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Bryce
Canyon Hoodoos
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Bryce
Canyon National Park is located in the High
Plateaus region of the Colorado Plateau in Utah.
Elevation, climate, rock type and the plateau's
orientation are elements that, when combined,
form unusual shapes called hoodoos. No where
else in the world can one find a concentration
of pinnacles with odd shapes like those found
in Bryce Canyon.
Erosion
Most visitors come to Bryce Canyon National
Park by way of other National Parks on the Colorado
Plateau such as Arches, Canyonlands, Natural
Bridges, Capitol Reef and Zion. Each park attracts
visitors for different reasons.
The Virgin River cuts down through resistant
sandstone forming the deep canyon of Zion National
Park. Gravity defying arches of Arches National
Park form in resistant sandstone by frost wedging
and water erosion in fractures. Continuous down
cutting by the Colorado River forms deep incised
meanders in sandstone layers at Canyonlands
National Park.
Bridges
form in sandstone by river action eroding into
fins at Natural Bridges National Monument. Capitol
Reef National Park was formed by water erosion
that exposed vibrant rock layers folded into
a monocline by an ancient fault. All the parks
mentioned contain massive structures, which
tower over awed spectators. It seems inconceivable
that anything other than the strong erosive
force of water could have carved and exposed
these immense landforms.
Visitors at Bryce Canyon National Park come
to see the unique shapes formed in the Claron
Formation. Bulbous, wavy spires and fins protrude
from the plateau's sides like the veins on plant
leaves. These are commonly known as Hoodoos.
The mystical shapes inspire imagination and
intrigue.
It
appears impossible that the destructive forces
of water carved these fragile landforms. Instead
many believe the hoodoos of Bryce Canyon were
formed by wind. This is a mistaken idea. Wind
is an effective form of erosion for many locations.
However, for Bryce Canyon wind has little effect
on the creation and destruction of the various
shapes.
Hoodoos formed over thousands of years by the
same processes that form the features of surrounding
parks. Water, ice (at varying intervals) and
gravity are the forces that form Bryce Canyon.
These three erosive forces coupled with the
differential erosion of the four rock types
of the Claron Formation produced a different
morphology than that of other parks. 10-15 million
years ago the Paunsaugunt Plateau was caught
and uplifted by the Colorado Plateau. Breaks
called joints formed in the plateau during the
uplift. Joints allowed water to flow into the
rock. As water flowed through joints erosion
widened them into rivulets and gullies. Over
time, deep slot canyons formed in the sides
of the plateau.
Bryce
Canyon receives an average rainfall of 10 inches
a year in the valley and approximately 19 inches
a year on the plateau. Majority of the precipitation
falls in mid to late summer. It comes in the
form of monsoons, usually in the afternoon.
These thunderstorms can be fierce, dropping
an inch or two of rain in under an hour. Hail
storms often accompany heavy rains in the region.
Most of the rainfall is not absorb by
the thin layer of soil covering the rocks. Because
soils at Bryce Canyon are very dry, much of
the water runs off the surface. Only the top
inch, or so,of soil absorbs rainfall before
it starts to run off. When this happens at Bryce
Canyon flash floods are the result.
At Bryce Canyon water in the form of ice is
the most efficient form of erosion for breaking
rock into smaller pieces. The Paunsaugunt Plateau
receives approximately 100 inches of snowfall
a year. It also experiences about 200 days of
freeze/ thaw. Which means that everyday a small
amount of snow melts and runs into the joints
and freezes at night. When water freezes it
expands to form an ice wedge in the joint widening
the space. As the ice wedge grows by more water
leaking into the joint and freezing it will
finally break the rock. This is called frost
wedging.
Small
pebbles and large Volkswagen bus sized boulders
commonly fall from the sides of existing hoodoos
and the sides of the Paunsaugunt Plateau by
frost wedging and gravity. The smaller pieces
are washed away by the monsoons and snow melt.
Boulders explode into cobble sized pieces when
they impact the ground. The resulting debris
is washed down slope by snowmelt, flashfloods
and gravity. Rock type is another factor in
the creation of the bizarre shapes of hoodoos.
The hoodoos at Bryce Canyon are carved in the
Claron Formation. Limestone, siltstone,dolomite
and mudstonemake up the four different rock
types that form the Claron Formation. Each rock
type erodes at different rates. The rock's resistance
to erosion is what causes the undulating shapes
of the hoodoos.
Dolomite, limestone and siltstone are very hard
and form the protective caprock on most of the
spires. Frost wedging is the erosional force
that breaks apart the harder rocks. Mudstone
is the softest rock in a hoodoo and is easily
identified because it forms the narrowest portion
of the pinnacles. As mudstone moistens it erodes
easily and will run down the sides forming a
stucco or protective coating. Every time it
rains the stucco is renewed.
