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Running head: UTAH’S GEOLOGICAL PAST 1

Utah’s Geological Past and its Effect on the Geography, Climate and Animals

Christina Tinsley

Dixie State College

UTAH’S GEOLOGICAL PAST 2

Abstract

The state of Utah has experienced immense geological changes over the millennia. Plate

tectonics have shifted the location of Utah from about 30 degrees south of the equator to its

current position of about 40 degrees north of the equator. Utah has been the floor of shallow

seas as well as the site of vast Sahara like deserts. Plate tectonics created the mountain ranges

that make up the Basin and Range Province of Western Utah, the uplift of the Colorado Plateau

and the volcanism that existed across the entire state. Changes in latitude and elevation have

directly affected the climate and thus the animals that have been able to thrive. Detailed are the

different geological processes that have taken place and their effect on the geography, climate

and animals.


Utah’s Geological Past and the Effect on the

Geography, Climate, Plants and Animals

Changes in latitude and longitude have greatly changed Utah’s climate from that of sub-tropical

shorelines, vast Sahara like deserts, swamp lands like those seen in the Okefanokee swamp in

Georgia, to the semi-arid desert of today (Hintze & Kowallis, 2009). Changes in global position

and elevation determine the types of animals that have been able to thrive in Utah. Hintze and

Kowallis (2009) describe in their book, Geologic History of Utah, “Through-out the vast

stretches of geologic time, Utah’s geology has been controlled by its place on the ever-moving

North American continent as it traveled about, colliding with other continental masses and

occasionally growing by accretion” (p. 3). Geologic forces have shaped and evolved the

geography, climate and animals that have existed in the past and have become indigenous to

Utah today. Earth’s history is broken up into eons, eras, periods and epochs. New eras, periods

and epochs mark the end or the beginning of a significant event or species (USGS, 2006). This

paper will cover the geography of Utah as it progressed through the eons from an early molten

state with no life to modern day Utah.

Hadean, Archean and Proterozoic Eons

Up until recent technological advancements, everything that happened prior to the

Mesozoic Era was referred to as the Precambrian Eon. Earth’s history is now divided into three

distinct and separate eons: the Hadean, Archean and Proterozoic. These eons make up 88% of

earths total history and are the oldest rocks in existence (USGS, 2010).

Hadean Eon- 4600 to 4000 Million Years Ago

The most important event that took place during the Hadean was the formation of the

moon. The event that formed the moon is often referred to as the Giant Impact Theory. In the


USGS fact sheet, Precambrian Time - The Story of the Early Earth, author Lindsey (2007)

wrote:

Scientists know from studying the age of craters on the Moon that the early Earth was

bombarded by millions of large objects. One of these objects, a giant perhaps the size of

Mars, struck the Earth near the end of its formation and burst into a huge cloud of hot

particles that coalesced into the Moon (para. 5)

It is unlikely that the earth had cooled enough during the Hadeon for plate tectonics to have

occurred; the temperature of the earth’s crust is thought to have been too hot and pliable to have

formed a solid crust (Zahnle, et al.).

Archean Eon- 4000 to 2500 Million Years Ago

A third of the earth’s crust is thought to have formed

during the Archean. The North American continent was

formed by volcanic island arcs colliding and fusing

together to form plutons. These early plutons form the

basement rocks of the continental crust. Much of the data

that has been collected about how these ancient rocks

were formed comes from research on rocks located in the

Beaver Dam Mountains, Wasatch Mountains, Raft River

mountains of Utah and the Colorado River; which has cut

a path directly through the Colorado Plateau, showing a

near complete history of deposition (Hintze & Kowallis,

2009).

FIGURE 1. Grand Canyon, Deer Creek Falls, Mile marker 136. Top layer of the canyon is 550 mya. Kaibab Limestone. Bottom most layer is 1.7 mya. Gneiss and Schist.


The earliest evidence of primitive life has been found in rocks formed during the

Archean. Oxygen also became available in the atmosphere, albeit at only one to two percent of

modern day levels (Sharma & Shukla, 2009). These early life forms would grow to become more

and more complex in the coming eons.

