The Study of Geography


Geography is the study of where people, places, and things are located and how they relate to each other. Geographers use a variety of geographic tools, including maps, charts, and computer and satellite technologies. Geographers use concepts, or ideas, to organize the way they think about geography.Many geographers use five main themes to study geography. The theme of location describes where a place is found. A location may be an absolute loca- tion, or its position on the globe. Relative location describes where a place is in relation to another place. An example of relative location is, “Mexico is south of the United States.” The theme of place describes how areas are alike or different. Places can be described by their physical features or in terms of their human characteristics, or how people live there. The third geographic theme deals with regions. A region is a group of places with at least one thing in common. Geographers divide the world into many different regions based on various criteria. The theme of movement describes the ways people, goods, and ideas move from one place to anoth- er. Geography has an important effect on movement. The final geographic theme examines how people use and change their envi- ronment. People expand areas by build- ing homes, roads, and factories, which have positive and negative effects on the surroundings.

1- Name the five themes of geography.
2- Which two continents are bordered on the west by the Atlantic Ocean?

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CHANGES WITHIN THE EARTH


Forces of nature, like volcanoes, are con- stantly changing the earth. Geology is the study of the earth’s history and physical structure. The center of the earth is called the core. It is made of very hot metal. The inner core is probably solid, while the outer core is liquid. The mantle is a thick layer of rock around the core. The crust is the earth’s rocky outside layer. It is very thin, like the icing on a cake. More than 70 percent of the earth’s surface is covered by water, mostly oceans and seas. The seven continents are the largest areas of land. Forces inside the earth shape the earth’s landforms. Volcanoes, for exam- ple, are mountains that form when molten, or melted, rock inside the earth breaks through the crust. On the surface, the molten rock flows as lava. Breaks in the earth’s crust cause faults. Sudden movement along a fault can cause an earthquake. Most geologists believe that the earth’s landmasses have broken apart, rejoined, and moved apart again. According to the theory of plate tectonics, the earth’s crust and upper mantle are broken into moving plates. These plates can pull apart, crash into each other, or slide past each other. Oceans and continents ride on top of the plates.

3- How much of the earth’s surface is water?
4- What are the four layers of the earth?

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CHANGES ON THE EARTH’S SURFACE


The surface of the earth is constantly changing. The forces that change the earth’s surface are usually grouped into two categories: weathering and erosion.Weathering is the process of breaking down rock into smaller pieces. Mechanical weathering breaks down or weakens rocks physically. Ice is the chief cause of mechanical weathering. Ice widens cracks and splits rocks. Chemical weathering changes the chemical makeup of rocks. Water and car- bon dioxide are the main causes of chem- ical weathering. They combine to form an acid that can dissolve rocks. Erosion is the movement of weath- ered materials, such as soil, sand, and gravel, from one place to another. Moving water is the major cause of erosion. The water carries pieces of rock that act like sandpaper, grinding away the surface of rocks. Then the moving water carries away the bits of rocks and soil and deposits them elsewhere. Wind is another cause of erosion. Winds lift away soil that has little to hold it. Then the winds deposit the soil elsewhere. Sand in the wind can carve or smooth the surfaces of rocks. Glaciers, or slow-moving sheets of ice, are another cause of erosion. They wear away land and move rocks and soil to other places. Glaciers have carved out lakes and valleys.

WeatheringandErosion
5- What is the difference between weathering and erosion?
6- What are two kinds of weathering?

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