Edurev Geo Topics Flashcards
(79 cards)
1
Q
Deepest depth of oil well drilled
A
8 km
2
Q
Deepest mine in the world
A
Mponeng Gold Mine, 4 km
3
Q
Deepest drilling project
A
Kola Superdeep Borehole, Murmansk Oblast, Russia (Arctic Ocean)
12 km
4
Q
Indirect sources of info on earth’s interior
A
- Temperature
- Pressure
- Density
- Behaviour of seismic waves
- Meteorites
- Moon
5
Q
On average, there is a rise of 1° for every ____ m of depth
A
32 m
6
Q
Reasons for increase in heat and temperature in the earth’s interior
A
- Radioactive disintegration within rocks releases heat
- Internal and external forces like gravitational pull, weight of overlying rocks etc
- Chemical reactions
7
Q
Due to the extreme temperatures in the interior of the earth, all matter within exists in liquid or gaseous state
A
FALSE
The extreme pressure solidifies matter, resulting in liquid state rocks
8
Q
Properties of Aluminum in the Earth’s crust
A
- Third most abundant element in the crust
- Exists in stable combination with other materials like silicates and oxides
- High strength-to-weight ratio due to low density
- Superior malleability, corrosion resistance, good thermal and electrical conducitivity
9
Q
Earth’s density
A
5.5 g/cm³
10
Q
True or false: Earth’s density increases with depth
A
True
11
Q
True or false: The gravitational force changes at different latitudes on the surface
A
True
12
Q
Earth’s interior consists of how many sections? Name them
A
- Crust
- Asthenosphere
- Upper Mantle
- Lower Mantle
- Outer Core
- Inner Core
13
Q
Direct sources of info about earth’s interior
A
- Deep earth mining and drilling
- Volcanic Eruptions
14
Q
Second deepest mine in the world
A
TauTona Mine, 3.9 km
15
Q
Seismic waves can be divided into 2:
A
- Body Waves
- Surface waves
16
Q
Seismic body waves can be divided into 2:
A
- Primary waves (P waves)
- Secondary/ Shear waves (S waves)
17
Q
Features of seismic body waves
A
- Generated due to release of energy at the focus of earthquake
- Move in all directions through the interior of the earth
18
Q
Features of seismic surface waves
A
- Generated when body waves interact with surface rocks
- Longitudinal in nature
- Aka L-waves
- They move only along the surface
19
Q
Features of P waves
A
- Longitudinal
- Fastest velocity: 6-15 km/s
- Can travel through solids, liquids and gases
20
Q
Features of S waves
A
- Transverse
- Reach lower velocities compared to P waves
- Can’t pass through liquids or gases, only solids
- Particles swing side by side under the impact of S waves hence the name shear waves
21
Q
How do seismic waves help us understand the earth’s interior
A
- Differences in arrival times
- Refraction - waves taking different paths than expected
- Shadow zones - absence of seismic waves
- Discontinuity in velocity as a function of depth indicate changes in composition and density
22
Q
Velocities achieved by P waves
A
6-15 km/s
- Earth’s crust - less than 6 km/s
- Lower mantle - 13.5 km/s
- Inner core - 11 km/s
23
Q
Velocities achieved by S waves
A
0-6 km/s
- Earth’s crust - 3-4 km/s
- Upper Mantle - 4-6 km/s
- Lower Mantle - 6-7 km/s
- Core indiscernible (0 - 3 km/s)
24
Q
What’s a shadow zone
A
Area of the earth’s interior where seismic waves disappear
25
Depth of earth's crust
0-70 km
26
What's the lithosphere
Crust + uppermost solid mantle
27
Features of the earth's crust
1. Uppermost layer
2. Solid, rigid and thinner
3. Brittle
28
True or False: The continental crust is thinner than oceanic crust
FALSE
Oceanic crust is thinner
29
Average depth of oceanic crust
5 km
30
Average depth of continental crust
30 km
31
Where is the continental crust thickest, and by how much
Mountainous regions - Himalayas has 70 km crust
32
What are the 2 main parts of the earth's crust
SIAL and SIMA
33
What is SIAL
1. Uppermost thin layer of the earth's crust
2. Rocks contain large proportions of Silica (Si) and Aluminium (Al), hence the name
3. Continental crust is primarily SIAL
4. Avg. density - 2.7 g/cm³
5. Avg thickness - 28 km
34
What is SIMA
1. Comparatively heavier rocks than SIAL
2. Large proportions of Silica (Si) and Magnesium (Ma)
3. Primarily forms the oceanic crust
4. Avg density 3 g/cm³
5. Avg thickness 6-7 km
