Intelligent Life

Front 1

1. What is the definition of intelligent life?

Back 1

Any beings who develop their technology to the point where they send either their communications or themselves to Earth

Front 2

2. Is there evidence for extraterrestrial intelligent life?

Back 2

NO

Front 3

3. What is astrobiology?
(Four parts)

Back 3

1. Our ability to detect planets orbiting other stars is rapidly improving
2. Our understanding of how planets form is rapidly advancing
3. Studies of bacteria living in extreme environments have dramatically expanded
4. We have several places in our own solar system where we might find primitive life

Front 4

4. What does the solar system consist of?

Back 4

The sun, its 8 planets, a bunch of moons, an asteroid belt, and a couple of comet belts

Front 5

5. What does the milky way galaxy consist of?

Back 5

Includes our sun, 100 billion other stars, plus any planets, comets, etc., orbiting these stars

Front 6

6. What does the universe contain?

Back 6

The observable Universe contains some 100 billion galaxies in addition to our milky way

Front 7

7. What is the key point regarding the size of the Universe?

Back 7

A LOT of stars potentially hosting planets

Front 8

8. How long would it take to cross the Milky Way Galaxy?

Back 8

One Billion years

Front 9

9. What is a light year?

At what speed does light travel?

How close/far is the nearest star to Earth?

Back 9

One light year is the distance that light travels (in a vacuum) in a year

Light travels at 300,000 km/sec (186,000 miles/sec)

Nearest star is 4 light years away

Front 10

10. What is light?

Back 10

Part of the electromagnetic spectrum

*all electromagnetic radiation travels at the same speed (this would include radio waves)

Front 11

11. What does all of this mean in terms of communication?

Back 11

A radio message sent to a start 4 light years away would take 4 to reach the star

Any radio message we would receive today would probably be thousands of years old

Front 12

12. Is the Universe expanding?

Back 12

YES!
Hubble concluded that the Universe is expanding

Front 13

13. How is expansion occurring?

Back 13

Expansion is taking place ONLY between galaxies or relatively small galaxies

Thus, most galaxies are moving away from each other

Front 14

14. What happens within a galaxy?

Back 14

WITHIN a galaxy, gravitational attraction keeps stars in orbit around the center of the galaxy

Thus, gravity keeps a galaxy from expanding

Front 15

15. How far is the Earth from the center of the Milky Way Galaxy?

Back 15

28,000 light years

Front 16

16. How did the Universe begin?

Back 16

Began with an enormous explosion (Big Bang)

Big Bang hurled matter and energy outward and created the ever expanding Universe

*Before the bang the laws of physics break down

Front 17

17. What is the age of the Universe?

Back 17

13.7 +/- 0.2 Byr

13.7 Billion Years

Front 18

18. How big is the Universe?

Back 18

We don't really know

The edge of the observable Universe is 46 billion light years away from the Earth

Front 19

19. What is nucleosynthesis?

Back 19

The production of elements

Front 20

20. What is an atom?

Back 20

The smallest particles that can participate in chemical reactions

Front 21

21. What are the parts of an atom?

Back 21

Nucleus: protons and neutrons
-define element by # of protons

Electrons that orbit the nucleus
-electron shells make chemical reactions happen

Front 22

22. What is weight % and atom %?

Back 22

Weight %: percent of total mass taken up by a given element

Atom %: percent of all atoms taken up by a given element (same and mole %)

Front 23

23. What is the average composition of the Universe?

Back 23

Nearly all H
(75 weight % and 92 atom %)

Little bit of He and very little else

Front 24

24. What is the relative abundance of elements in the Universe?

Back 24

H, He, C, N, O, and Fe have the largest abundance

Front 25

25. In order to explain the Universe what elements are necessary?

Back 25

HUGE amounts of H and some He

Need other elements, with the heavy elements (esp those heavier than iron) being less abundant than the light elements

Front 26

26. How were the first atomic particles formed?

Back 26

Big Bang first produced just quarks BUT as the Universe rapidly expanded it cooled

Rapid cooling allowed for first atomic particles to form: Neutrons

Front 27

27. How was the H formed then?

Back 27

Further cooling allowed neutrons to radioactively decay into protons and electrons

Protons are nucleus of hydrogen

Front 28

28. So then when did this H form?

Back 28

H began forming within one second of the Big Bang

All of the H in the water in your body dates back 13.7 Byr to the very earliest moments of the Universe

Front 29

29. How did the He form?

Back 29

Four H atoms happened to fuse together and He was formed within the first 5 minutes of the Universe

Front 30

30. What other elements are particularly important in order to make Earth?

Back 30

Oxygen (O)
Silicon (Si)
Magnesium (Mg)
Iron (Fe)

Front 31

31. What happened as the Universe further cooled?

Back 31

Atoms and molecules gathered into huge patchy clouds call Nebulae

Front 32

32. What happened to the nebulae?

Back 32

When the nebulae clouds were cool enough, the force of gravity cause them to collapse to form stars

Front 33

33. What is a protostar?

Back 33

A growing sphere of super-hot H gas

Front 34

34. How is the heat generated?

Back 34

If the starting cloud is large enough, the central sphere will end up getting very, very hot

