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EarthSci > chap 6&7&8 > Flashcards

chap 6&7&8 Flashcards

1
Q

What characteristic is used to differentiate gas planets from terrestrial planets?

A

Gas planets are differentiated from terrestrial planets by their density (their mass). The terrestrial planets, which are closer to the Sun, have much lower Earth masses than the gas planets.

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2
Q

What elements are common in the rocky planets?

A

silicon (Si), oxygen (O), aluminum (Al), magnesium (Mg), sulfur (S), and iron (Fe)

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3
Q

What is the most abundant rock type?

A

most abundant rock-type is common to all the rocky planets, and is called basalt, which is an igneous rock, the primary product of volcanic lava, fine grained, dark grey to black

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4
Q

Do planets close to the Sun experience more or fewer bombardments? Why?

A

The closer a planet is to the Sun - which has a massive gravitational attraction - the more often will it be bombarded by incoming asteroids and comets. Therefore, closer planets experience more bombardments

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5
Q

Learn the different models of the Moon’s origin and why one model is favoured

A

The Giant Impact Hypothesis is the preferred model. Here is what happened:

  • collision(s) and melting of both bodies
  • The glancing blow gave inc angular momentum to Earth (spin rate increased)
  • The metal core of the impactor (the Mars-sized body) seperated and dropped into Earth, giving Earth its large metal core and remarkably high density
  • To some degree, the molten mantle material of both bodies mixed, and formed debris in space just above Earth
  • Over a relatively short period of time, some of the debris fell back to Earth, but most of it collected into a single mass to become the Moon
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6
Q

Fission Hypothesis – how did the Moon supposedly form? Why was this
hypothesis rejected?

A
  • The earth was spinning very quickly and a chunk broke off that became the moon
  • Rejected because it suggests the earth had to rotate once ever 2.5 hours which was difficult to reconcile with the current rotational rate
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7
Q

Condensation Hypothesis – how did the Moon supposedly form? What are the
two arguments against this hypothesis?

A

Both the earth and the moon formed from the same parental cloud of dust and gas

Rejected because 1) moon and earth would need to be the same composition which they don’t and 2) the moon would need to orbit earth exactly on an equatorial plane which it doesn’t

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8
Q

Capture hypothesis – how did the Moon supposedly form? Three reasons for
rejecting it?

A

The moon was captured by the earths gravitational force

Rejected because

1) the probability of an object the size of earth to fall into orbit about the earth is astronomically unlikely,
2) some chemicals (mostly oxygen isotopes) were so similar on the earth and moon that they must have some close ‘genetic’ relationship
3) every computer simulation of a capture failed miserably

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9
Q

Giant Impact hypothesis – what is it? (Why do we like this one?)

A

The Giant Impact hypothesis proposed that a planet somewhat smaller than Earth (hypothetical planet called Theia), in a progressively unstable orbit about the Sun, gave Earth a glancing blow sometime about 4.5 billion years ago

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10
Q

What is kinetic energy – how are energy and velocity related?

A
  • Energy a body has by virtue of motion

- Kinetic energy increases exponentially with velocity

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11
Q

What is Theia?

A
  • The hypothetical planet that was in a progressively unstable orbit about
    the Sun

-Gave earth a glancing blow

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12
Q

How did the giant impact affect Earth’s structure?

A
  • The energy of the impact(s) was enough to melt both planets
  • Increased its spin rate
  • The metal core of the impactor dropped into earth giving it its large metal
    core and high density
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13
Q

What material makes up the Moon? Why is its composition similar to Earth?

A

The molten mantle of both bodies formed debris in space

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14
Q

What evidence is used to support that the Moon formed as a result of a large
impact?

A
  • Tungsten isotopes that date more recently than the start of the solar system
  • Oldest Moon rocks were formed when magma cooled so must have been
    energy input enough to largely melt the moon
  • Oxygen isotopes almost same proportions as earth rocks
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15
Q

Was the impactor (Theia) large or small? Do we know?

A

It is not known for sure the size of Theia

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16
Q

Relate this hypothesis to the size of the Earth’s iron-rich core

A

The metal core of the impactor dropped into earth giving it its large metal
core and high density

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17
Q

EARTH..

be familiar with Size, density and internal zones

A

-Fifth largest planet
­- Most dense at 5.5g/cm 3
- Zones: inner core, outer core, mantle, crust

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18
Q

EARTH..

Continental drift, plate tectonics, and magnetism

A

­-Continents used to be a super continent called Pangea
­- Then continents drifted apart­
-Plate tectonics controls volcanism and earthquakes
­-Strong magnetic field created by electric currents in iron-rich core
­- Flow of liquid outer metal round solid inner metal core

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19
Q

EARTH..

Geological time and age dating

A

Two types of ways to date rocks:

  • relative age dating (getting an age relative to rocks around it), or absolute dating (absolute years old).
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20
Q

EARTH..