Eolian or wind forces erode at slow rates. If
wind does not erode the stucco layer fast enough
it will renew before eolian erosion affects
the rock. For this reason wind has little to
no affect on hoodoo formation or destruction.
Another sign that wind is not responsible for
hoodoo formation is the absence of a dominant
wind direction pattern carved into the plateau.
If eolian forces were responsible for erosion
in the area hoodoos would erode parallel with
the prevailing wind direction.
At
Bryce Canyon National Park hoodoos do not align
with the prevailing air currents. Hoodoos protrude
from the sides of the plateau in lines that
follow joint patterns caused by faults that
uplifted the area. Some of the walls and fins
meet at almost a 90-degree angle. Wind erosion
would not form patterns like this. (Below is
a photo showing fins in a linear patterns extending
from the plateau).
After
a heavy rain, soil in the region dries out and
forms a hard crust. Wind erosion requires loose
particles to be transported with in the air
column and impacted into a surface for erosion
to take place. The particles need to be free
and not attached to a crust. Because of the
crust there is not a large supply of loose particles
to be used for wind erosion in the area. Vegetation
also keeps loose grains in place by their roots
and by slowing the gusts of wind as it blows
through the branches.
Erosional
scours paralleling the hillslopes are carved
on the slot canyon walls. They are common in
many places within the park.
As
hikers descend into Wall Street on the Navajo
Loop a close inspectionof the canyon walls will
show diagonal erosive marks cutting through
horizontal bedding planes. (The photos show
show horizontal bedding planes and the diagnol
scour marks.) These scour marks show the erosion
point of historical hillslopes. If wind erosion
were responsible for the formation of walls,
fins and hoodoos the old scour marks would have
been eroded away along with the hillslope.
Hoodoo surfaces would be smoother and more round
if wind erosion were responsible for their creation.
Instead many hoodoos have sharp edges and jagged
tops like the skyline of 'The Silent City'.
Angular pinnacles, stuccoed sides, boxy erosional
patterns and scour marks are some of the more
obvious tells of water erosion.
While visiting Bryce Canyon National Park look
for signs of wind and water erosion. It is suprizing
how visible the numerous signs of water erosion
are, when you know what to look for.
Ancient
Sedimentation
Our dynamic planet is constantly being shaped
and reshaped by dramatic events such as earthquakes,
volcanoes, and mudslides. Other changes may
not be detected in a human lifetime. Geological
timespans or Periods cover millions of years.
The Cretaceous Period began some 144 million
years ago and lasted until about 63 million
years ago. The rock formations you see exposed
at Bryce Canyon began to develop during this
time. For 60 million years a great seaway extended
northwestward into this area, depositing sediments
of varying thickness and composition as it repeatedly
invaded, retreated, then re-invaded the region.
Retreating to the southeast, it left sediments
thousands of feet thick. Their remnants form
the oldest, lowest, gray-brown rocks at Bryce
Canyon.
In
the Tertiary Period, between 66 and 40 million
years ago, highlands to the west eroded into
shallow, broad basins. Iron-rich, limy sediments
were deposited in the beds of a series of lakes
and streams. These became the reddish rocks
of the Claron Formation from which the hoodoos
are carved and for which the Pink Cliffs are
named.
The Cretaceous Seaway moved northward from the
Gulf of Mexico into this region of North America
(left). Sediments deposited as the sea invaded
and retreated became the brown and gray marine
rocks now exposed at the park's lowest elevations
and across the Paria Valley.
Deformation,
Uplift, and the Grand Staircase
Horizontal compression related to the formation
of the Rocky Mountains deformed these rocks.
Then volcanic flows from the north covered parts
of the region: black rocks at the mouth of nearby
Red Canyon and on the Sevier Plateau to the
north still protect softer underlying layers.
About 10 million years ago the Earth pulled
apart, moving and tilting great blocks along
north-south trending fault lines. Layers, once
connected, were displaced vertically by several
thousand feet, forming the High Plateaus of
Utah.
Older
Cretaceous layers rested side by side with younger
Tertiary layers across fault lines. Streams
began to remove sediments deposited by their
ancestors. Working on the weakened edges of
the upthrown blocks, water gradually removed
the uppermost Tertiary layers and exposed Cretaceous
rocks once again. Now these drab former marine
sediments lay on the surface of the land side
by side with the brightly colored deposits of
freshwater lakes and streams.
Differential
Erosion
Water erodes rock mechanically and chemically.