Front 35

35. What is heat?

Back 35

Atomic or molecular motion

Very hot atom/molecules move very fast

Front 36

36. What happens to the central core of the protostar?

Back 36

It becomes so hot that electron orbitals are destroyed (form a plasma instead of true gas)

Now, the naked H nuclei can interact through COLLISIONS

Front 37

37. What is fusion?

Back 37

When some energetic head-on collisions force the 2 positively charges protons to overcome their mutual electrical repulsion and combine to make a new element with 2 protons

Front 38

38. What does fusion do then in term of making a star a star?

Back 38

Fusion releases the heat that makes a star a star otherwise the star would just be a big ball of hydrogen

Fusion is when two nuclei combine (fuse) together and form a new element and release a HUGE amount of energy

Front 39

39. How is the energy formed during fusion?

Back 39

When two atomic nuclei combine, a tiny amount of mass is converted to energy

E = mc^2

Front 40

40. What is the chemical reaction for hydrogen fusion?

Back 40

ⁱH+ ⁱH+ ⁱH+ ⁱH = ⁴He

Front 41

41. Where is H fusion the fastest?

Back 41

In the core where temperature and pressures are highest

Front 42

42. How does fusion expand the star?

Back 42

The energy and subatomic particles released by fusion push the overlying layers outward

This is what expands the star

Front 43

43. What happens when fusion in the core stops?

Back 43

The whole star collapses toward the core

This free-fall (gravitational acceleration) toward the center heats up the interior enough to do two things

Front 44

44. What two things happen?

Back 44

1. H in the layers around the core ignite releasing so much energy that the star expands into a red giant

2. He produced in the overlying layers sinks to the core; core heats up so the He burning can begin

Front 45

45. What is the reaction for He fusion?

Back 45

⁴He + ⁴He+ ⁴He = C + NRG

⁴He + C = O + NRG

Front 46

46. What happens when He runs out?

Back 46

The core collapses again

He burning migrates up to a layer surrounding the core

H burning occupies the next higher layer

Front 47

47. What's going on with the outer layers of the star at this point?

Back 47

The outer layers are so far out that they are barely held by the gravity of the star

Front 48

48. What happens with the carbon from the core?

Back 48

The C is carried up from the core and carried away from the star in slow, cool stellar winds

Front 49

49. What does the ejected carbon form?

Back 49

It forms solid grains of dust called:

Interstellar dust grains

Front 50

50. Do small or intermediate mass stars like our Sun burn carbon?

Back 50

NO, because they cannot get hot enough

Front 51

51. What happens to these small or intermediate stars like our Sun?

Back 51

They end their live by blasting off their outer layers

They leave behind a slowly cooling sphere of mostly carbon coated w/ a thin layer of H and He
*these are called White Dwarfs

Front 52

52. What do the cast-off layers make?

Back 52

Planetary Nebulae

A nebulae is any big cloud of gas and/or dust

Front 53

53. In summary how do planetary nebulae form?

(Four Parts)

Back 53

1. Dying stars episodically blast off their outer layers
2. These layers form complex clouds of gas around the star
3. Gases are ionized & heated by radiation blasting from the star
4. Here central bright star is visible

Front 54

54. In what types of stars form the rest of the periodic table of elements?

Back 54

Large stars more than 8 times the mass of our Sun

Front 55

55. In the red giant phase, what elements can a star burn?

Back 55

Large stars can burn carbon and several other elements up to iron in a series of concentric shells

Front 56

56. What happens when stars start to accumulate iron in their core?

Back 56

The star only has a few days to live

When enough of the core stops producing energy by fusion, the whole star collapses inward

Front 57

57. Once the star collapses inward what happens?

(two parts)

Back 57

The central part of the star gets crushed forming an incompressible sphere of neutrons

Outer layers free-fall toward neutron core, strike core, violently rebound causing star to explode

Front 58

58. What is this explosion called?

Back 58

Supernova

Front 59

59. What happens to the star after a supernova?

Back 59

Much of the entire mass of the star (including manufactured elements) are blasted into space forming huge clouds of gas and dust (nebulae)

These nebulae = raw materials for next generation of stars

Front 60

60. In short what are giant stars?

Back 60

Element Factories

Front 61

61. How many elements does fusion make?

How are the rest made?

Back 61

Fusion makes nothing heavier than iron

Rest of elements are made by neutron capture

Front 62

62. How does neutron capture work?

Back 62

1. In red giant phase, lots of neutrons zip around
2. Neutrons regularly enter atomic nuclei
3. If too many neutrons enter a nucleus, one or more will radioactively convert to one or more protons = new element

Front 63

63. Up to which element does neutron capture create?

Back 63

During red giant phase, elements up to bismuth (Z=83) are produce by neutron capture

Front 64

64. How are even heavier elements formed?

Back 64

During the death blast of a supernova many neutrons are produced

Neutrons instantly blast into nuclei producing elements all the way up to uranium

Front 65

65. So what produces all of the elements except for hydrogen?

Back 65

Fusion plus neutron capture

Front 66

66. Results of nucleosynthesis

Back 66

Big Bang: H & He

Fusion: C, N, O, & Fe

Neutron Capture: up to Ur

Front 67

67. Some final points on nucleosynthesis (three points).

Back 67

1. Stars smaller than our Sun last at least 10 byrs before dying
2. Stars more than 8 times the mass of our Sun burn through their fuel in as little as 20 myrs
3. Small stars in red giant phase send of carbon rich soot. When they blast off their outer layers on their way to becoming white dwarfs they eject mostly H & He