Basic properties of the hydrosphere and atmosphere

A
  • Atmosphere is 78% nitrogen, 21% oxygen and 1% traces of many other
    elements
    ­
  • Shelters earth from dangerous radiation
    ­
    -Hydrosphere formed when water vapour in the atmosphere condensed and
    it began to rain
    ­
    -Hydrosphere is a closed system and earth has been recycling water for a
    long time
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21
Q

What makes Earth unique among the terrestrial planets?

A
  • Only planet in solar system that can currently support life
  • Atmosphere is very unique to solar system
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22
Q

Explain the role of Accretion in the formation of the Earth

A

Accretion is growth by accumulation of smaller bodies, dust and gas. The first large object would have attracted others by simple gravity; and as the object grew larger, it attracted more and more material to it faster and faster

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23
Q

What is the iron catastrophe? How was the core formed? What are the layers of the core?

A

Hot liquid iron sunk deep to the core releasing energy that melted the whole
planet

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24
Q

What is the most common element in the Earth?

A

Iron making up around 30%

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25
Q

How did differentiation form different zones in the Earth?

A

Differentiation is the zoning of heavier elements generally sinking to the core and
lighter elements remaining at the top

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26
Q

Name the zones of the Earth (be able to label a simple diagram). How do the zones differ
from each other? Which is the largest zone?

A

Inner core is solid metal, outer core is liquid metal, mesosphere is “stiff plastic”
and is largest zone

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27
Q

How do pressure, temperature and density change as you move from the crust towards
the core?

A

All 3 increase as you move from surface to the core

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28
Q

Why does Earth have a magnetic field? What is a dynamo?

A
  • The flow of the liquid metal around the solid inner core causes an electric current
    which creates the magnetic field
  • Dynamo is a device that converts physical energy into electrical energy
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29
Q

What is the evidence that supported the hypothesis of continental drift?

A
  • Da Vinci discovered fossil seashells on the tops of mountains in Italy
  • Darwin observed the coastline of Chile had been raised up from an earthquake
    (supports uplift from da Vinci)
  • Jigsaw parallelism of coastlines of different continents across Atlantic Ocean
30
Q

What are the 3 types of plate margins? What happens at each kind of margin?

A
  • Divergent – plates moving apart, spreading centres
  • Convergent – plates moving towards each other, subduction (one plate moving
    beneath another)
  • Transform – two plates slide past each other
31
Q

What mechanism drives plate tectonics (a.k.a. continental drift)?

A

Convection currents beneath the plates move them around

32
Q

What is a mantle plume and how does it form?

A

Hot liquid metal seeps into the mesosphere and just continues to rise creating a ‘plume’

33
Q

What is “relative age dating”? Give an example of how you can tell the order in which rocks were formed based on their relative position.

A
  • Dating a rock based on the rocks around it
  • Found a rock between to layers of rocks you know the age of, can estimate rock is
    between those ages
34
Q

Describe (generally) how we can use radioactive elements to determine absolute ages of rocks.

A
  • Determine rate of decay i.e. the half life
  • Determine amount of isotope currently in process of breaking down
  • Typically use uranium or thorium
  • Organic dating is typically done with carbon
35
Q

How old is the Earth? How old is the surface of the Earth? How old are the ocean
floors?

A
  • Earth is 4.5 billion years old but because the earth recycles its surface, it is much
    younger
  • Ocean is no older than 250 million years old
36
Q

Describe how the Earth’s atmosphere, hydrosphere and biosphere are interconnected (e.g.
how do they affect each other).

A
  • When hydrosphere was introduced, earth must have been a hot and steamy place
  • Biosphere has photosynthesis which changed composition of atmosphere
37
Q

Why does Earth’s atmosphere differ from that on Mars? Venus?

A

Mars and Venus atmospheres are mostly CO 2 while Earth’s is mostly nitrogen and
oxygen thanks to photosynthesis

38
Q

Where did the Earth’s water come from?

A

Impactors that collided with Earth probably contained water in other forms such
as ice in small quantities which eventually got into atmosphere and then
condensed

39
Q

How did prokaryotes that lived in anaerobic ancient oceans avoid the toxic effects of the
oxygen they produced during photosynthesis? What evidence do we have? How do we
finally start to accumulate oxygen in the atmosphere and what were the effects on
biology/evolution?

A

Oxygen combined with iron to make iron oxides that settled on ocean floor

40
Q

How is CO2 removed from the atmosphere? How does this affect Earth’s temperature?

A
  • The carbon combined with other elements to form many different compounds that
    relate to life on earth
  • Changed composition of atmosphere from predominantly CO2 to mostly N2 and O2
41
Q

Explain two ways that biology has affected the composition of the atmosphere – how are
these changes beneficial to life?

A
  • Photosynthesis uses CO 2 to create oxygen gas

- Removal of carbon from atmosphere to form organic material

42
Q

What is tidal coupling?

A

After stabilization of big collision, Earth’s gravitational force has kept the moon
into exactly the same rotational period as the Earth

43
Q

What is a Trojan satellite?

A

An object that has the same orbit as another body but does not collide with said
body because it remains stable in its orbit

44
Q

Has Earth ever had more than one satellite?

