Some Wooden Blocks
Oblique View. Beds dip progressively less as you go to the left.
Block on right shows vertical beds.
Looking straight downwards (Map View). The vertical bed shows no "V", the two dipping
beds show "Vs" in the direction of dip, the horizontal bed shows horizontal stripes on either
side of the valley. Note that the "V" becomes increasingly pronounced as the dip decreases.
These blocks were made by John Lewis of Colorado Springs. He is a fine woodworker who is also a geologist. In fact, I got to know him because he taught my Introductory Geology (1978) and Structural Geology (1981) classes at Colorado College.
Here's another one of John's block models. While this one shows the rule of Vs, it also shows other effects of variable topography on the outcrop pattern. Note that where the terrain is steep, and so at a high angle to the dipping bed, the outcrop width is relatively narrow. However, where the terrain is gentle, and so nearly parallel to the dipping bed, the outcrop width is much wider.
So why can the Ogallala Fm., which is only a few hundred meters thick, cover much of the states of Oklahoma, Kansas, Nebraska, and eastern Colorado? ---The beds are horizontal and the terrain is pretty flat.
Click here to see a photograph and map which illustrates some of the same things.
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