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!