Earth Science Workbook PDF

8TH GRADE SCIENCE STUDENT WORKBOOK Introduction to Earth Science: Scientific Inquiry Everything in science is based on two assumptions. The first assumption is that the natural world behaves in a consistent and predictable manner. The second assumption is that through careful,...

8TH GRADE SCIENCE STUDENT WORKBOOK Introduction to Earth Science: Scientific Inquiry Everything in science is based on two assumptions. The first assumption is that the natural world behaves in a consistent and predictable manner. The second assumption is that 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. By knowing how oil deposits form, geologists can predict where oil will be found. All scientists approach the study of the natural world with certain habits of mind. Curiosity, honesty and openness to new ideas are important characteristics of a scientist. Skepticism is also an important quality. Skepticism is a willingness to question an idea unless that idea is supported with firm evidence. Scientists use a range of skills and methods, including methods to ensure safety in the laboratory. Hypothesis is a tentative explanation for an observation or phenomenon. New scientific knowledge begins when scientists collect data through observation and measurement. Once scientists have collected data, they 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 scientists develop more than one hypothesis to explain a given set of observations. A hypothesis is used to make testable predictions, but may not always be the true explanation. 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 and a new hypothesis is developed. 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. The theory of plate tectonics that you learned about in a previous Lesson provides the framework for understanding the origin of continents and ocean basins, plus the occurrence of mountains, earthquakes, and volcanoes. This theory began as a hypothesis and was then proven to become a theory. Scientific Methods - The scientific method is the process of gathering facts through observations and formulating scientific hypotheses and theories. There is no set of rules or procedures that scientists follow 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 41 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK How do we apply scientific theory to our world as we know it? Let’s take a “look” at our world and the different views which have grown into fact through careful exploration and scientific explanation. A globe can also represent the Earth. A globe is a sphere that shows the relative sizes and shapes of Earth’s land features and waters. Maps and globes provide different types of information about the Earth’s surface. Land Features on Maps Relief maps show what the landscape of an area actually looks like. A relief map shows how high or low each feature is on Earth. Relief maps show three main types of land features – mountains, plains, and plateaus. 42 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK Mountains are higher than the land around them. It is called a mountain range when there is a group of mountains together. Several mountain ranges connected in a long chain is called a mountain belt. Mountain belts can span several countries. Plateaus stand high above sea level, but unlike mountains, have fairly level surfaces. They are often found near mountain ranges. Plains are flat or rolling geological features and in the United States, there are generally two types of plains. There are coastal plains, which are near the eastern and southern shores, and interior plains, which are found in the center of the country. The Great Plains cover a third of the country. Map Symbols and Scale Usually, when someone is using a map, it is a road or city map. These maps provide information about human-made features and may include some natural features. In order to use these maps, you need to know how to use the map legend and how to read a map scale. The map scale shows the relationship between distances on a map and the actual distances on the Earth’s surface. Depending on the size of the area shown on the map, the scale may be in miles (kilometers) or yards (meters). To find more detail, you need to find a map that covers a smaller area. Map scales can be expressed in several ways: a ratio, a bar, or equivalent units of distance. A ratio of 1:25,000 means that 1 centimeter on the map represents 25,000 centimeters, or.25 kilometer, on Earth. A bar scale gives you a picture that shows how 43 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK much space on the map represents each unit of measure. Equivalent-units scales tell you how many inches/centimeters on the map equal a mile or kilometer. The map legend, or key, is the chart that explains the meaning of the symbols found on the map. There may be symbols for highways, parks, trails, or other points of interest. Most maps also include a compass to show which directions on the map are north, south, east, and west. Generally, north points up on a map. Latitude and Longitude To help locate things on the Earth’s surface, people use latitude and longitude. Latitude and longitude lines form an imaginary grid over the surface of the Earth. This grid makes it possible for everyone to use the same system to locate objects and places on the planet. Latitude is based on an imaginary line that circles the Earth halfway between the north and south poles. This imaginary line is called the equator. The equator divides the Earth into the northern and southern hemispheres. A hemisphere is one half of a sphere. Latitude is measured in the degrees north or south of the equator. The equator is 0. A degree is 1/360 of the distance around a full circle. Latitude lines are all parallel to the equator and are evenly spaced between the equator and the poles. Latitude lines are always labeled north or south, depending on their location in relation to the equator; this shows whether the location is in the northern or southern hemisphere. The North Pole is 90 N, and the South Pole is 90 S. Longitude is the distances east or west, in degrees, of the prime meridian. The prime meridian, like the equator, is 0. Longitude lines are labeled 0 to 180 west and 0 to 180 east. If you understand longitude and latitude, you can find any spot on the Earth. is based on an imaginary line that goes from the North Pole to the South Pole. This line is called the Prime Meridian and goes through Greenwich, England. The prime meridian divides the Earth into the Western and Eastern hemispheres. 