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Earth's Inner Structure Help

By — McGraw-Hill Professional
Updated on Aug 31, 2011

Introduction to Earth's Inner Structure

Ancient people thought the Earth was flat and had no idea of its inner workings. Over time, they mapped out surface features like continents and oceans, but they pretty much kept with what was always known.

Europeans, who thought there was nothing to the east but more oceans, had to rethink that idea. When the Vikings and Christopher Columbus discovered whole new continental landmasses to overrun, it turned a lot of people’s ideas upside down. They began to question all that they knew about the Earth, its creation, and ongoing development.

The stories of how the Earth was formed and what keeps it going have been varied over time and cultures. Around the globe, creative people came up with all kinds of explanations of what was going on in the center of the Earth. Early people thought that if they understood what made the Earth shake and destroy whole villages, especially if it was somehow their fault, they could prevent the problem from happening again.

Native Americans thought the Earth was like a mother and the sky a father that provided all their needs. This is easy to understand since everything, from their food supply (plants and herbs and buffalo) to their shelters and transportation (horses), were available from nature. When a natural disaster occurred, they took it as a sign that they had earned the displeasure of the earth or sky through careless stewardship of what they had been given. They thought they could prevent natural disasters from happening again by keeping a pure relationship with Mother Earth and Father Sky. Their problem with nonnative “invaders” was less about newcomers claiming the land for themselves (or their king), than their fear that dishonoring the land would bring disaster upon them.

In China, people thought a dragon lived in the center of the Earth. They believed that occasionally the dragon awakened, and unleashed rumbling, volcanic spewing, and major disasters on the surface. Earth dwellers were at the mercy of the dragon and its fits of displeasure. By living in harmony with the Earth, people thought they would have a lot less chance of disturbing the dragon. Maybe this was the beginning of the expression, “Let sleeping dragons lie.”

In India, people believed that the Earth was supported by elephants that stood on the back of a turtle that rested on a cobra. When the cobra moved, the turtle and elephants were unbalanced and the Earth shook and jolted in wild ways.

In the Polynesian islands, there are two legends describing the forming of the continents. The first describes how the gods fished the Earth out of the ocean, but the line broke releasing some of the catch back into the water. The part that stayed above the water level became the land and mountains. The second story tells how a turtle submerged deep in the ocean and came up with a huge clump of mud stuck to its back. This clump became the lands of the Earth.

Nebular Hypothesis

During the 18th century, early scientists moved beyond legends and started looking toward science for Earth Science answers. They started out by trying to understand how the solar system formed and where the Earth was placed in the system.

In 1755, Immanuel Kant, a German scientist/philosopher noted that the solar system must have formed from a large mass of gas and then gotten smaller and smaller from the tightening pull of gravity and rotation. After some time, rotation increased so much that the rings separated from the center mass. These rings eventually condensed to form planets that were held in orbit by gravity from the central mass.

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