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GEO1020 > Tectonic geomorphology > Flashcards

Tectonic geomorphology Flashcards

1
Q

What is important to consider when looking at tectonic geomorphology?

A

Time scale

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2
Q

What does a strainmeter measure?

A

Strain over time

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3
Q

Finding the long term trend of what is critical?

A

Long term trend of deformation rates

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4
Q

What do slip rates give an idea of?

A

Time scale

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5
Q

What can subduction cause?

A

Severe earthquakes

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6
Q

What is needed to date features?

A

Well defined markers

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7
Q

How can you identify a young fluvial terrace?

A

Young terraces aren’t deformed

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8
Q

How can you identify older fluvial terraces?

A

They have shifted along

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9
Q

What happens to a river if a fault activates?

A

The river becomes disrupted

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10
Q

Why does Faults Propagation need to be implemented?

A

In an active fault segment, the deformation rate varies so fault zones have varied seismic behaviours

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11
Q

What is the theory behind the earthquake cycle?

A

The size of an earthquake depends upon the amount of time since the previous earthquake

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12
Q

Explain the uniform earthquake model

A

Taking into account fault segmentation, the slip-at-point is constant which means that small catch up events are needed

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13
Q

What is the slip-at-point?

A

It is constant on a central “simple” segment with more complex geometry

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14
Q

Explain the variable slip model

A

Slip-at-point varies from event to event, it is random and there is no pattern

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15
Q

What are along-fault variations in slip distribution not filled with?

A

They are not filled with catch up events but reflect variations in long-term slip rate along the fault and or segmentation of the fault zone

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16
Q

What are short term data within?

A

The seismic cycle (2-3 ka)

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17
Q

Give 4 examples of data that can be used to quantify deformations

A

Seismological data
Paleoseismology data
Geodesy
Historical data

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18
Q

What are two issues with short term data?

A

Variable by faults

Variable with distribution of population today and in the past

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19
Q

What does long-term data do?

A

Average the seismic cycle (2-100ka)

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20
Q

What are 3 types of long term data for quantifying deformations?

A

Tectonic geomorphology
Morphochromology
Average quaternary slip rate

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21
Q

What is the rate equation?

A

Rate = distance / time

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22
Q

What is rate?

A

This is the slope of the linear regression between terrace ages and their offsets

23
Q

What two things are needed to estimate the general trend of slip-rate estimates from goemorphologic evidence?

A

Well-defined and well-preserved geomorphic offset markers

Datable markers

24
Q

Give 4 examples of geomorphic offset markers

A

Fluvial terraces
Alluvial fans
Moraines
Outwash, channel

25
Q

How do fluvial terraces work?

A

Emplacement of a terrace at the time of a large sedimentary discharge which buries the fault. After some energetic discharge the stream incises the channel and the original terrace is abandoned and begins to record faulting, but the riser is constantly refreshed by lateral cutting. During a new episode of entrenchment the terrace is abandoned and there is now a passive marker between this terrace and the original which records lateral displacement.

26
Q

What is an issue with river terraces?

A

All episodes may not be recorded by all rivers and older terraces can be eroded by further incision

27
Q

What can be used to determine the rates of slip, uplift and shortening?

A

Vertical offsets, ages and fault geometry

28
Q

What 3 things show evolution of a normal fault?

A

Triangular facets
Perched valleys
Sinuosity of mountain front

29
Q

What 6 tools are there that can be used for dating?

A 
Field and imagery analysis
Qualitative and quantitative mapping
Digital Elevation Motion(DEM)
Geochronology
Syntheses
Physical modeling
30
Q

The rates of what 7 things can be found from morphochronology?

A 
Deformation
Uplift
Erosion
Incision
Deglaciation
Glaciation
31
Q

What are 6 morphochronological dating techniques?

A 
Lichenometry
Carbonate coatings
Radio carbon dating
Luminescence 
Cosmogenic nuclide dating
U-Th/He
32
Q

How does lichenometry work?

A

Lichen growth determines the age of the exposed rock

33
Q

What is a requirement for lichenometry?

A

Local calibration curve

34
Q

What are the issues with lichenometry?

A

Delay between exposure and calibration curve
Varying growth rates from region to region
Growth rates may vary over time
Short historical timescale

35
Q

What is the timescale for lichenometry?

A

400 years

36
Q

What are carbonate coatings?

A

Pedogenic carbonate is amenable to uranium-series dating, such dates provide estimates o the age of the host rock and
paleoclimate proxy records contained in the carbonate itself

37
Q

What are the requirements for carbonate coatings?

A

Local calibration curve

38
Q

What are the problems with carbonate coatings?

A

Delay between host and exposure and coating development

Varying growth rates that vary over time

39
Q

What is the timescale for carbonate coatings?

A

Less than 0.5 Ma late pleistocene holocene

40
Q

What is radiocarbon dating?

A

A radiometric dating method that uses the naturally occurring radioisotope carbon 14 to determine the age of carbonaceous materials

41
Q

How far back does radiocarbon dating go?

A

Up to about 60,000 years

42
Q

Explain radiocarbon calibration

A

Calibration curve shows radiocarbon age vs calendar years, there is then a range of possible calendar ranges

43
Q

When can dendrochronology calibration be done up to?

A

11ka

44
Q

When can U/Th calibration be done up until?

A

45ka

45
Q

What are 4 methods of morphochronology?

A

Radiocarbon dating
Thermo luminescence (OSL)
Cosmogenic nuclide dating
U-Th/He

46
Q

How does cosmogenic isotope dating work?

A

Cosmic rays hit targets to produce products

47
Q

Explain the altitude dependence

A

Attenuation through the atmosphere

48
Q

Explain the latitude dependence

A

The Earth’s magnetic field deflects the charged particles of the cosmic ray flux

49
Q

How does quantitative morphology work?

A

Measure the offsets by matching piercing points on both sides of the fault

50
Q

What happens if there is lots of soft sediment?

A

There are more layers

51
Q

What is an issue with radiocarbon dating?

A

Difficult to find materials that can be radiocarbon dated

52
Q

Give two examples of materials that can be radiocarbon dated?

A

Charcoal and some shells

53
Q

What element is used for cosmogenic isotope dating?

A

This is non-atmospheric CO2 or an element that is not contained in the rock

54
Q

What increases the production rate?

A

Higher latitudes and altitudes have higher production rates

GEO1020 (16 decks)

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