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