44 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK How Do I Use Globes and Maps? GPS - You may have heard of GPS for your car or on your cell phone. GPS stands for Global Positioning System; it is a network of satellites that are used to find latitude, longitude, and elevation of any site. There are 24 GPS satellites around the Earth. These satellites send signals that can be picked up by receivers on the Earth’s surface. The computer inside the receiver uses the satellite signal to help find any position on the Earth’s surface. Many people use GPS to help find their way when driving, hiking, or boating. Maps and Distortions Because the Earth is a sphere, the most accurate way to represent it is on a globe. A globe would be pretty difficult to carry around and doesn’t show much detail, so people use flat maps to help them find their way. To represent the Earth’s curved surface on a flat map, a projection is used. Making a map of a curved surface into a flat map; causes distortions. There are several different kinds of projections used to make maps. A Mercator projection shows the Earth as if it were a large cylinder wrapped around the Earth. On this type of map, longitude and latitude lines are straight and form rectangles. Mercator maps are useful for navigating because they show nearly the entire world on one flat map. Because the curved latitude and longitude lines are straightened for this map, it distorts the areas far away from the equator. The farther you get from the equator on the map, the larger the distortion becomes. This causes land masses in the far north or far south to appear much larger than they actually are compared to the rest of the world. 45 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK Another type of projection is a conic projection. This map is based on the shape of a cone. Imagine wrapping a cone of paper around the globe. The paper would only touch the surface at the middle latitudes between the equator and North Pole. When this cone is flattened out, the latitude lines are curved. The curved lines represent the curved surface of the Earth. This map shows the true size and shape of some landmasses. Conic projections are most useful when mapping areas in the middle latitudes – such as the United States. Landmasses near the poles or equator are distorted on this type of map. A planar projection is based on a circle. Imagine that a circle of paper was laid on a part of the Earth’s surface and a map was made based on this. As you move away from the center point, the landmasses on the map become distorted. Each type of projection is an attempt to solve the problem of representing a sphere on a flat surface. Each type of map can show certain areas of the world correctly, but distorts other areas. Topographic Maps Have you ever hiked on a nature trail or in the mountains? Imagine that you are getting ready to take a hike through the state park and want to be prepared for anything that you might encounter. How will you know if you need to climb hills or cross streams? You will need to know about the topography of the land to answer these questions. Topography is the shape, or features, of the land. Topographic features can be natural features, such as mountains, rivers, or plateaus, or human-made, such as roads, bridges, and dams. To display these features you need a topographic map. A topographic map is a flat map that uses lines to show the Earth’s surface features. These maps show distance, as well as, elevation. These numbers may be given in feet or meters. 46 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK Look at the map above, notice the wiggly lines? These lines are called contour lines and these lines show the elevation, slope, and relief of an area. The elevation of a place is how high above sea level it is. The numbers on the contour lines show the elevations of different points. The slope of an area is how steep it is. The distance between the contour lines will tell you how steep an area is; the farther apart the lines, the more gradual the slope. A steep area has contour lines that are closer together. Relief is the difference between the highest point and lowest point of an area. If you find the elevation of the highest point of an area and then subtract the lowest elevation, you have just measured the relief of the area. Contour Lines The contour lines on a map help you to visualize what the area actually looks like. There are several facts about contour lines that can serve as rules to help you read a topographic map. Contour lines never cross. Contour lines never cross because each line represents a different elevation. Circles show highest and lowest points. Contour lines form closed circles around mountaintops, hilltops, and the centers of depressions in the land (sunken areas in 47 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK the ground). Often, the elevation of a mountain or hill is written in feet or meters in the center of the circle. Contour interval is always the same on a map. The contour interval is the difference in elevation from one contour line to the next. For example, if the contour interval on a map was 25 feet, then the difference in elevation from one circle