Reading and Interpreting Topographic Maps Peaks and Valleys Reading and Interpreting Topographic Maps

Peaks and Valleys

~ Key Terms ~ Elevation Topographic Map Contour Line Contour Interval

Elevation A term that describes the height of a point on Earth’s surface above (or below) sea level. This point is 6300 feet (1920 meters) above sea level. http://www.math.montana.edu/~nmp/materials/ess/mountain_environments/novice/yosemite.jpg

Topographic Map A map that show the elevation of the land, such as hills and valleys, using contour lines. http://www.math.montana.edu/~nmp/materials/ess/mountain_environments/novice/yosemite.jpg

Contour Lines http://www.topozone.com/map.asp?lat=35.16670759393963&lon=-106.71383553979156&s=25&size=l&symshow=n Contour lines are lines connecting points of equal elevation. Every point along the line lies at the same elevation above sea level. Imagine walking around a hill in such a way that you never go up or down the hill, but stay at the same level. The trace of your path would be a contour line of that elevation.

Contour Interval The vertical distance between one contour line and the next. On any map, the contour interval must be constant, and must be shown in the map’s legend. On this map, the contour interval is 20 feet, because each line represents a 20 foot increase in elevation.

Rules for Successful Contouring Rule #1 Every point along a contour line represents the same elevation. This entire line represents 1200 feet above sea level. 1200 1150 1250

Rules for Successful Contouring Rule #2 Contour lines NEVER split or divide! Can’t happen! 1150 1200 1150 1250

Rules for Successful Contouring Rule #3 This is fine! Contour lines cannot just stop. They must either form a closed loop, or run off the edge of your map. What’s the elevation here??? 1100 1200 1150 1250 ? ?

Rules for Successful Contouring Rule #4 Contour lines NEVER, EVER cross What’s going on?? Is this area above or below 1200 feet? 1100 1200 1150 1250 ?

Tip 1: What does contour line spacing indicate? The closer together the contour lines are, the steeper the hill is. The more spread apart they are, the gentler the slope. Traveling along the red line would be much steeper than traveling along the green line.

Tip 2: Which way is the stream flowing? When contour lines cross a stream or river, they form v-shaped kinks in the lines that always point upstream. Also remember - Water always flows DOWNHILL! Blue Creek flow towards the East.

Tip 3: Finding the hill tops Hill tops are easy to find. Just look for the concentric closed contour lines that form the top of a hill. Notice the contour lines that form the two peaks below.

Tip 4: What do those funny hachure marks mean? Some features, such as the Grand Canyon, lakes, mines, or sinkholes actually are holes in the ground. The hachured contours indicate a depression. Don’t confuse it with a hilltop! 800 700 600

Weathering and Erosion Weathering is the breakdown and alteration of rocks and minerals at or near the Earth's surface

Types of Weathering Physical or mechanical weathering Ice wedging - water expands when it freezes and breaks apart rocks

Types of Weathering Physical or mechanical weathering Thermal expansion - repeated daily heating and cooling of rock; heat causes expansion; cooling causes contraction. http://gpc.edu/~pgore/myphotos/georgia/popup1.gif

Types of Weathering Chemical weathering - Rock reacts with water, gases and solutions (may be acidic); will add or remove elements from minerals. http://uregina.ca/~sauchyn/geog323/485.jpg

Erosion Erosion is the wearing away of land or soil by the action of wind, water, or ice. http://www.ars.usda.gov/is/graphics/photos/k5951-1.htm

Types of Erosion Water Erosion – Water is the most important erosion agent and erodes most commonly as running water in streams. Water collecting on the surface of the soil collects as it moves towards tiny rivulets and streams and creates sheet erosion http://www.ngdc.noaa.gov/seg/hazard/slideset/24/24_slides.shtml

SIMPLY PUT WEATHERING: BREAKS IT DOWN EROSION: CARRIES IT AWAY DEPOSITION: SETS IT DOWN

TOPO QUIZ Now its time to test your topography map reading skills TOPO QUIZ Now its time to test your topography map reading skills. Good Luck!!

What landform do you think this map depicts? If you traveled from point A to point B, would you be going uphill or downhill? What landform do you think this map depicts? a. Valley b. Mountain c. Plain 700 750 A 800 X 825 B

Correct!

Sorry Actually, you would be going uphill. Look at the elevations on the contour lines you will be crossing.

Sorry Please try again.

In which direction does Maple Creek flow? Northeast Southwest Can’t tell from information given What is the contour interval of this map? 50 100 400 800 600 700 500 Maple Creek

5. What is the approximate elevation at the top of this hill? b. 1300 c. 1000 6. Which hike would be steeper, from A to B or from C to D? C D 1200 B 1150 A 1100

7. What is the contour interval of this map? a. 20 feet b. -20 feet c. 60 feet 8. What type of landform is depicted here? a. a mountain b. a depression c. a valley 60 40 20

Link to Topozone The USGS publishes topographic maps of the entire country. This website allows you to view any of these topographic maps. Go to this site and use the map search to try to locate your city, town, school, or maybe even your own house. When you find a familiar area, examine the contours to see how well you recognize your own topographic features!