does Los Angeles get most of its water from the Colorado River rather than from the Pacific Ocean? * Certain kinds of waves travel fast through solid rock but do not move at all through liquid. What do you think happens when the waves run into partly-melted rock? * How could you get an idea of how deep a pit is without actually looking into it? * Suppose a scientist finds the remains of palm trees in northern Canada which are millions of years old, how might this discovery be a clue that the continents moved? * On the ocean floor, where would you look to find the youngest rocks? The oldest rocks? |
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Many scientists think so. Their theory is that the land broke apart due
to certain internal or external forces and are still moving! They have
even found clues that seem to prove their theory.
The floor of this valley has many large cracks with melted rock or
magma rising out of these cracks. The Magma rises from the mantle.
