Section 1 Finding Locations on Earth Chapter 3 Latitude • Earth is a nearly perfect sphere. (1) • The points at which Earth’s axis of rotation intersects Earth’s surface are used as reference points for defining direction. These points are the geographic North Pole and South Pole. (2) (3) (4) • Halfway between the poles, a circle called the equator divides Earth into North and Southern Hemispheres. (5) • A reference grid that is made up of equator and additional circles is used to locate places on Earth‘s surface. (6)

Section 1 Finding Locations on Earth Chapter 3 Latitude, continued • One set of circles describes positions north and south of the equator. These circles are known as parallels, and they express latitude. (7) • parallel any circle that runs east and west around Earth and that is parallel to the equator; a line of latitude (8) • Labeled N and S of equator (15) • latitude the angular distance north or south from the equator; expressed in degrees (9)

Chapter 3 Parallels

Section 1 Finding Locations on Earth Chapter 3 Latitude, continued The diagram below shows Earth’s parallels.

Section 1 Finding Locations on Earth Chapter 3 Latitude, continued Degrees of Latitude • Latitude is measured in degrees, and the equator is 0° latitude. The latitude of both the North Pole and the South Pole is 90°. (10) (11) (13) • Distance from equator to either pole is ¼ of a circle. (12) • In actual distance, 1° latitude equals about 111 km. (14) Minutes and Seconds • Each degree of latitude consists of 60 equal parts, called minutes. One minute (symbol: °) of latitude equals 1.85 km.(16) • In turn, each minute is divided into 60 equal parts, called seconds (symbol: °). (17)

What is the latitude of Washington, D.C.? • 38◦ 53’ 23“ (18) To determine specific location of a place, you must know latitude, how far east or west place is along its circle of latitude. (19)

Section 1 Finding Locations on Earth Chapter 3 Longitude, continued • East-west locations are established by using meridians. (20) • meridian any semicircle that runs north and south around Earth from the geographic North Pole to the geographic South Pole; a line of longitude (21) • longitude the angular distance east or west from the prime meridian; expressed in degrees (24)

Section 1 Finding Locations on Earth Chapter 3 Longitude, continued The diagram below shows Earth’s meridians.

Section 1 Finding Locations on Earth Chapter 3 Longitude, continued Degrees of Longitude • The meridian that passes through Greenwich, England is called the prime meridian. This meridian represents 0° longitude. Established by international agreement. (22) (23) • The meridian opposite the prime meridian, halfway around the world, is labeled 180°, and is called the International Date Line. (24) Distance Between Meridians • The distance covered by a degree of longitude depends on where the degree is measured. The distance measured by a degree of longitude decreases as you move from the equator toward the poles. (30) (33)

Longitude • All locations east of prime meridian have longitudes between 0° and 180° E. (26) • All locations west of prime meridian have longitudes between 0° and 180° W. (27) • Longitude expressed more precisely in degrees, minutes and seconds. (28) • Precise location of Washington, D.C. is 38° 53’ 23” N and 77° 00’ 33” W (29)

Longitude • A degree of longitude equals 111 km at equator. (31) • All meridians meet at the North and South Poles. (32)

Section 1 Finding Locations on Earth Chapter 3 Comparing Latitude and Longitude

Section 1 Finding Locations on Earth Chapter 3 Great Circles • A great circle is any circle that divides the globe into halves, or marks the circumference of the globe. (35) • Any circle formed by two meridians of longitude that are directly across the globe from each other is a great circle. (36) • The equator is the only line of latitude that is a great circle. (37) • The route along a great circle is the shortest distance between two points on a sphere. As a result, great circles are commonly used in navigation, such as for air and sea routes. (34) (39) • Great circles can run any direction around globe. (38)

Section 1 Finding Locations on Earth Chapter 3 Great Circles, continued The diagram below shows what a great circle is.

Section 1 Finding Locations on Earth Chapter 3 Finding Direction • One way to find direction on Earth is to use a magnetic compass. It points to geomagnetic north pole (44) • A magnetic compass can indicate direction because Earth has magnetic properties as if a powerful bar-shaped magnet were buried at Earth’s center at an angle to Earth’s axis of rotation. (40) (41) • The areas on Earth’s surface just above where the poles of the imaginary magnet would be are called the geomagnetic poles. (42) • The geomagnetic poles and the geographic poles are located in different places. (43)

Section 1 Finding Locations on Earth Chapter 3 Finding Direction, continued Magnetic Declination • The angle between the direction of the geographic pole and the direction in which the compass needle points is called magnetic declination. (45) • In the Northern Hemisphere, magnetic declination is measured in degrees east or west of the geographic North Pole. (46) • Because Earth’s magnetic field is constantly changing, the magnetic declinations of locations around the globe also change constantly. • By using magnetic declination, a person can use a compass to determine geographic north for any place on Earth. (48)

Finding Direction, continued • Compass needle aligns with geographic North Pole and geomagnetic north pole for all locations along 0° magnetic declination (47)

Section 1 Finding Locations on Earth Chapter 3 Finding Direction, continued The diagram below shows the magnetic declination of the United States.

