Mapping Earth’s Surface A field is any region or space in the environment that is measurable. Atmospheric pressure, wind speed, elevation, levels of infra-red.

Mapping Earth’s Surface

A field is any region or space in the environment

that is measurable.

Atmospheric pressure, wind speed, elevation,

levels of infra-red radiation are all examples

of fields.

Maps are used by Earth scientists to interpret how a field is impacted by its

environment or vice versa.

Isolines

Isolines are used on a map to connect points of equal value.

This isoline indicates an elevation of 3000

feet.

Common examples of isolines include:

ISOTHERMS = lines of equal temperatureISOBARS = lines of equal air pressureCONTOUR LINES = lines of equal elevation

Contour lines

Gradient: Changes in Fields

gradient = change in (amount of) field value change in distance (horizontal

distance)

An environment is continually changing

and therefore fields will also change. Gradient represents the rate of change from “place to place” within the field.

City A = 42°F

City B = 30°F

What is the temperature gradient between two cities in North Carolina on the date shown?

Gradient = change in (amount of) field value change in distance (horizontal

distance)

Gradient = 42°F – 30°F 100 miles

Gradient = 12°F = 0.12 °F/mi

100 miles

RT = Pg. 1

Contour Maps

A contour map (topographic map) is

a model used to show the elevation field of the Earth’s

surface at a particular location.

Contour maps are used as hiking aids, planning for areas of

construction and resource

development.

Brown = landforms/elevation Blue = Water features Green = woodlands Red/Black = Human constructs (boundaries, roads, etc..)

Reading a Contour MapWhen contour lines cross a stream they bend towards the direction of higher elevation.

An index contour appears thicker/bolder than the other contour lines.

A series of consecutively smaller and smaller contour lines indicates a peak in elevation.

Closely spaced contour lines indicate a steep slope (gradient).

Contour lines that are spaced wide apart indicate a gentle slope (gradient).

Reading a Contour Map

A depression represents a decrease in elevation. Sink holes and craters represent landscape features that are depressions.

A depression is represented by “hachures” on the contour lines. The first “depression contour line” will have the same contour interval as the last contour line.

Each succeeding “depression contour line” will be drawn at the same contour interval as the rest of the map.This first “depression

contour line” would have an elevation of 140 ft; the same as the previous contour line.

The second “depression contour line” would have an

elevation of 130 ft.

The contour interval represents the change in elevation between two consecutive contour lines on a map.

The contour interval for this map is 10 ft.

Determining Horizontal Distance on a Contour Map

The horizontal distance on a contour map is usually represented as a map scale in the legend of the contour map.

To determine the horizontal distance between two locations on a contour map:

1. Place a piece of paper with a straight edge on the map and mark the two locations

2. Match up the marks on the map scale to estimate the horizontal distance between the two points.

What is the distance between the school and post office?

2.3 km

Topographic Profile

A topographic profile is a cross section of a landscape constructed from data collected from a contour map. To make a topographic profile, complete the following steps:

1. Place the edge of a strip of paper along the line to be profiled.

2. Make a mark on the paper at each point where a contour line crosses it. Record the elevation at each point.

3. Align the paper along the x-axis of a graph and plot the points of elevation onto the graph.

4. Connect the points with a smooth, curved line.

Map Direction

Compass Rose

Maps are usually constructed so that geographic North is at the top of the map.

An arrow or a “compass rose” is most usually placed on the map to show the direction of geographic North.

Knowing where North is on a map, allows the observer to determine the other 7 cardinal directions

Where can Bluewater Lake be found with relation to Kennedy Lake?

Southeast