Page 5 - sarahbrewer_ch1geology

Left: Desert varnish as it appears
on the reddish colored sandstone,
which is part of the older Lower
Vasquez Formation. The minerals
from within the sandstone were
affected by moisture and heat over
time, resulting in thickened, almost
paint-like darkening on the surface
of the rock. As these minerals form
a layer that is usually harder than
the sandstone, it is often stronger
than the rock underneath and often
slows erosion on certain areas of
the stone (see Differential
Erosion). This phenomenon is
found throughout the park, with
some rocks having a large amount
of the desert varnish covering their
surfaces, giving them a dark,
painted appearance. Photograph
by Sarah Brewer, 2014.

Differential Erosion: The erosion of only softer, nonresistant portions of the rock or other material,
with surrounding layers (which may be harder or more compact) eroding more slowly. This effect
creates some of the most interesting shapes and textures within the formations at the Rocks. The effect
of the desert varnish is another example of differential erosion on a smaller scale.

Right: Millions of years
of differential erosion
have resulted in some
very interesting shapes
in rocks throughout the
park. Pictured here is a
large, unique out-
cropping, which is
located off of the Pacific
Crest Trail in the
southeastern portion of
the park. Photograph by
Sarah Brewer, 2012.

Displacement: Geologic movement or shifting or objects such as rocks or portions of rock
formations.

13