1. November 12, 2005 Dr. Clodfelter
Earth Science
November 12, 2005
Dr. Clodfelter

2. Geologic Time Scale

3. The Geologic Time Scale
The history of the Earth is broken up into a hierarchical set of divisions for describing geologic time

4. The Geologic Time Scale, cont.
Highlights of recent fossil finds from throughout geologic time (from most ancient to most recent) are:
Precambrian Era: the first fossil bacteria, sponges, corals, and algae appear
Cambrian Period: abundant invertebrate fossils such as mollusks, crustaceans

5. The Geologic Time Scale, cont.
Triassic Period: the first fossils of primitive dinosaurs appear
Jurassic Period: the first fossil mammals and birds; first fossil flowering plants appear
Cretaceous Period: large fossil dinosaurs appear

6. Time and Space Quaternary Tertiary Cretaceous Jurassic Triassic
Permian
Carboniferous
Devonian
Silurian
Ordovician
Cambrian
Precambrian

7. Precambrian Eon 4.5 Billion to 543 Million Years Ago
Nearly 4 thousand million years after the Earth began
The first animals left their traces
Makes up roughly 7/8 of the Earth's history

8. Archaean Era 3.8 to 2.5 Billion Years Ago
The atmosphere was very different from what we breathe today
The Earth's crust cooled enough that rocks and continental plates began to form
Life first appeared on Earth
bacteria microfossils

9. Phanerozoic Eon 543 Million to
Majority of macroscopic organisms, fungal, plant and animals lived
Appearance of animals that evolved external skeletons – like shells – and animals that formed internal skeletons – like vertebrates

10. Paleozoic Era 543 to 248 Million Years Ago
In the beginning, multicelled animals underwent a dramatic "explosion" in diversity
At the end, the largest mass extinction in history wiped out approximately 90% of all marine animal species

11. Paleozoic Era 543 to 248 Million Years Ago
- Paleozoic rocks are economically important
- much of the limestone quarried for building and industrial purposes, as well as the coal deposits of western Europe and the eastern United States, were formed during this period

12. Mesozoic Era 248 to 65 Million Years Ago
Mesozoic means "middle animals”
Lasted 70 Million Years
Time of transition
The world-continent of Pangaea existed
The time in which life as it now exists on Earth came together
Important today because of the fossils and oil left behind

13. Mesozoic Era 248 to 65 Million Years Ago
Divided into three time periods:
the Triassic ( Million Years Ago)
the Jurassic ( Million Years Ago)
the Cretaceous ( Million Years Ago)

14. Dinosaurs in the Mesozoic Era
Evolved in the Triassic Period
Became more diversified in the Jurassic Period
Became extinct in the late Cretaceous Period
Fossils of some of the last dinosaurs to walk the Earth can be found in Montana

15. The Cretaceous/Tertiary Boundary in Montana
Some of the last dinosaurs to have lived are found in the late Cretaceous deposits of Montana in the United States

16. Cenozoic Era
The most recent of the three major subdivisions of animal history
The other two are the Paleozoic and the Mesozoic
Spans only about 65 million years
Sometimes called the “Age of Mammals”
Chipmunk-like mammal

17. A Continental Jigsaw Puzzle: Putting the Pieces Together
1911
German meteorologist
Alfred Wegener
theorized that about 300 million years ago all the continents we know today were joined together in a single continent
he named it “Pangaea” (pronounced Pan JEE uh)

18. A Continental Jigsaw Puzzle: Putting the Pieces Together, cont.
Wegener suggested that Pangaea split apart and its pieces began to “drift,” or move away from each other
He put together his own evidence, as well as others’, to support his Theory of Continental Drift

19. A Continental Jigsaw Puzzle: Putting the Pieces Together, cont.
At first, Wegener’s ideas were very popular because his evidence seemed quite convincing
Yet a number of observations still remained unexplained
What forces caused the continents to move?
Due to these remaining problems, Wegener’s theory rapidly lost support and continental drift became “just another theory”

