Sea-floor Spreading
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In 1960 Harry Hess, an American Geologist, proposed a radical idea. He suggested that ocean floors move live conveyor belts, carrying the continents along with them. This movement begins along the mid ocean ridge which contains the longest chain of mountains on Earth. At the mid ocean ridge, molten materials rise up between the mountain chain from the mantle and adds new sea floor. The molten material then spreads out, pushingolder rocks to both sides of the ridge. The rock coming out of the mid ocean ridge is hotter, younger, and less dense than the rock further away from the ridge causes the dept of the ocean to increase as you get further from th eridge. Hess calls this movement that adds new material to the ocean floor sea-floor spreading.
When scientist studied patterns in the rock of the ocean floor, they found three pieces of evidence that supports sea floor spreading. The Earth acts like a giant magnet, with the North and south pole. Evidence shows that the Earths magnetic poles have reversed themselves. The last pole reversal happened 780,00 years ago. The Basalt that makes up the ocean floor contains high levels of iron cooled, the crystalline patterens in iron lined up in the direction of Earths magnetic poles.
The second peice of evendence was gathered by the submersible Alvin, which was built to withstand the crushing pressure of the ocean. While submerged the photographed pillow lava along the ridge. These 'pillows' form underwater when cold ocean water causes a crust to form on erupting molten material. Each pillow expands until it burst, allowing molten material to flow out and form the next pillow.
Last but not least the third piece of evidence is drilling samples. In 1968, a ship named the Glomar Challenger gathered samples from the ocean floor up to 6 kilometers in depth. this feat is similar to trying to use a sharp endedd wire to dig a hole into a sidewalk from the top of the Empire State biulding. When the samples gathered were analyzed they found that the samples further away from the ocean where older than samples near the ridge.
When scientist studied patterns in the rock of the ocean floor, they found three pieces of evidence that supports sea floor spreading. The Earth acts like a giant magnet, with the North and south pole. Evidence shows that the Earths magnetic poles have reversed themselves. The last pole reversal happened 780,00 years ago. The Basalt that makes up the ocean floor contains high levels of iron cooled, the crystalline patterens in iron lined up in the direction of Earths magnetic poles.
The second peice of evendence was gathered by the submersible Alvin, which was built to withstand the crushing pressure of the ocean. While submerged the photographed pillow lava along the ridge. These 'pillows' form underwater when cold ocean water causes a crust to form on erupting molten material. Each pillow expands until it burst, allowing molten material to flow out and form the next pillow.
Last but not least the third piece of evidence is drilling samples. In 1968, a ship named the Glomar Challenger gathered samples from the ocean floor up to 6 kilometers in depth. this feat is similar to trying to use a sharp endedd wire to dig a hole into a sidewalk from the top of the Empire State biulding. When the samples gathered were analyzed they found that the samples further away from the ocean where older than samples near the ridge.