GEOLOGY

Detailed explanation-1: -Rule # 4-Contour lines that cross a valley or stream are V-shaped. Contour lines “point” upstream when they cross a river or stream. Look at the Mill River in the map to the right. The V points toward the area of higher elevation.

Detailed explanation-2: -As a contour approaches a stream, canyon, or drainage area, the contour lines turn upstream. They then cross the stream and turn back along the opposite bank of the stream forming a “v". A rounded contour indicates a flatter or wider drainage or spur.

Detailed explanation-3: -All rivers flow downhill from higher to lower elevations, perpendicular to the contour line above them. As a rule of thumb, the V-shaped contour is pointing upstream (the opposite direction from the flow of a stream or river). The “V” shape contours indicate streams and drainage.

Detailed explanation-4: -When contour lines cross streams or dry stream channels, they form a V that points upstream. Draw arrows on the copy of Figure 3.10 next to the three streams (shown in blue) to show the direction in which the each is flowing. Estimating the elevations of places not located on a contour line is done by extrapolation.