Middle Life During The Mesozoic Era
Geological of the western interior during the Mesozoic Era
Abstract
The Mesozoic Era “the middle life” is the second major Era that lies between the Paleozoic Era and the Cenozoic Era. Geologist believe that this Era took place from 248 to 65 million years ago. The earth during this time was different from what we know today. The shape of the earth and life during this time period has changed dramatically. Starting with an overview of the Mesozoic Era and its subdivisions periods I will focus on major events during those time periods that took place in the western side of the North America, which made this time period so significant in the earth history. Each period of the Mesozoic Era was marked for certain events that makes it especial from other periods. During the Triassic period extensive Red Beds deposits along western interior of North America that made the beauty of the landscape in that region. Major tectonic activities occurred starting from the Triassic period and expanding throughout …show more content…
the Jurassic and cretaceous, and eventually created huge mountain ranges such as the Rocky Mountains. Life flourished mostly during the Jurassic and cretaceous periods, and new living organisms appeared and some went extinct such as dinosaurs. The Mesozoic Era lies between two major mass extinctions one at the end of the Permian age, and the other one occurred at the end of Cretaceous period.
Introduction
The Mesozoic Era holds special interest because of many major events that occurred. Some of these events include the major tectonic activities due to the breakup of Pangaea, the super continent which affected the world. The western interior of the North America was a major part affected by this breakup, the Pacific Ocean plate (Farallon plate) was subducted underneath the North American plate which produced many of the western formations such Sevier orogeny, and Laramide orogeny which was the final phase for a huge range of mountains called the Rocky Mountains. The Mesozoic Era was so significant in the earth’s history not only because of tectonic activities but also because of many other important events that changed the earth. It is so famous for its important history of life. The revolution of dinosaurs started in this time period and also went to extinct at the end of this Era. Also the appearance of reptiles which made this Era known as the “age of reptiles”, also the appearance of birds and mammals started in this time period. At the end of this time period there was a mass extinction that caused many of the living organisms to be extinct.
The Mesozoic Era is the time period from 66 to 250 million years ago. It is a significant time period in the earth history that is divided into three main periods Triassic, Jurassic and Cretaceous. Each period is divided into subdivisions early, mid, and late. The first period was the Triassic period that occurred right after the Paleozoic Era. Geologists believe that this period occurred about 248 to 208 million years ago. The Triassic period began after a major mass extinction that extinct most of the living organisms in the earth. Throughout the Triassic period life on earth was rare due to the climate that occurred after the major mass extinction. Massive of Red Beds were deposited in the western interior (Idaho, Montana, and Wyoming) during this time period that indicated the climate condition. Moreover, the end of Triassic period was marked by worldwide mass extinction that counts as a minor extinction compared to the Permian extinction. The second period was the Jurassic about 208 to 146 million years from now. Life during this period became more dominant and many living organisms such as dinosaurs, reptiles, and birds started to flourish. The third Mesozoic period was the cretaceous (146 to 65 million years ago). During this time period, Dinosaurs became the dominant on earth, and other animals became so flourished. Cretaceous period has witnessed the most transgression in earth’s history. The end of this time period was also marked by a major mass extinction that led to the extinct of dinosaurs and other living organisms.
Triassic red beds
The Triassic Red Beds makes up the beauty of the landscape throughout the western United States. These red beds deposits are such deposits that considered to be good indicator of climate condition. The abundance of the Red Beds deposits associated with evaporate deposits indicate hot and dry environment, meaning high evaporation rates in that area. Red Beds also associated with coal deposits in some areas as well as fossils that indicate moderate humidity. These evidences indicate that Red Bed deposits develop in both arid and humid conditions. However, the red color indicates oxidation environment. The appearance of iron even with small percentage would affect the color where iron is considered as the most misleading color element and becomes stable with the appearance of oxygen. Mostly red color would indicate non-marine environment. The Triassic Red Beds indicate that these areas went through these types of climate conditions.
Tectonic activities
By the late Paleozoic and early Mesozoic about 250 to 200 million years ago all major continents were united into a super continent called Pangaea. By the late Triassic time this super continent began to break up and continents started to spread away from each other to be in the position that they in today. The uplift of Pangaea ignited the tectonic plates all around the earth. In the western interior of North America the pacific plate called the Farallon plate was subducting under the North American plate which made this area an active margin. This subduction with a shallow angle created what’s called the “Cordillera” which contains huge mountain ranges such as Sevier orogeny, Laramide orogeny which is connected to the latest face of the rocky mountain building.
