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Geologic History of the Earth 1 the Precambrian

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Geologic History of the Earth 1 the Precambrian Geologic History of the Earth 1 algae = very simple plants that Geologists are scientists who study the structure grow in or near the water of rocks and the history of the Earth. By looking at first = in the beginning at and examining layers of rocks and the fossils basic = main, important they contain they are able to tell us what the beginning = start Earth looked like at a certain time in history and billion = a thousand million what kind of plants and animals lived at that breathe = to take air into your lungs and push it out again time. carbon dioxide = gas that is produced when you breathe Scientists think that the Earth was probably formed at the same time as the rest out of our solar system, about 4.6 billion years ago. The solar system may have be- certain = special gun as a cloud of dust, from which the sun and the planets evolved. Small par- complex = something that has ticles crashed into each other to create bigger objects, which then turned into many different parts smaller or larger planets. Our Earth is made up of three basic layers. The cen- consist of = to be made up of tre has a core made of iron and nickel. Around it is a thick layer of rock called contain = have in them the mantle and around that is a thin layer of rock called the crust. core = the hard centre of an object Over 4 billion years ago the Earth was totally different from the planet we live create = make on today. There were no plants or animals, only rock, desert, water and ice. creature = a living thing The atmosphere probably consisted of carbon dioxide and steam with almost crust = the hard outer layer of the Earth no oxygen to breathe. desert = an area of hot, dry land develop = grow dust = dry powder made up of dirt evolve = grow , develop examine = to look at closely and find out more about an object fossil = an animal or plant that lived many thousands or mil- lions of years ago and that has been preserved in rock layer = sheet, cover nickel = a hard silver-white metal oxygen = a gas that is in the air and which we need to breathe particle = a very small piece of something probably = likely The Precambrian Era solar system= our sun and the planets that go around it The oldest period of the Earth’s history lasted from the beginnings four and a sponge = a soft material with half billion years ago to about 600 million years ago. At first, simple forms of small holes in it that can ab- one-celled life developed in the oceans. Later on bacteria and algae evolved. sorb water or other liquids Towards the middle of the Precambrian, about 2 billion years ago, more com- steam = gas that comes up plex organisms, sponge-like creatures and soft-bodied animals lived in the from hot water towards = just before seas. During this time there was no life on land because there was not enough oxygen to breathe. Geologic History of the Earth 2 absorb = to take something in although = while amphibian = animal that lives on land and in the sea appear = show up carbon dioxide = gas that is produced when you breathe out Carboniferous period = later part of the Palaeozoic era creature = living thing develop = grow divide = break up, separate dominate = control, to be the most important enormous = very big era = time, period evolve = grow As the Precambrian came to an end the oceans were full of life. Plants started invertebrate = a living thing absorbing the carbon dioxide from the atmosphere and turned it into oxygen. that does not have a back- Early continents formed, but they looked quite different than they do today. bone moss = a very small green plant that grows on the ground or on wet rocks The Paleozoic Era oxygen = a gas that is in the The Paleozoic era lasted from 600 million to about 240 million years ago. Geolo- air and which we need to gists divide this era into six periods. From the earliest to the latest these are breathe the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and the Permian. period = time, section, era Although most animals and plants still lived in the oceans, life started to devel- quite = very op on land and by the end of this era there was life in both the sea and on land. reptile = animal whose body The earliest living objects on land were simple plants and mosses, the first temperature always changes; creatures to appear on land were animals that looked like spiders, scorpions it lays eggs to have babies and insects. spider = a small creature that has eight legs and catches The middle of the era was dominated by all sorts insects of fish and invertebrates. Early amphibians, ani- mals that could live on land and in water, ap- peared. During the Carboniferous period the first reptiles evolved and insects grew to an enormous size. The end of the era was the time of big forests and Geologic History of the Earth 3 asteroid = a small planet-like swamps. The Earth got hot and wet. object that moves around the Plants and big trees died and were bur- sun ied in sediments. block out = not let in Over millions of years they turned into border = line between two gigantic coal deposits which we find in objects the eastern United States, Europe, Rus- bury = if something is hidden sia and China. under the ground cause = the reason for some- During the Paleozoic era the land masses were constantly moving and by the thing end of the era they joined together to become a single continent called Pan- gaea. As these land masses collided several mountain chains, for example the collide = crash into each oth- er Appalachian and Ural Mountains, emerged. constantly = always creature = a living thing deposit = layer of rock that has metal or minerals in it drift = move , float dust = dry powder made up of dirt emerge = show up, start to exist era = time, period eruption = if a volcano ex- plodes and sends out smoke, fire and ash into the sky gigantic = very big join = to become one mountain chain = group of mountains, usually in one line scientist = a person who is trained in science and works in a laboratory sediment = material that falls Millions of years ago there was one continent, Pangaea. It broke apart down to the bottom of the along the borders of today‘s continents . The separate landmasses sea started drifting away from each other. swamp = land that is always wet or covered with water thrust = to send out quickly The Mesozoic Era and with a lot of power The Mesozoic era lasted from about 240 million to about 65 million years ago. At the end of the Paleozoic 90 % of all living creatures on Earth died out. We don’t know what caused this to happen but many scientists think that our climate started to change dramatically. Maybe a big volcanic eruption thrust gas into the atmosphere or maybe a large asteroid hit the Earth and dust blocked out sunlight for many years. Geologic History of the Earth 4 abruptly = very quickly appear = show up asteroid = a small planet-like object that moves around the sun block out = not let in cattle = cows continue =go on creature = a living thing deer = a large wild animal that can run very fast, has thin legs , eats grass and has horns The Mesozoic era is often called the age of dinosaurs because they dominated the Earth’s landmasses. These reptiles were the most powerful and fearsome direction = route, way creatures of that time. The archaeopteryx was a flying reptile, probably the divide = separate first bird on earth. Some dinosaurs, like the Tyrannosaurus rex, were meat eat- dominate = to be in control of ing predators; others only ate plants and leaves. The 30 meter long brontosau- dust = dry powder made up of rus was the largest land animal that ever lived. dirt During the Mesozoic era the first mammals also appeared on Earth but they era = period of time were very small and could not match the size and greatness of dinosaurs. Eurasia = the combined land- mass of Europe and Asia In this time Pangaea started breaking up and land masses formed the continents fearsome = very frightening we know today. They started moving in all directions. By the end of the Meso- greatness = here: power zoic era South America had separated from Africa. including = also Australia and Antarctica was one continent and North mammal = an animal that America had started to move away from Eurasia. Just drinks milk from its mother’s like the Paleozoic era before it, the Mesozoic also body when it is young ended abruptly. About 65 million years ago 75 per match = to be the same as cent of all animals on Earth, including the dinosaurs, period = era of time died out. Geologists are pretty sure that a large as- predator = an animal that teroid hit Mexico and sent dust into the atmosphere kills and eats other animals which blocked out sunlight for years. It killed off present = now many plants, and animals could not survive without reptile = animal whose body food. temperature always changes; it lays eggs to have babies rhinoceros = a large heavy African or Asian animal with thick skin and one or two The Cenozoic Era horns on its nose The Cenozoic era started about 65 million separate = to move away from years ago and continues into the present. It is divided into the Tertiary period which size = how big something is ended about 1.8 million years ago and Qua- sure = certain, there is no doubt ternary period.
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