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ERB304 Dynamic Earth: Plate Tectonics > Week 1 > Flashcards

Week 1 Flashcards

1
Q

Temperature

A

Average kinetic energy of the particles in a substance.

Scalar quantity units of Temperature, [T] = Kelvin (K)

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2
Q

P-hacking

A

Artificially producing statistically significant results

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3
Q

Heat

A

A form of energy that flows due to temperature differentiation. It is the total kinetic energy of the particles in a substance.

Units of Heat, [Q] = Joules (J)

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4
Q

Specific Heat Capacity

A

The amount of heat required to raise the temperature of one unit of mass of a substance by one degree Celsius.

It is a measure of a substance’s ability to store heat.

Units of specific heat capacity
[Cp] = J / kg / K

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5
Q

Latent Heat

A

The heat absorbed or released during a phase transition (e.g., from solid to liquid or liquid to gas) at constant temperature.

Latent heat can be either latent heat of fusion (melting/freezing) or latent heat of vaporization (boiling/condensation).

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6
Q

Thermal Conduction / Diffusion

A

The transfer of heat through a material due to molecular collisions. Heat flows from a hotter region to a colder region.

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7
Q

Earth’s Thermal Gradient

A

The rate at which temperature increases with depth in the Earth’s interior.

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8
Q

What is Earth’s Surface Heat Flux?

A

The rate at which heat flows from the Earth’s interior to the surface. It is influenced by factors such as the thickness of the crust, the presence of volcanic activity, and the thermal conductivity of rocks.

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9
Q

What is the source of Earth’s Internal Heat?

A

The primary sources of Earth’s internal heat are:

** Radioactive decay: The decay of radioactive elements within the Earth’s interior releases heat.
Accounts for 50% of present-day surface heat flow

  • Gravitational potential energy: The conversion of gravitational potential energy into heat as the Earth contracts over time.

** Residual heat: Heat left over from the Earth’s formation.

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10
Q

Heat conductor and example

A

Small specific heat capacity

Gold, [Cp] = 0.13 J/kg/K

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11
Q

Heat insulators and example

A

Large specific heat capacity

Aluminium, [Cp] = 0.91 J/kg/K

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12
Q

What are the mechanisms of heat transfer?

A
  • Conduction: The transfer of heat through a material due to molecular collisions.
  • Convection: The transfer of heat by the movement of a fluid (liquid or gas).
  • Electromagnetic Radiation: The transfer of heat through electromagnetic waves, which can travel through a vacuum.
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13
Q

Heat flux density

A

Is the amount of thermal energy
that flows across a unit area of a material per unit time.

[q] = J/m2/s = W/m2

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14
Q

Thermal conductivity

A

Rate of thermal energy transfer over unit distance per unit change in temperature.

[k] = W/m/K

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15
Q

Thermal diffusivity and equation

A

the relative thermal “mobility” of
different materials.

[Df] = m2/s

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16
Q

Fourier’s Second Heat Law

A

Assumes that the rate of change of internal heat is proportional to the spatial gradient of the heat flux density.

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17
Q

Earth’s surface heat flux

Continent
Ocean
Globally

A

Continent
Area = 2.073 x10^14
Heat Flow = 14.7
Mean Heat Flow = 70.9

Ocean
Area = 3.028 x10^14
Heat Flow = 31.9
Mean Heat Flow = 105.4

Global
Area = 5.101 x10^14
Heat Flow = 46.7
Mean Heat Flow = 91.6

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18
Q

How do you calculate the Earth’s
surficial heat flux

A

By independently measuring the thermal conductivity of crustal rocks

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19
Q

Define Convection / Buoyancy and there connection

A

Convection is buoyancy-driven circulating motion within fluids exposed to a thermal gradient.

Buoyancy is responsible for convection: hotter material is less dense (rises) and colder material is more dense (sinks).

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20
Q

Heat Engine

A

A heat engine is a device that converts thermal energy (heat) into mechanical/electrical energy.

exploit thermal expansion, e.g. during a phase transition (liquid->gas), to complete work.

It operates by absorbing heat from a high-temperature source, converting some of it into work, and rejecting the remaining heat to a lower-temperature sink.

21
Q

Discontinuities depths and causes

A

Upper mantle contains distinct
discontinuities at 450km and 670km depth. They are associated chemical phase transitions.

