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1B Earth A > 1-2 > Flashcards

1-2 Flashcards

1
Q

Drift Lithologies

A

The poorly consolidated sediment on top of rock

- usually from Quaternary

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2
Q

Generalised vertical section

A

THe side of a map - show CAT

C = Contact between rock types
A = Age
T = Thicknesses (Relative)
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3
Q

Cross Sections

A

Display spatial distribution in Vertical Plane of all units, structural data etc

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4
Q

Scale of maps of continents, oceans, planets?

A

1:10,000,00 and smaller

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5
Q

Map scale of continents, countries - over multiple sheets

A

1:5,000,000
to
1:1,000,000

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6
Q

Map scale countries, provinces, states

A

1:500,000

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7
Q

Map scale of regional geology

A

1:250,000

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8
Q

Standard map scales for reasonably detailed published maps (3)

A

1) 1:63,360
2) 1:50,000
3) 1:25,000

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9
Q

Standard map scale for field mapping and SSSI

or economic interest

A

1:10,000 and larger

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10
Q

Stratigraphy

A

Description of all rock bodies forming the Earth;s crust and their organisation into distinctive, useful, mappable units

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11
Q

Stratigraphic unit

A

Body of rock established as distinct entity based on any of the properties share by entire rock

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12
Q

Lithostratigraphy

A

Subdivision of rock bodies by lithological properties

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13
Q

What is a formation

A

A basic mappable unit
10s-100s m thick

  • usually of one or more members or beds
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14
Q

What is a group

A

multiple, similar formations

supergroup is several groups

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15
Q

Biostratigraphy

A

Subdivision of rock bodies by fossil content

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16
Q

Biostratigraphic unit

A

biozone

- named for specific index fossil

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17
Q

Chonostratigraphy

- the units

A

based on the time of fomration of rock bodies - form basis of geological time scale

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18
Q

What is a global stratotype

GSSP = global stratotype section and point

A

a fixed positoon in a real rock section - used to define the base of each subdivision of timescale

  • drill in a golden spike
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19
Q

Oldest rock

A

Acasta gneiss
Canada
4.03Ga

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20
Q

Oldest rock in UK

A

Lewisian gneiss

3Ga

21
Q

Geochronology

A

chronostratigraphy provides order

- geo calibrates time - radiometric dating

22
Q

Chronostratigraphic time period names

A

Eonothem, erathem, system, series and stage

23
Q

Geochronological units

A

Eon, era, period, epoch and age

24
Q

Magnetostratigraphy

A

magnetic reversals to order rock bodies

25
Q

Chemostratigraphy

A

geochemical variations such as trace elements and isotopic signatures to order

26
Q

Cyclostratigraphy

A

Study of astronomically-forc ed clmate cycles within sediment successions

  • MILANKOVICH CYCLES
27
Q

Diachronous

A

Opposite to synchronous - sediments layed down in different areas of a single seddiment basin
- so overlap of deposit through time

28
Q

Closure temperature

A

temperature at which diffusion does not occur within a crystal and so the decay system of radioacftive isotopes does not diffuse and mix

  • point at which age can be measured from
29
Q

Rheology

A

study of the flow of matter

- in structural geology - relating response of a material to forces that act upon it

30
Q

Igneous or metamorphic complexes

A

when too difficult to divide rocks

31
Q

Date of anthropocene epoch

A

July 16th 1945

  • Plutonium 239 fallout from nuclear test
  • so can identify in rock record
32
Q

Outlier

A

Younger rock within older rock on the surface - due to erosion and topography

33
Q

Inlier

A

Older rock in younger

34
Q

Waterman-Butterfly Projection

A

Miliar indicatrix across whole map - so size and shape of continents conserved

  • but not on a small scale does it work
35
Q

Structural Geology

A

measurement and interpretation of 1D, 2D and 3D structures in rocks

  • things by deformation - not really sedimentary of magmatic processes
36
Q

Linear Structures in rocks

A

aligned mineral grains, fold axes, fault striae

37
Q

How are linear structures defined?

A

00/000

So plunge first, the angle down from horizontal that a linear feature

38
Q

Planar structures

A

Bedding planes
cleavage
fault surfaces
joints

39
Q

How are planar structures defined?

A

000/00
Strike - the direction from which if you face the plane is dipping to the right

Dip - from horizontal downwards

dip direction - if have no strike measaurement

40
Q

St Francis Dam Collapse

A 
1928
431 deaths
Failure due to rock properties
- west side had conglomerate which was already pretty weak when dry but then
wet = too soft and collapsed
41
Q

Hazard Assessment example - Central Asia

A

Large deformation zones and less money to prevent mass damage

  • so structural geology to prioritise and predict the next fault movement via stress field
42
Q

What is the pitch of a line?

A

when a linear feature is within a bedding plane, the pitch is the angle of direction from the horizontal down the dip

43
Q

Wulff vs Schmid pojection

A

Wulff is equal angle

Schmid is equal area - so preserve density of data points - so more useful

44
Q

Polar vs meridional projection

A

Polar from side - cangt plot planes but can plot poles of planes
- always measure angles

Meridional = to plot planes

45
Q

What does it mean when the poles to bedding form a tight cluster on a stereonet?

A

The beds are uniformally dipping

46
Q

On a stereonet, the pooles of bedding are distributed along a great circle

  • What does this mean?
A

This is a cylindrical fold

- the angle that spans all the points along the great circle is the interlimb angle

47
Q

The profile shape of a fold can be determined by the distribution of the poles of bedding planes along the great circle of a steronet.

What is associated with

a) An angular fold?
b) A rounded fold?

A

a) 2 clusters of poles - so 2 similarly dipping planes

b) A roughly even spread of poles along the great circle

48
Q

What problems can using a stereonet to determine geology present?

A

Hard for asymmetrical folds and overturned limbs

There can also be a sampling bias which can make things look like others

1B Earth A (5 decks)

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