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Intro to Earth materials > Sedimentary Rocks > Flashcards

Sedimentary Rocks Flashcards

1
Q

What are Siliciclastic sedimentary rocks?

A

Silica based
Example - Sand
Formed of fragments/grains of pre-existing rock and material.

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2
Q

How are siliciclastic rocks form?

A
  • Erosion
  • Transportation
  • Deposition
  • Burial
  • Diagenesis
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3
Q

What is a turbidity current?

A

Rapid, downhill flow of water caused by increased density due to high amounts of sediment.

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4
Q

Give 3 examples of a sedimentary feature.

A

Wave ripples.
Turbidity currents.
Storm surges.

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5
Q

Define a rock.

A

A naturally occurring aggregate of minerals.

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6
Q

What kind of texture do igneous rocks have?

A

Interlocking with a preferred mineral orientation.

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7
Q

What texture does sedimentary rocks have?

A

Fragmentary.

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8
Q

What is the definition of a sedimentary rock?

A

Rocks that are formed at the earth’s surface a low temperature, <50 degrees, formed by surface processes and are the product of physical and chemical breakdown of other rocks, and biological processes.

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9
Q

What depth does diagenesis occur at?

A

10 Km depth.

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10
Q

What is diagenesis?

A

When grains are fused together by heat and pressure.

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11
Q

What is the average geotherm?

A

25 degrees C/ 1 Km

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12
Q

What is physical weathering?

A

Mechanical breakdown.

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13
Q

What is chemical weathering?

A

Breakdown through chemical means.

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14
Q

Give 5 examples of physical weathering.

A 
Frost action.
Movement of ice.
Salt.
Water.
Wind.
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15
Q

What is frost action?

A

When water enters a crack, freezes and expands, breaking the rock.

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16
Q

What is detrital sedimentation?

A

Solid particles settling out of fluid. (liquid or air)

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17
Q

What is precipitate sedimentation?

A

Solid particles formed out of solution.

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18
Q

What group is limestone in?

A

Carbonate.

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19
Q

Ironstones are evaporates, what does this mean?

A

The ironstones are deposited in a rock by chemical replacement.

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20
Q

What do glaciers grind rocks into?

A

Rock-flour.

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21
Q

U-shaped valleys, hanging valleys, cirques, aretes, fjords and roche montonnes are created by what?

A

Glaciers.

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22
Q

How does salt erode?

A

Salt crystals expanded by periodic hydration and dehydration.

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23
Q

What makes rivers and coasts good at eroding?

A

The sediment they carry.

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24
Q

What are Aeolian processes?

A

Wind.

25
Q

What kind of erosion makes rounded edges?

A

Aeolian and chemical.

26
Q

What minerals are stable at the earths surface?

A

Muscovite, quartz, clay and calcite (sometimes unstable)

27
Q

Minerals that are unstable at the earths surface are?

A

Olivine, pyroxene, garnet, amphibole, plagioclase, k feldspar and biotite.

28
Q

When deep minerals are are brought to the surface are they stable?

A

They become thermodynamically unstable at the surface due to their interaction with water. Compared with shallow formed minerals that are more stable.

29
Q

How does temperature and humidity effect chemical weathering?

A

Higher temperature and humidity increases chemical weathering.

30
Q

What do feldspars weather into?

A

Clay and dissolved ions.

31
Q

What do carbonates weather into?

A

Carbonic acid and calcium.

32
Q

What minerals are easiest to remove from solution?

A

Ca, K and Na.

33
Q

What minerals are next hardest to remove from solution after the 3 easiest?

A

Mg and Fe2 then Si.

34
Q

What are the hardest minerals to remove from solution?

A

Al and Fe3+, they are often left as residue.

35
Q

What is a regolith?

A

A mineral not transported after weathering.

36
Q

What do minerals react with?

A

Temperature, humidity and pH.

37
Q

Rain water is acidic, what is the pH?

A

pH 6.

38
Q

When organic matter oxidizes what is produced?

A

Acidity.

39
Q

What is H+

A

A proton.

40
Q

Is a Low pH acidic or alkaline?

A

Acidic.

41
Q

What are 5 ways weathered material can be transported?

A

Slumps, slides, in solution, as bedload and in suspension.

42
Q

What determines the transport mechanism of weathered material?

A

Grain density, size and current velocity.

43
Q

What does the Hjulstrom diagram show?

A

Velocity against grain diameter.

44
Q

What is Strokes law?

A

This basically says that diameter is the most variable. Finer-grained material is more likely to be carried in suspension. Velocity is proportional to the diameter and density of the grain.

45
Q

What is saltation?

A

The bouncing of grains on a riverbed.

46
Q

What is the bedload?

A

Sediment that rolls along the riverbed.

47
Q

How are sandstones in the UK formed?

A

Aeolian.

48
Q

Where does ice transport material?

A

Within, above and below it.

49
Q

What can ice do to material it is transporting?

A

It can alter it.

50
Q

What kind of sorting is left by ice?

A

Poor sorting.

51
Q

What is required for deposition?

A

A change in physical/chemical environment. e.g. ice melting or a river slowing.

52
Q

What is required for sediments to be preserved?

A

Deposition rates to exceed erosion rates.

53
Q

What is Flocculation?

A

Coming out of solution.

54
Q

Do terrestrial environments have a net erosion or net deposition?

A

Net Erosion.

55
Q

Do marine environments have a net erosion or net deposition?

A

Net deposition.

56
Q

What is induration?

A

Hardening/squeezing out water.

57
Q

What is cementation?

A

Joining of grains.

58
Q

What is the process of diagenesis?

A

Burial with an increase of temperature, compaction, induration, recrystallization and cementation.

Intro to Earth materials (2 decks)

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