Objectives Explain the breakup of Pangaea. Mesozoic Paleogeography Distinguish between the different tectonic characteristics of the Mesozoic Orogenies

Objectives• Explain the breakup of Pangaea.

Mesozoic Paleogeography

• Distinguish between the different tectonic characteristics of the Mesozoic Orogenies.

– Cordillera

Vocabulary

Mesozoic Paleogeography• The Mesozoic Era

consisted of the Triassic, Jurassic, and Cretaceous periods.


The Breakup of Pangaea• The breakup of Pangaea was an important event

that occurred during the Mesozoic Era.


– Extreme heat from within Earth beneath Pangaea caused the continent to expand, cracking and breaking apart the lithosphere by the Late Triassic.

– As the landmasses spread apart, the ocean flooded the rift valleys resulting in the formation of new oceans, including the Atlantic.

– Some of the spreading areas joined together to form a continuous rift system called the Mid-Atlantic Ridge.

Active Tectonism in Western North America

• Active subduction along the western coast of North America continued through the Middle Triassic.


• The Cordillera, which means “mountain range” in Spanish, refers to the mountain ranges that formed by subduction in western North America during the Mesozoic.

Active Tectonism in Western North America

• Three major episodes of orogenies—mountain-building—occurred along the western margin of North America during the Mesozoic.


– The oldest orogeny was characterized by a large number of igneous intrusions and the resulting batholiths.

– Beginning in the Late Jurassic and continuing through the Late Cretaceous, the next orogeny was characterized by low-angle thrust faulting and folding.

– Beginning in the Late Cretaceous and continuing into the Cenozoic, the third Mesozoic orogenic event was characterized by vertical uplifts.

Seaways and Sand Dunes• Throughout the Early and Middle Triassic, the

supercontinent Pangaea and a single global ocean defined Earth’s paleogeography.


• The Triassic ended with a rapid drop in sea level that caused western North America to become much more arid and sandy.

• Strong winds shaped the sand into dunes that are preserved in large-scale, cross-bedded sandstone deposits.

Seaways and Sand Dunes• Sea level rose again in the Jurassic, and a

shallow sea covered central North America.


– Deposits of the Late Jurassic river systems are preserved today as multicolored sandstones, siltstones, and mudstones.

– The ocean continued to rise onto North America during the Cretaceous Period, flooding the entire southeastern margin of North America.

– As a result, a sea covered the interior of North America from Texas to Alaska.

Section Assessment

1. What caused rifts to form in Pangaea?


Extreme heat from within Earth beneath Pangaea caused the continent to expand.

Section Assessment

2. What is the Cordillera?


The cordillera refers to the mountain ranges that formed in western North America during the Middle Triassic.

______ The Mid-Atlantic Ridge is still active today.

______ The Cretaceous Period came before the Triassic Period.

______ The Triassic ended with a dramatic rise in sea level.

______ A sea covered the interior of North America during the Cretaceous Period.

Section Assessment

3. Identify whether the following statements are true or false.


true

false

false

true

Objectives• Discuss why many paleontologists theorize that birds are

descended from dinosaurs.• Describe how paleontologists distinguish among reptile,

dinosaur, and mammal fossils.

• Explain the evidence indicating that a meteorite impact caused the Cretaceous-Paleogene mass extinction event.

– modern fauna

– angiosperm

– dinosaur

– Ornithischian

– Saurischian

– ectotherm

– endotherm

– iridium

Vocabulary

Mesozoic Life

Mesozoic Life• The Mesozoic is commonly referred to as the

Age of Reptiles.

Mesozoic Life

• The first mammals, birds, and flowering plants appeared during the Mesozoic.

• Modern fauna refers collectively to the new marine organisms which arose during the Mesozoic.

Life in the Oceans• The base of the food chain that supported all the

large animals consisted of tiny, ocean-dwelling organisms called phytoplankton.

Mesozoic Life

• Phytoplankton float near the surface of oceans and lakes and make their own food through the process of photosynthesis.

Life in the Oceans

Reef Builders Arise Again

Mesozoic Life

– Modern corals had evolved by the end of the Triassic.

– A new group of clams called rudists developed the ability to build reefs during the Cretaceous.

– Rudists built very porous reefs that today contain some of the largest Cretaceous oil deposits in areas such as west Texas.

Life in the Oceans

Important Index Fossils

Mesozoic Life

– Ammonites are related to modern nautiluses, octopuses, and squids.

– Ammonites were abundant and diverse throughout the Late Paleozoic and Mesozoic, and their abundance indicates that they were very successful predators.

– Swimming reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs ruled the Mesozoic oceans during the Cretaceous.