Front 68

68. What does nucleosynthesis mean then?
(three points)

Back 68

1. H should be distributed throughout the Universe
2. Raw materials to make stars were and are universally distributed
3. Wherever we have star, we make new elements

Front 69

69. So are there raw materials to build other earth like planets?

Back 69

Likely that raw materials for rocky planets have been widely distributed for >10byrs

Front 70

70. What are the four main steps in the formation of a planet?

Back 70

1. Gravitational Collapse
2. Condense
3. Accretion
4. Differentiate

Front 71

71. What is gravitational collapse?

Back 71

A nebular cloud gravitationally collapses in a free-fall gas/dust

Front 72

72. What does this
in-fall/contraction produce?

(two things)

Back 72

1. Rapidly spinning central sphere (future star)

2. Rotating disk

Front 73

73. Where does the material for the rotating disk come from?

Back 73

Disk is built from material spun into orbit by the accelerating rotation of the contracting nebula

Front 74

74. Is the rotating protoplanetary disk likely to start out hot or cold?

Back 74

Hot because of friction

Inner disk ends up hottest b/c its farthest to fall and thicker

Front 75

75. What happens when the disk get really hot?

Back 75

It vaporizes everything so planet starts out as hot gas!

*gravitational in-fall heats everything up

Front 76

76. What does the second step condense mean?

Back 76

Must condense solids from cooling vapor

Front 77

77. What is the general order temperature at which vapors condense?

Back 77

Metals: condense at highest temp
Rocky Materials: middle temp.
Hydrogen: never condense

Front 78

78. Where did condensation occur in our solar system?

Back 78

Next to star: too hot for anything to condense
Near Mercury's (current)orbit: metals/rocks only cond.
Asteroid belt: metals, rocks, and rocky carbon compounds

Front 79

79. Where was the 'frost line'?

Back 79

Between asteroid belt and Jupiter

*line moves in and in as cooling occurs

Front 80

80. What happens at the 'frost line'?

Back 80

Beyond this: metals, rocks, rocky carbon compounds, and water ice/methane ice/ and other ices could ALL condense

Front 81

81. Which planets had more solid to grow form?

Back 81

The planets beyond the frost line

B/C ices are more than twice as abundant as metals and rocky materials

Front 82

82. What were the results of the condensation phase?

Back 82

Inner Four Planets: Rocky
(mercury, venus, earth, mars)

Outer Five Planets: Ice/Gassy
(jupiter, saturn, uranus, neptune, pluto)

Front 83

83. If the nebula had cooled all the way what would have happened?

Back 83

The inner planets would also be large and dominated by ice and/or gas

Front 84

84. Where did all of the hydrogen go though?

Back 84

Early stars have an early violent phase (T-Tauri phase) that produces intense solar wind and some outburts

These swept the H and He out from the inner solar system and vaporized/removed many H compounds b4 inner solar system cooled

Front 85

85. What are the two main results of condensation phase?

Back 85

1. Condensation by temperature nicely explains bulk composition of planets except for the lack of H gas in especially the inner solar system

2. Violet T-Tauri phase of early Sun drove out these gases into the outer solar system helping Jupiter and Saturn attain their impressive sizes

Front 86

86. What is accretion?

Back 86

The process by which solid particles in a planetary disk grows in size from dust to sand to asteroid to planetessiaml (baby planet) to planet

Front 87

87. Why do the tiny particles rotating around a star in a protoplanetary disk stick together?

Back 87

Due to chemical bonds and electrical forces

Front 88

88. What happens as the particles grow?

Back 88

Become massive enough to have their own gravitational fields

Front 89

89. What is the importance of the gravitational fields?

Back 89

These fields allow the first big dudes to win and become planets

Front 90

90. If all planets grow in a single disk of material rotating around a central star; all planets should:

Back 90

1. Rotate around the star in the same direction as the star
2. Rotate on their axis in the same direction as the star
3. Have moons that rotate around the planets in the same direction as the star

Front 91

81. What is the orbital motion of the planets?

Back 91

Perfect Order: all counter-clockwise orbit

Front 92

82. What about planetary rotation?

Back 92

5 of 8 go counterclockwise

Venus, Uranus, & Pluto have retrograde rotation

Front 93

83. What about the rotation of the main moons?

Back 93

4 are counter-clockwise

3 are not!
(Neptune, Uranus, & Pluto)

Front 94

84. Why did this happen?

Back 94

Accretion is Violent!

