Visualizing Earth’s Surface

Maps: Represent a portion of the Earth’s surface Maps: Represent a portion of the Earth’s surface. Different maps are used to show different information about the Earth.

A. Types of Maps: 1-Weather

2.Geologic: Shows rock formations and soil compositions.

3. Road: Shows roads, towns, and cities.

II-Field Maps: A map on which similar measurements are plotted Examples: could be temperature, pressure, or elevation. A- Isolines - Connect points of equal value on a field map. “Iso-” means same

Examples of Field Maps 2- Isotherms - Lines connecting equal temperatures 1- Isobars - Lines connecting equal pressures 3- Contour Lines - Lines connecting equal elevations

B- Topography: general form and shape of the land on Earth’s surface (mountains, valleys, streams, ect)

C- Topographic Maps - -show the shape of earth’s surface -isolines on a topographic map are called contour lines - Contour lines show points of equal elevation

1- Index Contour Lines - Heavy lines spaced at a predetermined elevations on a topographic map.

Benchmark – tells the real elevation at that point 2- Contour Interval- The vertical distance that separates each contour line on a topographic map. Benchmark – tells the real elevation at that point

-Closed contours on a map as an ellipses or circles represent hills.

hachure marks represent depressions (holes). -Closed contours with hachure marks represent depressions (holes). Contour Interval = ?

The contour line with the marks, or hatchers, has the same elevation as the line before it.

From a higher elevation to a lower elevation Water flows down hill From a higher elevation to a lower elevation

(water flows in the opposite direction) -When a contour lines cross a river they make a “V” that points upstream. (water flows in the opposite direction)

III- Rules for Contour Lines: A contour line represents a single equal elevation: that is, all points on the same contour line have the same elevation. 5 5 10 10 10 10 15 15

2. Where one closed contour line surrounds another, the inner contour line represents the higher elevation. Lowest elevation 0 m 400 m Highest elevation

3. The elevation represented by a contour line is always a simple multiple of the contour interval. (5, 10, 50, 100) 0 m 100 m 200 m 300 m 400 m

A contour line that closes within the limits of the map indicates a hill, ridge or plateau.

5. On the same map, closely spaced contour lines indicate a relatively steep slope, widely spaced contour lines indicate a relatively gentle slope. Steep Gradient Gentle Gradient

6. Contour lines do not cross other contour lines 6. Contour lines do not cross other contour lines. Exception: on a vertical cliff or a nearly vertical cliff, contour lines touch because they are on top of one another Cliff

7. Every contour line eventually closes against itself 7. Every contour line eventually closes against itself. However, the map area may not be large enough to show this closure. Therefore, the contours will end at the edge of the map.

8. Closed depressions are shown by hachured contour lines 8. Closed depressions are shown by hachured contour lines. The hachures point into the depression. (Hachures = short dashes)

9. A hachured contour line, lying between two different contour lines, is the same elevation as the lower contour line. Count down Count up Contour Elevation Repeats

10. Where a contour line crosses a stream or valley, the contour bends to form a “V” that points upstream or up the valley.