Page 57 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 1 Essentials of Geography 21
Latitudinal Location
Latitude Degree Length (km)
Longitude Degree Length (km)
North Pole
60° 50° 40° 30°
Equator
90° (poles)
60° 50°
40°
30°
0° (equator)
111.70 km = 1° of latitude
111.42 111.23
111.04 km = 1° of latitude
110.86
110.58 km = 1° of latitude
▲Figure 1.14 Physical distances represented by degrees of latitude and longitude.
latitude), parallel names the line (49th parallel), and both indicate distance north of the equator. As noted in Geosystems Now that opened the chapter, the 49th parallel is significant in the Western Hemisphere, for part of it forms the boundary between Canada and the United States from Lake of the Woods on the Ontario–Manitoba–Minnesota border west to the British Columbia–Washington state border on the Strait of Georgia.
From equator to poles, the distance represented by a degree of latitude is fairly consistent, about 100 km; at the poles, a degree of latitude is only slightly larger (about 1.12 km) than at the equator (Figure 1.14). To pinpoint location more precisely, we divide degrees into 60 minutes, and minutes into 60 seconds. For ex- ample, Cabo San Lucas, Baja California, Mexico, in Figure 1.2 is located at 22 degrees, 53 minutes, 23 sec- onds (22° 539 230) north latitude. Alternatively, many geographic information systems (GIS) and Earth visu- alization programs such as Google EarthTM use deci- mal notation for latitude and longitude degrees (an online conversion is at www.csgnetwork.com/gpscoordconv .html). In decimal units, Cabo San Lucas is at +22.8897° latitude—the positive sign is for north latitude, a nega- tive sign for south latitude.
Latitude is readily determined by observing fixed celestial objects such as the Sun or the stars, a method dating to ancient times. Go to this chapter on our MasteringGeography website to learn more about determining latitude using the north star (Po- laris) in the northern hemisphere and the Southern Cross (Crux Australis) constellation in the southern hemisphere.
“Lower latitudes” are those nearer the equator, whereas “higher latitudes” are those nearer the poles. You may be familiar with other general names describ- ing regions related to latitude, such as “the tropics” and “the Arctic.” Such terms refer to natural environ- ments that differ dramatically from the equator to the poles. These differences result from the amount of solar energy received, which varies by latitude and season of the year.
Figure 1.15 displays the names and locations of the latitudinal geographic zones used by geographers: equa- torial and tropical, subtropical, midlatitude, subarctic or subantarctic, and arctic or antarctic. These general- ized latitudinal zones are useful for reference and com- parison, but they do not have rigid boundaries; rather, think of them as transitioning one to another. We will discuss specific lines of latitude, such as the Tropic of Cancer and the Arctic Circle, in Chapter 2 as we learn about the seasons.
1° of longitude =
1° of longitude =
1° of
longitude = 111.32 km
0 km
55.80
71.70
85.40 km
96.49
CRitiCAlthinking 1.2 Latitudinal Geographic Zones and Temperature
Refer to the graph in Figure 5.5 that plots annual temper- ature data for five cities from near the equator to beyond the Arctic Circle. Note the geographic location for each of the five cities on the latitudinal geographic zone map in Figure 1.15. In which zone is each city located? Roughly characterise changing temperature patterns through the seasons as you move away from the equator. Describe what you discover. •