Sevier Orogeny
The first phase of the cordilleran mountain building occurred during late Jurassic and early cretaceous usually called the “Nevadan orogeny”. This phase “is inferred from the extensive clastic wedges in the rocky mountain foreland and from late Jurassic and early cretaceous radiometric dates within the batholith”. The shallow angle style subduction continued through the entire cretaceous moving toward eastern North America. At the late cretaceous the Sevier orogeny rose. The sliding oceanic plate underneath northern American plate caused combination of compressive forces and produced heat that caused folding and thrusting of the thick crust and eventually formed a range of mountains that located in western Utah and eastern Nevada. The major effect of the Sevier orogeny was “high compressional forces” that led to massive back arc thrusting. Sequence of Paleozoic shallow marine rocks such as limestone were sheared off the Precambrian basement rock pushed away tens of kilometers toward the east. Mountains belts were built from eroded thrust- fault sheets of Paleozoic sedimentary strata with remarkable folding. As a result, a “thin-skinned” thrusting was created in the foreland in western Nevada, Idaho, and Montana. Since the pressure was transferred eastward along the weak sedimentary layers the “thin-skinned” thrusting of Paleozoic materials over Mesozoic was generally getting younger toward the east.
Laramide Orogeny
The last phase of the cordilleran mountain building was Laramide orogeny that began at the end of the cretaceous period. For the same cause as the Sevier orogeny of the shallow angle subduction of the pacific plate underneath the north American plate the laramide orogeny was produced to the eastern of the Sevier orogeny. Unlike the Sevier orogeny style of thin-skinned thrust the Laramide orogeny had a different style. The Precambrian metamorphic and plutonic basement rocks were uplifted and overlying the Mesozoic strata called “thick-skinned tectonic.” The subduction zone was almost horizontal due to the shallow angle subduction. Looking at the bottom of these folds we see asymmetrical basin coming from the west toward the east. Most of the sedimentation are right next to the thrust belt (maximum subsidence). Moreover, these uplifts located much further towered the east than the Sevier belt stretching through central Colorado and Wyoming.
The foreland basin during the Cretaceous During the late Jurassic and early cretaceous very high sedimentation rate due to thrusting caused an Asymmetric subsidence of the western foreland. The thrusting and folding deformed Paleozoic units from the bottom creating course conglomerates of the “Indianola Group” and transform it into the basin of western Utah as shown in the figure above. As shown in the figure above the conglomerate of the “Indianola Group” did not continue and stayed next to the thrust belt. This proximal deposits of the conglomerate created unconformities due to the rapid erosion. Due to thrusting the Paleozoic unit was uplifted above the Jurassic and Triassic units. The maximum subsidence would be located right next to the thrust belt. The courser sediments are deposited next to the thrust belt, then get finer toward the east. Erosion would first drop the course sediments such as the conglomerate right next to the thrust, then sandstone then sale and siltstone.
Formation of Rocky Mountains
The current rocky mountains were formed during the Laramide orogeny at the end of the cretaceous period about 60 to 80 million ago. Mountains usually form close to plate boundaries, but the southern Rockies set a long way from the plate margin, the range of rocky mountains in Colorado is about a 1000 miles from where the pacific and northern American plates actually meet. Till the 70s no one knew the secret behind of Rocky Mountains formation. Geologist came up with an explanation of this event. They believed that the subduction of the Pacific Ocean plate is responsible. Ocean crust of the pacific was subducted and pushed deep into the mantle beneath the North American plate. Pacific plate subducted in a shallower angle, instead of going steeply it went beneath the northern American plate horizontally as shown in the fallowing image.
As the pacific plate slide beneath the North American plate it would compresses it and creates friction breaking up the basement granite of the North American plate and pushing it upward. This broken granite became the rocky mountain of the south that lies in the western interior of Northern America.