Venus, Uranus, & Pluto rotate slowly 'backward' b/c a large object struck a glancing blow during accretion

Front 95

85. What evidence is there for collisions?

Back 95

Mercury, Moon, Mar, & others are all heavily cratered

*Largest craters are mostly obliterated by younger ones

Front 96

86. What are the dark areas on the moon called?

Back 96

Maria

They are huge craters filled with lava flows

Front 97

87. What does differentiate mean?

Back 97

The separation of a planet (or asteroid or moon) into chemically distinct layer

Front 98

88. What are the five layers Earth separated into?

Back 98

1. Core: center; iron-nickel alloy
2. Mantle: dark green rock
3. Crust: thin layer of different rocks on top of mantle
4. Hydrosphere: oceans, ice sheets, & other reserves of liquid or solid water on Earth
5. Atmosphere: gaseous outer envelope

Front 99

89. What are meteorites and what are the three types?

Back 99

Meteorites are extremely old and preserve things from early phase of solar system

Chondrites, Metallic Meteorites, and Achondrites

Front 100

90. What are Chondrites?

(Four points)

Back 100

1. Have spherical masses called chondrules
2. Never found in Earth rocks (only assoc. w/ outer space)
3. Oldest rocks in solar system (4.57 Byr)
4. Never been differentiated

Front 101

91. What are metallic meteorites?

(two points)

Back 101

1. Made of iron and nickel

2. Slightly younger than chondrites

Front 102

92. What are achondrites?

(Three points)

Back 102

1. Rocky but lack chondrules
2. Diverse group
3. Most are same age as metallic meteorites

Front 103

93. What is special about chondrites?

Back 103

They are the most primitive objects in our Solar System

They were the raw building blocks of the rocky planets

Front 104

94. What happens if you melt a chondrite?

Back 104

Separates into blobs of iron and nickel that spontaneously combine to form a single mass of iron and nickel

Forms a core and rest forms a rock similar to the mantle

Front 105

95. What are iron meteorites and achondrites considered?

Back 105

Iron Meteorites = ancient cores of dead baby planets

Achondrites = ancient mantle of dead baby planets

Front 106

96. What is necessary to do differentiate a planet made of solid

Back 106

Melt it!

Front 107

97. What are the three heat sources for melting a planet?

Back 107

1. Impacts
2. Radioactive decay
3. Sinking of iron and rising of rocky melts

Front 108

98. Summary points of gravitational collapse.

Back 108

1. Form flattened disk
2. Need elements heavier than C to form Earth-like planets
3. Need nebulae that undergo several cycles of star-supernova-nebula-star-etc.

Front 109

99. Summary of condense phase.

Back 109

Inner disk = hottest
Outer disk = cooler and cools fastest

Front 110

100. Summary of Planetary Formation.

Back 110

Many planetary systems feature gas giants orbiting very close to their star

Front 111

112. What happened in the last phase of accretion?

Back 111

Massive collision

Small planet collided w/ Earth blasting a huge blob of molten rock into orbit around Earth

Front 112

113. What was the blob?

Back 112

Bits of Earth's mantle as well as Theia's

Became the Moon

*Theia's metallic core joined Earth's core

Front 113

114. What was the surface of the earliest Earth like?

Back 113

Entirely molten surface
-moon forming collision created this molten surface

Solid dark crust of rock began to form after this last heavy bombardment

Front 114

115. Was there any volcanic activity on early Earth?

Back 114

Hot early Earth supported almost continuous volcanic eruptions

Front 115

116. What did these eruptions release?

Back 115

Water vapor and other gases

These were incorporated during accretion

Front 116

117. When did the ocean form?

Back 116

Surface oceans by 4.4 byr ago

Data comes from grains of mineral zircon

Front 117

118. Was the whole planet under water?

Back 117

It may have been since the early crust was thin everywhere

Exception would have been where larger volcanoes breached the surface

Front 118

119. What contributed the most to our oceans/atmosphere?

Back 118

Volcanic out gassing

Icy comets may have also added a lot

Front 119

120. What was the atmosphere like in the early Earth?

(three points)

Back 119

Not breathable!

Contained: CO₂,NH₃,CH₄,SO₂,OH₂,N₂,H₂

Much denser and probably very, very cloudy

Front 120

121. What is early history of the Earth based upon?

Back 120

Evidence from meteorites, comets, the Moon and other planets

Front 121

122. What are the oldest solids on Earth?

Back 121

Zircon (tiny grains)

4.4 billion years old
*don't give a rich/detailed record of conditions at the Earth's surface

Front 122

123. What are the earliest rocks recorded?

Back 122

Oldest: 4.03 Byr

Several places where rocks date back to about 3.8 Byr

Rocks from 3.5 Byr to present form a relatively continuous succession

Front 123

124. Why is the rock record so sparse?

Back 123

Late Heavy Bombardment!
(bwt about 3.8 to 4.0 Byr)

*only zircon minerals were tough enough to survive times before 4 Byr ago!

Front 124

125. What triggered the late heavy bombardment?

Back 124

Gravity of Jupiter and Saturn may have flung Neptune from initial position near Saturn to current position beyond Uranus

This triggered a hail of debris from beyond the orbit of Uranus and Pluto

Front 125

126. What was the effect of the late heavy bombardment?

Back 125

Heavy impacts may have repeatedly vaporized oceans, extinguishing any early-formed life and destroyed the Earth's oldest rocks

Front 126

127. What is of fundamental importance to the long-term habitability of the Earth?

Back 126

Plate tectonics

Front 127

128. What is plate tectonics?

Back 127

Earth's surface is broken into a number of rigid plates that move around

Boundaries bwt the plates are where the action is: earthquakes, volcanoes, mountain belts, rift valleys

Front 128

129. What are the three general types of plate boundaries?

Back 128

1. Divergent Boundaries
2. Convergent Boundaries
3. Transform Boundaries

Front 129

130. What are divergent boundaries?

What are the two types

Back 129

Where two plates pull apart

1. ocean-ocean: called mid-ocean ridges or sea-floor spreading centers (most common type)
2. continent-continent: called a continent rift

Front 130

131. What happens at mid-ocean ridges?

Back 130

Plates grow (pull apart from each other at 2 to 15 cm/yr)

Instead of a gap forming bwt the plates, a series of volcanic eruptions produce new solid rock along the crest of the ridge (thus new crust is continuouslyouslly made)

Front 131

132. What are convergent plates?

What are the three types?

