Unit 2 Measuring the Earth Mapping. Size and Shape Almost a perfect sphere- slight flattening in the polar regions and a slight bulging at the equatorial.

Unit 2

Measuring the EarthMapping

Size and Shape

Almost a perfect sphere- slight flattening in the polar regions and a slight bulging at the equatorial region.

Evidence- photos from space, ships “disappearing” over horizon

Earth’s circumference is about 40,000 km

Spheres of the Earth

Series of spheres held together by gravity, arranged from lowest density to highest.- Atmosphere (gas)- Hydrosphere (liquid)- Lithosphere (solid)- Earth’s interior (mostly solid, some liquid)

Atmosphere

The atmosphere can be divided into more spheres.- Thermosphere (highest)- Mesosphere- Stratosphere- Troposphere (lowest)

Atmosphere

Composed mainly of nitrogen and oxygen

Furthest sphere from the Earth’s center because it is the least dense.

The interfaces between layers are called pauses

Hydrosphere

Layer of water Includes the oceans, (70% of Earth’s

surface) lakes, streams, and rivers. Composed mainly of H2O

Lithosphere

Layer of rock that forms the hard outer shell of the Earth’s interior.

100 km thick and lies beneath the atmosphere and hydrosphere.

Composed of plates called lithospheric plates

Upper portion is called the crust

Earth’s Interior

Region extending from the rocky part of the Earth’s crust to the Earth’s center.

Locating Positions on Earth To find a location on a two dimensional surface

you need two numbers or coordinates. Coordinate system- system for determining

coordinates. What is the name of the coordinate system

used to find a location on the Earth’s surface? Latitude-longitude Measured in degrees and minutes: 60minutes

In 1 degree.

Latitude

The angular distance north or south of the equator.

Latitude con’t.

These circles are called parallels of latitude or just parallels

Latitude increases north and south of the equator to a maximum of 90 degrees.

When writing a location with latitude you must indicate N or S.

Longitude

The distance east or west of the prime meridian.

Meridian- semi circle on the Earth’s surface connecting the north and south poles.

Prime Meridian- meridian of zero longitude. When writing a location with longitude you

must indicate W or E.

Longitude con’t.

To read a location on an Earth model such as a map or globe you need to locate the coordinates for both latitude and longitude. Latitude values can be found on the left and right sides of the map and longitude can be found at the top and bottom.

Fields

Any region of space or the environment that has some measurable value at every point.

Examples: temperature fields, wind speeds, atmospheric pressure. More?

Example of a Field

Isolines

Lines on a map that connect points of equal field values

Different kinds: Isotherms- points of equal temperatureIsobars- points of equal air pressureContour lines- points of equal elevation

Gradients and Changes in fields Gradient- the rate of change from place to

place within the field Gradients can be determined two ways:

- estimate; the closer together the lines, the greater the gradient- calculate; gradient = change in field value

-------------------------- change in distance

Mapping Earth’s Surface

Topographic maps (contour map)- maps that attempt to show the elevation of a field on the Earth’s surface.

Some reasons to use a topographic map:

- Construction site selection- Hiking or fishing- Finding natural resources such as water

Reading Contour Lines

Contour interval- the difference in elevation between consecutive lines

Contour interval usually found in key or legend.

Rules to Follow When Reading a Contour Map When contour lines

cross a stream, they bend upward. Contour lines “point” upstream

When there is a series of consecutively smaller and smaller lines, the elevation is increasing toward the top of a hill or mountain.

Every 4th or 5th line shows the elevation

Benchmarks indicate an exact elevation and are indicated on a map as BM X

Depression lines are marked with small lines pointing towards the center of the depression.

Contour Map Showing a Depression

Symbols on Topographic maps There are hundreds of symbols. Most government maps use colors:- red and black: human constructions - Blue: water- Green: woods or areas of vegetation- Purple: where map has been revised

using aerial photographs.

Horizontal Distance on Maps Map Scale- a ratio of distance between two

places on a map and the actual distance on Earth’s surface.

Can be expressed three ways:1. Verbally, “one inch equals a mile”2. Fractionally, 1/500,000 or 1:500,000- this

means any one distance on the map equals 500,000 of the same units on Earth’s surface

3. Graphically, as seen in fig. 2-8 pg. 24

Finding the distance of a curved line How do you measure the distance on a

map of a curved line?

Map Profile Profile- side view of an area’s landscape. Steps to create a profile:1. A line X-Y is drawn on the map. Place a piece of

paper along the line.2. Mark the paper wherever a contour line crosses

the paper. 3. Label the marks with the correct elevation.4. Place the paper horizontally on a piece of lined

paper. Project the lines upward onto the paper and mark with a dot when you reach the corresponding altitude.

5. Finally the dots are connected using a curved line.

Map Direction

Most maps are constructed so the top of the map is north the bottom is south the right side is east and the left side is west.

Magnetic north is labeled MN. What does a compass rose look like?