20. What are Crustal Plates?
Earth’s crust isn’t one continuous surface like the skin of an orange
It is made up of gigantic pieces, like pieces of a jigsaw puzzle
Each piece is called a crustal plate
Some plates form the floor of the oceans while other carry the continents

21. How do
the crustal plates
move?

22. Crustal Plates
Molten rock around the Earth’s core heats up the mantle above
Currents of molten rock rise up through the mantle like boiling water
As each current hits the underneath of the crustal plates, it starts to spread out
This slowly pushes or tears the crust apart

23. Crustal Plates The plates are always on the move
There are three basic types of plate boundaries
where they are sliding past each other
where plates are separating
where they are converging (approaching each other)

24. Crustal Plates
Spreading Center - the boundary between separating plates
Usually found in mid-ocean and are marked by rugged mountain chains called mid-ocean ridges
As plates move apart a gap continuously opens between them
Molten rock from the earth’s interior flows into this gap
New crust is continuously formed

25. Plates and Sea Floor Spreading

26. Crustal Plates
When plates collide, the force can fold and thrust upward to form mountains
Or the force can push the ocean floor downward to form a deep valley called a trench
Here, molten rock can break through the seabed to form chains of islands like the Hawaiian Islands

27. The Mariana Trench Example of a trench in the ocean floor
Deepest place on earth
Located in the Pacific Ocean just off the Mariana Islands near Japan
The Kaiko is an unmanned Remotely Operated Vehicle (ROV)
The Kaiko first touched down on the bottom of the Pacific Ocean's Mariana Trench in 1995

28. The San Andreas Fault
Forms part of the boundary between the North American Plate and the Pacific Plate

29. Crustal Plate Activity
Crustal plate activity can…
Cause earthquakes, volcanic activity, and tsunamis
Earthquakes are signs of the great stresses and which affect the Earth’s crust
Over a million earthquakes occur every year
Tsunamis are giant tidal waves and can travel at 500 mph!
Just before an earthquake, dogs howl, chickens flee their roosts, rats leaves their holes, fish leap out of ponds, and wells bubble

30. Dinosaur Fossils
Dinosaur Fossil bones have been found in many different parts of the world
Further supports Wegener’s single continent theory
The dinosaurs disappeared suddenly
Different theories as to why
Most widely accepted is the Big Bang Theory

31. Big Bang Theory
Scientists theorize that a meteor hit the Earth at nearly the speed of light (186,000 miles per second!)
Caused a total black out of the sun
This meteor is believed to have caused the Gulf of Mexico

32. Gulf of Mexico

33. Pangaea

34. Breakup of Pangaea

35. Earth's Fast Facts
The Earth weighs about 6000 million million million tons
Two-thirds of the earth is covered by water
It would take more than 250 days to walk around the equator
Every year, North America and Europe separate by 3/4ths of an inch
Scientists predict that life on Earth will only last 50 million more years

36. Earth = Onion
Crust – outermost layer, solid rock, but very thin like skin
Mantle – denser and heavier than the crust, inner part of the mantle is described as “plastic” because it is semi-liquid rock
Core – outer part is made of molten liquid rock that is very dense and heavy, “core” of the core becomes solid and even more dense

37. Magma Forms when rocks deep under the Earth’s crust melt
Heat from friction as the rocks rub together can also form magma
In places where the Earth’s crust is weak, magma wells up on the surface as volcanoes or lava flows
As it cools, it becomes solid forming new rock

39. Rocks Igneous Rock – formed form cooled magma
Sedimentary Rock – formed by the combining together of broken bits of other rocks or sediments
Metamorphic Rock – changed by extreme pressure or heat

40. Rocks Contain complex chemicals called minerals
Kinds of Minerals + Size of Crystals = how the rock was Formed
Small crystals = rapid cooling
Large crystals = more lengthy cooling

