This EarthCache is found in Garden of the Gods Park, a Colorado
Springs City Park. Park hours are as follows: May 1 – October 31, 5
am – 11 pm; November 1 – April 30, 5 am – 9 pm. There is no charge
for entry into the park. Please bring a ruler or tape measure as
you will be measuring the particle sizes making up the Fountain
Arkose.
The Three Graces is a rock formation made up of Fountain Arkose,
the oldest type of rock found in the Garden of the Gods. Fountain
Arkose is a conglomerate made up of coarse-grained sediments. About
300 million years ago, the Ancestral Rocky Mountains were eroding
and the sediments were being deposited as stream gravels and
alluvial fan deposits. The Ancestral Rocky Mountains were formed
from granite, like much of today’s Rocky Mountains, and this is
where the feldspar in the Fountain Arkose came from (an “arkose” is
a rock formed from at least 25% feldspar). The presence of the
feldspar is what gives the Three Graces its pink hue.
Rocks formed from alluvial fan deposits often have a large
difference in the particle size due to the nature of this type of
deposition. Alluvial fans are formed from material which is carried
in streams which travel through restricted areas such as canyons or
narrow washes. When the water reaches the end of the restriction,
the water spreads out and the energy of the water is dissipated.
With the reduction of energy in the water, the material which was
carried along drops out, with the larger material dropping first.
Weather events have a large effect on the erosion of this material.
Storms and spring snowmelt often cause larger particle sizes to be
moved in the streams (boulders and gravels) versus smaller material
(gravels, sands, and mud) which is moved during dry seasons.
Catastrophic events, such as extreme floods (the Big Thompson
Canyon Flood in 1976) or dam breaks and resultant flooding (the
Lawn Lake Dam failure in 1982) are known to have moved boulders 20’
or more in diameter, along with a range of other smaller
material.
Look closely at the particle sizes and layering which you see in
the Three Graces. To log this EarthCache, send me an email with the
following: 1.) Measure the largest and smallest particles you can
find. 2.) Measure the width of one of the distinct layers found in
this formation.
After you have emailed me the answers to these questions, post
at least 1 picture of you with the Three Graces in the
background.
The above information was compiled from the following sources:
Colorado Springs City Webpage: Garden of the Gods Park.
(visit link)
Colorado Springs City Webpage: Important Events in Garden of the
Gods Geology.
(visit link)
2007. Chronic H., and F. Williams. Roadside Geology of Colorado,
2nd Ed.
2004. Hopkins, R.L., and L.B. Hopkins. Hiking Colorado’s
Geology
Thanks to the City of Colorado Springs and the Parks, Recreation
& Cultural Services Department for allowing placement of this
EarthCache!