Back 131

Where two plates collide

1. ocean-ocean: subduction zone
2. ocean-continent: subduction zone
3. continent-continent: doubling of crust can produce very tall mountains

Front 132

133. What happens at a subduction zone?

Back 132

Two oceanic plates meet and one (usually the older one) is pushed under the other and sinks into the mantle

*subduction recycles sea floor

Front 133

134. What forms on the overriding plate?

What else happens at subduction zones?

Back 133

String of volcanoes form

Great place for earthquakes

Front 134

135. What happens at a continent-ocean convergence plate boundary?

Back 134

The oceanic plate always subducts under the continental plate

Front 135

136. What forms at continent-ocean convergence plate boundaries?

Back 135

A string of volcanoes forms on the overriding plate

A mountain belt may also form

Front 136

137. What happens at a continent-continent convergence plate boundary?

Back 136

One plate may try to subduct under the other but it can't b/c not dense enough

Front 137

138. What is the result of continent-continent plate boundaries?

Back 137

A belt of high mountains marking the zone of collision

Front 138

139. What are transform plate boundaries?

Back 138

This is where plates slide by one one another

Have continent-continent and ocean-ocean transform boundaries

Front 139

140. What is the most famous transform plate boundary?

Back 139

San Andreas Fault in CA (continent-continent)

*also mid-ocean ridges are offset by many small transforms

Front 140

141. So keeping in line with plate tectonics, why is there a lack of pre-3.8 Byr rocks?

Back 140

Takes long time for continents to form

Before 3.5 Byr all rocks were on oceanic crust

Sea floor subducts and nearly all rocks forming before 3.8 Byr were subducted (destroyed)

Front 141

142. What is the rock cycle?

Back 141

A process in which plate tectonics constantly makes new rocks and destroys old ones

Rock cycle is what has kept the planet habitable

Front 142

143. What are the three types of rocks?

Back 142

1. Igneous Rocks

2. Sedimentary Rocks

3. Metamorphic Rocks

Front 143

144. How are igneous rocks formed?

Back 143

Form when melted rocks cool and solidfy

Volcanoes are famous formers of fresh igneous rocks

Also form deep under ground

Front 144

145. Where are rocks the melt to form igneous rocks located?

(two places)

Back 144

1. Upper mantle

2. Older igneous, metamorphic, or sedimentary rocks in the crust

Front 145

146. How do sedimentary rocks form?

What makes up sedimentary rocks?

Back 145

From from eroded bits of older rocks

Made up of sand, silt, clay, and gravel

Other sed. rocks precipitate from sear water, either with or without the help of organisms

Front 146

147. How do metamorphic rocks form?

Back 146

Form when older rocks are recrystallized but not melted

Front 147

148. What are the two common setting in which metaphoric rocks form?

Back 147

1. A body of melted rock intrudes and cools nearby

2. Lots of rocks are metamorphosed deep under mountain belts (temp and pressures are high here)

Front 148

149. What are the three way in which the rock cycle recycles rocks?

Back 148

1. Melting of pre-existing rocks
2. Disintegration and recycling of rocks exposed at the Earth's surface
3. Recrystallization of pre-existing rock

Front 149

150. What is the key point of the rock cycle?

Back 149

An given rock type can get recycled back into the same type or converted into any of the other three rock types

Front 150

151. What two things have made the Earth habitable?

Back 150

1. Maintained a temp that has allowed liquid water to exist at the surface

2. Has an atmosphere rich in oxygen (necessary for multicellular life)

Front 151

152. Liquid water implies what kind of temperature range?

Back 151

Narrow range between 0°C to 100°C

Front 152

153. What evidence exists indicating that the Earth has always supported liquid water?
(three things)

Back 152

1. Chemical clues in zircon crystal 4.4 Byr old indicate liquid water at surface
2. Sedimentary rocks 3.8 Byr deposited in water
3. Water-lain sedimentary deposits 3.5 Byr and younger are found throughout geologic time

Front 153

154. What is the one possible exception for Earth always supporting liquid water?

Back 153

Ice seems to have covered the entire surface of Earth one or several time between 750 and 580 Myr ago

*deeper though oceans were liquid so only top portion frooze

Front 154

155. What was the sun like 4.5 Byr ago?

Back 154

Sun gave off 30% less heat

Front 155

156. So why didn't Earth plunge into a permanent deep freeze?

Back 155

Green House Effect

Warming is due entirely to atmosphere

Front 156

157. What would Earth be like without any atmosphere?

Back 156

Ave. Temp. of -17°C (1°F)

Today ave. temp. of +15°C
(59°F)

Front 157

158. What are the three most important greenhouse gases in the atmosphere?

Back 157

Water Vapor

Carbon Dioxide (CO2)