Geography of Rocky Mountains
Rocky Mountain is a huge range of mountains in western North America that extends about two thousand miles, stretches from Canada through central New Mexico. It stretches all the way from the “Liard River” Columbia south to the “Rio Grande” river in New Mexico passing through Idaho, Montana, Wyoming, and Colorado. Including other mountain ranges that continue beyond those two rivers such as: the “Selwyn Range” in Yukon, the “Brooks Range” in Alaska, and the “Sierra Madre” in Mexico. However, these Mountain Ranges are not considered to be part of the United States Rockies, though they are part of the American mountain ranges. The united states Rockies includes the mountain range that lies along Idaho, Montana, Wyoming, and Colorado. The Rocky Mountains were formed during the Laramide orogeny from late Mesozoic to early Cenozoic time. Right after the Laramide orogeny the Rockies were about 6000m (20,000 ft) above sea level. After erosion took place and eroded the high rocks exposing the basement rocks beneath, the current landscapes of the Rockies were formed. Later on during the Cenozoic Era, the ice ages left marks on the Rockies, forming extensive glacial land-forms. Due to glaciation erosion complex sets of rocks such as granite and gneiss were exposed to the surface. The appearance of basement tocks made the Rockies an important natural resource for mining important minerals such as: gold, silver, lead, and zinc.
Life in the Mesozoic
During the early Triassic, life in the earth was rare due to the Permian mass extinction. By the late Triassic life on both land and ocean started flourish. Many new living organisms appeared and started to be dominant on earth. The dinosaurs which is a diverse group of animals lived during the Mesozoic Era. The first dinosaur appeared in the Triassic period then became dominant from early Jurassic till the end cretaceous. Mammals also first appeared in the late Triassic but they remained small throughout the Mesozoic. Pterosaurs fossils formed another significant branch of life, appearing in the late Triassic along with the dinosaur. These fossils continued to grow in size and became dominant throughout Jurassic and cretaceous and formed into a variety of species. Like dinosaurs and other animals pterosaurs became extinct at the end of the cretaceous period due to the major mass extinction. Along with the pterosaurs, birds also started during this time and grow their way through history. The ocean life during this time period had flourished and many marine living organisms evolved including “Mosasaurs”, and “Ichthyosaur”, a marine reptile appeared during the Triassic period. Other main marine creatures such as “ammonite fossils” which evolved in the Triassic. During the cretaceous a shallow marine micro fossil called “Coccoliths” became dominant. In addition to the coccoliths another a new group of foraminifera called “globigerinids” lived in the oceans during cretaceous period. Along with all of these marine creatures fish became dominant through Jurassic and cretaceous. Life of plants evolved greatly throughout the Mesozoic. Plants such as “Glossopteris”, cycads, horsetails, and early gymnosperms all developed the Mesozoic Era started in the late Triassic. Coral reefs flourished during this Era due to the warm climate accord during the cretaceous period. There are also other groups such as clams and snails, snakes and lizards evolved during the Mesozoic.
Climate
During the Triassic period after the mass extinction the climate in the western interior along Idaho, Montana, and Wyoming was mostly hot and dry. Fossils and Rocks deposited along that region such as the Triassic Red Beds and evaporates indicate the climate during that time period. This hot and dry climate continued through early Jurassic and then changed into warm and moist climate. During the cretaceous the climate was warm. Geologists believe that the warm climate was due to intense volcanoes on the earth that produced lots amounts of carbon dioxide. The sea level rose to a very high latitude. This was the most transgression during the earth history that covered most of the earth’s surface. Large areas of the continents were covered by shallow warm seas. Limestone (a sedimentary rock that forms under shallow marine environment) was an evidence an indicator of the environment during the cretaceous period. Massive deposits of limestone rocks were found almost everywhere including the western interior of the North America. Chalk deposits was also found in many places of the western interior.