41. Ring of Fire

42. Mount St. Helen

43. Krakatoa, Indonesia Volcanic eruption was heard 3,000 miles away
Caused great tidal wave that killed perhaps 36,000 people
Crystals from the magma are smaller because they cooled quickly

44. Crater Lake, Oregon
The caldera has filled creating one of the deepest lakes
It may erupt again

45. Old Faithful and Pagosa Springs

46. Sedimentary Rock
Made by the action of water and wind as they laid down like layers of a cake
Pressure increases and they are warmed by the heat from deep in the Earth
Sediment becomes a solid mass of rock

47. Arbuckle Mountains

48. Sedimentary Rock
Sandstone
Limestone

49. Decaying Plant Material
Peat
Coal

50. How are Fossils Formed? Sea Creature dies and sinks to the sea bed
The soft body slowly decays creating oil with a layer of gas sitting on top
Skeleton is covered in layers of mud which gradually become solid rock
Sea bed rises above sea level
Erosion moves rock covering fossils so they are now exposed on land

51. Carbon - 14 Radio-active carbon found in all living things
Begins to break down after an animal or plant dies
By measuring the amount of Carbon – 14 in a fossil, scientists can tell how old it is
This is called Carbon Dating

52. Earth's Atmosphere Layer of air surrounding the Earth
Consists of different kinds and amounts of gases
Nitrogen, Oxygen, Carbon Dioxide
Protects the Earth’s surface
Filters out harmful radiation from the sun
Insulates Earth and stops the sun’s heat from escaping back into space

53. Earth's Atmosphere Three Main Layers Ionosphere
Extends about 50 miles above the surface
Rarified air
Temperature gradually rises as you move away from the Earth

54. Earth's Atmosphere Stratosphere
Extends about 30 miles above the Earth’s surface
Contains very little air or water vapor
Colder than Ionosphere, but warmer than the Troposphere

55. Earth's Atmosphere Troposphere Bottom layer About 10 miles thick
Contains nearly all the atmosphere’s air, water vapor, and clouds
Temperature gradually drops until is reaches the stratosphere

56. Air Temperature Warm air… Cold air…
Lighter and less dense than cold air
Rises up into the atmosphere
Produces low pressure
Cold air…
Presses down heavily on the Earth’s surface
Produces high pressure

57. Types of Clouds Cirrus Thin, curly, and wispy shapes
Formed in the upper Troposphere
Contain ice crystals

58. Types of Clouds Cumulus Heaped clusters like loose cotton balls
Have flat bases and dome shaped tops
Sometimes build up into thunder clouds

59. Types of Clouds Stratus
Formed when Cumulus clouds group together to form a continuous layer
Grayer in color than Cumulus
Bottom of the Stratus layer is in the lower Troposphere

60. A Meteorologist Measures…
Air pressure
Temperature
Humidity
Winds speeds and directions
Precipitation (rain, hail, snow, sleet, fog)
Cloud types and their heights
Visibility

61. Cyclones Name used in Asia Like a tornado and hurricane combined
Rapidly rotating tunnel of air
Moves over land
Can be 300 miles in diameter
Winds speed at more than 125 mph

62. Tornadoes Similar to cyclones, but much smaller
Sometimes only a mile or so across

63. Hurricanes
The name given to a cyclone which develops in the western Atlantic Ocean
Hurricane Francis

64. Ages of Rivers or Mountains
Infancy
Youth
Maturity
Old Age

65. Mountains in Infancy/Youth
Alps
Rocky Mountains
Left – Alps
Right – Rocky Mountains

66. Mountains in Maturity/Old Age
Arbuckle Mountains
Cumberland Mountains

67. Rivers in Infancy/Youth
Yellowstone River
Colorado River

68. Rivers in Maturity/Old Age
Rio Grande
Red River
Left – Rio Grande
Right – Red River

69. Geologic Time Scale