Methane (CH4)

Front 158

159. How does the green house effect work?

(four points)

Back 158

1. Sun emits electromagnetic radiation in UV, visible, and infrared wavelengths (most in form of visible light)
2. Visible light passes through atmosphere and strikes ground
3. Ground is warmed by visible light
4. Warm surface emits electro-magnetic radiation (heat) in infrared wavelengths

Front 159

160. What is key to the greenhouse effect?

Back 159

Incoming visible light is transformed into outgoing infrared light

Front 160

161. What do the greenhouse gases do?

Back 160

They absorb and re-emit this infrared light

Front 161

162. What warms up the atmosphere and in turn the Earth's surface?

Back 161

This sharing of infrared energy

*the warmer the atmosphere gets, the more infrared energy it radiates

Front 162

163. What happens at stead-state?

Back 162

The total amount of energy coming in from the Sun is exactly balanced by the infrared energy leaving the upper atmosphere of the Earth

Front 163

164. What is going on today?

Back 163

We have increased the concentration of CO2 and CH4 in the atmosphere

Thus, more energy is coming in than is leaving

Front 164

165. What four things are volcanic gases from the Earth's mantle dominated by?

Back 164

1. Water
2. Carbon Dioxide
3. Nitrogen
4. Sulfur Compounds

Front 165

166. What was the ancient atmosphere rich in due to volcanic outputs?

Back 165

CO2

Today's atmosphere contains only 0.35% CO2

Front 166

167. What did the higher CO2 concentration do ?

Back 166

Created a much stronger greenhouse effect

This is how Earth made do with 30% less solar energy

Front 167

168. What is the total amount of carbon that could end up in the atmosphere due to normal biology and chemistry?

What about from volcanoes?

Back 167

3.5 x 10^18 moles

6.9 x 10^18 moles

*volcanoes output TWICE as much CO2 as exists in ALL surface reservoirs today

Front 168

169. What process removes exactly the amount of CO2 that volcanoes add every one million years?

Back 168

Silicate mineral weathering plus the deposition of limestone

Front 169

170. What is rock weathering?

Back 169

Rocks exposed at Earth's surface weather

Minerals in the rocks are chemically attacked and mechanically break down such that the rock disintegrate (this is how soil forms)

Front 170

171. What mineral weathering is vital to life?

Back 170

Silicate mineral

Silicate minerals include all those that have oxygen and silicon as part of their composition

Silicate minerals dominate Earth's surface

Front 171

172. What is the reaction that describes the weathering of a generic silicate mineral?

Back 171

CaSiO3+ 3H2O+ 2CO2⟶Ca2⁺+HCO3⁻

1. CO2 from air is converted to HCO3⁻ dissolved in water (bicarbonate ion)
2. This water flows to ocean where it reacts with Ca to form limestone, water, and CO2

Front 172

173. So what is the net reaction of silicate mineral weathering?

Back 172

For 2 molecules of CO2 removed from the air by weather, one ends up forming sedimentary rock on the sea floor (CaCO3 is limestone); the other is recycled back into the ocean-atmosphere system

Front 173

174. What is limestone?

Back 173

1. CaCO3
2. Very common
3. Stores huge amounts of ancient CO2 that used to be in the atmosphere

Front 174

175. What else stores ancient atmospheric CO2?

Back 174

Coal and other fossil fuels

CO2 that was once in the Precambrian atmosphere is buried at solid rock and fossil fuels

Front 175

176. What is meant by Precambrian atmosphere?

Back 175

Oldest major period in Earth history

Stretches from 4.57 Byr to 542 Myr

Front 176

177. Since volcanic activity varied a lot, how did weathering and limestone burial vary in such a way as to closely balance changes in volcanic output in order to avoid the atmosphere getting too much or too little CO2?

Back 176

Has to do with chemical reaction rates varying with temperature

*every 10° C rise in temp doubles or triples reaction rate

Front 177

178. How did this reaction rate varying work?

Back 177

Volcanoes put out more CO2, climate warms up, rates of chemical weathering speed up

Faster weathering leads to faster burial of CO2, climate cools

Conversely, cool climate, weathering slows, and more CO2 builds up, climate warms

Front 178

179. How does plate tectonics affect the climate?

Back 178

Most volcanoes erupt along plate boundaries result of plate motion (stop P.T. and volcanic CO2 emissions drop a lot)

Continental collision & volcanic eruptions create new mountains, exposing fresh rock to weathering (w/o P.T. landscape would erode flat, rock weathering slow a lot)

Front 179

180. Do other planets have plate tectonics?

Back 179

No, Earth is uniquely geologically active

Front 180

181. Why don't Mercury, Mars, and the Moon have plate tectonics?

Back 180

Small size means they cooled off fast

Interiors were not hot enough to have rocks soft enough for tectonic plate to move around

Front 181

182. Venus is close to Earth's size so why does it not have plate tectonics?

Back 181

Earth is a uniquely wet planet
Water is essential to the igneous processes that grew the continents that expose rocks to weathering

Addition of water to mantle by subduction zones has kept the mantle fluid enough to allow plates to move

Front 182

183. Why do we have oxygen in our atmosphere today?

Back 182

Due to sunlight-driven photosynthesis in plants

Plants actively maintain O2 in our atmosphere

Front 183

184. What gases did the early Earth atmosphere contain?

Back 183

CO2, SO2, H2O, N2, CH4, NH3, and H2

NO OXYGEN!