The end of Cretaceous period was marked by a major mass extinction that caused more than two thirds of the living organisms in the earth to extinct. Scientists believe that this extinction was caused by different factors. The major factor of this extinction was the asteroid impact. Scientists believe that during this time (the end of cretaceous period about 65 million years ago) an asteroid
almost the size of the earth hit the planet earth that caused many of the living organisms to go extinct. As mentioned earlier the breakup of the super continent Pangaea was mostly during the Cretaceous period. This breakup caused extensive volcanic activity all around the earth. Volcanoes would produce CO2 and many other toxic gases and spew them into the atmosphere. The dusts and gases produced by volcanoes would block the sunshine to get to the earth surface which would cause global cooling. Many living organisms such as dinosaurs couldn’t adapt to the climate change and went extinct. In conclusion, the Mesozoic Era holds special interests because of many changes happened during this time. Many major events occurred during this Era that made it one of the most eventful periods in the earth’s history. This Era has witnessed a changed from being one super continent Pangaea than splitting apart into many continents. Tectonic activities due to the breakup of Pangaea was a major event during this period. The western interior of Northern America was part of these events, and played a role in the evolution of life during the Mesozoic Era. The subduction of the Pacific underneath the Northern American plate with a shallow angle formed major formations such as Sevier orogeny and Laramide orogeny which was the final phase of the Rocky Mountains. Thriving in rich animal and plant life throughout the Era to the end of the cretaceous where nearly all the life forms became extinct, and many of these organisms became index fossils of this time such as dinosaurs and ammonites.
References
Dott, Robert H., and Donald R.
Prothero. Evolution of the Earth. New York: McGraw-Hill, 1994. Print.
Poul, Link, and DeGrey Laura. "Mesozoic Thrust Belt." Digital Geology of Idaho. N.p., 15 May 2004. Web. 29 Apr. 2013.
Beck, Kvale, R.A. "Thrust Controlled Sedimentation Patterns of the Earliest Cretaceous Nonmarine Sequence of the Montana-Idaho-Wyoming Sevier Foreland Basin."EasyBib. N.p., 01 Jan. 1985. Web. 25 Apr. 2013.
"Geology of the Rocky Mountains." Wikipedia. Wikimedia Foundation, 16 Mar. 2013. Web. 29 Apr. 2013.
J.E., Morris. "The Mesozoic Era." Home Page. N.p., 15 July 2010. Web. 29 Apr. 2013.
Mule, Tools. "Natural History of the Rocky Mountains." 8750-Rocky Mountains: History, Information and Stories. N.p., 19 Oct. 2013. Web. 25 Apr. 2013.
Carroll, Wegemann H. "A Guide to the Geology of Rocky Mountain National Park." A Guide to the Geology of Rocky Mountain National Park. N.p., 11 Dec. 2006. Web. 29 Apr.
2013.
Abstract
The Mesozoic Era “the middle life” is the second major Era that lies between the Paleozoic Era and the Cenozoic Era. Geologist believe that this Era took place from 248 to 65 million years ago. The earth during this time was different from what we know today. The shape of the earth and life during this time period has changed dramatically. Starting with an overview of the Mesozoic Era and its subdivisions periods I will focus on major events during those time periods that took place in the western side of the North America, which made this time period so significant in the earth history. Each period of the Mesozoic Era was marked for certain events that makes it especial from other periods. During the Triassic period extensive Red Beds deposits along western interior of North America that made the beauty of the landscape in that region. Major tectonic activities occurred starting from the Triassic period and expanding throughout …show more content…
the Jurassic and cretaceous, and eventually created huge mountain ranges such as the Rocky Mountains. Life flourished mostly during the Jurassic and cretaceous periods, and new living organisms appeared and some went extinct such as dinosaurs. The Mesozoic Era lies between two major mass extinctions one at the end of the Permian age, and the other one occurred at the end of Cretaceous period.
Introduction
The Mesozoic Era holds special interest because of many major events that occurred. Some of these events include the major tectonic activities due to the breakup of Pangaea, the super continent which affected the world. The western interior of the North America was a major part affected by this breakup, the Pacific Ocean plate (Farallon plate) was subducted underneath the North American plate which produced many of the western formations such Sevier orogeny, and Laramide orogeny which was the final phase for a huge range of mountains called the Rocky Mountains. The Mesozoic Era was so significant in the earth’s history not only because of tectonic activities but also because of many other important events that changed the earth. It is so famous for its important history of life. The revolution of dinosaurs started in this time period and also went to extinct at the end of this Era. Also the appearance of reptiles which made this Era known as the “age of reptiles”, also the appearance of birds and mammals started in this time period. At the end of this time period there was a mass extinction that caused many of the living organisms to be extinct.
