Objectives

1
Objectives
Mesozoic Paleogeography

• Explain the breakup of Pangaea.

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

Vocabulary

• Cordillera

2
Mesozoic Paleogeography
Mesozoic Paleogeography

• The Mesozoic Era consisted of the Triassic,
  Jurassic, and Cretaceous periods.

3
The Breakup of Pangaea
Mesozoic Paleogeography

• 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.

4
Active Tectonism in Western North America
Mesozoic Paleogeography

• 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.
5
Active Tectonism in Western North America
Mesozoic Paleogeography

• Three major episodes of orogeniesmountain-buildin
  goccurred 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.

6
Seaways and Sand Dunes
Mesozoic Paleogeography

• Throughout the Early and Middle Triassic, the
  supercontinent Pangaea and a single global ocean
  defined Earths 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.

7
Seaways and Sand Dunes
Mesozoic Paleogeography

• 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.

8
Section Assessment
Mesozoic Paleogeography

• 1. What caused rifts to form in Pangaea?

9
Section Assessment
Mesozoic Paleogeography

• 2. What is the Cordillera?

10
Section Assessment
Mesozoic Paleogeography

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

______ 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.
11
End of Section 1
12
Objectives
Mesozoic Life

• 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.

Vocabulary

• modern fauna
• angiosperm
• dinosaur
• Ornithischian

• Saurischian
• ectotherm
• endotherm
• iridium

13
Mesozoic Life
Mesozoic Life

• The Mesozoic is commonly referred to as the Age
  of Reptiles.

• 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.

14
Life in the Oceans
Mesozoic Life

• The base of the food chain that supported all the
  large animals consisted of tiny, ocean-dwelling
  organisms called phytoplankton.

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

15
Life in the Oceans
Mesozoic Life

• Reef Builders Arise Again

• 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.

16
Life in the Oceans
Mesozoic Life

• Important Index Fossils

• 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.

17
Life on the Land
Mesozoic Life

• During the Mesozoic the large, temperate coal
  swamps dried up, and the climate gradually
  warmed, dramatically changing life on land.

• Paleobotanists call the Mesozoic the Age of
  Cycads.
• Cycads are seed plants that do not have true
  flowers.

18
Life on the Land
Mesozoic Life

• Angiosperms Evolve

• 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.

19
Life on the Land
Mesozoic Life

• Early Mammals

• 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.

20
Life on the Land
Mesozoic Life

• Flying Reptiles

• 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.

21
Dinosaurs Rule the Land
Mesozoic Life

• Dinosaurs were a group of reptiles that
  developed an upright posture about 228 million
  years ago.

• 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.

22
Dinosaurs Rule the Land
Mesozoic Life
23
Dinosaurs Rule the Land
Mesozoic Life

• Dinosaur Hips

• 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.

24
Dinosaurs Rule the Land
Mesozoic Life

• Dinosaur Hips

• 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.

25
Dinosaurs Rule the Land
Mesozoic Life

• Dinosaur Hips

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

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

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

• The sauropods were all quadrupedal, herbivores,
  and some grew to enormous sizes.
• All theropods were bipedal and carnivores.

26
Dinosaurs Rule the Land
Mesozoic Life

• Dinosaurs to Birds?

• 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.

27
Dinosaurs Rule the Land
Mesozoic Life

• Ectotherm or Endotherm?

• 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.

28
Mass Extinctions
Mesozoic Life

• A major mass extinction event ended the
  Mesozoic.

• 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.

29
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.

30
Mass Extinctions
Mesozoic Life

• Iridium is a metal that is rare in rocks at
  Earths surface but is relatively common in
  meteorites and asteroids.

• 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.

31
Mass Extinctions
Mesozoic Life

• Most scientists agree that both a large meteorite
  impact and massive volcanism occurred at the end
  of the Cretaceous.