Life on the Land• During the Mesozoic the large, temperate coal

swamps dried up, and the climate gradually warmed, dramatically changing life on land.

Mesozoic Life

• Paleobotanists call the Mesozoic the Age of Cycads.

• Cycads are seed plants that do not have true flowers.

Life on the Land

Angiosperms Evolve

Mesozoic Life

– Angiosperms, which are seed-bearing plants that have flowers, evolved during the Cretaceous.

– Before the Cretaceous, there were no flowers.

– By the end of the Cretaceous, the land was covered with flowering trees, shrubs, and vines.

Life on the Land

Early Mammals

Mesozoic Life

– Small, primitive mammals evolved during the Late Triassic.

– The structure of the lower jaw, middle ear, and teeth can be used to identify fossils of mammals.

– A reptile has one ear bone and multiple lower jawbones, whereas a mammal has one lower jawbone and three ear bones.

– Mammals have differentiated teeth while reptiles generally have only one kind of tooth.

Life on the Land

Flying Reptiles

Mesozoic Life

– Pterosaurs were flying reptiles that dominated the air during the Mesozoic.

– Pterosaurs had light, hollow bones, like modern birds.

– The modification that allowed them to fly was the growth of a membrane from a greatly lengthened fourth finger.

– Two groups of reptiles that arose during the Mesozoic and still exist are the crocodiles and turtles.

Dinosaurs Rule the Land• Dinosaurs were a group of reptiles that

developed an upright posture about 228 million years ago.

Mesozoic Life

• Dinosaurs came in all sizes, from the very small to the extraordinarily large, and all were terrestrial.

• Although the largest dinosaurs were most likely slow and plodding animals, many of them were quick and agile.

Dinosaurs Rule the Land

Mesozoic Life


Dinosaur Hips

Mesozoic Life

– Two major groups of dinosaurs are recognized based on their hip structure: Ornithischia and Saurischia.

– In ornithischian, or “bird hipped” dinosaurs, the ischium and pubis were parallel to one another, similar to modern birds.


Dinosaur Hips

Mesozoic Life

– In Saurischian, or “lizard hipped” dinosaurs, the ischium and pubis were at an angle to one another, similar to the orientation observed in modern lizards.

– Scientists hypothesize that birds are actually descended from the Saurischia.


Dinosaur Hips

Mesozoic Life

– There were five different groups of ornithischian dinosaurs: stegosaurs, ankylosaurs, pachycephalosaurs, ceratopsians, and ornithopods.

– There were two different groups of saurischian dinosaurs: sauropods and theropods.

• All ornithischian dinosaurs were plant eaters, also called herbivores.

• The sauropods were all quadrupedal, herbivores, and some grew to enormous sizes.

• All theropods were bipedal and carnivores.


Dinosaurs to Birds?

Mesozoic Life

– The idea that birds are related to dinosaurs stems from the amazing similarities between theropods and the oldest known bird, Archaeopteryx.

– Fossils of feather impressions and a wishbone provide clear evidence that Archaeopteryx was definitely a bird, even though it did have teeth and a theropod-like skeleton.


Ectotherm or Endotherm?

Mesozoic Life

– All living reptiles are ectotherms, meaning that their body temperatures vary in response to external temperatures.

– All living mammals and birds are endotherms, meaning that they maintain relatively constant body temperatures, regardless of external temperatures.

– At least some groups of dinosaurs may have been endotherms. but this hypothesis is still controversial.

Mass Extinctions• A major mass extinction event ended

the Mesozoic.

Mesozoic Life

• Most major groups of organisms were devastated, and all known species of dinosaurs, pterosaurs, ammonites, mosasaurs, and plesiosaurs became extinct.

• Geologists theorize that a large meteorite slammed into the Yucatan Peninsula.

Mass Extinctions

Mesozoic Life

The circular shape and underlying layer of iridium-rich rock provides evidence of a meteorite impact. It was named the Chicxulub crater after a nearby village.

Mass Extinctions• Iridium is a metal that is rare in rocks at Earth’s

surface but is relatively common in meteorites and asteroids.

Mesozoic Life

– Iridium is found in Cretaceous-Paleogene boundary sites worldwide, providing evidence of a major impact.

– A buried crater in the Gulf of Mexico contains iridium, which has a radiometrically dated age of approximately 65 million years.

– Volcanism can also release high levels of iridium.

Mass Extinctions• Most scientists agree that both a large meteorite

impact and massive volcanism occurred at the end of the Cretaceous.

Mesozoic Life

• The extraordinary stress that the impact added to an already stressed ecosystem likely caused the climax of the Cretaceous-Paleogene mass extinction.

