Earth Science Textbook - Chapter 1 PDF

# 1.1 What Is Earth Science? ## Reading Focus * What is the study of Earth science? * How did Earth and the solar system form? ## Vocabulary * Earth science * geology * oceanography * meteorology * astronomy ## Reading Strategy | Branch | Studied | |---|---| | geology | | | oceanography | | | meteorology | | | astronomy | | The spectacular eruption of a volcano, the magnificent scenery of a rocky coast, and the destruction created by a hurricane are all subjects for Earth science. The study of Earth science deals with many fascinating and practical questions about our environment. What forces produced the mountains shown on page 1? Why does our daily weather change? Is our climate changing? How old is Earth? How is Earth related to the other planets in the solar system? What causes ocean tides? What was the Ice Age like? Will there be another? Understanding Earth is not an easy task because our planet is always changing. Earth is a dynamic planet with a long and complex history. ## Overview of Earth Science Earth science is the name for the group of sciences that deals with Earth and its neighbors in space. Earth science includes many subdivisions of geology such as geochemistry, geophysics, geobiology and paleontology, as well as oceanography, meteorology, and astronomy. Units 1 through 4 focus on the science of geology, a word that means "study of Earth." Geology is divided into two broad areas-physical geology and historical geology. Physical geology includes the examination of the materials that make up Earth and the possible explanations for the many processes that shape our planet. Processes below the surface create earthquakes, build mountains, and produce volcanoes. Processes at the surface break rock apart and create different landforms. Erosion by water, wind, and ice results in different landscapes. You will learn that rocks and minerals form in response to Earth's internal and external processes. Understanding the origin of rocks and minerals is an important part of understanding Earth. In contrast to physical geology, the aim of historical geology is to understand Earth's long history. Historical geology tries to establish a timeline of the vast number of physical and biological changes that have occurred in the past. See Figure 1. We study physical geology before historical geology because we must first understand how Earth works before we try to unravel its past. #### Reading Checkpoint What are the two main areas of geology? ## Formation of Earth Earth is one of several planets that revolve around the sun. Our solar system has an orderly nature. Scientists understand that Earth and the other planets formed during the same time span and from the same material as the sun. The nebular hypothesis suggests that the bodies of our solar system evolved from an enormous rotating cloud called the solar nebula. It was made up mostly of hydrogen and helium, with a small percentage of heavier elements. Figure 3 on page 4 summarizes some key points of this hypothesis. # 1.2 A View of Earth ## Reading Focus * What are the four major spheres into which Earth is divided? * What defines the three main parts of the solid Earth? * What theory explains the position of continents and the occurrence of volcanoes and earthquakes? ## Vocabulary * hydrosphere * atmosphere * geosphere * biosphere * core * mantle * crust ## Reading Strategy | Term | Before you Read | After you Read | |---|---|---| | hydrosphere| | | | atmosphere | | | | geosphere | | | | biosphere | | | | core | | | | mantle | | | | crust | | | A view such as the one in Figure 5A provided the Apollo 8 astronauts with a unique view of our home. Seen from space, Earth is breathtaking in its beauty. Such an image reminds us that our home is, after all, a planet-small, self-contained, and in some ways even fragile. If you look closely at Earth from space, you may see that it is much more than rock and soil. A The swirling clouds and the vast global ocean emphasize the importance of water on our planet. ## Earth's Major Spheres The view of Earth shown in Figure 5B should help you see why the physical environment is traditionally divided into three major spheres: the water portion of our planet, the hydrosphere; Earth's gaseous envelope, the atmosphere; and the geosphere. Our environment is characterized by the continuous interactions of air and rock, rock and water, and water and air. The biosphere, which is made up of all the life forms on Earth, interacts with all three of these physical spheres. Earth can be thought of as consisting of four major spheres: the hydrosphere, atmosphere, geosphere, and biosphere. ## Plate Tectonics You have read that Earth is a dynamic planet. If we could go back in time a billion years or more, we would find a planet with a surface that was dramatically different from what it is today. Such prominent features as the Grand Canyon, the Rocky Mountains, and the Appalachian Mountains did not exist. We would find that the continents had different shapes and were located in different positions from those of today. There are two types of forces affecting Earth's surface. Destructive forces such as weathering and erosion work to wear away high points and flatten out the surface. Constructive forces such as mountain building and volcanism build up the surface by raising the land and depositing new material in the form of lava. These constructive forces depend on Earth's internal heat for their source