to the next is 25 feet. Contour intervals can differ from one map to the next, but the interval always remains the same on each individual map. Index contour lines mark elevations. On a topographic map, you will notice that there are contour lines that are darker than the others. These darker lines are called index contour lines and often have numbers written on the line. These numbers tell you the elevation of the land at that contour line. These lines help you to calculate the elevation of any contour line on the map. To do this, count the number of lines above or below the index line and multiply by the contour index. For example, if you want to find the elevation of the top of a hill on a map with a contour index of 25 feet, you would count the number of lines between the index line and the top of the hill. (Let’s say this is 5 lines for this example.) To find the elevation of the top of the hill, you need to multiply the number of lines (5) by the contour index (25) and then add to the number on the index line (for this example, use 100). So the elevation of our hill is: 5 (lines) x 25 feet (contour interval) = 125 feet + 100 feet (the index line from this example). Our hill’s elevation is 225 feet. Topographic maps also contain many different symbols for natural and human-made features. The United States Geological Survey (USGS) has created a list of symbols to make reading these maps easier. On the left side of the page you will see several common symbols. Note: Not all symbols needed: Only symbols for railroad, small tree, grass or meadow, marsh, trail, and paved road. The USGS makes topographic maps for almost every part of the United States. These maps are used by engineers, archaeologists, forest rangers, and biologists rely on topographic maps. 48 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK Using Technology to map the Earth Earlier in this text, you read about GPS – Global Positioning System which uses a network of satellites to find longitude, latitude and elevation at any site. You may not be familiar with GPS in your own life – but you may have used a telescope or binoculars to help you see something? If you have, you have used remote sensing. Remote sensing is the use of scientific equipment to gather information about something from a distance. Remote sensing can be as simple as a pair of binoculars or as complex as a satellite orbiting the Earth. Remote sensing is very important in the study of the Earth. Once, you would have had to climb to the top of the highest point and carefully draw a map by hand based on what you could see. The map would not have been able to tell you how high things were or even an accurate measure of the distance from one point to the next. U.S. Geological Survey satellite image of the Pentagon, taken April 26, 2002. The reconstruction of the section damaged in the September 11 terrorist attacks is visible on the building's west (left) side; the diagonal line is a construction crane. Courtesy of the U.S. Geological Survey. 17:40, 13 June 2005 Today, it is much easier to make maps. Remote sensing is used to help make maps much more detailed and accurate. Mapmakers can use satellite images and pictures taken from airplanes to create detailed maps of the Earth’s surface. Satellites use sensors to help build images of the Earth. A sensor is a mechanical or electrical device that receives and responds to a signal, such as light. These sensors are able to detect much more than the eye can see. They collect information about the different types of energy coming from the Earth’s surface and then send that information to computers on Earth. The computers then turn that information into images. Satellites can help create images of entire planets, single continents, states, or even a single landmark. If you look at the image above, you will see how satellites can help create images of a single object on the Earth’s surface. 49 www.AllinOneCurriculum.com  8TH GRADE SCIENCE STUDENT WORKBOOK To study changes in the Earth’s surface, scientists use false-color images. False-color images are images that assign different colors to different features. True-Color Image of Chesapeake Bay False-Color Image of Chesapeake Bay Geographic Information Systems You can easily find a map of the surface of a city. On this map you will see buildings, streets, parks, and landmarks; but what if you need to know about what is below the city? Or what if you need to know the places where most of the people in the city live? An ordinary map cannot tell you this information. A map created with geographic information systems can display this information for you. Geographic information systems (GIS are computer systems that can store arranged geographic data and then display it in many different kinds of maps. Geographic information systems can be used to store data about the surface of an area, what is under the surface, the human-made structures of the area, and even population information. All of this information can then be combined to create almost any kind of map that is needed. Scientists, engineers, and city planners then use these maps to study an area and help make decisions. For example, a developer may want to find the best place to build a new shopping mall and use GIS to determine where a good location would be based on population and land features. Any information can be entered into GIS and then converted into a map. This is especially useful in tracking changes in the environment. For example, if the plants or wildlife of an area suddenly begin changing, scientists can map these changes. They can also take measurements of the chemicals and elements present and map theses changes. Maps like this can help the scientists to discover what is causing changes. : Reminder - discuss with your teacher any vocabulary words or text that you need assistance with. 50 www.AllinOneCurriculum.com