Page 6 - sarahbrewer_ch1geology

Erosion: the breaking down and removal of material by various processes, such as the wearing away
of rock by water running over its surfaces, wind, heat, and cold temperatures. This process
completes a cycle of sorts of the “life” of sandstone- just as it was made from sand, it gradually
returns to sand as it erodes.

A favorite spot for visitors of all ages, the “Witch’s Hat” rock, located off of the Nature Heritage Trail near the
front of the park is an excellent example of the effects of weathering and erosion on the rock. Note the
roundness of the edges on the rocks, which have been worn down over time from wind, rain, human activity,
and other erosional forces. Photograph by Sarah Brewer, 2016.

Fanglomerate: Coarse-grained rock, similar to conglomerate, but with pebbles which are more angular,
with corners and edges; these were originally deposited in an alluvial fan. These typically indicate a
more violent, heavier, and faster episode, such as a raging flood that carried a lot of material down
without allowing it time to become weathered and rounded.

Fault: Fracture where once-whole rocks suffered displacement. Earthquakes are caused by the
movement of landmasses along fault lines and the friction between the land masses as they move.

Solution Holes: Occur when water flows over, or is left standing in, small depressions in the rocks. Over
time, the water dissolves some of the rock’s minerals, which are later carried away by rain, wind, and
other erosional forces. Eventually, a solution hole may develop, which over time can grow from the size
of a small pebble to the size of a school bus or larger! These solution holes, combined with differential
erosion, have created interesting shapes in the rocks throughout the park.

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