of energy # 1.3 Representing Earth's Surface ## Reading Focus * What lines on a globe are used to indicate location? * What problems do mapmakers face when making maps? * How do topographic maps differ from other maps? ## Vocabulary * latitude * longitude * topographic map * contour line * contour interval ## Reading Strategy | What I Expect to Learn | What I Learned | |---|---| | | | | | | **Determining Location** Long ago, people had to rely on maps made by travelers and explorers. During the twentieth century, photographs of the land surface taken from airplanes became important in mapmaking. Later, satellite images provided even more accurate data about Earth's surface. In addition to accurate data, mapmakers need a way of precisely describing the location of features on Earth's surface. Mapmakers use a global grid to help determine location. **Global Grid** Scientists use two special Earth measurements to describe location. The distance around Earth is measured in degrees. **Latitude** is the distance north or south of the equator, measured in degrees. **Longitude** is the distance east or west of the prime meridian, measured in degrees. Earth is 360 degrees in circumference. Lines of latitude are east-west circles around the globe. All points on the circle have the same latitude. The line of latitude around the middle of the globe, at 0 degrees (°), is the equator. Lines of longitude run north and south. The prime meridian marks 0° of longitude as shown in Figure 8. Lines of latitude and longitude form a global grid. This grid allows you to state the absolute location of any place on Earth. For example, Savannah, Georgia, is located at 32º north latitude and 81° west longitude. ## Globes The shapes and sizes of islands, continents, and bodies of water. Mapmakers wanted to present this information accurately. The best way was to put the information on a model, or globe, with the same round shape as Earth itself. By using an accurate shape for Earth, mapmakers could show the continents and oceans of Earth much as they really are. The only difference would be the scale, or relative size.. But there is a problem with globes. Try making a globe large enough to show the streets in your community. The globe might have to be larger than your school building! A globe can't be complete enough to be useful for finding directions and at the same time small enough to be convenient for everyday use. # Maps and Mapping A map is a flat representation of Earth's surface. But Earth is round. Can all of Earth's features be accurately represented on a flat surface without distorting them? The answer is no. No matter what kind of map is made, some portion of the surface will always look either too small, too big, or out of place. Mapmakers have, however, found ways to limit the distortion of shape, size, distance, and direction. **The Mercator Projection** In 1569, a mapmaker named Gerardus Mercator created a map to help sailors navigate around Earth. On this map, the lines of longitude are parallel, making this grid rectangular, as shown on the map in Figure 10. The map was useful because, although the sizes and distances were distorted, it showed directions accurately. Today, more than 400 years later, many seagoing navigators still use the Mercator projection map. # 1.4 Earth System Science ## Reading Focus * How is Earth a system? * What is a system? * Where does the energy come from that powers Earth's systems? * How do humans affect Earth's systems? * What makes a resource renewable or nonrenewable? ## Vocabulary * system ## Reading Strategy 1. Earth System Science 1. What is a System? * * 2. 3. 4. 5. As we study Earth, we see that it is a dynamic planet with many separate but interactive parts or spheres. Earth scientists are studying how these spheres are interconnected. This way of looking at Earth is called Earth system science. Its aim is to understand Earth as a system made up of numerous interacting parts, or subsystems. Instead of studying only one branch of science, such as geology, chemistry, or biology, Earth system science tries to put together what we know from our study of all of these branches. Using this type of approach, we hope to eventually understand and solve many of our global environmental problems. #### Reading Checkpoint What is Earth system science? ## What Is a System? Most of us hear and use the term system frequently. You might use your city's transportation system to get to school. A news report might inform us of an approaching weather system. We know that Earth is just a small part of the much larger solar system. A system can be any size group of interacting parts that form a complex whole. Most natural systems are driven by sources of energy that move matter and/or energy from one place to another. A simple analogy is a car's cooling system. It contains a liquid (usually water and antifreeze) that is driven from the engine to the radiator and back again. The role of this system is to transfer the heat generated by combustion in the engine to the radiator, where moving air removes the heat from the system. This kind of system is called a closed system. Here energy moves freely in and out of the system, but no matter enters or leaves the system. In the case of the car's cooling system, the matter is the liquid. By contrast, most natural systems are open systems. Here both energy and matter flow into and out of the system. In a river system, for example, the amount of water flowing in the