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Biology 1 > Geology > Flashcards

Geology Flashcards

(55 cards)

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1
Q

What are the three types of plate margins?

A

Constructive, destructive, conservative

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2
Q

Properties of terrestrial planets

A
  • Composed of silicate minerals
  • Have topographic features
  • Have secondary atmospheres
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3
Q

What is the density of continental crust

A

2.7g/cm3

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4
Q

Which discontinuity separates the outer and inner core and what depth is it at?

A

Lehmann discontinuity at 5150km

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5
Q

What is the order of the planets from the sun

A 
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
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6
Q

On average how thick is oceanic crust and what is its composition

A

~7km thick and mafic in composition

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7
Q

Which layers of the earth make up the Lithosphere?

A

Crust and uppermost part of the mantle

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8
Q

Which discontinuity separates the mantle and outer core and what depth is it at?

A

Gutenburg at 2900km

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9
Q

How did the asteroid belt form and where is it in the solar system?

A

Formed by rocks that were not large enough to form planets and it separates the terrestrial and gas giant planets between Mars and Jupiter.

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10
Q

What physical state is the asthenosphere?

A

Rheid - a solid that can flow with 1-5% partial melt.

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11
Q

What are the properties of the gas giant planets and which planets are these?

A

Jupiter, Saturn, Uranus and Neptune

  • Composed predominantly of gas
  • Elaborate system of moons
  • Have planetary rings
  • Stripes due to fast rotation and strong east to west wind direction
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12
Q

What is the composition of the continental crust and on average how thick is it?

A

Granitic in composition and around 35km thick

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13
Q

What depth is the centre of the earth at?

A

6371km

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14
Q

How old is the earth?

A

4.5 Ga

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15
Q

What is the Kuiper Belt

A

Millions of icy bodies beyond Neptune

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16
Q

Describe the formation of the solar system

A
  • Cloud of dust and gas - nebula
  • Cloud begins to contract due to gravity and temperatures start to rise
  • Nebula starts to spin then flattens into a proto-planetary disc
  • Pressure and temp increases and nuclear fusion occurs
  • Materials accrete to form planets
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17
Q

What is a meteorite?

A

Fragments of rock and/or metal that fall to earth from space.

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18
Q

What are the direct pieces of evidence for a meteorite impact?

A
  • Impact crater
  • Iridium anomalies
  • Shocked minerals
  • Impact melts
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19
Q

Stony meteroites

A

93% of falls
Contain silicate minerals e.g. peridotite
Chondrites are similar structure to the mantle
Carbonaceas chondrites contain organic compounds such as proteins that are thought to be similar to the composition of solar nebula.

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20
Q

Which are the two famous impact craters and how old are they?

A

Vredefort Dome - South Africa 2.0 Ga

Chicxulub Crater - Mexico 65 Ma

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21
Q

Iron meteorites

A

6% of falls
Represent the composition of the inner core
Contain iron and nickel

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22
Q

What is the oldest rock on earth?

A

Acasta Gneisses - 4.03 Ga found in Canada

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23
Q

Describe radiometric dating

Study These Flashcards
A

Isotopes are unstable and decay over time.
The rate of decay for a particular isotope is constant.
Half life is the time taken for half the unstable parent atoms to decay and form stable daughter products.

24
Q

What is the oldest mineral and where is it found?

Study These Flashcards
A

Zircon - 4.4 Ga found in Jack Hills, Australia

25
What is the density of the oceanic crust?
3.0 g/cm3
26
What depths does the lower mantle extend from and to and what is its composition?
670 - 2900km solid state
27
What state is the inner core and what is its composition?
Solid and ultramafic - very rich in iron and nickel
28
Where are the deepest mines and boreholes?
Deepest mine: 3.9km South Africa | Deepest Borehole: 13km Russia
29
What rocks provide direct evidence for the earth's structure?
Kimberlites - volcanic rocks that form in kimberlite pipes deep within the mantle between 150 and 450km. Kimberlites erupt and carry diamonds and mantle xenoliths (fragments of foreign rock to the earth's surface) Mantle xenoliths form as fragments of rock break off and fall into the magma and are carried to the surface. Ophiolites are sections of crust that have been thrust up onto land at plate margins to expose different rock types that form at different rates in the mantle e.g. basalt, dolerite and gabbro.
30
How are seismic waves used as a source of indirect evidence for the internal structure of the earth?
The velocity of the waves changes as the density and compressibility of the sections of the earth changes.
31
What are the two types of body waves and their properties?
P waves ~ compressional waves travel the fastest travel through all mediums S waves ~ Shear waves Secondary waves Cannot travel through liquids
32
What happens to seismic waves if a material becomes more incompressible?
They speed up
33
What type of wave is an L wave and what is its properties?
Surface wave - travel on earth's surface Slowest of all the seismic waves Causes damage to buildings
34
what happens to seismic waves at discontinuities and why?
They are either reflected or refracted due to a change in physical state and/or composition.
35
What is the P wave shadow zone?
Between 103 and 143 degrees - no p waves occur here due to angle of refraction.
36
Why is the asthenosphere sometimes referred to as the "low velocity zone"?
P and S waves slow down in the asthenosphere due to the change in composition, the material becomes more compressible due to the 1-5% partial melt.
37
Where does the S wave shadow zone occur?
Between 103 and 103 degrees
38
Why do seismic waves travel on a curved path?
They are constantly being refracted due to a variation in density and incompressibility with depth.
39
Mark points for earthquakes
* Elastic rebound causes earthquakes * A body becomes under stress due to opposing tectonic forces * Rocks begin to distort and strain * Rocks jerk free and pressure is released as seismic waves
40
What depths do intermediate focus earthquakes occur at?
70 - 300km
41
Which plate margins do earthquakes occur at?
All plate margins
42
What is the focus?
The point below the earth's surface that an earthquake originates at
43
What does the Mercalli Scale measure?
The intensity or damage caused by earthquakes. Measured on a scale from 1 to 12.
44
What do isoseismal lines do?
Deliniate different zones of earthquake intensity
45
What is the epicentre?
The point on the earth's surface directly above the focus- most damage caused here.
46
What factors may affect the intensity reading of an earthquake?
Infrastructure or building quality Population density Rock type / sediment Degree of urbanisation
47
What does the Richter Scale measure?
The magnitude/ energy released from an earthquake on a scale of 1 to 10
48
What two measurements are needed to measure the magnitude of an earthquake?
* Distance from epicentre | * The amplitude of the waves
49
What device is used to detect seismic waves?
Seismometer
50
What factors affect the magnitude of an earthquake?
* Length of the fault | * Total amount of displacement
51
Give examples of earthquake hazards
* Avalanches * Tsunamis * Liquefaction * Collapse of infrastructure * Fires * Floods * Disease
52
What happens to the ground during liquefaction?
a condition in which a soil or sediment behaves like a fluid. * Under normal circumstances contact between grains provide cohesive strength and water fills the spaces. * Shaking during an earthquake moves the grains apart and the water rises from between the grains. * After an earthquake the water rises and the grains fall to the bottom.
53
Give some factors that increase the risk of landslides
* Deforestation * Precipitation * Gradient of land * Degree of weathering and erosion
54
What is a tsunami?
A giant wave of water generated by an off shore earthquake that displaces a large section of seafloor which leads the the displacement of a large volume of water
55
What are the three types of landslide?
* Mass movement - any movement of soil or rock down slope due to gravity. * Landslide - Rapid down slope movement of blocks of rock along a slip plane. * Slump - Rotational downwards and outwards movement of incompetent rock and material.

Biology 1 (2 decks)

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