A

Yes, between September 2006 and June 2007 an asteroid was captured by Earths
gravitational force

45
Q

Before visiting the Moon how did we know::

A) That the Moon had no atmosphere?
B) That there are no plate tectonics?

A

A) - An atmosphere would break up smaller meteoroids
­- We see craters of all sizes on Moon so atmosphere not possible

B.) no mountain belts

46
Q

Explain how studying impact craters can tell us about the age of the Moon.

A
  • The more impact craters a surface has, the older it is

- If we can estimate rate of crater production, we can estimate Moon’s age

47
Q

What is the maria? Why does it only occur on the near side of the Moon?

A

Maria is the darker areas on the near side of the moon

48
Q

Are you more likely to see small craters form on the Moon or Earth? Why?

A

Moon because smaller bodies would be broken up by Earth’s atmosphere

49
Q

If the same size meteorite were to hit the Earth and Moon, which would form the bigger crater?

A

Crater on Moon would be bigger because regardless of size, Earth’s atmosphere
will slow the meteorite down

50
Q

What are the general steps of crater formation?

A
  • Upon impact, kinetic energy is converted to thermal, acoustic and mechanical
    energy
  • Thermal energy makes the surface deform around the impact site
  • A shockwave releases energy around impact and pushes rock outwards and
    upwards
  • Rim around crater is formed by rock being forced upwards
51
Q

What is crater saturation?

A

When surface is so covered in craters that for a new one to form, it would destroy at least one other one

52
Q

Why are all Moon rocks igneous rocks?

A

Igneous rocks are formed by cooling of molten rock which makes sense with moon’s formation as it would be very hot

53
Q

Why aren’t sedimentary rocks found on the Moon?

A

Sedimentary rocks cannot form without water and moon has never had liquid water

54
Q

What is the regolith and how is it formed?

A
  • A layer of powdered rock and crushed fragments
  • Mostly made of smashed remains of moon rocks that have been ground up by
    constant blasting of meteorites
55
Q

Is there seismic activity on the Moon?

A

Moon is 100 million times lest seismically active than Earth (so not really)

56
Q

What is the geological history of the Moon?

A
  • Pre-Nectarian Period: very heavy bombardment, lots of craters formed
  • Nectarian Period: formation of Nectaris basin
  • Imbrian Period: accumulation of flood basalts
  • Eratosthenian Period: little more basalt
  • Copernican Period: not much activity, goes until present day
57
Q

Why is it hard for us to view Mercury’s surface?

A

Mercury always stays in the same region of the sky as the Sun making seeing its
surface difficult, it also doesn’t get any closer than 80 million km

58
Q

How is Mercury similar to the Moon? How do their surfaces differ?

A
  • Their surfaces are both very cratered
  • Both are small, airless and have ancient, inactive surfaces
  • Different because Mercury has enormous cliffs
59
Q

What mission/craft provided us with the most information about Mercury?

A

MESSENGER launched in 2004

60
Q

Which is longer, a day or a year on Mercury?

A

A day on Mercury is much longer (58.65 Earth days)

61
Q

Is the surface hot or cold? Why?

A
  • Very hot during the day (350 o C) and very cold at night (-170 o C)
  • Orbit differs from 46 million km from sun to 70 million km
  • Combine that with long days to get drastic differences in temp
62
Q

What is the origin on the atmosphere on Mercury?

A

It is constantly replenished by atoms blasting from solar winds

63
Q

What is the evidence for lava flows on Mercury?

A
  • Inner-crater plains have smaller impact craters and secondary craters produced by
    ejecta
  • Inner-crater plains are not totally saturated suggesting lava flows
64
Q

Why does Mercury have a low albedo?

A

Recent report suggests that a dusting of carbon from remains of cometary impacts

65
Q

Since there are no plate tectonics on Mercury why do we see things like faults and
scarps?

A

Formed by compression when Mercury cooled and shrunk

66
Q

How are hollows formed?

A
  • When material beneath the surface vapourized away after asteroid impacts
  • Require high concentrations of volatile elements in Mercury’s crust
67
Q

How does the interior of Mercury compare with Earth’s?

A
  • Mercury’s core is much larger proportionately than earths
  • Mercury’s mantle is also much thinner and has a layer of solid iron sulphide
    between the core and mantle
68
Q

What is the geological history of Mercury?

A

Stage 1: formed in inner most part of nebula, an impact may have taken some
lower density rock

Stage 2: heavy cratering, creation of Caloris Basin

Stage 3: flooding began with lava flows, later formed the smooth plains

Stage 4: Now an inactive world, nearly dead

69
Q

What two elements are surprisingly common on the surface of Mercury?

A

Sulphur and Magnesium are surprisingly abundant on Mercury

70
Q

Is there water on the surface of Mercury? How do we know? Why hasn’t the heat of the
Sun evaporated it?

A
  • At the poles, there are high levels of water-ice, measured by MESSENGER
  • Because Mercury’s rotational axis is less than 1 o , the poles are never hit by
    sunlight

EarthSci (5 decks)

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