Topography

Learning Objectives Students will describe what is shown on a topographic map. Students will explain how to read a topographic map.

Key Terms Elevation Topography Contour line Contour interval

Look at this map! How come there are two roads from Louberg to Luluville? Why would anyone bother to build a curvy, indirect route like Dingle Road when the Bo Ring Way route is straight and so much shorter?!"

Dingle Road must have been easier to build! It must be old! Old but scenic! It goes around all the hills! Bo Ring Way goes up, over and through the mountains! A miracle of modern, fast highway building! But a little dull!

Topography Topography is the shape, or features, of the land.

These Features Can Be: Natural such as – Mountains Plateaus plains Human made – Dams Roads

Contour Lines The wiggly lines on a map that show an area’s elevation, slope, and relief.

"Get a map with topographic contours! A contour map!"

"You mean those brown lines? How'm I gonna understand all that spaghetti?!"

"Take it step by step, step by step! Take a look at this picture!"

"The heights above sea level (that is, the elevations) of the three peaks are 3047 feet for Mt. Riddle, 3998 feet for Mt. Ginger, and 2186 feet for Mt. Tipster!"

"Those lines are called contour lines! They're lines of equal elevation above sea level! All the points on the lowest line are zero feet above sea level! All the points on the next higher contour line are 500 feet above sea level! And so on!"

That's not all! If you flew over the island and looked straight down from way up high, this is what you would see!"

"Now pay attention to this! If we want to know the elevation of any of the lines, all we have to remember is that the first one (the one on the outside) was at sea level - elevation 0'! And because we pretended that sea level rose by 500 feet each time, as we go inland, away from the sea, each line that we hit is 500 feet higher than the one before!"

"If we had made sea level 'rise' by 250 feet each time (instead of 500 feet), we would have had twice as many contours! They would have been at 0', 250', 500' and so on! "

Contour Interval’s But you can see it gets to be a bit messy, what with all those numbers! Instead of labeling every line, we can let everyone know the vertical distance between the contour lines! We call that the contour interval, abbreviated C.I.!" "Then all we do is label every fifth contour, starting with the zero contour. We also make the labeled lines heavier! People can do the counting on their own and the map is easier to see!"

Index Contour Lines

Slopes The slope of a landform or area is how steep it is. Where the slopes are steeper, the contour lines are closer together! Where the slopes are gentler, the contours lines are further apart!"

But what happens if you have a cliff - a vertical cliff?!

Contour Lines Follow certain Rules Contours never touch or cross each other. Circles show highest and lowest points. Contour interval is always the same on a map. Index contour lines mark elevations.

The End