channel can vary a great deal. At one time or place, the river may be fuller than it is at another time or place. ## Earth as a System The Earth system is powered by energy from two sources. One source is the sun, which drives external processes that occur in the atmosphere, hydrosphere, and at Earth's surface. Weather and climate, ocean circulation, and erosional processes are driven by energy from the sun. Earth's interior is the second source of energy. There is heat that remains from the time Earth formed. There is also heat continuously generated by the decay of radioactive elements. These sources power the internal processes that produce volcanoes, earthquakes, and mountains. The parts of the Earth system are linked so that a change in one part can produce changes in any or all of the other parts. For example, when a volcano erupts, lava may flow out at the surface and block a nearby valley. This new obstruction influences the region's drainage system by creating a lake or causing streams to change course. Volcanic ash and gases that can be discharged during an eruption might be blown high into the atmosphere and influence the amount of solar energy that can reach Earth's surface. The result could be a drop in air temperatures over the entire hemisphere. #### Reading Checkpoint: How do we know that Earth's systems are connected? Over time, soil will develop on the lava or ash-covered surface and, as shown in Figure 18, plants and animals will reestablish themselves. This soil will reflect the interactions among many parts of the Earth system-the original volcanic material, the type and rate of weathering, and the impact of biological activity. Of course, there would also be significant changes in the biosphere. Some organisms and their habitats would be eliminated by the lava and ash, while new settings for life, such as the lake, would be created. The potential climate change could also have an effect on some life-forms. The Earth system is characterized by processes that occur over areas that range in size from millimeters to thousands of kilometers. Time scales for Earth's processes range from milliseconds to billions of years. Despite this great range in distance and time, many processes are connected. A change in one component can influence the entire system. Humans are also part of the Earth system. Our actions produce changes in all of the other parts of the Earth system. When we burn gasoline and coal, build breakwaters along a shoreline, dispose of our wastes, and clear the land, we cause other parts of the Earth system to respond, often in unforeseen ways. Throughout this book, you will learn about many of Earth's subsystems, such as the hydrologic (water) system, the tectonic (mountain-building) system, and the climate system. Remember that these components and we humans are all part of the complex interacting whole we call the Earth system. ## People and the Environment Environment refers to everything that surrounds and influences an organism. Some of these things are biological and social. Others are nonliving such as water, air, soil and rock as well as conditions such as temperature, humidity, and sunlight. These nonliving factors make up our physical environment. Because studying the Earth sciences leads to an understanding of the physical environment, most of Earth science can be characterized as environmental science. #### Reading Checkpoint: What are examples of nonliving factors? Today the term environmental science is usually used for things that focus on the relationships between people and the natural environment. For example, we can dramatically influence natural processes. A river flooding is natural, but the size and frequency of flooding can be changed by human activities such as clearing forests, building cities, and constructing dams. Unfortunately, natural systems do not always adjust to artificial changes in ways we can anticipate. An alteration to the environment that was intended to benefit society may also have some negative effects, as shown in Figure 19. ## Resources Resources are an important focus of the Earth sciences. They include water and soil, metallic and nonmetallic minerals, and energy. Together they form the foundation of modern civilization. The Earth sciences deal not only with the formation and occurrence of these vital resources but also with maintaining supplies and the environmental impact of their mining and use. **Renewable resources** can be replenished over relatively short time spans. Common examples are plants and animals for food, natural fibers for clothing, and forest products for lumber and paper. Energy from flowing water, wind, and the sun are also considered renewable resources. **Nonrenewable resources** continue to form, the processes that create them are so slow that it takes millions of years for significant deposits to accumulate. Earth contains limited quantities of these materials. Although some nonrenewable resources, such as aluminum, can be used over and over again, others, such as oil, cannot. When the present supplies are exhausted, there will be no more. #### Reading Checkpoint: How do renewable and nonrenewable resources differ? ## Population Figure 20 shows that the population of Earth is growing rapidly. Although it took until the beginning of the nineteenth century for the population to reach 1 billion, just 130 years were needed for the population to double to 2 billion. Between 1930 and 1975, the figure doubled again to 4 