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

32
Section Assessment
Mesozoic Life

• 1. Match the following terms with their
  definitions.
• ___ angiosperm
• ___ ectotherm
• ___ endotherm
• ___ iridium

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
33
Section Assessment
Mesozoic Life

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

34
Section Assessment
Mesozoic Life

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

______ 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.
35
End of Section 2
36
Objectives
Cenozoic Paleogeography

• Describe the type of tectonism that characterized
  the Cenozoic orogeny.

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

Vocabulary

• Basin and Range Province
• Tethys Sea

37
Cenozoic Paleogeography
Cenozoic Paleogeography

• The Cenozoic Era encompasses approximately the
  last 66 million years of Earths history to the
  present.

38
Cenozoic Paleogeography
Cenozoic Paleogeography

• 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.

39
Cenozoic Paleogeography
Cenozoic Paleogeography

• 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.

40
Cenozoic Paleogeography
Cenozoic Paleogeography

• 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.

41
Tectonic Events
Cenozoic Paleogeography

• 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.

42
Tectonic Events
Cenozoic Paleogeography

• 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.

43
Tectonic Events
Cenozoic Paleogeography

• 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.

44
Tectonic Events
Cenozoic Paleogeography

• Hot Spots in the West

• Hot spots are mantle plumes that rise to Earths
  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.

45
Tectonic Events
Cenozoic Paleogeography

• 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.

46
Tectonic Events
Cenozoic Paleogeography

• 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.

47
Section Assessment
Cenozoic Paleogeography

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

48
Section Assessment
Cenozoic Paleogeography

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

49
Section Assessment
Cenozoic Paleogeography

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

______ 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.
50
End of Section 3
51
Objectives
Cenozoic Life

• 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

• primate
• hominoid

• hominid
• Homo sapiens

52
Cenozoic Life
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.

• Whales and dolphins evolved during the Cenozoic
  as completely aquatic mammals.
• Walruses and sea lions returned to the oceans but
  remain partly terrestrial today.

53
Life on Land
Cenozoic Life

• Most of the currently living groups of mammals
  had evolved by the Eocene.

• 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.

54
Life on Land
Cenozoic Life

• Pleistocene Mammals

• 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.

55
Primates and Humans
Cenozoic Life

• The scarcity of fossils is a difficult problem to
  overcome in studies of the origin of humans and
  our relationship to other primates.

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

56
Primates and Humans
Cenozoic Life

• Primates

• 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.

57
Primates and Humans
Cenozoic Life

• Primates

• 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.

58
Primates and Humans
Cenozoic Life

• The Rise of Homo Sapiens

• 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.

59
Primates and Humans
Cenozoic Life

• The Rise of Homo Sapiens

• 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.

60
Primates and Humans
Cenozoic Life

• The Rise of Homo Sapiens

• 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.

61
Section Assessment
Cenozoic Life

• 1. Match the following terms with their
  definitions.
• ___ primate
• ___ hominoids
• ___ hominids
• ___ Homo sapiens

A. a group of bipedal primates with upright
posture that use sophisticated tools B. the
process of collecting data about Earth from far
above Earths surface C. the species to which
humans belong D. a primate group that includes
the great apes
62
Section Assessment
Cenozoic Life

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

63
Section Assessment
Cenozoic Life

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

______ 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.
64
End of Section 4
65
Section 24.1 Main Ideas
Section 24.1 Study Guide

• 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.

66
Section 24.2 Main Ideas
Section 24.2 Study Guide

• 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.

67
Section 24.3 Main Ideas
Section 24.3 Study Guide

• 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.

68
Section 24.4 Main Ideas
Section 24.4 Study Guide

• 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.

69
Short Answer
Chapter Assessment

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

70
Short Answer
Chapter Assessment

• 7. How were Neanderthals different from modern
  humans?

71
True or False
Chapter Assessment

• 8. Identify whether the following statements are
  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
  Earths surface.
• ______ All hominoids are bipedal with an
  upright posture.

72
Chapter 24 Images
Image Bank
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Chapter 24 Images
Image Bank
74
Chapter 24 Images
Image Bank