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The
Needles District of Canyonlands
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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