FORMATION OF EARTH. Today we are going to talk about the earth.how it was formed.

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1 FORMATION OF EARTH Have you ever wondered about the universe? What made it possible.how it was formed? Of course, religion has explained for centuries the intricacies of creation. And as always, science has decided to find its own answer to that question. Today we are going to talk about the earth.how it was formed. JUST how the earth was formed is not known for sure. After all, no one has been really around for that long. But scientists research and formulate theories based on their research. They study the earth, the rocks, the water and the air. And based on their findings, they come up with plausible answers. These are called theories. There are two popular theories for why and how the earth formed. We will cover both today. The most common view of scientists is that the earth started out as a ball of fiery gas. THE BALL OF GAS The earth wasn t formed by itself. It formed with the rest of our solar system. Just in case you didn t know.our solar system consists of the Sun, the nine planets that orbit it, and their moons. Billions of years back, scientists suppose that the solar system started out as one huge, VERY HOT ball of gas. Gradually, over MILLIONS of years, the ball cooled. And, as it cooled, it shrank.as most bodies do when they cool. Nobody is sure if this ball was already rotating. But if it wasn t, it must have come to do so as it shrank. As the ball cooled, it rotated faster and faster.so fast that the outer part, which was moving fastest separated in the form of a ring. And this ring began to move away, still continuing to spin (see if you can simulate this part). THE EARTH The big ball continued to cool and shrink.and whirl faster. And more rings separated. Each of these rings also moved away, to stand in areas where today the planets orbit the sun. They continued to rotate, and cool.and shrink. At some point, each of these rings parted and began to gather together into independent globes of gas. One of these rings formed a globe of gas that later became our earth. The process from this point to today is believed to be 4.6 billion years!!! Over time, the earth (which was still a ball of gas) cooled so much that it became mostly liquid.mostly lava. (Lava is molten iron) THE OCEAN & ATMOSPHERE FORM At this stage.when the earth was still liquid.it was still too hot for the water around to condense. So it remained in the form of steam or vapor, forming a vast envelope all about the earth. Many other vapors were in the air at this time, making it atmosphere very dense. Slowly, the lava cooled so that the outer part crusted over, and this crust grew thicker and thicker as time went on. Once the crust cooled enough, water condensed on the surface and the ocean began to form. The water grew in depth until nearly all the steam from the atmosphere condensed. Other vapors that had been in the air also condensed and settled

2 around the earth s crust or in the water. All the gases that could NOT condense form the air much as it is today. That is the way the atmosphere is supposed to have come about. THE NEBULAR THEORY! Of course, like we said in the beginning, this is all theory. It cannot be proved. No one was really around to see the earth evolve. And this evolution took billions of years. But research by many scientists shows this theory to be most probable. Of course the first fact that points to this theory comes from studying old rocks and the inside of the earth. This is how scientists are able to explain the incredible heat trapped inside the earth. How do they know that it is so hot? As wells and mines are sunk deep in the ground it is found that the earth grows warmer and warmer. Volcanoes pour out molten rock from the bowels of the earth. This shows that it is very hot somewhere beneath them. Many of the mountains on the earth are really wrinkles in its crust, and it has been thought that these are caused by the cooling and shrinking of the globe. It is because these and other things fit in so well that most scientific men have come to accept it. This theory is known as the NEBULAR THEORY. THE ACCRETION THEORY In science, no one ever takes one theory for granted unless it has been proven to be true. But like we ve said before, NO ONE was around at the time the earth was evolving, so everything just stands at theory. Some scientists have supposed that the earth was formed by small masses or particles of matter gathered in from space. I m sure you have seen shooting stars on clear nights. These "stars" are little bits of stone or metallic matter shooting through space. They fall through our atmosphere at very high speeds and burn up. Now most shooting "stars never make it to the earth itself. They burn up on the way. But larger pieces actually end up landing on earth. These pieces are called meteorites. Scientists have studied the composition of these meteorites and found that the materials in them resemble the materials they have found inside the earth. Therefore it is theorised that a great number of these meteorites collided together to form one larger planetoid, viz. The premature earth. When these meteorites collided with such high speeds, they generated tremendous amounts of heat. This heat was trapped* and explains why the earth is still so hot inside. The interesting part is that this theory also borrows from the Nebular Theory s rings. The premature earth attracted matter from one of the rings that it was near. Slowly it attracted enough material to form a large planet. This is called the Accretion theory. *(If you want to explain "trapped", read this part. If the earth was built up this way we must account for the heat in the interior, but this would come naturally enough. As the little bodies fell upon the surface they would strike hot. But unless they came fast they would coot off before others struck the same spot and the earth would not get very hot. But as they gradually built up the surface the matter below would be pressed together harder and harder because of the growing weight upon it, and this pressing together would make it hot. It is figured out that it would become very, very hot indeed, though this might not seem so at first thought, and that