35
What is average density of SIAL
2.7 g/cm³
36
What is average thickness of SIAL
28 km
37
What is average density of SIMA
3 g/cm³
38
What is average thickness of SIMA
6-7 km
39
What percentage of earth's volume is the crust
0.01
40
What is the earth's radius
6,378 km
41
Thickness of earth's mantle
2,900 km
42
What percentage of earth's volume is the mantle
0.83
43
True or False: Velocity of P waves increase near the mantle
TRUE
from about 6.4 km/s to 8 km/s
44
Why does the velocity of P waves increase near the earth's mantle
Due to the Moho/ Mohorovic Discontinuity
45
What is the asthenosphere
- Upper portion of the mantle
- Lies just below the lithosphere
- 80-200 km
- Highly viscous
- Mechanically weak
- Ductile
- Higher Density than crust
- Main source of magma
46
From what depth does the earth's core begin
2,900 km, extending till the centre of the earth
47
What feature distinguishes the mantle from the core
Gutenberg Discontinuity
48
True or False: The outer core is solid
False
Wholly liquid or semi liquid
49
Extent of outer core
5,150 - 6,378 km
50
Density of outer core
12-13 g/cm³
51
What percentage of earth's volume is the outer core
0.16
52
What percentage of the earth's mass makes up the core
0.32
53
Core is made up of heavier metals, mainly ____
Nickel and Iron (NIFE)
54
Core is also known as ____
Barysphere (heavy metallic rocks)
55
At what depth do diamonds form
150-200 km
56
True or False: Gravity is uniform across the earth
False
Differs at different latitudes - greater near the poles and less at the equator
Gravity also influenced by other factors, causing **gravitational anomalies**
57
How are gravitational anomalies useful
1. Provide info about the distribution of mass of the material in the earth's crust
2. Provide info about the distribution of molten material in the earth's crust
58
How is the earth's magnetic field created
Rapid spinning of the earth creates electric currents in its molten outer core, in turn creating a magnetic field
59
True or False: The magnetic and geographical north and south poles do not coincide.
t
60
How does the earth's magnetic field provide info on earth's interior
Provides info on the distribution of magnetic materials in the crustal portion
61
How do meteorites provide info on the earth's interior?
Meteorites also originated during the formation of the solar system, and therefore may be made of the same materials as the earth.
62
Types of meteorites
Rock and metallic
63
How does the moon provide information on the earth's interior?
The moon is influenced by the earth's mass and the gravitational field exerted by it. Movements of the moon and its distance from the earth help determine the mass of the earth
64
Depending on the depth of the focus of the earthwave, delay between the arrival of the P wave and other destructive waves could be up to ____
60-90 seconds
65
Why are P waves called longitudinal waves
They oscillate in the direction of their movement, making them faster
66
What are transverse waves
Waves that oscillate in the direction perpendicular to their movement
67
Surface waves are also called ____ due to their long wavelength
long-period waves
68
Slowest type of seismic wave
surface waves
69
Why are Secondary (S waves) considered more destructive
Higher frequency and amplitude
70
Why can't S waves pass through liquids or gases
Fluids don't support shear stress
71
True or False: Surface waves die out at great depths in the earth
FALSE
They die out close to the surface
72
What are love waves
Fastest surface wave, movces the ground from side to side
73
What's a Rayleigh wave?
Rolls along the ground, moving the ground up and down as well as side-to-side. The ground moves in the same direction as the wave.
74
Fastest kind of seismic wave
P waves
75
Shadow zones for P waves designated between
103° and 142° on each side of the epicenter
76
Shadow zones for S waves designated between
Everything beyond 103° on each side
77
True or False: Sound waves travel faster in a denser medium whereas light travels slower
True
78
Which types of rocks make up large portions of the earth's crust
Granitic and Basaltic
79
Depth up to which the mantle extends
400 km
