Reviewing Chapter 1 Planet Earth Measuring the Earth

Reviewing Chapter 1: Planet Earth (Measuring the Earth)

The shape of the Earth: • Oblate Spheroid (though we LOOK like a perfect circle!) • Slightly wider across the Equator. The Structure of the Earth: • Litho- hydro- and atmosphere = crust, water and air. • See p. 10 in the ESRTs.

Locating positions on Earth • Latitudes = parallel lines. Equator = 0 degrees, NP and SP = 90 degrees N and S. • Longitudes = meet at the Poles. Prime Meridian = 0 deg. Total number = 180 deg East/West. • Our latitude and longitude measurements = our angle from the Equator and Prime Meridian. (see p. 16)

Useful info: • You can always tell your latitude if you can find Polaris. (Polaris’s altitude = your latitude. ) This is only true for places north of the Equator. • You can find Polaris (the North Star) by finding the last 2 stars in the Big Dipper’s “cup. ” See p. 17. • You can also find NORTH by finding Polaris! Or…by using a compass. (There is a slight incorrectness to the direction of “true north. ”)

Solar Time/Clock Time • There are 24 time zones on Earth…. and 24 hours in a day! • The Earth turns 15 degrees/hour…so there is a new “time zone” every 15 degrees of LONGITUDE. • If you know the solar time on the Prime Meridian and your own solar time, you can figure out your approximate longitude.

Maps • Scale = the ratio of how a real object’s measurements compare to that on a map. • Maps can be made for many types of measurements…. elevations, temperatures, air pressure, pollution concentrations…. • Contour lines are used to show elevations…. . like on a topo map. (more on the next slide!)

Contour Maps • Special things about contour lines: • Close lines = steep slopes! (also – close lines on ANY isoline map = high gradient!) • When contour lines cross rivers, they bend UPHILL! • Closed circles = hills. • Always, the interval (difference in value from one line to the next) is the SAME on a map.

Making a Profile from a Topo map: • The profile represents a slice across a landscape. • Use the edge of a piece of paper to make marks representing each place a contour line touches the profile line. (see p. 24!) • Transfer this info onto the profile grid. • Don’t forget to make note of the measurements before you try to make the profile!

Gradient/Slope • Formula = change in field value/distance (p. 1 in ESRTs. ) • Don’t forget the units!!! It depends on the field you are measuring (is it elevation? Is it degrees? Is it ppm? . . . ) and the distance you are measuring (is it km? miles? cm? . . . )