Proterozoic Eon- 2500 to 542 Million Years Ago

During the Proterozoic, accretion continues to play a huge role in Utah’s formation.

Blakey and Ranney (2009) explain in their book Ancient Landscapes of the Colorado Plateau,

“when volcanic islands collided with North America, the former basin deposits were folded

accordion style and placed at great depths within the crust…During this process, the rocks

became sutured or attached to the continent and became part of its basement” (p. 2).

The first supercontinent, named Rodinia, was constructed, fractured and broken apart

during the Proterozoic. Evidence of the breakup of Rodinia can be seen in northern Utah in the

Uinta Rift-Basin, sediment deposits nearly three miles deep can be found in this ancient rift.

Glaciation was prominent during the Proterozoic and is often referred to as Snow Ball

Earth. It is unclear what the caused this ice age, but it included at least three distinct periods

Fig. 2. Paleogeography map of North America after the breakup of Rodinia.Late Precambrian 550 million years ago Ron Blakey, NAU Geology


where earth was blanketed in snow and ice. Large glacial deposits can be found in the Wasatch

Range, Sheeprock and the Deep Creek Mountains of Utah (Hintze & Kowallis, 2009).

Life forms on earth became more diverse and complex, cyanobacteria bacteria emerged

and with it more available oxygen in the atmosphere, which may have been the cause of the

Cambrian Explosion of new organisms in the Phanerozoic Eon (Sharma & Shukla, 2009).

Phanerozoic Eon

The Phanerozoic eon is divided into three eras: the Paleozoic, meaning ancient life, the

Mesozoic, meaning middle life, and Cenozoic meaning recent life. The Phanerozoic was a time

of great change in Utah. During the Paleozoic, Utah spent much of the time beneath the surface

of warm, shallow seas. The Mesozoic and Cenozoic show evidence of tremendous continental

upheaval. Plate tectonic collisions would build on to the North American plate, creating the land

that would become Utah. Dramatic shifts in climate impacted the types of animals that could

survive in the area (Hintze & Kowallis, 2009). As the Phanerozoic continued, life forms became

more advanced and moved out of the oceans and onto dry land, to become the largest and most

advanced the world has ever seen.

Paleozoic Era- 542 to 251 Million Years Ago

The Paleozoic is divided into seven periods: the Cambrian, Ordovician, Silurian,

Devonian, Mississippian, Pennsylvanian and the Permian Periods. Rifting caused by Laurentia

breaking away from Australia, Antarctica and China caused the state to be stretched, resulting in

the future basin and range to subsidize or lower in elevation (Hintze & Kowallis, 2009). A

continental shelf divided the state in the approximate location of the Wasatch Fault Line and the

border of the Colorado Plateau. Blakey and Ranney (2008) explain that sediment deposits

“document the prior existence of a broad continental shelf (defined as a low-lying margin of


continental crust that may be often flooded with seawater), that was crossed many times by

repeated transgressions and regressions of shallow seas” (p. 13). Some of these deposits in the

western basin range in depth from 1,500 to 10,000 feet in depth, while the area to the east of the

shelf on the Colorado Plateau has only a few hundred feet of sedimentation (Blakey & Ranney,

2008).

The warm, shallow marine environment in the first half of the Paleozoic, created the perfect

setting for the formation of limestone and dolomite, which make most of Utah’s marine rock

formations. Stokes (1986) explains in the Geology of Utah, “the present day red color of the

Permian unit’s results from an “aging” process of iron-bearing minerals in what may originally

have been drab-looking sediments (p. 96). The red rock strata found in national parks such as;

Monument Valley, Canyonlands National Park, and Dinosaur National Monument are examples

iron rich formations (Stokes, 1986).


During the Pennsylvanian, the continents were once again moving towards one another to

form the supercontinent of Pangaea. By the end of the Proterozoic, Pangaea was fully assembled.

If someone were traveling during this time period they would have been able to cross from Utah

all the way through Africa and into Antarctica by land (Blakey & Ranney, 2008).