The Mesozoic Era is the time period from 66 to 250 million years ago. It is a significant time period in the earth history that is divided into three main periods Triassic, Jurassic and Cretaceous. Each period is divided into subdivisions early, mid, and late. The first period was the Triassic period that occurred right after the Paleozoic Era. Geologists believe that this period occurred about 248 to 208 million years ago. The Triassic period began after a major mass extinction that extinct most of the living organisms in the earth. Throughout the Triassic period life on earth was rare due to the climate that occurred after the major mass extinction. Massive of Red Beds were deposited in the western interior (Idaho, Montana, and Wyoming) during this time period that indicated the climate condition. Moreover, the end of Triassic period was marked by worldwide mass extinction that counts as a minor extinction compared to the Permian extinction. The second period was the Jurassic about 208 to 146 million years from now. Life during this period became more dominant and many living organisms such as dinosaurs, reptiles, and birds started to flourish. The third Mesozoic period was the cretaceous (146 to 65 million years ago). During this time period, Dinosaurs became the dominant on earth, and other animals became so flourished. Cretaceous period has witnessed the most transgression in earth’s history. The end of this time period was also marked by a major mass extinction that led to the extinct of dinosaurs and other living organisms.
Triassic red beds
The Triassic Red Beds makes up the beauty of the landscape throughout the western United States. These red beds deposits are such deposits that considered to be good indicator of climate condition. The abundance of the Red Beds deposits associated with evaporate deposits indicate hot and dry environment, meaning high evaporation rates in that area. Red Beds also associated with coal deposits in some areas as well as fossils that indicate moderate humidity. These evidences indicate that Red Bed deposits develop in both arid and humid conditions. However, the red color indicates oxidation environment. The appearance of iron even with small percentage would affect the color where iron is considered as the most misleading color element and becomes stable with the appearance of oxygen. Mostly red color would indicate non-marine environment. The Triassic Red Beds indicate that these areas went through these types of climate conditions.
Tectonic activities
By the late Paleozoic and early Mesozoic about 250 to 200 million years ago all major continents were united into a super continent called Pangaea. By the late Triassic time this super continent began to break up and continents started to spread away from each other to be in the position that they in today. The uplift of Pangaea ignited the tectonic plates all around the earth. In the western interior of North America the pacific plate called the Farallon plate was subducting under the North American plate which made this area an active margin. This subduction with a shallow angle created what’s called the “Cordillera” which contains huge mountain ranges such as Sevier orogeny, Laramide orogeny which is connected to the latest face of the rocky mountain building.
Sevier Orogeny
The first phase of the cordilleran mountain building occurred during late Jurassic and early cretaceous usually called the “Nevadan orogeny”. This phase “is inferred from the extensive clastic wedges in the rocky mountain foreland and from late Jurassic and early cretaceous radiometric dates within the batholith”. The shallow angle style subduction continued through the entire cretaceous moving toward eastern North America. At the late cretaceous the Sevier orogeny rose. The sliding oceanic plate underneath northern American plate caused combination of compressive forces and produced heat that caused folding and thrusting of the thick crust and eventually formed a range of mountains that located in western Utah and eastern Nevada. The major effect of the Sevier orogeny was “high compressional forces” that led to massive back arc thrusting. Sequence of Paleozoic shallow marine rocks such as limestone were sheared off the Precambrian basement rock pushed away tens of kilometers toward the east. Mountains belts were built from eroded thrust- fault sheets of Paleozoic sedimentary strata with remarkable folding. As a result, a “thin-skinned” thrusting was created in the foreland in western Nevada, Idaho, and Montana. Since the pressure was transferred eastward along the weak sedimentary layers the “thin-skinned” thrusting of Paleozoic materials over Mesozoic was generally getting younger toward the east.
Laramide Orogeny
The last phase of the cordilleran mountain building was Laramide orogeny that began at the end of the cretaceous period. For the same cause as the Sevier orogeny of the shallow angle subduction of the pacific plate underneath the north American plate the laramide orogeny was produced to the eastern of the Sevier orogeny. Unlike the Sevier orogeny style of thin-skinned thrust the Laramide orogeny had a different style. The Precambrian metamorphic and plutonic basement rocks were uplifted and overlying the Mesozoic strata called “thick-skinned tectonic.” The subduction zone was almost horizontal due to the shallow angle subduction. Looking at the bottom of these folds we see asymmetrical basin coming from the west toward the east. Most of the sedimentation are right next to the thrust belt (maximum subsidence). Moreover, these uplifts located much further towered the east than the Sevier belt stretching through central Colorado and Wyoming.