billion, and by about 2010, as many as 7 billion people may inhabit Earth. Clearly, as population grows, so does the demand for resources. However, the rate of mineral and energy resource usage has increased more rapidly than the overall growth of the population. How long will the remaining supplies of basic resources last? How long can we sustain the rising standard of living in today's industrialized countries and still provide for the growing needs of developing regions? How much environmental deterioration are we willing to accept to obtain basic resources? Can alternatives be found? If we are to cope with the increasing demand on resources and a growing world population, it is important that we have some understanding of our present and potential resources. ## Environmental Problems In addition to the search for mineral and energy resources, the Earth sciences must also deal with environmental problems. Some of these problems are local, some are regional, and still others are global. Humans can cause problems, such as the one shown in Figure 21. Significant threats to the environment include air pollution, acid rain, ozone depletion, and global warming. The loss of fertile soils to erosion, the disposal of toxic wastes, and the contamination and depletion of water resources are also of considerable concern. The list continues to grow. People must cope with the many natural hazards that exist such as the one shown in Figure 22. Earthquakes, landslides, floods, hurricanes, and drought are some of the many risks. Of course, environmental hazards are simply natural processes. They become hazards only when people try to live where these processes occur. It is clear that as world population continues to grow, pressures on the environment will increase as well. Therefore, an understanding of Earth is essential for the location and recovery of basic resources. It is also essential for dealing with the human impact on the environment and minimizing the effects of natural hazards. Knowledge about Earth and how it works is necessary to our survival and well being. Earth is the only suitable habitat we have, and its resources are limited. # 1.5 What Is Scientific Inquiry? ## Reading Focus * What is a hypothesis? * What is a theory? ## Vocabulary * hypothesis * theory ## Reading Strategy | | Hypothesis | Theory | |---|---|---| | | | | | | | | All science is based on two assumptions. First, the natural world behaves in a consistent and predictable manner. Second, through careful, systematic study, we can understand and explain the natural world's behavior. We can use this knowledge to predict what should or should not be expected. For example, by knowing how oil deposits form, geologists can predict where oil will be found. Scientists approach their study of the natural world with certain habits of mind. These include curiosity, honesty, openness to new ideas, and skepticism. Skepticism is a willingness to question an idea unless that idea is supported with firm evidence. Scientists also use a range of skills and methods, including methods to ensure safety in the laboratory. You can learn more about these skills, methods, and safety procedures in the Skills Handbook on pages 728-733. ## Hypothesis The development of new scientific knowledge begins as scientists collect data through observation and measurement. Once data have been gathered, scientists try to explain how or why things happen in the manner observed. Scientists do this by stating a possible explanation called a scientific hypothesis. Sometimes more than one hypothesis is developed to explain a given set of observations. Just because a hypothesis is stated doesn't mean that it is correct. Before a hypothesis can be accepted by the scientific community, it must be tested and analyzed. If a hypothesis can't be tested, it is not scientifically useful. Hypotheses that fail rigorous testing are discarded. One example of a discarded hypothesis is the Earth-centered model of the universe. ## Theory When a hypothesis has survived extensive testing and when competing hypotheses have been eliminated, a hypothesis may become a scientific theory. A scientific theory is well tested and widely accepted by the scientific community and best explains certain observable facts. For example, the theory of plate tectonics provides the framework for understanding the origin of continents and ocean basins, plus the occurrence of mountains, earthquakes, and volcanoes. Theories differ from laws. A scientific law is a statement that summarizes a pattern found in nature. Similar to theories, laws are based on repeatable observations and are widely accepted. However, unlike theories, laws describe relationships but do not explain why the relationships exist. ## Scientific Methods The process of gathering facts through observations and formulating scientific hypotheses and theories is called the scientific method. There is no set path that scientists must follow in order to gain scientific knowledge. However, many scientific investigations involve the following steps: (1) the collection of scientific facts through observation and measurement, (2) the development of one or more working hypotheses or models to explain these facts, (3) development of observations and experiments to test the hypotheses, and (4) the acceptance, modification, or rejection of the hypothesis based on extensive testing.

Earth Science Textbook - Chapter 1 PDF

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