Section Assessment

1. Match the following terms with their definitions.

___ angiosperm

___ ectotherm

___ endotherm

___ iridium

Mesozoic Life

A. a metal that is relatively common in meteorites and asteroids

B. animals that have relatively constant body temperatures, regardless of outside temperatures

C. animals that have body temperatures that vary in response to outside temperatures

D. seed-bearing plants that have flowers

D

C

B

A

Section Assessment

Mesozoic Life

2. What were the movement and diet characteristics of theropods?

Theropods were bipedal carnivores.

Section Assessment


Mesozoic Life

______ It is hypothesized that birds descended from the Saurischia.

______ All living reptiles are endotherms.

______ Dinosaurs are the only reptiles to have developed an upright posture.

______ Crocodiles and turtles arose during the Mesozoic.

true

false

true

true

– Basin and Range Province

– Tethys Sea

Objectives• Describe the type of tectonism that characterized the

Cenozoic orogeny.

• Understand the extent of glaciation that occurred in North America.

Vocabulary

Cenozoic Paleogeography

Cenozoic Paleogeography• The Cenozoic Era

encompasses approximately the last 66 million years of Earth’s history to the present.



The Ice Ages


– The warm climate began to deteriorate during the Middle-to-Late Eocene, possibly due to a change in ocean circulation.

– When Antarctica and Australia were connected, a current of warm water from the north moderated the temperature of Antarctica.


The Ice Ages


– When Antarctica was isolated over the south pole, a cold current began to flow around Antarctica, and glaciers began to form.

– The climate began to warm again during the Early Miocene.

– The glaciers on Antarctica began to melt, and the sea rose onto the margin of North America.

– Glaciers returned to Antarctica during the Middle and Late Miocene, setting the stage for the ice ages of the Late Pliocene and the Pleistocene.


The Ice Ages


– During the Late Pliocene through the Pleistocene, the northern hemisphere experienced extensive glaciation, or an ice age.

• Glaciers from the arctic advanced and retreated in at least four stages over North America.

• The paths of the Ohio River and the Missouri River roughly mark the southernmost point to which glaciers advanced in North America.

Tectonic Events• Western North America had been tectonically

active throughout the Cenozoic.


– The orogenic events that occurred at the end of the Mesozoic formed the Rocky Mountains.

– The basins in Wyoming that filled with huge, swampy river deposits provided an ideal environment for the accumulation of vast amounts of coal.

– The coal there is especially valuable because it has a very low sulfur content, and thus, it burns cleanly.

Tectonic Events

Subduction in the West


– The Cascade Mountains are the result of the subduction of an oceanic plate beneath the western coast of North America at the end of the Eocene.

– During the Miocene, the North American Plate was forced over the East Pacific Rise resulting in the creation of the San Andreas Fault.

– The Basin and Range Province is a series of mountains that trend north-to-slightly-northeast, are separated by long, linear valleys, and extend from Nevada and western Utah to north-central Mexico.

Tectonic Events

Subduction in the West


– Extensional tectonism pulled the crust apart, causing large blocks of the crust to drop down along normal faults to form the basins, leaving other blocks at higher elevations to form the mountain ranges.

– This extension is still occurring today.

Tectonic Events

Hot Spots in the West


– Hot spots are mantle plumes that rise to Earth’s surface.

– Some of the hot spots that occur in the western United States are related to the continuing subduction along the western coast of North America.

– The land that makes up Yellowstone National Park is situated on a hot spot that has been active since the Early Cenozoic.

Tectonic Events

Continental Collisions


– While the final breakup of Pangaea occurred during the Cenozoic, plate tectonics also brought continents together during this time.

• The Himalayan Mountains formed when India traveled north and collided with the southern margin of Asia.

• Africa collided with the connected landmass of Europe and Asia, or Eurasia, forming the Alps.

• The Tethys Sea was a narrow sea that separated the two continents before Africa collided with Eurasia.

Tectonic Events


The Tethys Sea had a strong, westward-flowing current that transported organisms across long distances. Cretaceous-aged fossils from the Tethys Sea are found as far west as the Hawaiian Islands.

Section Assessment

1. What was the extent of the North American glaciers of the Late Pliocene through the Pleistocene?


The Ohio and Missouri Rivers roughly form the southern boundary of the glaciation.

Section Assessment

2. Why is the coal found in Wyoming especially valuable?


The coal in Wyoming is especially valuable because it has a very low sulfur content, and thus, it burns cleanly.

