THE GEOGRAPHER’S TOOLS - Discovering Physical Geography - page 16

General Zones of LatitudeT

T A B L E 2 . 1

Latitude Zone Range General Characteristics

Low latitudes About 35° N-35° S Very warm region of Earth with generally consistent weather over

the course of the year

Midlatitudes About 35°-55° in both hemispheres Seasonal weather with warm/hot summers and cool/cold winters

High latitudes From about 55° to 90° in both

hemispheres

Very cold region of Earth with very short summers

relationship and will be discussed in much more detail in the
next chapter.
Lines of latitude are also called parallels because they
are parallel to the Equator and each other. The value of any
given line of latitude remains the same no matter the location,
whether it is on one side of Earth (such as in China) or the other
(such as in the United States). A common misconception is that
lines of latitude must indicate direction east and west because
that is the direction that these lines follow. To remember how
the system really works, think of degrees of latitude as being
numbered sequentially north and south of the Equator.
Although you can certainly think of lines of latitude in in-
dividual terms to locate specific places, it is also useful to think
of them collectively by region. In that context, lines of latitude
can be lumped into nine geographic zones (see Figure 2.5).
These nine regions can be further grouped into three general
zones (Table 2.1) in which many distinct physical processes
occur. The low latitudes range from about 35° N to 35° S of
the Equator and are generally the warmest part of Earth. The
midlatitudes range from about 35° to 55° latitude, in both
hemispheres, and are typically regions of Earth that experience
highly variable weather over the course of the year. Finally, the
high latitudes range from 55° to 90° latitude, again in both
hemispheres, and are typically the coldest places on Earth.

2. Lines of latitude are determined by measuring the geo-

metric arc between two lines projected from the center
of Earth to the surface at the Equator and at the location
in question. The reference point for latitude designa-
tions is the Equator (or 0°); latitude designations extend
to 90° N and S.

3. Lines of latitude never intersect with one another and

therefore have the same value over the entire circle.

4. Zones of latitude can be grouped into nine geographic

zones. These nine can be further grouped into three
broad categories: the low, middle, and high latitudes.

Longitude
The previous discussion demonstrated how latitude is used
to identify location north and south of the Equator. Now let's
examine how east and west locations are determined with
longitude . The foundation of the longitude system is the
complex of great circles that pass through the poles. Half of such
a great circle is a spherically shaped outline that connects each
pole. Each of these half circles is called a meridian of longitude,
or simply a meridian . In contrast to the latitude system, which
uses the Equator as the foundation because it is the only great
circle of the parallels, the easterly and westerly longitude
calculations require an arbitrary reference meridian because all
of them are half outlines of the great circles that pass through
the poles. The arbitrary reference meridian for longitude is the
Prime Meridian , which passes through Greenwich, England,
at the Old Royal Observatory (Figure 2.6). This meridian
was chosen as the reference meridian of longitude at an 1884
conference in Washington, D.C.

KEY CONCEPTS TO REMEMBER
ABOUT LATITUdE

1. Lines of latitude run exactly east and west; they are also

called parallels because they always parallel the Equator.

Lines of latitude.

Parallels Longitude The part of the Earth's grid system that determines

location east and west of the Prime Meridian.

The zone of latitude that lies between about Low latitudes

35° N and 35° S. Meridians

Lines of longitude.

Midlatitudes The zone of latitude that lies between about 35°
and 55° in both hemispheres.

Prime Meridian The arbitrary reference point for longitude
that passes through Greenwich, England.

High latitudes The zone of latitude that lies from about 55˚ to
90˚ in both hemispheres.