22
Q

Mantle convection

A

The temperature of the Earth increases with depth – a thermal gradient. On geological timescales the mantle is a viscous fluid and therefore convects.

23
Q

Models for mantle convection

A
  1. Whole mantle convection
  2. Two-layer convection
24
Q

What drives plate tectonic motion?

A
  • ridge-push and slab-pull, induced by negative

buoyancy of cold oceanic lithosphere,
* “suction” force of the overlying plate(s)

  • Mantle convection (basal drag)
25
Q

Plate-tectonic probable position “relative”

A

To other tectonic plates

26
Q

Plate-tectonic probable position “absolute”

A

To a fixed reference (usually Earth’s spin axis or hotspot/mantle)

27
Q

Earth’s global magnetic anomalies

A

Magnetic variations in successive bands of ocean floor parallel to the mid-ocean ridges provide evidence of the temporal evolution of oceanic crust.

Can be read like wood rings.

28
Q

Isochron

A

Magnetic anomalies + Fracture zone picks.

A line joining points of equal time intervals or ages.

29
Q

How to calculate the age of tectonic plates

A

Half spreading = stage rotation computed by finite reconstruction rotations.

Spreading asymmetry estimates = Percentage of crustal accretion between pairs of adjacent isochrons by dividing the angular distance between them by the half-stage rotation angle.

30
Q

What causes magnetisation in rocks?

A

Once minerals cool dipoles align with the Earth’s magnetic field.

31
Q

Polar-wander path

A

The path that the magnetic pole appears to take according to the data on a continent.

32
Q

The Wilson Cycle

A

A model that describes the opening and closing of ocean basins and the subduction and divergence of tectonic plates during the assembly and disassembly of supercontinents.

Stages: Continental rifting, oceanic divergence, oceanic convergence, continent-continent collision, post-collisional orogeny, and peneplanation.

Key Processes: Seafloor spreading, subduction, mountain building, and erosion.

33
Q

The Wilson Cycle

Stage A

A

Stage A: Continental Rifting

Initiation: A mantle plume or hot spot upwells beneath a stable continental craton.

Magmatism and Extension: The increased heat from the mantle plume causes the overlying crust to thin, stretch, and develop a rift system. Magmatism often accompanies this process, leading to the formation of basaltic volcanic rocks.

34
Q

The Wilson Cycle

Stage B

A

Stage B: Oceanic Divergence

Seafloor Spreading: As the continental crust continues to rift, a new oceanic basin begins to form. Seafloor spreading occurs along the divergent plate boundary, creating oceanic crust.

Passive Margins: The edges of the separating continents become passive margins, characterized by thick sedimentary wedges deposited from erosion of the adjacent landmasses.

35
Q

The Wilson Cycle

Stage C

A

Stage C: Ocean Basin Maturation

Continued Spreading: The oceanic basin continues to widen as seafloor spreading progresses.

Sedimentation: Sedimentation rates on the passive margins gradually decrease as the distance from the continents increases.

36
Q

The Wilson Cycle

Stage D

A

Stage D: Oceanic Convergence

Subduction Initiation: A subduction zone forms at one or both margins of the oceanic basin, leading to the convergence of tectonic plates.

Oceanic-Continental Subduction: In the most common scenario, oceanic crust subducts beneath continental crust due to its higher density.

37
Q

The Wilson Cycle

Stage E

A

Stage E: Continent-Continent Collision

Mountain Building: As the subducting oceanic plate carries continental margin sediments and volcanic arcs towards the overriding continent, intense deformation and metamorphism occur, leading to the formation of a collisional mountain belt (orogeny).

Magmatism: Magma generated from the subduction zone can rise to the surface, forming volcanic arcs and intrusive igneous rocks.

38
Q

The Wilson Cycle

Stage F

A

Stage F: Post-Collisional Orogeny

Erosion and Isostasy: The collisional mountain belt is subjected to intense erosion, gradually reducing its elevation over time. Isostatic adjustment occurs as the thickened crust rebounds due to the removal of overlying material.

Sedimentation: Sedimentation in foreland basins occurs as eroded material is transported and deposited.

39
Q

The Wilson Cycle

Stage G

A

Stage G: Peneplanation

Long-term Erosion: Over extremely long-time scales, the collisional mountain belt may be reduced to a peneplain, a flat surface formed by erosion.

