Basins and domes have similar outcrop patterns in map view. What distinguishing characteristics would you look for to determine one from the other in a map view with no legend?

• A. V's streams/valleys pointing outward for the dome and inward for the basin
• B. V's streams/valleys pointing inward for the dome, outward for the basin
• C. Rivers flow away from domes
• D. Erosional remnants differ

Answer: (A)

The main idea is using how drainage signs appear on a map: the V shapes formed by valleys point toward the source of the stream (upstream). By looking at whether those V’s open toward the center or away from it, you can tell if the feature is a basin or a dome.

In a dome, the center sits higher and water drains away from the center toward the surrounding area. The upstream ends of streams are toward the outer edges, so the V shapes point outward from the center.

In a basin, the center is lower and drainage concentrates toward the center. The upstream directions lie toward the outer rim, making the V shapes point inward toward the center.

So, without a legend, V’s pointing outward indicate a dome, while V’s pointing inward indicate a basin.