Topography & Topographic Maps 8th Grade Science

KEY CONCEPTS Key Concept 1: Topographic maps can be used to examine the elevation of an area. The elevation can be measured and monitored for changes over time. Key Concept 2: Satellite technology allows scientists to photograph land and erosional features and study them for changes over time. Key Concept 3: Evidence of changes that occurred in the past can be observed from space, allowing scientists to predict changes that might occur in the future due to sediment deposition, glacier movement, and river courses.

Vocabulary & Key Questions

What is a topographic map?

A topographic map is a special kind of map that provides 3 dimensional information in a drawing.  Natural structures like mountains, valleys, plains, lakes, and rivers are shown on a topographic map. You will also find manmade structures like roads, boundaries, radio towers, and major buildings Topographic maps are used by engineers as they look for coal, oil, and gas. They can be used to plan residential and commercial . And they are used by the military and for recreational purposes like hiking and camping.

Important Topography Terms…

What is ELEVATION? Sanger is 669 feet above sea level. The city of New Orleans is 6.5 feet below sea level. What does sea level mean?

Relief- The representation (as depicted by the topographer) of the differences in elevation and slope between higher and lower parts of the land surface of a given area. The differences in elevation are represented by: Contour Lines Hachure Shading Feature Type: School Latitude: N30.19243ｰ (NAD83 datum) Longitude: W98.08946ｰ Elevation: 1154 ft MSL County: Hays County, Texas USGS 24K Map: Dripping Springs, TX

Aerial View A map that shows the view or pictures of the earth from the air. Images from: http://www.athro.com/geo/topo/mc3_air_photo.jpeg

Satellite View A map that shows an aerial image of the Earth from a satellite in space. image at: www.kidsmaps.com/geography/United+States/Topo.. Image at: www.lib.utexas.edu/.../states_sites.html

Profile View Notice the two high points on the island. What is the elevation of the two high points?

Contour Lines- Imaginary lines that join points of equal elevation on a surface of land above or below a reference surface. In this example: knowing that the elevation of the contour lines ranges from 700 to 800 feet. What are the Elevations at Contour Line A and at Contour Line B? “A” ________ft “B” ________ft. B A

Contour Interval- The change in elevation between one contour line and the next. Example: The contour interval is 20 ft. between the contour lines. Index Contour- Contour line that is accentuated in thickness and is often labeled with the appropriate measure or elevation. Index contours occur every fourth to fifth contour interval and helps the map user to read the elevation on the map.

More index contours…

How is elevation used in a topographic map?

What is the elevation of Point A? Point A sits right on the 0 ft contour line.  Since all points on this line have an elevation of 0 ft, the elevation of point A is zero.

What is the elevation of Point B? Point B sits right on the 10 ft contour line.  Since all points on this line have an elevation of 10 ft, the elevation of point B is 10 ft.

What is the elevation of Point C? Point C does not sit directly on a contour line so we can not determine the elevation precisely.  We do know that point C is between the 10ft and 20 ft contour lines so its elevation must be greater than 10 ft and less than 20 ft.  Because point C is midway between these contour lines we can estimate the elevation is about 15 feet (Note this assumes that the slope is constant between the two contour lines, this may not be the case). 

What is the elevation of Point D? We are even less sure of the elevation of point D than point C.  Point D is inside the 20 ft. contour line indicating its elevation is above 20 ft.  Its elevation has to be less than 30 ft. because there is no 30 ft. contour line shown.  But how much less?  There is no way to tell.  The elevation could be 21 ft, or it could be 29 ft.  There is now way to tell from the map. 

What is the elevation of Point E? Just as with point C above, we need to estimate the elevation of point E somewhere between the 0 ft and 10 ft contour lines it lies in between.  Because this point is closer to the 10 ft line than the 0 ft. line we estimate an elevation closer to 10.  In this case 8 ft. seems reasonable.  Again this estimation makes the assumption of a constant slope between these two contour lines.

Notice how the contour lines are used to show how gentle or steep the slope is.

Topographic maps also identify natural structures and structures made by man.

Reading a topographic map- Streams *The direction a streams is flowing is shown on a topographic map by the way a contour line crosses the stream. *Streams are shown as a blue line on maps. *When contour lines cross a stream it looks like an upside down V. *The point in the V points upstream. It opens in the direction the water is flowing.

Reading a topographic map- Depression Contours *Depression contours show areas of lower elevation. *Drawn like contour lines with marks on the inside. *Hachure marks- tick marks on inside of closed circle.

Benchmark- A marked point of known or assumed elevation from which other elevations may be established. The Benchmark!

Can you match them up?

Practice Time! Get out a sheet of notebook paper and number from 1-10. You will need to read and answer each question. We will grade this as a class!

Green River Topographic Map Activity What is the contour interval?

Green River Topographic Map Activity 2. What do the contour lines do when they cross Green River?

Green River Topographic Map Activity 3. Which mountain has an old volcanic crater at its top?

Green River Topographic Map Activity 4. What is the elevation of point A?

Green River Topographic Map Activity 5. Which side of Fire Mountain is the steepest? (North or South)

Green River Topographic Map Activity 6. What is the elevation of point B?

Green River Topographic Map Activity 7. If you walk from point D to point E would you be going uphill or downhill?

Green River Topographic Map Activity 8. When the stream first begins, what direction is it flowing?

Green River Topographic Map Activity 9. What is the difference in elevation between points A and C?

Green River Topographic Map Activity 10. What is the elevation of the highest contour line on this map?

Green River Topographic Map Activity 11. Select the most accurate profile that runs from A to A` from the choices. A A` A C B D

Green River Topographic Map Activity What is the contour interval? 20

Green River Topographic Map Activity 2. What do the contour lines do when they cross Green River? They point upstream and show that the river flows out of the “V”

Green River Topographic Map Activity 3. Which mountain has an old volcanic crater at its top? Fire Mountain: it is shown by Depression Contours.

Green River Topographic Map Activity 4. What is the elevation of point A? 150

Green River Topographic Map Activity 5. Which side of Fire Mountain is the steepest? (North or South) The South side because the contour lines are closer together.

Green River Topographic Map Activity 6. What is the elevation of point B? 110

Green River Topographic Map Activity 7. If you walk from point D to point E would you be going uphill or downhill? Uphill

Green River Topographic Map Activity 8. When the stream first begins, what direction is it flowing? Southeast

Green River Topographic Map Activity 9. What is the difference in elevation between points A and C? 40

Green River Topographic Map Activity 10. What is elevation of the highest contour line on this map? 260

Green River Topographic Map Activity 11. Select the most accurate profile that runs from A to A` from the choices. A A` A C B D