1. Essential Question: How do contour Lines show elevation on a field map?
OBJECTIVES:
Describe isolines and contour lines
Explain the rules of Isolines
Drawing isolines
Using contour lines to show shape, distances and elevation.

2. ISOLINES
ISOLINES ARE LINES ON A FIELD (MAP SURFACE) THAT CONNECT POINTS OF EQUAL VALUE.
Examples:
CONTOUR LINES- ELEVATION
ISOTHERMS-TEMPERATURE
ISOBARS-AIR PRESSURE

3. How to draw isolines Connect the points with the same values
Begin and end along the edges of the map
Lines may never intersect or cross each other
Do not make sharp edges.

9. Isotherm Map of USA

10. CHARACTERISTICS OF CONTOUR LINES
All points on the same contour line have the same elevation.
Contour lines are always at elevations that are even multiples of the contour interval.
Contour Interval at Sea level is always 0 elevation

11. Characteristics -continued
4. All contour lines close, but not necessarily on the map. Contour lines that do not close on the map will always end at the edge of the map. If the map is not large enough, the lines will not close and will run off the sides of the paper.
5. Contour lines are closer together on steep slopes.

12. Characteristics -continued
6. Contour lines which close on a map encircle regions of higher elevation, i.e., hill or mountain.
7. Contour lines bend in valleys to form a "V" as they cross the low part of the valley. Since streams are usually in the low parts, the contour lines form V's as they cross the streams. The apex of the V always points upstream (or up valley, or to higher elevation).

13. Depressions
Depressions ( dips,craters or holes) are indicated by hachure marks.
A contour line with hachure marks indicates a drop in elevation