Activity 2: Streams and the Rule of Vs
On flat surfaces, rock layers have fairly simple outcrop patterns. On a map, horizontal layers underlying flat topoography will produce a map pattern showing only one pattern (Fig. 1). However, a distinct pattern develops when beds cross stream valleys or gullies. If a valley cuts the same sequence, more layers will appear on the map, and those layers will define a particular pattern, a V shape (Fig. 2). Interpreting these patterns leads to the rule of Vs. From it, you can determine the dip direction of rock  layers and something of the subsurface nature of an area.

Fig. 1: Map pattern produced by horizontal
layers exposed on flat topography.

Fig. 2: Map pattern produced by
horizontal strata cut by a valley.

To help you visual this type of interaction, use the strike-and-dip applet with a valley.
To complete Activity 2, select one of the following files:word.gif (252 bytes)

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