Front 184

185. How do we know early atmosphere lacked O2?

Back 184

Deposits older than 1.8 Byr include sandstones with uraninite (UO2) and pyrites (FeS)

Both minerals rapidly break down in presence of O2

Front 185

186. What is the snowball Earth hypothesis?

Back 185

An illustration of how the Earth system regulates its own climate

Front 186

187. Where are the coldest places on Earth?

Back 186

Polar regions (Antarctica, Arctic areas)

High elevations (snow-capped peaks)

Front 187

188. What happens during a typical ice age?

Back 187

Ice sheets and glaciers advance from their normal homes down into warmer climates

Front 188

189. How was the last ice age (100,000 yrs ago) triggered?

(parts 1-4)

Back 188

1. Oceans sucked up atmospheric CO2
2. Warm surface waters in N. Pacific provided moisture (snow) to cooling N. Canada
3. Canada became very white
4. White snow reflects back a lot of visible light

Front 189

190. How was the last ice age triggered?

(parts 5-7)

Back 189

5. Higher albedo (expansion of area of year-long snow in Canada) reflected back more sunlight, further cooled
6. Cyclic effect were cooler, more snow, more heat reflected
7. Snow packs thickened and bottom layers compressed into solid ice

Front 190

191. How was the last ice age triggered?

(parts 8-9)

Back 190

8. Thick ice flows
9. Snow packs turned into vast glaciers called ice sheets

Front 191

192. How did the ice age end?

Back 191

After 100,000 yrs of growth, ice sheets destabilized and collapsed, ocean circulation was affected, and CO2 returned to atmosphere

Front 192

193. In comparison to recent ice ages were ice sheets formed near the poles, where did glacial deposits form between 750 and 580 Myr ago?

Back 192

Located in the tropics

Tropical glaciation does appear to have happened

Front 193

194. What evidence is there for 'Snowball Earth' ice ages?

Back 193

1. Glacial striations

2. Dropstones

Front 194

195. What are glacial striations?

Back 194

Distinctive scratches made in rocks when they are dragged against each other by glaciers

Front 195

196. What are dropstones?

Back 195

Icebergs that float over lakes or oceans drop gravel or boulders where otherwise only very fine-grained sediments accumulate

Front 196

197. What is albedo?

Back 196

The amount of sunlight reflected back into space as visible light (i.e. not able to trigger the greenhouse effect by warming surface and radiating IR light)

Front 197

198. An ice-covered planets has such a high albedo it's tough to image how it could ever warm up. So how did it thaw out?

Back 197

Emissions of volcanic CO2 pumped up atmospheric CO2 concentrations to where they overcame the incredibly high albedo and warmed the planet

As ice sheets melted, albedo decreased, more visible light was absorbed, planet got hot

Front 198

199. How come volcanoes still erupted when it was so cold?

Back 198

Volcanism is fueled by internal heat

Erupt regardless of whether climates are hot or cold

Front 199

200. How does weathering play a role?

Back 199

All the rocks are under snow or ice so rates of chemical weathering drop to zero

Shut down all-important sink of volcanic CO2

Front 200

201. When the planet began getting hotter faster, what happened to chemical weathering?

Back 200

Sped up weathering, which increased flux of Ca & HCO3- to oceans

Limestone (normally hot climates) deposited directly on glacial deposits

Front 201

202. When is this sequence of limestone over glacial dropstones typical?

Back 201

Typical of interval from 750 to 580 Myr

Such deposits are rare for the rest of the glacial intervals

Very odd to have hot-climate rocks deposited directly on cold-climate rocks

Front 202

203. So what is the sequence of the Snowball Earth Hypothesis?

Back 202

1. Polar areas freeze up
2. Ice sheets spread to tropics
3. Temp's drop; oceans freeze
4. Entire surface freezes
5. CO2 induced warming
6. Back to normal

Front 203

204. What is an isotope?

Back 203

An isotope of an element has the same number of protons, but they have variable numbers of neutrons in the nucleus

Front 204

205. What are some common isotopes?

Back 204

Carbon: C¹², C¹³,C¹⁴

Uranium: U²³⁵& U²³⁸

*235U is more radioactive than 238U

Front 205

206. When is an isotope radioactive?

Back 205

If its nucleus is unstable

The nucleus is unstable if it has too many (or too few) neutron relative to protons

Front 206

207. Which elements have roughly equal neutrons and protons?

Which elements show larger excess of neutrons?

Back 206

Light elements

Heavier elements

Front 207

208. During radioactive decay, what three things can happen?

Back 207

1. Alpha Decay
2. Beta Decay
3. Electron Capture

Front 208

209. What is alpha decay?

Back 208

2p & 2n are ejected as a He nucleus

He nuclei are alpha particles (=radiation)

Front 209

210. What is beta decay?

Back 209

Neutron decays into a proton and ejects an electron

Electron is the beta particle (=radiation)

Front 210

211. What is electron capture?

Back 210

An electron falls into the nucleus and converts a proton into a neutron

Front 211

212. In each case of radioactive decay what two things occur?

Back 211

1. Various types of radiation are created

2. One element is converted into another

Front 212

213. How are rocks dated?

Back 212

Based on the radioactive decay of one isotope (parent) into another (daughter)

Front 213

214. What are decay rates?

Back 213

They give the proportion of the starting number of radioactive atoms that decay in a year

Also called decay constants

Front 214

215. Why are decay rates called decay constants?

Back 214

Because radioactive elements decay at constant rates

Front 215

216. Radioactive decay is what kind of process?

Why?