Scouring, abrading, and gullying occur when
fast-moving water scrapes its silt, gravel,
and rock debris against firmer bedrock. Slow-moving
or standing water enters minute rock pores and
dissolves cements holding the rock together.
This leaves loose grains to wash away. Softer
Cretaceous rocks were loosened and carried away
from the upthrown block by the Paria River.
The resulting Paria Valley is carved out of
rocks that lie deep beneath the Paunsaugunt
Plateau, whose edge now is exposed to erosion.
Along the plateau rim, conditions are optimal
for erosion. Its steep slope increases water
speed and energy. Faults and joints from ancient
compressional forces influence erosion patterns.
Freezing and thawing loosen slope surfaces.
Debris carried by runoff, scours softer rock
and creates gullies; harder rock remains as
fins.
As
gullies widen to canyons, fins (left) become
exposed to further erosion along vertical cracks.
In winter, freezing water expands within cracks
to peel off layers and carve vertical columns
(right).
Hoodoos
Cast Their Spell
Hoodoo - a pillar of rock, usually of
fantastic shape, left by erosion.
Hoodoo - to cast a spell. At Bryce Canyon
National Park erosion forms a remarkable array
of fantastic shapes we know as hoodoos. Surrounded
by the beauty of southern Utah, these hoodoos
cast their spell on all who visit. Geologists
say that ten million years ago forces within
the Earth created and then moved the massive
blocks we know as the Aquarius and Paunsaugunt
plateaus. Rock layers on the Aquarius now tower
2,000 feet above the same layers on the Paunsaugunt.
Ancient rivers carved the tops and exposed edges
of these blocks, removing some layers and sculpting
intricate formations in others. The Paria Valley
was created and later widened between the plateaus.
The
Paria River and its many tributaries continue
to carve the plateau edges. Rushing waters carrying
dirt and gravel gully the edges and steep slopes
of the Paunsaugunt Plateau on which Bryce Canyon
National Park lies. With time, tall thin ridges
called fins emerge. Fins further erode into
pinnacles and spires called hoodoos. These in
turn weaken and fall, adding their bright colors
to the hills below.
Early
Native Americans left little to tell us of their
use of the plateaus. We know that people have
been in the Colorado Plateau region for about
12,000 years, but only random fragments of worked
stone tell of their presence near Bryce Canyon.
Artifacts tell a more detailed story of use
at lower elevations beyond the park's boundary.
Both Anasazi and Fremont influences are found
near the park. The people of each culture left
bits of a puzzle to be pieced together by present
and future archaeologists. Paiutes lived in
the region when Euro-Americans arrived in southern
Utah. Paiutes explained the colorful hoodoos
as "Legend People" who were turned
to stone by Coyote.
The
Paiutes were living throughout the area when
Capt. Clarence E. Dutton explored here with
John Wesley Powell in the 1870s. Many of today's
place names come from this time. Dutton's report
gave the name Pink Cliffs to the Claron Formation.
Other names — Paunsaugunt, place or home
of the beavers; Paria, muddy water or elk water;
Panguitch, water or fish; and Yovimpa, point
of pines— were derived from the Paiute
language.
The
Paiutes were displaced by emissaries of the
LDS Church who developed the many small communities
throughout Utah. Ebenezer Bryce aided in the
settlement of southwestern Utah and northern
Arizona. In 1875 he came to the Paria Valley
to live and harvest timber from the plateau.
Neighbors called the canyon behind his home
Bryce's Canyon. Today it remains the name not
only of one canyon but also of a national park.
Shortly
after 1900, visitors were coming to see the
colorful geologic sights, and the first accommodations
were built along the Paunsaugunt Plateau rim
above Bryce's Canyon. By 1920 efforts were started
to set aside these scenic wonders. In 1923 President
Warren G. Harding proclaimed part of the area
as Bryce Canyon National Monument under the
Powell (now Dixie) National Forest. In 1924
legislation was passed to establish the area
as Utah National Park, but the provisions of
this legislation were not met until 1928. Legislation
was passed that year to change the name of the
new park to Bryce Canyon National Park.
Each
year the park is visited by more than 1.5 million
visitors from all over the world. Languages
as varied as the shapes and colors of the hoodoos
express pleasure in the sights. Open all year,
the park offers recreational opportunities in
each season. Hiking, sightseeing, and photography
are the most popular summer activities. Spring
and fall months offer greater solitude. In the
winter months, quiet combines with the area's
best air quality for unparalleled views and
serenity beyond compare. In all seasons fantastic
shapes cast their spell to remind us of what
we protect here in Bryce Canyon National Park.
Need
More Information? Find out more about the Southern
Utah Area
and get detailed information regarding Lodging
around Bryce Canyon National Park.
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