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Needles
Red and White Bands
The Needles are a series of spires located to
the southwest of Squaw Flat campground that
surround the Chesler Park area of the Needles
District. They are formed out of a resistant
red and white sandstone layer called Cedar Mesa
Sandstone which makes up most of the rock features
in the Needles District. This 245 to 286 million
year old layer was once a dune field on the
eastern edge of a shallow sea that covered what
is California, Nevada and western Utah today.
Sand was blown in from this direction and formed
the white bands in the Cedar Mesa Sandstone.
The red bands came from sediment carried down
by streams from a mountainous area near where
Grand Junction is today. These layers of sand
were laid down on top of each other and created
the distinctive rocks seen today.
How
Needles Form
Starting about fifteen million years ago, the
Colorado Plateau was pushed up thousands of
feet and rivers, such as the Colorado and the
Green, cut down and carved deep canyons. Water,
the primary force of erosion, eats away or weathers
rock by attacking the cement holding the sand
grains together. Moreover, during storms, rushing
water knocks loose sand and rocks as it flows
down washes causing additional erosion. The
water naturally acts faster on areas of weakness
within the rock, such as fractures and cracks.
The Needles occur in an area with many fractures
called joints.
How
Joints Form
The joints were formed in two different manners.
The first was the Monument uplift, which begins
around the Needles District and trends slightly
southwest all the way to Monument Valley. This
uplift caused brittle, surface rock like the
Cedar Mesa Sandstone to crack as it was bent
upward, forming a set of joints in a northeast-southwest
direction.
A
thick salt layer underneath the Needles district,
known as the Paradox Formation, is the second
cause of joint formation. The salt is flowing
slowly toward the Colorado River and dragging
the overlying layers with it. As the upper layers
became stretched, they also fractured into joints.
This action created a set of joints running
northeast-southwest. In the Needles area, these
two joint sets meet and form square blocks of
rock between the joints. As water widened the
joints, the squares were sculpted into pillars
and spires that are today the Needles of Canyonlands.
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