40
Q

Supercontinents Throughout Earth’s History and there ages

A

Vaalbara: Formed around 3.6 billion years ago from the collision of the Kaapvaal and Pilbara cratons. It was the earliest known supercontinent.

Kenorland: Assembled around 2.7 billion years ago, consisting of parts of present-day North America, Greenland, Scandinavia, and southern Africa.

Columbia (or Nuna): Existed between 2.1 and 1.8 billion years ago, formed from the amalgamation of several smaller continents.

Rodinia: Formed around 1.1 billion years ago and broke apart around 750 million years ago. It was a massive supercontinent that included most of Earth’s landmass.

Pannotia: Assembled around 600 million years ago from the fragments of Rodinia. It was a short-lived supercontinent that existed for about 60 million years.

Pangaea: Formed around 335 million years ago and began breaking apart around 175 million years ago. It was the most recent supercontinent and is well-known for its C-shape.

41
Q

Potential Connections Between Plate Tectonics and Natural Resources? List three points

A

Mineral Formation: Tectonic processes can create conditions for mineral formation, such as hydrothermal vents associated with volcanic activity or metamorphic processes during plate collisions.

Sedimentary Basins: The formation of sedimentary basins through plate tectonics can provide environments for the accumulation of sedimentary rocks, which may contain fossil fuels and other valuable resources.

Geothermal Activity: Areas of volcanic activity and tectonic plate boundaries often have high geothermal gradients, making them suitable for geothermal energy development.

41
Q

The plate tectonics pump

A

Evolution can be driven by continents and continental shelves and moving them to different latitudes and recombining them.

42
Q

How do plate tectonics relate to tropical reefs? List five points

A

Ocean basins can provide suitable conditions for coral reef development, especially in warm, shallow waters.

Island Formation: Volcanic activity often occurs along convergent plate boundaries and hotspots.

Sea Level Changes: This can affect the distribution and survival of coral reefs.

Climate Change: Tectonic plate movements can influence global climate patterns, which in turn affect ocean temperatures and currents. These factors can impact the health and survival of coral reefs.

Nutrient Upwelling: Plate tectonics can influence ocean currents and nutrient upwelling, which can provide essential nutrients for coral reefs to thrive.

43
Q

The oldest oceanic lithosphere is

A

180/230 Ma

44
Q

Geodynamics

A

The study of the forces and processes driving plate tectonics, including mantle convection and heat flow.

45
Q

Geological Features and what causes them. List four.

A

Oceans: Formed through seafloor spreading at divergent plate boundaries.

Mountains: Created by plate collisions and volcanic activity.

Volcanoes: Associated with both convergent and divergent plate boundaries, as well as hotspots.

Earthquakes: Occur along plate boundaries due to tectonic stress.

46
Q

List the three main points of Geophysical Evidence

A

Seismology: The study of earthquakes and seismic waves, used to determine the Earth’s internal structure.

Magnetometry: The study of Earth’s magnetic field, used to reconstruct the movement of tectonic plates over time.

Geochemistry: The study of the chemical composition of rocks and minerals, providing clues about Earth’s history and processes.

47
Q

What are the driving and resisting forces acting on tectonic plates. List nine.

A

RESISTING:
TF = TRANSFORM FAULT FRICTION
DF, CD = BASAL DRAG (CD ON CONT)
CR = CONTINENTAL RESISTANCE
SR = SLAB RESISTANCE BY MANTLE

DRIVING:
RP = RIDGE PUSH
SP = SLAB PULL
SU = SLAB SUCTION
DF = DRAG FORCES CAN PULL PLATES ALONG

48
Q

What drives plate tectonics?

A

THE SLABS DRIVE PLATE TECTONIC

SLAB PULL ~ 1X10 14 N/M

Mueller and Phillips (1991)
analysed force balance on
oceanic margins

They concluded that you
needed between 7x10 12 N/m to
1x10 13 N/m to initiate subduction on a passive margin.

The only force big enough to
do this is a mature subduction
zone.

FLEXURE RESISTANCE ~ 8X10 12 N/M
SHEAR RESISTANCE (OCEAN TRENCH FAULT) ~ 1X10 12 N/M
SLAB RESISTANCE ~ 8X10 12 N/M
RIDGE PUSH ~ 3X10 12 N/M
BASAL DRAG ~ 1X10 12 N/M

ERB304 Dynamic Earth: Plate Tectonics (2 decks)

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