Topographic Maps

Topographic Map

shows the surface features, or topography of Earth or a certain area.

What does a topographic map show?

it shows natural features such as rivers and lakes. They also show some features made by people such as brodges. They also show elevation.

Elevation

The height of an object above the surface of the sea.

What is the elevation at sea level?

The elevation at sea level is zero meters.

How can a flat map show elevations?

Contour lines are used to show elevation on a topographic map.

Contour lines

Lines or isolines on a map that connect points with the same elevation.

What does each contour line on a map show?

Each contour line shows a different elevation.

Contour lines rules:

1. Contour lines never cross.

2. All points on a contour line are at the same elevation.

3. The space between contour lines depends

on the slope of the ground.

Contour lines that are close together show what type of slope?

A steep slope.

Contour lines that are far apart show what type of slope?

A gentle slope.

What shape are the contour lines that cross a valley or stream?

V shaped. the "V" points to the area of higher elevation or upstream.

How are the tops of hills, mountains or depressions (dips) shown on a topographic map?

They are shown by closed circles.

How are depressions marked on a topographic map?

They are marked with short, straight lines inside the circle. The lines point toward the center of the depression.

Why can 2 contour lines never cross?

At the point where 2 contour lines would cross would have 2 different elevations which is impossible.

Contour Interval

The difference between adjacent contour lines. Adjacent means next to. It is usually shown in or near the map's legend. The difference in elevation between one contour line and the next.

What is the contour interval on a map based on?

The relief in the area.

Relief

The difference in elevation between the highest and lowest points in the area on the map.

What type of relief do mountains have?

A high relief. They are usually mapped with large contour intervals.

What type of relief do plains have?

A low relief. They are usually mapped with small contour intervals.

Index Contour

A darker, heavier contour line that is labeled with an elevation. It is usually every fifth line that indicates a change in elevation. This makes reading the map easier.

Which lines are index contour lines?

In most maps, every fifth contour line is an index contour.

A map has index contours at 250m, 500m, and. 750m. What is the contour interval?

Index contours increase by 250.

250/5 = 50. 50m

Why are colors and symbols used on topographic maps?

To show information. To show different features of Earth's surface.

What color shows buildings, bridges and railroads?

Black

What color shows contour lines?

Brown

What color shows major roads?

Red

What color shows bodies of water?

Blue

What color shows wooded areas?

Green

What color shows cities?

Gray or red.

What is the relationship between the relief of an area and the contour interval on a map of he area?

If the relief is high (bigger change) you will need a bigger contour interval.

Features shown on topographic maps:

Mountain/Hill Depressions

Streams/Rivers Escarpments/Cliffs

Lakes/Ponds

The highest point on a topographic map is marked as 345m. The lowest contour line is at 200m. What is the relief of the area in the map?

345m - 200m = 145m

How is the top of a mountain shown on a topographic map?

It is shown by a closed loop.