Section Assessment



______ Yellowstone National Park sits on top of a geologically active hot spot.

______ The mountains in the Basin and Range Province were caused by uplift.

______ The Himalayan Mountains were formed through a continental-oceanic collision.

______ The Mediterranean Sea will likely become narrower over the next 50 million years.

true

false

false

true

– primate

– hominoid

Objectives• Describe the landscape of the Oligocene in Central

North America.

• Discuss the changes in animals in North America during the Cenozoic.

• Identify the characteristics of primates.

• Explain what separates hominids from the other hominoids.

Vocabulary

Cenozoic Life

– hominid

– Homo sapiens

Cenozoic Life• The modern marine fauna, including clams,

snails, sea urchins, crustaceans, bony fishes, and sharks, survived the Cretaceous mass extinction to populate the modern oceans.

Cenozoic Life

• Whales and dolphins evolved during the Cenozoic as completely aquatic mammals.

• Walruses and sea lions returned to the oceans but remain partly terrestrial today.

Life on Land• Most of the currently living groups of mammals

had evolved by the Eocene.

Cenozoic Life

• Forests dominated North America during the Paleocene and Eocene, giving way to open land as the climate cooled during the Late Eocene.

• Grasses, which were important to many large mammals, appeared during the Eocene.

• The resulting savannas supported a large diversity of mammals, most of which are members of groups living today.

Life on Land

Pleistocene Mammals

Cenozoic Life

– As the Pliocene ice age began, the great savannas were replaced by more arid land.

– The change in climate caused many of the savanna mammals to become extinct.

– A new group of animals, such as the woolly mammoth, dire wolf, and sabre-toothed cat, evolved and populated the land.

Primates and Humans• The scarcity of fossils is a difficult problem to

overcome in studies of the origin of humans and our relationship to other primates.

Cenozoic Life

• The discovery of a single new fossil can dramatically change our understanding.

Primates and Humans

Primates

Cenozoic Life

– Primates are distinguished from other mammals by a grasping hand with an opposable thumb and two eyes directed forward that result in stereoscopic vision.

– Other primate characteristics include smaller, fewer, and less-specialized teeth than other mammals and a relatively large brain.

Primates and Humans

Primates

Cenozoic Life

– Hominoids are a primate group that includes hominids and the great apes.

– Hominids, the group of hominoids that includes Homo sapiens, are differentiated from other hominoids by being bipedal with an upright posture, having larger brains, smaller canine teeth, and smaller faces than other hominoids, and through the use of sophisticated tools due to greater manual dexterity.

Primates and Humans

The Rise of Homo Sapiens

Cenozoic Life

– Homo sapiens is the species to which humans belong.– In the 1850s, a fossilized Neanderthal skull was discovered in Neander Tal near Dusseldorf, Germany.

– Most fossil evidence indicates that Neanderthals were most likely a side branch of H. sapiens and not direct ancestors of modern humans.

– The Neanderthals were hunters that inhabited Europe and the Near East approximately 200 000 to 30 000 years ago.

Primates and Humans


Cenozoic Life

– Neanderthals had heavier brows, mouths that projected forward, receding chins, more massive, muscular bodies, and slightly larger brains than modern humans do.

– A characteristic of Neanderthals (top) is a gap that occurs between the rear teeth and the jaw bone. Modern humans (bottom) do not possess this gap.

Primates and Humans


Cenozoic Life

– There is evidence that Neanderthals buried their dead and placed items such as tools in their graves.

– The fossil skeleton of Australopithecus afarensis provides evidence that bipedal, upright-walking hominids existed at least 3.5 million years ago.

– Compared to the rest of the fossil record, there are relatively few hominid fossils.

Section Assessment

1. Match the following terms with their definitions.

___ primate

___ hominoids

___ hominids

___ Homo sapiens

Cenozoic Life

A. a group of bipedal primates with upright posture that use sophisticated tools

B. the process of collecting data about Earth from far above Earth’s surface

C. the species to which humans belong

D. a primate group that includes the great apes

C

D

A

B

Section Assessment

2. What type of land animals dominated the Eocene? What allowed them to evolve?

Cenozoic Life

Large mammals evolved and dominated the Eocene as grasslands, or savannas, became common.

Section Assessment

Cenozoic Life


______ Modern humans descended from Neanderthals.

______ Bipedal, upright-walking hominids existed at least 8.5 million years ago.

______ Neanderthals had slightly larger brains than modern humans.

______ Most of the modern marine fauna survived the Cretaceous mass extinction.

false

false

true

true

Chapter Resources Menu

Chapter Resources Menu

Study Guide

Section 24.1

Section 24.2

Section 24.3

Section 24.4

Chapter Assessment

Image Bank

Section 24.1 Main Ideas• Geologists hypothesize that Pangaea broke

apart as heat built up beneath it. Expansion occurred and ultimately resulted in the rifting apart of Pangaea.