All life during the Early Proterozoic existed in water; there were not yet any plants or

animals that had adapted to living on dry land (Blakey & Ranney, 2008). Life during the

Proterozoic eon became more numerous and complex, this is often called the Cambrian

FIGURE 3. Paleogeography maps of Western North America during the Proterozoic Eon. A. Late Cambrian- 500million years ago, B. Carboniferous Mississippian- 340 million years ago, C. Permian- 280 million years ago.

A B C


Explosion. As Blakey and Ranney explain (2008), “the Cambrian fossil fauna is replete with

multicellular organisms that had intricate shells and advanced complex organs such as eyes and

body appendages” (p.19).

Utah’s warm, shallow seas were favorable to a broad range of organisms that were spread

uniformly across the state, suggesting generally calm conditions. In the Devonian age,

Sarcoperygii fish, meaning flesh-finned, developed fins that enabled them to move on dry land.

These fins would eventually evolve to become the limbs of the first Terapods, or four footed

invertebrate land based life (Foster, 2007). Fossilized evidence of an unidentified amphibian or

reptile has been found in Labyrinth Canyon outside of Green River, Utah. At the end of the

Proterozoic, the oceans receded to record low levels across the globe (Stokes, 1986). Blake and

Ranney (2008) explain that dry conditions” created havoc for these shallow marine organisms as

most of their territory was lost. The ensuing extinction of marine life, perhaps attributed to the

loss of shallow marine environments worldwide, was the greatest in the entire rock record; more

than 90 percent of all species went extinct” (p.52).

FIGURE 4. Representation of the Paleozoic ocean floor. Species include Brachiopods, nautiloids and crinoids (Blakey & Ranney, 2008).


At the close of the Paleozoic, Pangaea is fully formed and mass extinction has wiped out

almost all of the organisms. The Mesozoic would move earth into a more tectonically violent

period and plants and animals would become the largest the planet would ever see.

Mesozoic Era- 251 to 65 Million Years Ago

The Mesozoic Eon is made up of the Triassic, Jurassic and the Cretaceous Periods.

During the Mesozoic tectonic forces molded and formed the early continents into the more

recognizable configurations that they are today. The super continent of Pangaea was lifted up in

elevation. Blakey and Ranney (2008) explain the reason for continental uplift occurs when

“continents, especially large ones, become places where heat accumulates. This causes

continental rocks to become less dense, making them more buoyant and causing continents to

become elevated” (p. 57). This raise in elevation produced a climate that was increasingly arid

and more conducive to erosion. During the Jurassic and Cretaceous, the North American

continent drifted away from Pangaea. Deserts would be replaced by tropical swamps and coastal

beaches, as an inland sea made its way into Eastern Utah (Blakey & Ranney, 2008).

There were three major periods of orogenic activity that have altered Utah, starting in the

Mesozoic and continuing into the Cenozoic; the Nevada Orogeny, the Sevier Orogeny and the

Laramide Orogeny. These orogenies created the western most states of Washington, Oregon,

California, and Nevada. They also produced Utah’s mountain ranges and created widespread

volcanic activity across Utah (Hintze & Kowallis, 2009).

The description above tells what happened in a very organized, scientific way. However,

Orogenesis is not an organized or peaceful process. Huge earthquakes would have ripped

through the land twisting, bending and folding the crust to form massive mountain ranges and

lowered basins. For example, oceanic crust and seashells have been found at the summits of


Utah’s mountain ranges. Much of Utah is made up of a series of upwarps and downwarps,

similar to ripples on water. Island arc eruptions are the most violent of volcanic events; explosive

pyroclastic flows, huge boulders being shot into the sky and rivers of magma would have been

common occurrences.

Utah’s environment fluctuated between semi-arid interdune conditions; which contained

lakes, rivers and swamps, to arid dune conditions, containing vast deserts that were only broken

up by the occasional oasis. Shibata, Matsukawa and Lockley (2006) found in their study of the

Late Triassic and Early Jurassic ecosystems that “the low diversity of dune ecosystems

represents a severe and stressed ecosystem with limited food. On the other hand, based on track

estimates, the interdune ecosystem was almost as diverse as the Late Triassic Chinle formation”

which was characterized by a diverse population of dinosaur species (p. 33). Carbon dioxide

levels were higher than that of today, causing higher sea levels and a warmer environment, both

in the oceans and on land. There was little change in temperature year round between north and

south latitudes. The polar ice caps and snowcapped winter mountains did not exist during this

time because of the warmer temperatures (Foster, 2007).