The foreland basin during the Cretaceous During the late Jurassic and early cretaceous very high sedimentation rate due to thrusting caused an Asymmetric subsidence of the western foreland. The thrusting and folding deformed Paleozoic units from the bottom creating course conglomerates of the “Indianola Group” and transform it into the basin of western Utah as shown in the figure above. As shown in the figure above the conglomerate of the “Indianola Group” did not continue and stayed next to the thrust belt. This proximal deposits of the conglomerate created unconformities due to the rapid erosion. Due to thrusting the Paleozoic unit was uplifted above the Jurassic and Triassic units. The maximum subsidence would be located right next to the thrust belt. The courser sediments are deposited next to the thrust belt, then get finer toward the east. Erosion would first drop the course sediments such as the conglomerate right next to the thrust, then sandstone then sale and siltstone.
Formation of Rocky Mountains
The current rocky mountains were formed during the Laramide orogeny at the end of the cretaceous period about 60 to 80 million ago. Mountains usually form close to plate boundaries, but the southern Rockies set a long way from the plate margin, the range of rocky mountains in Colorado is about a 1000 miles from where the pacific and northern American plates actually meet. Till the 70s no one knew the secret behind of Rocky Mountains formation. Geologist came up with an explanation of this event. They believed that the subduction of the Pacific Ocean plate is responsible. Ocean crust of the pacific was subducted and pushed deep into the mantle beneath the North American plate. Pacific plate subducted in a shallower angle, instead of going steeply it went beneath the northern American plate horizontally as shown in the fallowing image.
As the pacific plate slide beneath the North American plate it would compresses it and creates friction breaking up the basement granite of the North American plate and pushing it upward. This broken granite became the rocky mountain of the south that lies in the western interior of Northern America.
Geography of Rocky Mountains
Rocky Mountain is a huge range of mountains in western North America that extends about two thousand miles, stretches from Canada through central New Mexico. It stretches all the way from the “Liard River” Columbia south to the “Rio Grande” river in New Mexico passing through Idaho, Montana, Wyoming, and Colorado. Including other mountain ranges that continue beyond those two rivers such as: the “Selwyn Range” in Yukon, the “Brooks Range” in Alaska, and the “Sierra Madre” in Mexico. However, these Mountain Ranges are not considered to be part of the United States Rockies, though they are part of the American mountain ranges. The united states Rockies includes the mountain range that lies along Idaho, Montana, Wyoming, and Colorado. The Rocky Mountains were formed during the Laramide orogeny from late Mesozoic to early Cenozoic time. Right after the Laramide orogeny the Rockies were about 6000m (20,000 ft) above sea level. After erosion took place and eroded the high rocks exposing the basement rocks beneath, the current landscapes of the Rockies were formed. Later on during the Cenozoic Era, the ice ages left marks on the Rockies, forming extensive glacial land-forms. Due to glaciation erosion complex sets of rocks such as granite and gneiss were exposed to the surface. The appearance of basement tocks made the Rockies an important natural resource for mining important minerals such as: gold, silver, lead, and zinc.
Life in the Mesozoic
During the early Triassic, life in the earth was rare due to the Permian mass extinction. By the late Triassic life on both land and ocean started flourish. Many new living organisms appeared and started to be dominant on earth. The dinosaurs which is a diverse group of animals lived during the Mesozoic Era. The first dinosaur appeared in the Triassic period then became dominant from early Jurassic till the end cretaceous. Mammals also first appeared in the late Triassic but they remained small throughout the Mesozoic. Pterosaurs fossils formed another significant branch of life, appearing in the late Triassic along with the dinosaur. These fossils continued to grow in size and became dominant throughout Jurassic and cretaceous and formed into a variety of species. Like dinosaurs and other animals pterosaurs became extinct at the end of the cretaceous period due to the major mass extinction. Along with the pterosaurs, birds also started during this time and grow their way through history. The ocean life during this time period had flourished and many marine living organisms evolved including “Mosasaurs”, and “Ichthyosaur”, a marine reptile appeared during the Triassic period. Other main marine creatures such as “ammonite fossils” which evolved in the Triassic. During the cretaceous a shallow marine micro fossil called “Coccoliths” became dominant. In addition to the coccoliths another a new group of foraminifera called “globigerinids” lived in the oceans during cretaceous period. Along with all of these marine creatures fish became dominant through Jurassic and cretaceous. Life of plants evolved greatly throughout the Mesozoic. Plants such as “Glossopteris”, cycads, horsetails, and early gymnosperms all developed the Mesozoic Era started in the late Triassic. Coral reefs flourished during this Era due to the warm climate accord during the cretaceous period. There are also other groups such as clams and snails, snakes and lizards evolved during the Mesozoic.