Section 1 Finding Locations on Earth Chapter 3 Finding Direction, continued The Global Positioning System • Another way people can find their location on Earth is by using the global positioning system, or GPS. (49) • GPS is a satellite navigation system that is based on a global network of 24 satellites that transmit radio signals to Earth’s surface. (50) • A GPS receiver held by a person on the ground receives signals from three satellites to calculate the latitude, longitude, and altitude of the receiver on Earth. (51)

Section 2 Mapping Earth’s Surface Chapter 3 Objectives • Explaintwo ways that scientists get data to make maps. • Describethe characteristics and uses of three types of map projections. • Summarizehow to use keys, legends, and scales to read maps.

Mapping Earth’s Surface • A globe is a familiar model of Earth in the shape of a sphere. (1) • Globes can accurately represent the locations, relative areas, and relative shapes of Earth’s surface features. (2) • They are especially useful in studying large surface features, such as continents and oceans. (2)

Section 2 Mapping Earth’s Surface Chapter 3 How Scientists Make Maps • Because most globes are too small to show details of Earth’s surface, such as streams and highways, a great variety of maps have been developed for studying and displaying detailed information about Earth. (3) • The science of making maps is called cartography. Scientists who make maps are called cartographers. (4) • Cartographers use data from a variety of sources, such as from field surveys and remote sensing. (5) • Field surveys are conducted by walking or driving through an area to be mapped and making measurements of that area. (6)

How Scientists Make Maps, continued • Cartographers take the information gathered from field surveys and plot that information on a map. (7) • remote sensing the process of gathering and analyzing information about an object without physically being in touch with the object. (8) • Cartographers can collect information about a site without being there. They use equipment on satellites and airplanes to obtain images of Earth’s surface. (8) • Maps are often made by combining information from images gathered through remote sensing and information from field surveys. (9)

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections • A map is a flat representation of Earth’s curved surface. • Transferring a curved surface to a flat map results in a distorted image of the curved surface. An area shown on a map may be distorted in size, shape, distance, or direction. (14) (15) • Over the years, cartographers have developed several ways to transfer the curved surface of Earth onto flat maps. These methods are called map projections. • map projection a flat map that represents a spherical surface (10) • No map projection is entirely accurate, but each kind of projection has advantages and disadvantages.

Map Projections, continued • The larger the area being shown, the greater the distortion tends to be. (16) • A map of the entire Earth would show the greatest distortion. (16) • But a map of a city would only be slightly distorted.(16)

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections, continued Cylindrical Projections • If you wrapped a cylinder of paper around a lighted globe and traced the outlines of continents, oceans, parallels, and meridians, a cylindrical projection would result. (11) • A cylindrical projection is accurate near the equator but distorts distances and sizes near the poles. (18) • One advantage to cylindrical projections is that parallels and meridians form a grid, which makes locating positions easier. (19) • On a cylindrical projection, shapes of small areas are usually well preserved. (19)

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections, continued • Cylindrical projections differ from globes in that they appear as straight, parallel lines have an equal amount of space between them, while meridians on a globe come together at the poles. (17) The diagram below shows a cylindrical projection.

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections, continued Azimuthal Projections • A projection made by placing a sheet of paper against a globe such that the paper touches the globe at only one point is called an azimuthal projection. (12) • On an azimuthal projection, little distortion occurs at a the point of contact, but the unequal spacing between parallels causes a distortion in both direction and distance that increases as distance from the point of contact increases. (20) • One advantage of azimuthal projections is that on these maps, great circles appear as straight lines. Thus, azimuthal projections are useful for plotting navigational paths.

Map Projections, continued Azimuthal Projections • Azimuthal projections are very helpful in plotting navigational routes in air travel. • This is because a great circle appears as a straight line on an azimuthual projection. (21) • By drawing a straight line between any two points on this projection, navigators can find a great-circle route. (21)

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections, continued The diagram below shows an azimuthal projection.

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections, continued Conic Projections • A projection made by placing a paper cone over a lighted globe so that the axis of the cone aligns with the axis of the globe is known as a conic projection. (13) • Areas near the parallel where the cone and the globe are in contact are distorted least. (23) • A series of conic projections where the cone touches the globe at slightly different latitude and can be used to increase accuracy by mapping a number of neighboring areas and fitting the adjoining areas together to make a polyconic projection. (24) • On a polyconic projection, the relative sizes and shapes of small areas on the map are nearly the same as those on the globe.

Section 2 Mapping Earth’s Surface Chapter 3 Map Projections, continued • The cone touches a globe in a conic projection along one parallel of latitude. (22) The diagram below shows a conic projection.