FIGURE 4. Maps showing the geography and tectonic processes during the Mesozoic Period


A-B. Late Triassic-215 Million Years Ago

Elevation was still predominately flat, except for the Ancestral Rocky Mountains in east central area of the state. As the oceans receded, fluvial rivers stretched across Utah. Some of these rivers were relative in size to that of the Nile and the Mississippi (Blakey & Ranney, 2008).

C-D. Early Jurassic-180 Million Years Ago

Dry, trade winds continually blew moisture away from Utah, creating a massive Sahara like desert. Three major dune systems occupied Utah during the Jurassic: the Wingate, Navajo, and Entrada. Orogenies formed the mountain ranges that started to push eastward into Utah (Blakey & Ranney, 2008).

E-F. Middle Cretaceous-100 Million Years Ago

Orogenies created fault-block mountains in the west, causing the eastern half of the state to subsidize and form a basin. The drop in elevation in the interior of the continent allowed the sea to enter from the north (Blakey & Ranney, 2008).

A B

C D

E F


All of the species that are currently living on earth today can trace their ancestors to

animals that evolved during the Mesozoic Era. Some examples of animals that lived during the

Mesozoic include: crocodilians, turtles, theropod dinosaurs, sauropod dinosaurs, pterosaurs,

plesiosaurs, mammals. During the more arid conditions of the Mesozoic research shows that

dinosaur populations decreased, those that did stay in the area lived near annually fed rivers or

oasis’s that spotted the ancient sand dunes, similar to the present day Serengeti Plains in Africa.

The climate during the Cretaceous was more humid and brought about a more diverse population

of animals (Shibata, Matsukawa, & Lockley, 2006). Mammals actually outnumbered the

dinosaurs by sheer numbers during the Mesozoic. Foster (2007) said in his book Jurassic West,

“the diversity of mammals far exceeds all other groups. In fact, there are nearly as many types of

mammals in the formation as there are of all four groups of dinosaurs combined…mammals had

obviously created enough ecological niches for themselves to equal the dinosaurs in species

richness, if not in size or flashiness” (p. 252). The largest mammals were probably only about the

size of modern squirrels, until after the extinction of the dinosaurs (Foster, 2007).

The Mesozoic ends with the impact of an asteroid, thought to have been nearly 10 miles

wide near the Yucatan Peninsula in Mexico (Blakey & Ranney, 2008). The impact blast

exterminated everything in its path, enormous tidal waves spread out across the globe, and

sediment from the impact blocked out the sun for months on end, killing plant life. As the food

chain broke down, all large dinosaurs disappeared, opening a window of opportunity for

mammals to come out of hiding and become the new dominate species (Lieberman & Kaesler,

2010).


Cenozoic Era- 65 Million Years Ago to Present

The Cenozoic is made up of the Tertiary and the Quaternary Periods. The relatively flat flood

plain that had existed in the Mesozoic is uplifted to form the Wasatch Mountains and the

Colorado Plateau. The climate changed considerable during the Cenozoic Era. The early

Cenozoic climate was hot and humid, followed by a period of glaciation, and finally to our

current semiarid desert conditions. The small mammals that existed in the Mesozoic, evolved

into a massive array of new species. Including, but not limited to mammoths, bison, horses, saber

tooth cats, giant sloths and a new species that would change everything across the globe,

humans!

Tectonic forces in previous Nevada and Sevier Orogenies of the Mesozoic exhibited

plates that subducted at an angle of about 45 to 60 degrees, resulting in mountain ranges and

volcanic activity that were very close to their respective continental margins. Plate subduction of

Laramide Orogeny decreased to an angle of approximately 25 degrees. Blakey and Ranney

(2008) describe this as an:

Unusual angle for a plate to descend but could explain how and why the Rocky

Mountains were uplifted almost a thousand miles inland from the plate boundary. The

position of the Rockies so far from a plate boundary makes them one of the most

enigmatic mountain ranges on Earth. This far reaching deformation event is what uplifted

the Colorado Plateau … as much as 15,000 to 17,000 feet (p. 104-105).

