Contour Lines Are Isolines Intro
Method for finding highest possible elevation
Add contour interval to the highest line. Then, subtract 1.
Contour Line
Represents the same elevation everywhere on the line
Depression Contour
Shows a depression with hachure marks drawn on the inside of the line
Contour Map
Shows the shape and elevation of the land
Isoline
A line that connects points of equal value
Index Contour
A line that is darker than the other lines; usually, every 5th line is darkened to make reading the lines easier
Depression
An isolated area of lower elevation than the surrounding land. Ex: swamp, crater, quarry
Highest Possible Elevations On Hilltops
Are assumed to be 1 unit less than the next higher contour line, if there was another higher contour line
Lowest Possible Elevations Inside Depressions
Are assumed to be 1 unit more than the next lower contour line, if there was another lower contour line
Steep Slopes
Are evidenced by contour lines that are closer together. The closer the contour lines, the steeper the slope(gradient).
Gentle Slopes
Are evidenced by contour lines that are farther apart. The farther the contour lines, the more gentle the slope(gradient).
Streams or Rivers
Are evidenced by contour lines that bend in the same direction along the stream. Where a stream crosses contour lines, the lines will bend upstream; so if the lines all bend toward northeast, the stream is flowing southwest.
Cliffs
Are indicated by contour lines that touch or overlap in one area of the map
Hills
Are indicated by one or more sets of closed contours that may form ovals or circles, one inside the other
Field Values
Connected by isolines on a field map to observe patterns and in some cases make predictions
River Direction
Contour lines bend upstream
Bench Marks
On contour maps indicate an exact elevation at the point given. The letters BM usually accompany the point.
Spot Elevation
Is indicated either by an "X" or by a "spot" inside of a triangle and indicates an exact elevation at that spot
Isotherm
Isolines that show temperature on a weather map
Isobar
Isolines that shows BARometric pressure on a weather map
Method for finding lowest possible elevation
Subtract the contour interval from the lowest line. Then, add 1.
How to find contour interval when none is given
Take the difference between 2 adjacent index contours and divide by the number of spaces between them
Labeling a Depression Contour
The 1st depression contour is labeled at the same elevation as the lower line before it. If there is another depression contour inside of the first one, it's value will be less by the amount of the contour interval.
If the land feature is round
The contour lines will be round
If the land shows a straight-line feature
The contour lines will be straight
Contour Interval
The difference in elevation between two adjacent contour lines
Elevation
The height above or below sea level
Identifying a Depression Contour
Tiny lines drawn on the inside of a contour line. 2 adjacent contour lines that have the same elevation.
Hachure Marks
Tiny lines drawn on the inside of the depression contour line to show the direction of the depression
