Category The Earth, Earth Science, Planet Earth

Where does the Earth’s energy come from?

 

               There is a basic law of physics that says that energy is never created or destroyed; it is simply transferred from one place to another or from one form of energy to another. So all the energy that exists today has been around since the formation of the Universe.

               The Earth’s energy comes from heat trapped inside the Earth when it was originally formed, or from energy radiated out from the Sun. We cannot make energy, but we can extract it from coal, oil, fast-flowing rivers, nuclear fuel and various other sources. Even the wind can supply us with a source of energy.

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The Changing Earth

How do we know that the climate has changed?

In more recent times, geologists and paleontologists have been able to make more accurate measurements of the age of ancient rocks. Trees produce a new ‘ring’ every year, and these can be measured and counted. The width of the ring shows how well the tree grew in any year, reflecting climatic conditions at that time. The rings of even partly fossilized trees buried in bogs can be measured, and these measurements provide accurate records of climate changes over the past 750,000 years. By measuring the radioactivity of once living material, scientists can make accurate measurements up to 40,000 years ago. 

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How was oil formed?

Most scientists think that oil was formed from the remains of tiny plants and animals that inhabited the seas millions of years ago. When these creatures died, their remains were buried in layers of rock. Substances in their bodies gradually altered to form oil. Other scientists disagree, and believe that oil formed from carbon-containing materials that were trapped inside the rock when the Earth was formed. Oil is found in rocks buried beneath the continents, and beneath the shallow parts of the oceans. More than half of the world’s known oil resources are in the Middle East. 

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The Changing Earth

 

 

Why did the world’s climate change?

The appearance of living things changed the Earth’s atmosphere, providing the conditions for climate change. The first living things were plant-like creatures. They used the Sun’s energy to change carbon dioxide and water into sugars, which they used for food, and oxygen, which they released into the atmosphere. Some of this oxygen turned into ozone, forming the layer that now protects us from the Sun’s ultraviolet radiation. 

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What effect did the Ice Age have on the world and its animals?

During an Ice Age, the enormous weight of the ice sheet presses the underlying rocks down, while those around the edges rise to form hills and valleys. The constant scouring action of glaciers shapes the Earth’s surface, wearing away complete mountain ranges. In an Ice Age, animals are forced to migrate to warmer areas. The ones that cannot adapt, for example mammoths and the woolly rhinoceroses, become extinct. The ice sheets on Greenland and in the Antarctic are the remains of the most recent Ice Age. 

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The Changing Earth

Poisonous air

The Earth’s original atmosphere was very poisonous. It contained almost no oxygen. It consisted of gases such as hydrogen, helium, methane and ammonia, as well as carbon dioxide. It would have been impossible to breathe in such an atmosphere Lightning and the Sun’s radiation caused chemical reactions in these gases, producing some of the substances characteristic of life, and this may have triggered the development of the first primitive life forms.

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How has the Earth been reshaped?

Erosion is one of the most powerful ways in which the Earth’s surface has been altered. Moving ice and flowing water wear away the surface of rocks and cut out valleys, as well as wearing down the peaks of mountains. Along the coast, tides and wave action wear away exposed cliffs, and currents carry away sand and mud to be deposited elsewhere. The tides and wind-blown sand polish and wear away rocks and pebbles. 

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The Changing Earth

What is an Ice Age?

Ice Ages were periods when large parts of the Earth’s surface were covered by sheets of ice. Each Ice Age has lasted about 100,000 years, with gaps between of up to 20,000 years when the weather was warmer and the ice melted. The last Ice Age ended about 12,000 years ago. Ice ages appear in groups in geological time, each lasting for 20 to 50 million years. The oldest known glacial periods were as long as 2.3 billion years ago. A minor ice age began in the 1500s and lasted for 300 years, during which glaciers were more widespread than at any time for thousands of years.

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Gigantic waterfall!

More than five million years ago, the Mediterranean Sea was a dry basin. Then, movements in the Earth’s crust opened up the Straits of Gibraltar between the land masses of Europe and Africa. The waters of the Atlantic Ocean poured through the gap, flooding the basin. The result was the creation of a gigantic waterfall, at least 800 m high, which let through so much water that the whole of the Mediterranean filled up in few years. 

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The Changing Earth

 

What was the Earth like when it was formed?

The Earth had probably existed for around 3,000 million years before the first signs of life appeared. As it cooled after forming from a ball of hot gases, the Earth would have been a relatively smooth sphere. It was covered with shallow seas that contained a mixture of dissolved chemicals, and surrounded by an atmosphere of mixed gases. The atmosphere was full of swirling clouds of vapour, which probably caused huge electrical storms. 

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When did life first appear?

The first signs of life are thought to have appeared about 3,500 million years ago. Some rocks from this time contain substances that are characteristic of life, although fossils appear from much later. Scientists believe that primitive life forms altered the original poisonous composition of the atmosphere, eventually releasing the oxygen that we need to survive. The seas were probably once filled with a mixture of chemicals from which life may have developed. It is more likely, however, that life first appeared in areas such as those around undersea vents. These first forms of life would have been bacteria and microscopic blue-green algae. 

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