The Laramide Orogeny produced volcanoes and laccoliths throughout Utah. A laccolith is an

intrusion of molten magma that is squeezed horizontally between two layers of sedimentary rock.

As the magma billows up, the sedimentary rocks are pushed up to form domes and mountains.

The Henry, La Sal, Abajo and Pine Valley Mountain ranges are examples of laccoliths, though


Pine Valley Mountain was formed later and is one of the largest laccolith mountains in the world

(Blakey & Ranney, 2008).

There were three main climatic conditions during the Cenozoic: the early semi tropical, ice age

glaciation and lastly to our present semiarid desert. The Early Tertiary climate was hot and

humid. Deposits of coal, tar and oil shale have been found in rocks of this age, representing semi

tropical conditions, dense with plant life and a thriving populace of animals that evolved from

the early shrew like creatures of the Mesozoic (Blakey & Ranney, 2008).

Scientists do not know the exact cause of an ice age. Research suggests a combination of

factors such as reduced CO2 in the atmosphere, continental drift redirecting oceanic currents and

the widespread uplift of new mountain ranges, collectively cause periods of glaciation (Hay,

Soeding, DeConto, & Wold, 2002).

While the mountains and high plateaus would have been covered with snow, ice and

glaciers, Utah’s ice age valleys would have been lush with vegetation. Heaton explains in his

article, Quaternary Mammals of the Great Basin: Extinct Giants, Pleistocene Relicts, and Recent

Immigrants “the largest mammals such as mammoths, sloths, bison, and oxen never seem to

have been abundant in the Great Basin, some large mammals are found in great numbers at most

fossil sites, especially horses (several varieties), camels, llamas, and bighorn sheep. When the

Paleogeography Maps of Western North America during the Cenozoic Era.A-50 Million Years Ago. B- 15 Million Years Ago. C- Present Day

CA B


valleys, which make up 95% of the land area, had much more vegetation and water during the

last glacial, the region could probably support a much greater mammalian biomass” (Section 4).

Humans appeared in Utah approximately 10 to 12 thousand years ago. They probably did not

settle in the area, but travelled through in search of large prey animals, such as mammoth. By

about 8,000 years ago large mega faunal mammals were forced to extinction, most likely by

abrupt climate change and possible over hunting by early humans (Elias., 1997).

Up until about two thousand years ago, humans eked out an existence as hunter-gathers. It

was not until about 750 AD that evidence of permanent housing structures has been found. The

Fremont people of Central Utah and the Anasazi people of the Four Corners region either built

sophisticated villages, consisting of underground pit houses or elaborate cliff dwellings. Both

cultures were known to use advanced irrigation techniques for farming corn and squash. The

Fremont and the Anasazi Indians disappeared between 1250 and 1500 A.D., reasons for their

disappearance are unknown, but extensive drought is the most common theory (Madsen, 1989).

Indian tribes such as the Paiute and Navajo Indians survived the drought and still live in Utah

today.

Conclusion

Earth has undergone great changes in its geography, climate and animal species since its

beginning four and a half billion years ago. Utah had a tumultuous beginning; involving plate

tectonic collisions, volcanic eruptions and periods of extensive submersion by oceans. These

forces have sculpted and formed the crust into the geography that is seen in today.

Climate in Utah is tremendously affected by plate tectonics. As the North America plate

drifted into its current position, weather patterns also changed. Utah has experienced conditions

ranging from hot dry deserts to cold glacier valleys and everything in-between.


The animals that have lived in Utah have had to adapt to significant changes in

temperature and climate in order to survive. Mass extinctions have wiped out all but a few of the

organisms that have existed in Utah; these hardy creatures have evolved into the animals that

exist in Utah today.

As tectonic forces continue to affect Utah into coming millennia, what changes are in

store for Utah’s continued history?


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Utah’s Geological Past and its Effect on the Geography ...christinatinsley.weebly.com/.../utahs_geologic_past_final_… · Web viewCalifornia, and Nevada. They also produced Utah’s