Maps – What Can They Tell Us?

The shape of the landDirection of water flow in a river or streamSlope of the landWeather patterns

MapsAll maps have fields, which are regions of

space or areas that have a measurable value of a given property.

Isolines – Lines on a field map connecting all points of equal valueIsobars – connect points of equal air pressureIsotherms – connect points of equal

temperatureContour Lines – connect points of equal

elevation

Isoline Rules Lines must connect equal points in equal

intervalsIf there is not a point for a given interval, you

must draw the isoline where it would fit.Isolines must either close or run off the mapIsolines can never touch

Practicing Isolines1. Draw elevation isolines

for 40, 50, 60, 70, & 80 feet.

2. What is the approximate elevation of point:

• Point A

• Point B

• Point C

Elevation measured in feet

71-79 feet

41-49 feet

51-59 feet

Practicing Isolines1. What measurable property is

shown on this map?

1. Based on this property, the isolines on this map are called

1. What is the approximate measurement of this property for New York State?

Temperature

Isotherms

5°C

Practicing Isolines – Average Yearly Number of Thunderstorms in the

USApproximately how many thunderstorms occur each year in:•Albany, NY

•Los Angeles, CA

•New Orleans, LA

20-30

>10

<70

Topographic Maps – Maps of an Elevation Field

Topographic Maps show the elevation of the land by using contour lines, and show other natural and man-made features by using symbols.Contour Lines – isolines on a map connecting points

of the same elevation Elevation – distance (feet) above sea level

Contour Interval – difference in elevation between two consecutive contour lines

Index Contour Line – heavy, dark contour line, usually with numerical value for elevation marked

Depression – special contour lines used to show a hole or crater on Earth’s surface.

Depressions

http://www.iihr.uiowa.edu/~illman/courses/eg/webslides/12-179%20Part3%20Topo%20and%20Geomap%20Spr07.pdf

http://www.iihr.uiowa.edu/~illman/courses/eg/webslides/12-179%20Part3%20Topo%20and%20Geomap%20Spr07.pdf

Contour Lines

Index Contour

Depression Contour

3. What is the contour interval?

3. What is the highest possible elevation of the hilltop?

3. Which side of the hill is the steepest?

3. How do contour lines show a steeper slope?

20 feet

259 feet

East/right

The contour lines are closer together

River Valleys – The Law of the V’s• Contour lines form a V pattern when crossing streams.

• The V always points UPSTREAM

Which way is the stream flowing?

Downstream(Downhill)

http://www.iihr.uiowa.edu/~illman/courses/eg/webslides/12-179%20Part3%20Topo%20and%20Geomap%20Spr07.pdf

Drawing Contour Lines on a Field Map – 20, 40 ,60, 80, 100, 120 feet

Calculating GradientGradient is the rate at which elevation

changes from place to place.

Gradient = change in field value distance

Calculating GradientUse the elevation field map that you drew

contour lines on to calculate the gradient between:

Point A & CGradient =

Gradient =

110-20 ft

3.5 miles

25.7 ft/mile

Point B & DGradient =

Gradient =Point B & E

Gradient = Gradient =

Point F & CGradient =

Gradient =

123 – 13 ft

3 miles

36.7 ft/mile

123-80 ft

1.5 mile

28.7 ft/mile

27-20 ft

1.5 mile

4.7 ft/mile

Parts of a MapParts of a Map:

Scale – relates distance on the Earth’s surface and is often given as a ratio.

Map Key – a list of all the symbols used on a map with an explanation of their meaning.

Symbols – pictures used to describe a feature on Earth’s surface.

Let’s take a walk up a hill!

We’re now at an elevation of 100 meters.

100m

Let’s keep going!

100m

Now we’re at 200m.

100m

200m

Shall we march on?

100m

200m

We’ve made it to 300m!

100m

200m

300m

On to the peak!

100m

200m

300m

We’re on the peak, but what’s our elevation?

100m

200m

300m

Any ideas?

100m

200m

300m

Let’s add contour lines for every 50 meters and see if that helps.

100m

200m

300m

We know that we are above 350m, but less than 400m.

50m

150m

250m

350m

100m

200m

300m

Let’s head down the hill, it’s getting late!

50m

150m

250m

350m

100m

200m

300m

Now what’s our elevation?

50m

150m

250m

350m

If you said somewhere between 200m and 250m you are right!

100m

200m

300m

Let’s try this again!

50m

150m

250m

350m

100m

200m

300m

What’s our elevation now?

50m

150m

250m

350m

If you said 50m or just under, you’re right!

Each color change represents a 50 meter increase.

Now, let’s try the same hike! Our elevation is 0 meters.

Now what is our elevation?

If you said more than 150 meters, but less than 200 meters your

right!

Let’s go a little higher.

Think you know our elevation now?

More than 300 meters

But less than 350 meters

If we were standing on the peak, what would be our elevation?

More than 350 meters, less than 400 meters

Let’s head down hill.

Know our elevation?

More than 100 meters,

less than 150 meters

Let’s see what you know.

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

Grab a piece of paper and write your answers to the following questions.

Ready?

1. Could the elevation at the peak (B) be 1410 meters?

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

No :The elevation must be under 1400 meters, but over 1300 meters.

2. What is the elevation at (E)?

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

400 meters

3.What is the elevation difference between (A) and (B)?

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

(A) Is 750 meters, (B) is above 1300 meters. The difference between would be 650 to 700 meters.

4. Could the elevation at (F) be 417 meters?

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

No: It must be more than 700m and less than 800m

5. If you walked a straight line from (D) to (C) would you walk over a ridge or down a valley?

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

Down a valley

6.Just looking at the map, would it be easier to head down from the peak going East, or going North?

400m 800m

1000m

1200m

A

B

C

D

E

F

600m

E

N

S

W

East

6. East: When contour lines are close together that means there is a steep slope, the further apart the lines, the more gentile the slope and therefore an easier walk! Go east!