• The first orogeny is characterized by igneous intrusions, whereas the second orogeny is characterized by thrust faulting and folding.

Section 24.1 Study Guide

Section 24.2 Main Ideas• The modern marine fauna include crabs, lobsters,

shrimps, sponges, sea urchins, modern corals, snails, and clams. The major vertebrate groups of the modern fauna include bony fishes, sharks, aquatic reptiles, and aquatic mammals.

• The oceans contained vast numbers of ammonites that are now index fossils. The most common land plants were cycads, and the dominant land animals were dinosaurs.

• An upright posture distinguishes dinosaurs from other reptiles.


Section 24.3 Main Ideas• The Cenozoic tectonism is characterized by

vertical normal faulting.

• During the Pleistocene, glaciers extended as far south as the courses of the Ohio and Missouri Rivers.


Section 24.4 Main Ideas• Large mammals evolved to feed on the

abundant grasslands that developed during the Cenozoic. As the ice ages approached, many of the mammals that lived on these grasslands became extinct and were replaced by large mammals that were adapted to the cold and arid land south of the glaciers.

• Primates are mammals that developed specialized traits, including a grasping hand with an opposable thumb, stereoscopic vision, smaller, fewer, and less-specialized teeth, and a relatively large brain.


1. How many episodes of orogenies did the western margin of North America experience during the Mesozoic?

a. one c. three

b. two d. four

Multiple Choice

Chapter Assessment

The three episodes of orogenies along the western margin of North America during the Mesozoic resulted in a tremendous number of igneous intrusions, low-angle thrust faulting, and vertical uplifts.

2. What organism was the base of the marine food chain during the Mesozoic?

a. phytoplankton c. coral

b. trilobites d. sponges

Phytoplankton are tiny, ocean-dwelling organisms that float near the surface of the oceans and make their own food through photosynthesis. They are still the base of the marine food chain today.

Multiple Choice

Chapter Assessment

Multiple Choice

3. All ornithischian dinosaurs were ____.

a. carnivores c. endotherms

b. herbivores d. “lizard hipped”

Chapter Assessment

There were five different groups of ornithischian dinosaurs: stegosaurs, ankylosaurs, pachycephalosaurs, ceratopsians, and ornithopods. They were “bird-hipped” even though modern birds probably descended from saurischian, or “lizard hipped” dinosaurs. It is possible that some were endotherms, but it is not widely accepted that all were.

Multiple Choice

4. Which of the following is a modern remnant of the Tethyan Sea?

a. Arctic Ocean c. North Sea

b. Baltic Sea d. Mediterranean Sea

Chapter Assessment

The Tethyan Sea separated Eurasia from Africa. As Europe and Africa continue to collide, the Mediterranean Sea will become narrower over time as the two continents move toward each other.

Multiple Choice

5. All hominids are ____.

a. bipedal c. herbivores

b. carnivores d. Neanderthals

Chapter Assessment

The most recognizable feature that differentiates hominids from other hominoids is that they are bipedal. They have an upright posture resulting from the modification of the hipbone and they walk on two legs. Homo sapiens are hominids.

Short Answer

6. What event led to the mass extinction that ended the Mesozoic?

Chapter Assessment

It is generally accepted that a large meteorite impact and massive volcanism occurred at the end of the Cretaceous. In the midst of a stressful time of climatic cooling, changing plant populations and a gradual decline in dinosaur diversity and abundance, the impact of a large meteorite likely caused the climax of the Cretaceous-Paleogene mass extinction.

Short Answer

7. How were Neanderthals different from modern humans?

Chapter Assessment

Neanderthals had heavier brows, mouths that projected forward, receding chins, more massive, muscular bodies, and slightly larger brains than modern humans do. They also had a gap between their rear teeth and their jaw bone.

True or False


______ The Basin and Range Province formed through

compressional tectonism.

______ Mammals have two sets of teeth whereas reptiles continuously replace older teeth.

______ Ginkgoes are an example of an angiosperm.

______ Ammonites are important Mesozoic index fossils.

______ Iridium is not common in rocks at Earth’s surface.

______ All hominoids are bipedal with an upright posture.

Chapter Assessment

false

true

false

true

true

false

Image Bank

Chapter 24 Images

Image Bank

Chapter 24 Images

Image Bank

Chapter 24 Images

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Objectives Explain the breakup of Pangaea. Mesozoic Paleogeography Distinguish between the different tectonic characteristics of the Mesozoic Orogenies