Climate
During the Triassic period after the mass extinction the climate in the western interior along Idaho, Montana, and Wyoming was mostly hot and dry. Fossils and Rocks deposited along that region such as the Triassic Red Beds and evaporates indicate the climate during that time period. This hot and dry climate continued through early Jurassic and then changed into warm and moist climate. During the cretaceous the climate was warm. Geologists believe that the warm climate was due to intense volcanoes on the earth that produced lots amounts of carbon dioxide. The sea level rose to a very high latitude. This was the most transgression during the earth history that covered most of the earth’s surface. Large areas of the continents were covered by shallow warm seas. Limestone (a sedimentary rock that forms under shallow marine environment) was an evidence an indicator of the environment during the cretaceous period. Massive deposits of limestone rocks were found almost everywhere including the western interior of the North America. Chalk deposits was also found in many places of the western interior.
The end of Cretaceous period was marked by a major mass extinction that caused more than two thirds of the living organisms in the earth to extinct. Scientists believe that this extinction was caused by different factors. The major factor of this extinction was the asteroid impact. Scientists believe that during this time (the end of cretaceous period about 65 million years ago) an asteroid
almost the size of the earth hit the planet earth that caused many of the living organisms to go extinct. As mentioned earlier the breakup of the super continent Pangaea was mostly during the Cretaceous period. This breakup caused extensive volcanic activity all around the earth. Volcanoes would produce CO2 and many other toxic gases and spew them into the atmosphere. The dusts and gases produced by volcanoes would block the sunshine to get to the earth surface which would cause global cooling. Many living organisms such as dinosaurs couldn’t adapt to the climate change and went extinct. In conclusion, the Mesozoic Era holds special interests because of many changes happened during this time. Many major events occurred during this Era that made it one of the most eventful periods in the earth’s history. This Era has witnessed a changed from being one super continent Pangaea than splitting apart into many continents. Tectonic activities due to the breakup of Pangaea was a major event during this period. The western interior of Northern America was part of these events, and played a role in the evolution of life during the Mesozoic Era. The subduction of the Pacific underneath the Northern American plate with a shallow angle formed major formations such as Sevier orogeny and Laramide orogeny which was the final phase of the Rocky Mountains. Thriving in rich animal and plant life throughout the Era to the end of the cretaceous where nearly all the life forms became extinct, and many of these organisms became index fossils of this time such as dinosaurs and ammonites.
References
Dott, Robert H., and Donald R.
Prothero. Evolution of the Earth. New York: McGraw-Hill, 1994. Print.
Poul, Link, and DeGrey Laura. "Mesozoic Thrust Belt." Digital Geology of Idaho. N.p., 15 May 2004. Web. 29 Apr. 2013.
Beck, Kvale, R.A. "Thrust Controlled Sedimentation Patterns of the Earliest Cretaceous Nonmarine Sequence of the Montana-Idaho-Wyoming Sevier Foreland Basin."EasyBib. N.p., 01 Jan. 1985. Web. 25 Apr. 2013.
"Geology of the Rocky Mountains." Wikipedia. Wikimedia Foundation, 16 Mar. 2013. Web. 29 Apr. 2013.
J.E., Morris. "The Mesozoic Era." Home Page. N.p., 15 July 2010. Web. 29 Apr. 2013.
Mule, Tools. "Natural History of the Rocky Mountains." 8750-Rocky Mountains: History, Information and Stories. N.p., 19 Oct. 2013. Web. 25 Apr. 2013.
Carroll, Wegemann H. "A Guide to the Geology of Rocky Mountain National Park." A Guide to the Geology of Rocky Mountain National Park. N.p., 11 Dec. 2006. Web. 29 Apr.
2013.