Advanced World Geography Chapter 1 – Exploring Geography .Advanced World Geography Chapter 1 –

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    Changes Within the EarthOne of the chief tasks geographers take on is to understand the earths continuous changes. Earth is not a stagnant, quiet planet. Earthquakes knock over buildings and create huge cracks in the ground. Volcanoes erupt with scorching lava and hazardous gasses. These changes are dramatic and spectacular, but they are not the only ways in which the earth changes. There are manydifferent processes, some striking and others subtle, that are always hard at work shaping the earth we inhabit.

    Structure of the EarthGeology is the study of the earths physical structure and history. It looks to the ancient history of the earth for answers. Geologists try to figure out what changes occurred in the earths past and why these changes occurred. From their findings, they try to predict any future changes that could occur.

    David Wunsch and the New Hampshire state geologist, examining an area where the Suncook River once flowed.

    Source: New York Times

    Advanced World Geography Chapter 1 Exploring Geography

    Lesson 2 A Changing Earth

    In this lesson you will learn how to: describe how the earth is a changing planet that is affected by geologic processes. describe the forces within the earth and how they create and change landforms on the surface. describe the theory of plate tectonics and how it suggest multiple answers regarding the earths landforms.

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    Inside the Earth. Scientists have come up with a pretty good idea of what the center of the earth is like. Its center is known as the core. It consist of extremely hot metal, which is mainly iron mixed with some nickel. It is divided into two layers, the inner core and the outer core. The inner core is believed to be dense and solid. It is about 780 miles thick. The outer core is so hot that its metals are molten, or liquid. It is about 1,370 miles thick. Because of the earths rotation, the outer core spins around the inner core, causing the earth's magnetism. Surrounding the core is the mantle. The mantle is a thick layer of rock. Scientists think the mantle is 1,800 miles thick and makes up nearly 80 percent of the earth's total volume. The rock in the mantle is mostly solid, with some of the upper layers possibly being pliable. The mantle also holds pockets of magma, which is melted rock.

    The crust, or the rocky surface layer, is astonishingly thin, like the icing on a cake. The oceanic crust, only 5-7 miles thick, is the thinner part of the crust, which is located below the oceans. The oceanic crust consists of mainly basalt without olivine, ortholeiitic basalt. Basalt is dark, fine and gritty, with a volcanic structure. It is fashioned out of molten lava, which cools off quickly. The grains are so tiny that they are only detectable under a microscope.

    Unlike the oceanic crust, the continental crust is thick, averaging 22 miles, and is extremely uneven. The continental crust is older than the oceanic crust, some rocks being 3.8 billion years old. It is primarily made up of igneous rocks and is divided into two layers. The upper layer primarily consists of granite rocks, while the lower layer consists of basalt and diorite. Granite is lightly-colored, course and grainy, magma. Diorite has the same composition, but it's scarcer than granite, and is probably formed by impurities in the granite-magma. Natural forces often interact with and affect the crust, sometimes creating landformsor natural features found on the earths surface.

    Source: uvm.edu

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    Land, Air, and Water. Often, geographers speak of the various elements of the natural environment of the earth as a set of related spheres which are dominated by various physical forms. Landforms, soil, rocks, and other features of the surface make up the lithosphere. The layer of air, water, and other substance about the surface of the earth is called the atmosphere. The hydrosphere, however, is made up of water in oceans, lakes, rivers, and even water found under the ground. The world of plants, animals, and other living organisms that inhabit the land and waters of the earth make up the biosphere. Physical geography looks at the way in which these spheres function and interact with one another and with people.

    Pictures taken of the earth from space give a clear picture of the saying that the earth is truly a watery planet. Over 70 percent of the earths surface is covered by water. Most of this water is salt water, which can be found in the oceans and seas. The huge landmasses seen in the oceans are the continents. Though some of these landmasses are not totally separated by ocean waters, geographers still classify them as seven separate continents. Of these continents, Asia is the largest and Australia is the smallest. Each continent contains various landforms. Antarctica, however, has its landforms hidden by ice. Often landforms are classified according to differences in relief, or the different in elevation between the lowest and highest points. Also important, is whether they rise little by little or suddenly.