Back 215

Probabilistic Process

We never know when a particular single atom will decay

Front 216

217. Why do decay constants work then?

Back 216

Because we're talking about huge numbers of atoms

Chances are that some fraction of them (determined by the decay constant) will decay in the next second

Front 217

218. What is half-life?

Back 217

How ling it takes one-half of the starting amount of a given parent to decay to its daughter

Front 218

219. How do parents decay?

How do daughters accumulate?

Back 218

Parents decay away at a constant rate

Daughter accumulates at the same constant rate

Front 219

220. What do radiometric dates record?

Back 219

The time since a given rock or mineral solidified from a liquid state

Front 220

221. To give an accurate age what is essential?

Back 220

The rock or mineral always remained a closed

It can NEVER have gained nor lost any parent or daughter or no accurate age is obtained

Front 221

222. What are the two most powerful parent-daughter systems?

Back 221

1. Potassium-argon
40Ar → 39Ar
(base on 40K → 40Ar)

2. Uranium-lead
238U → 206Pb & 235U → 207Pb

Front 222

223. When a mineral crystallizes in a magma does it pick up K or Ar?

Why?

Back 222

Picks up K

K is chemically active element, whereas Ar is noble gas and inert

Front 223

224. Thus, what do freshly formed igneous minerals contain?

What happens over time?

Back 223

K (parent) but no Ar (daughter)

40K decays and 40Ar accumulates

Front 224

225. How do we get the age?

What's wrong with this?

Back 224

Measure relative proportion of the two, take into consideration half-life, and get age

Problem is ratio is of elements in two different states (liquid and gas)

Front 225

226. How do we solve the problem?

Back 225

Measure 40Ar/39Ar ratios

Irradiate a sample with neutrons and 40K is turned into 39Ar

Front 226

227. What mineral commonly found in igneous rocks sucks up uranium?

Back 226

Zircon

Suck up huge amount of U but little or no Pb

Front 227

228. How do we measure age using this?

What's the problem here?

Back 227

Measure the relative amount of U and Pb to get an age

Have two parents and two daughters

Front 228

229. How do we solve the problem?

Back 228

Algebra involving equations that govern the change in parent/daughter isotopes

Make graphs indicating when a given sample has gained or lost parent and/or daughter

Front 229

230. What are inherited daughters?

In which cases is this common?

Back 229

A mineral forms with daughter isotopes already in them

Common especially with Rb-Sr and Sm-Nd dating

Front 230

231. What do we measure in Rb-Sr dating?

How do we do this?

Back 230

Measure ratios rather than absolute concentrations of a particular isotope

Divide through the equation by an isotope not produced by radioactive decay (86Sr in this case)

Front 231

232. What equation is used?

Back 231

Equation of Line:
y = b + mx

(87Sr/86Sr)t = (87Sr/86Sr)i + 86Rb/86Sr x (e^λt - 1)

Front 232

233. What is the 87Rb/86Sr ratio when rock forms?

Back 232

When a bunch of mineral crystallize from a liquid magma, each different mineral picks up a distinct Rb/Sr ratio

This gives a range of values across the x-axis

Front 233

234. What is the 87Sr/86Sr ratio when a rock forms?

Back 233

Identical when a bunch of different mineral crystallize in a magme

No spread on y-axis

Front 234

235. As time passes, what happens to the two ratios?

Back 234

87Rb decays to 87Sr

Thus, 87Rb/86Sr ration decreases and 87Sr/86Sr ratio increases

Front 235

236. How does the 87Sr/86Sr ratio increase?

Back 235

It increases proportionally to the 87Rb/86Sr ratio

Thus, high Rb/Sr ratios see faster increase in 87Sr/86Sr

Front 236

237. What does the slope of the line give?

What happens when the rock containing the mineral gets older?

Back 236

Slope of line gives the age of the sample

Older the rock, steeper the slope of the line

Front 237

238. What is an isochron?

Back 237

A linear array of parent-daughter isotope data

Front 238

239. In order to calculate the age what do you solve?

Back 238

solve m = (e^λt - 1) for t

Front 239

240. What are the best rocks to date?

Back 239

Igneous rocks

Sedimentary and metamorphic rocks are more difficult to date for a variety of reasons

Front 240

241. What are igneous rocks the best rocks to date?

(three reasons)

Back 240

1. A magma or lave tends to be very well stirred so isotope ratios are the same at each and every spot in the magma
2. When the minerals form they tend to have different parent-daughter ratios but identical daughter isotope ratios
3. Tend to crystallize over a short period of time making a nice single 'event' to date

Front 241

242. What is the best way to date the fossil record?

Why?

Back 241

Find areas where ancient volcanoes blasted ash into the nearby sea

Volcanic ashes often contain K (Ar-Ar dating) and zircon (U-Pb datin)