3 the volcanoes and mountains may all be explained in this way quite as well, and perhaps better, than in the other way. ) SO WHICH ONE S RIGHT? Well, that s the thing about science. Each of you is a scientist. We ve given you the basic background of each theory. Its up to you decide which one you d rather accept, OR you can come up with your own. But you should have scientific evidence to prove your theory.just like these scientists who have studied space, rocks, water, and other earth matter for years. It may be that neither of these theories is right, which is why they remain theories... POSSIBLE explanations for how the earth formed. Most scientists however, lean towards the Nebular theory. HOW OLD IS THE EARTH? So how long did this entire process take??? It is theorized that the true age of the earth is about 4.6 billion years old. And how did they come up with that figure.i mean, nobody was around then right??? Scientists believe that the earth formed at about the same time as the rest of our solar system. The oldest rocks geologists have been able to find are 3.9 billion years old. Using radiometric dating methods to determine the age of rocks means scientists have to rely on when the rock was initially formed (as in - when its internal minerals first cooled). We ve already discussed that during her infancy, our home planet was molten (melted) rock, a magma ocean. Since we can only measure as far back in time as we had solid rock on this planet, we are limited in how we can measure the real age of the earth. Even today the earth is constantly changing. Due to the forces of plate tectonics, our planet is very dynamic; new mountains are forming, old ones are wearing down, volcanoes are melting and reshaping new crust. The continual changing and reshaping of the earth s surface that involves the melting down and reconstructing of old rock has pretty much eliminated most of the original rocks that came with earth when it was newly formed. So the age is a theoretical age. So when did life begin? The Mystery Of Life Scientists are still trying to unravel one of the greatest mysteries of earth: When did "life" first appear and how did it happen? It is estimated that the first life forms on earth were primitive, one-celled creatures that appeared about 3 billion years ago. That s pretty much all there

4 was for about the next two billion years. Then suddenly those single celled organisms began to evolve into multicellular organisms. No one really knows why. Then an unprecedented profusion of life in incredibly complex forms began to fill the oceans. Some crawled from the seas and took residence on land, perhaps to escape predators in the ocean. A cascading chain of new and increasingly differentiated forms of life appeared all over the planet, only to be destroyed by an unexplained mass extinction. It would be the first of several mass extinctions in Earth s history. Scientists have been looking increasingly to space to explain these mass extinctions that have been happening almost like clockwork since the beginning of "living" time. Perhaps we ve been getting periodically belted by more space rocks (ie. asteroids), or the collision of neutron stars happening too close for comfort? Each time a mass extinction occurred, life found a way to come back from the brink. Life has tenaciously clung to this small blue planet for the last three billion years. Scientists are finding new clues as to how life first began on earth in some really interesting places - the deep ocean. The Fossil Record Scientists have studied rocks using radiocarbon dating methods to determine the age of earth. Another really cool thing they ve found in rocks that tells us more about the story of earth s past are the remains of living creatures that have been embedded in the rocks for all time. We call these fossils. It has been the careful study of earth s fossil record that has revealed the exciting picture about the kinds of creatures that once roamed this planet. Fossilized skeletons of enormous creatures with huge claws and teeth, ancient ancestors of modern day species (such as sharks) that have remained virtually unchanged for millions of years, and prehistoric jungles lush with plant life, all point to a profusion of life and a variety of species that continue to populate the earth, inspite of the periodic mass extinctions. By studying the fossil record scientists have determined that the earth has experienced very different climates in the past. In fact, general climactic conditions, as well as existing species, are used to define distinct geologic time periods in earth s history. For example, periodic warming of the earth - during the Jurassic and Cretaceous periods - created a profusion of plant and animal life that left behind generous organic materials from their decay. These layers of organic material built up over millions of years undisturbed. They were eventually covered by younger, overlying sediment and compressed, giving us fossil fuels such as coal, petroleum and natural gas. Alternately, the earth s climate has also experienced periods of extremely cold weather for such prolonged periods that much of the surface was covered in thick sheets of ice. These periods of geologic time are called ice ages and the earth has had several in its history. Entire species of warmer-climate species died out during these time periods, giving rise to

5 entirely new species of living things which could tolerate and survive in the extremely cold climate. Believe it or not, humans were around during the last ice age - the Holocene (about 11,500 years ago) - and we managed to survive. Creatures like the Woolly Mammoth - a distant relative of modern-day elephants - did not. Ah.the wonders of life! I hope this explains how wonderful and awesome it is that we are able to share this earth. Now what we need to do is respect it and take care of it, so that future generations can enjoy it.