Section 2 Mapping Earth’s Surface Chapter 3 Reading a Map • Maps provide information through the use of symbols. • You must understand the symbols, be able to find directions, and calculate distances in order to read a map. (25) Direction on a Map • Maps are commonly drawn with north at the top, east at the right, west at the left, and south at the bottom. (27) • Some maps use parallels of latitude and meridians of longitude to indicate direction and location. • Many maps also include a compass rose, which is a symbol that indicates the cardinal directions (north, east, south, and west), or an arrow that indicates north, which is generally labeled and may not point to top of map. (31) (32) (33)

Reading a Map, continued • The first step to read a map is determine how the compass directions are displayed. (26) • Parallels run from side to side. (28) • Meridians run from top to bottom. (28) • USGS maps mark the northern and southern boundary with parallels (29) • Eastern and western boundaries are marked with meridians of longitude. (30)

Section 2 Mapping Earth’s Surface Chapter 3 Reading a Map, continued Symbols • Symbols are commonly used on maps to represent features such as cities, highways, rivers, and other points of interest. • Symbols may resemble the features that they represent, or they may be more abstract. (35) • Symbols are commonly explained in a legend. • legend a list of map symbols and their meanings (34)

Section 2 Mapping Earth’s Surface Chapter 3 Information on Maps

Section 2 Mapping Earth’s Surface Chapter 3 Reading a Map, continued Map Scales • scale the relationship between the distance shown on a map and the actual distance (36) • Map scales are commonly expressed as graphic scales, fractional scales, or verbal scales. • A graphic scale is a printed line that has markings that represent units of measure, such as meters or kilometers. (37) • A fractional scale is a ratio that indicates how distance on Earth relates to distance on the map. (38) • A verbal scale expresses scale in sentence form. (39)

Reading a Map, continued Map Scales • To find the actual distance between two points on Earth using a graphic scale, you first measure the distance between the points as shown on the map. Then, you compare that measurement with the map scale. (40) • A fractional scale of 1:10,000 on a map means that one unit of distance on the map represents 10,000 of the same unit on Earth. (41) • A fractional scale stays the same with any system of measurement, regardless of units. An example would be the scale 1:100 could be read as 1 in. equals 100 in. or as 1 c m equals 100 cm. (42)

Section 2 Mapping Earth’s Surface Chapter 3 Reading a Map, continued Isograms • isogram a line on a map that represents a constant or equal value of a given quantity (43) • The second part of the word, -gram, can be changed to describe the measurement being graphed. For example, when the line connects points of equal temperature the line is called an isotherm. When the line connects points of equal atmospheric pressure, the line is called an isobar. (44) (45) • Isograms can be used to plot many types of data, such as atmospheric pressure, temperature, precipitation, gravity, magnetism, density, elevation, chemical composition, and many others. (48)

Reading a Map, continued Isograms • Isobars on a weather map show that all points along an isobar share the same pressure value. (46) • Isobars never cross each other because one location cannot have two air pressures. (47)

Chapter 3 Section 3 Types of Maps Objectives • Explainhow elevation and topography are shown on a map. • Describethree types of information shown in geologic maps. • Identifytwo uses of soil maps.

Types of Maps • Earth scientists look at characteristics of areas on maps, including: • Types of rocks • Differences on air pressure • Varying depths of groundwater (1) Advantages of Topographic Maps • Topographic maps provide more detailed information about the surface of Earth than either drawings or projection maps. Such as island size, shape, and elevation (9)

Chapter 3 Section 3 Types of Maps Topographic Maps • One of the most widely used maps is called a topographic map, which shows the surface features of Earth, both natural and constructed like buildings and roads. (2) (4) • Made by using aerial photographs and survey points collected in field. (5) • topography the size and shape of the land surface features of a region (3) • elevation the height of an object above sea level (6) • Mean sea level, or place from which elevation is measured is the point midway between highest and lowest tide levels of ocean. It is 0. (7) (8)

Chapter 3 Section 3 Types of Maps Topographic Maps, continued Elevation on Topographic Maps • On topographic maps, elevation is shown by using contour lines.(10) • contour line a line that connects points of equal elevation on a map (11) • The difference in elevation between one contour line and the next is called the contour interval. The contour interval is selected based on the relief of the area being mapped. (13) • relief the difference between the highest and lowest elevations in a given area (14) • Every fifth contour line is darker than the four lines one either side of it. This index contour makes reading elevation easier. (17)

Topographic Maps, continued • If relief is high on map, the contour interval is high. It may be 50 or 100 m. (15) • If relief is low on map, the contour interval is low. It may be 1 or 2 m. (16) • Exact elevations are marked with an x and label. (18)

Chapter 3 Section 3 Types of Maps Topographic Maps, continued Landforms on Topographic Maps • The spacing and direction of contour lines indicate the shapes of the landforms represented on a topographic map. (12)(19) • Closely spaced contour lines indicate that the slope is steep. (21) • Widely spaced contour lines indicate that the land is relatively level. (20)

Chapter 3 Section 3 Types of Maps Topographic Maps, continued Landforms on Topographic Maps, continued • A contour line that bends to form a V shape indicates a valley. The bend in the V points toward the higher end of the valley; this V points upstream, or in the direction from which the water flows, if there is a stream. Because water flows from high to low elevation. (22) (23) • Width of V shows the width of a valley. (24) • Contour lines that form closed loops indicate a hilltop or a depression. Closed loops that have short straight lines perpendicular to the inside of the loop indicate a depression. (25) (26)

Chapter 3 Section 3 Types of Maps Topographic Maps, continued The diagram below shows how topographic maps represent landforms.

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