    Source: Public Domains

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    A plateau is also an elevated area, but has a level surface. Many plateaus have deep gullets or canyons, which make the surface appear rough instead of flat. There is at least one side of the plateau that rises about the surrounding land steeply. Plains are also considered landforms. A plain is a flat or gently rolling areas that has very few changes in elevation. Many plains are located along coasts. Other landforms include valleys, canyons, and basins. There are also various geographical features of landscapes that consists of rivers, peninsulas, and islands.

    This picture shows the various land and water features that can be found on earth.

    The main kinds of landforms are mountains, hills, plateaus, and plains. Rising at least 2,000 feet about the terrain that surround it, mountains have high relief. Hills, however, are lower, rounded, and usually less steep than mountains. The elevation of the land around the landform determines whether it is a hill or a mountain. Also, what we may see as a mountain in western North America, may be seen as a hill in the British Isles. Everything depends on the relative height of nearby landmasses in the area.

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    The questions that is often asked by geographers or geologists when looking at an area of land is, What forces shaped the mountains, plains, and other land forms that are here? Internal forces that originate in the earths interior first shape landforms. Volcanism is one of these forces. It involves the movement of the magma inside the earth. The other main forces that occur internally are movements that fold, lift, bend, or break the rocks on the earths crust.

    Volcanoes. The people of ancient Rome believed the god Vulcan worked beneath the earth with hot iron and gold at his forge. In honor of Vulcan, a fiery island off Italys coast was named Vulcano, and all the mountains formed by molten rock were called volcanoes. Volcanoes form when molten rock, or magma, beneath the surface of the earth breaks through the earths crust. On the surface, the lava might flow evenly, making a plateau-like shield volcano. Cinders and ash erupting form the break in the ground sometimes produces small cinder cones. Unique cone-shaped mountains are fashioned as sporadic sequences of explosive eruptions and smooth lava flows from the volcano. A prime example of this type of volcano is Mount Fuji, which is located in Japan.

    Inner Forces

    Changes in the Earths Crust. The complex movements that bend and break the crust of the earth vary. A fold results from rock layers bending and buckling. Other stresses on rocks cause faults, or cracks in the earth's crust. Rocks on either side of a fault sometimes slip or suddenly move. On one side of a fault, rocks might move sideways, up or down in reaction to the rock on the other side of the fault. A rock on either side of a fault may slowly move and produce subtle, unnoticeable changes. A large, sudden movement along a fault, however, can send out shock waves through the earth and cause an earthquake. Nonetheless, whether rock layers fault or fold, it is determined by the solidity of the rock and the power of the movement.

    Mount Fiji located in Japan.

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    The majority of the changes to the surface of the earth happen so slowly that they are not immediately noticeable to the human eye. Much of the earths history has been reconstructed by geologists from the record they read in the rocks. For years and years, scientists believed that the essential arrangement of oceans and continents were secure and permanent. These days, the accepted idea by most is that the earths landmasses have broke apart, rejoined, and moved to other parts of the earth. The plate tectonic theory, which suggest answers to many perplexing questions concerning the landforms on earth, is formed partially by this concept.

    Plate Tectonics. The theory of plate tectonics suggest that the earth's outer shell is not one solid piece of rock. The lithosphere, or the earths crust and the brittle upper layer of the mantle, is broken into many different plates that move. These plates are different sizes and vary in thickness. The North American Plates reaches from the mid-Atlantic Ocean to the northern tip of Japan. In contrast, the Cocos Plate covers a tiny area in the Pacific Ocean, west of Central America. The plates are not fastened in place, sliding over a hot, pliable layer of mantle.

    Geologic History

    The oceans and continents of earth move atop the plat