Arches National Park

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Arches National Park
By Ryne Olson
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• Arches National Park
• Made from the water, ice, extreme weather
  temperatures,and underground salt movement
• 100 million years of erosion to create landscape

• 2,000 cataloged arches from 3 ft openings to
  Landscape Arch (306 ft from base to base)
• New arches are continually being created
• Old arches are being worn down and eroded away

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Geologic Map of Utah
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The geologic strata exposed in Arches and
Canyonlands range from the Paradox Formation
(Pennsylvanian Period) to the Marcos Shale
Formation (Cretaceous Period)

• intermixed layers of marine, freshwater and
  eolian deposition
• several thousands feet thick
• nearly horizontal layers but slight dip to the
  north
• quarter of area is exposed bedrock

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Lots of formations, but three of the formations
are more prevalent than the others
Three Main Landscape-Forming Formations

• Jurassic Navajo Sandstone
• Carmel Formation
• Entrada Formation

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Navajo Sandstone
Arches National Park

• arid conditions during the early Jurassic Period
  deposited a vast sand desert, not unlike todays
  Sahara

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Carmel Formation- Dewey Bridge Member
Transgression of the Carmel Sea from the north
left muddy sandstones and siltstones along
marginal tidal flats
Entrada Formation- Moab Tongue
During the Mid-Jurassic Period, the retreating
Carmel Sea laid down coastal eolian deposits
The jointing of these different formations are
important in the erosion and weathering of the
arches
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Example
The Entrada Formation forms the base and the
Moab member forms the top of the arch. The Moab
sandstone is whiter. The 60-120 foot contact zone
between the Entrada and Moab is fine to medium
grain quartz sandstone with a calcareous cement
deposited in a coastal setting as shown by cross
strata.
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GEOLOGIC HISTORY

• the jointing of the rock formations are key to
  the creation of the arches

------HOW DID THE JOINTING FORM?------

• Late Paleozoic collisions between South America,
  Europe, and Proto-North America caused stress
  that reactivated old faults on the Colorado
  Plateau
• The sea filled and evaporated from a large basin
  as many as to 29 times creating evaporite
  deposits
• Click HERE to watch animated version
• -late-Paleozoic basin called Paradox Basin and
  evaporites called Paradox Formation (10s-10,000
  feet deep)
• The evaporite deposits were covered by 1,000s of
  ft of sediment from surrounding uplifts

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HISTORY CONTINUED..
4. Late Pennsylvania to Jurassic- diapirism
(process of lower density salt layer flowing up
through higher density sedimentary
rocks) -formed many northwest trending salt
antilclines Click HERE to watch
diapirism
5. Jurassic and
Cretaceous formations draped over the diapirs 6.
Late Cretaceous to Early Tertiary Laramide
Compression- the diapirs were warped into gentle
folds
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7. Last 15 million years- uplift and lowering
base level caused groundwater to dissolve the
salt from the cores of the anticlines, collapsing
them
RESULT FRACTURES WITHIN FORMATIONS ALLOWING THE
CREATION OF ARCHES!!!
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Stages of Arch Formation

• arches are made possible by the massive
  sandstone over wavy surface of muddy sandstone
  and siltstone as well as systematic jointing
• arches are sculpted by the freeze-thaw activity,
  chemical weathering, and erosion

Click HERE to see this process animated!
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Step 1 water penetrates joints and weathers the
sandstone into
FINS
Step 2 local weathering at base level forms
depression in rock
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• Step 3 exfoliation (process of fracturing and
  pealing of rock in concentric layers driven by
  the release of pressure) occurs
• Joints are produced called exfoliation joints
  (visible on curved spans of arches)

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Step 4
ARCHES!
Step 5 deterioration of arches continual
weathering leads to its eventual collapse
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OTHER FANTASTIC FEATURES!
Pothole arches formed from waterpockets drilling
through a fin wall
The top of Balanced rock is from the Entrada
Formation and the support is from the Carmel
Formation
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These Petrified Sand Dunes are exposed Jurassic
dunes. The weaker Carmel Formation has been
eroded from the top of the Navajo Sandstone.
The Three Gossips are carved from a fin of
Entrada Sandstone
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MINING AROUND ARCHES

• No active mines are on National Park Service
  lands in the Colorado Plateau, but there are 44
  abandoned radium or uranium sites.
• Some of the geologic formations were created from
  marine environments so there is high
  concentration of dissolved solids. Fossil fuels
  are often located close to salt domes and old
  marine environments due to the traps created by
  salt domes (fossil fuel is caught between
  permeable and impermeable layers as the salt
  rises into a dome) and large amount of organic
  matter from the past marine life.

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Photographs and Information borrowed from
http//parkphoto.gruzi.info/images/NationalParksUS
A/ArchesNationalParkUtah.jpg http//www.rwongphoto
.com/RW1848_web.jpg http//image53.webshots.com/45
3/6/69/27/2602669270067443763xRvYTd_fs.jpg http//
www.nature.nps.gov/geology/parks/arch http//3dpar
ks.wr.usgs.gov/coloradoplateau/arches_strat.htm ht
tp//www.uwgb.edu/dutchs/StateGeolMaps/UtahGMap.HT
M http//www.hickerphoto.com/data/media/163/petrif
ied_dunes_t3179.jpg http//w3.salemstate.edu/lhan
son/gls110/GLS110_Arches.html http//www.globusjou
rneys.com/Common/Images/Destinations/arches-np2.jp
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