Sedimentary Rocks

Question 1

What are Siliciclastic sedimentary rocks?

Answer 1

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

Question 2

How are siliciclastic rocks form?

Answer 2

• Erosion
• Transportation
• Deposition
• Burial
• Diagenesis

Question 3

What is a turbidity current?

Answer 3

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

Question 4

Give 3 examples of a sedimentary feature.

Answer 4

Wave ripples.
Turbidity currents.
Storm surges.

Question 5

Define a rock.

Answer 5

A naturally occurring aggregate of minerals.

Question 6

What kind of texture do igneous rocks have?

Answer 6

Interlocking with a preferred mineral orientation.

Question 7

What texture does sedimentary rocks have?

Answer 7

Fragmentary.

Question 8

What is the definition of a sedimentary rock?

Answer 8

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.

Question 9

What depth does diagenesis occur at?

Answer 9

10 Km depth.

Question 10

What is diagenesis?

Answer 10

When grains are fused together by heat and pressure.

Question 11

What is the average geotherm?

Answer 11

25 degrees C/ 1 Km

Question 12

What is physical weathering?

Answer 12

Mechanical breakdown.

Question 13

What is chemical weathering?

Answer 13

Breakdown through chemical means.

Question 14

Give 5 examples of physical weathering.

Answer 14

Frost action.
Movement of ice.
Salt.
Water.
Wind.

Question 15

What is frost action?

Answer 15

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

Question 16

What is detrital sedimentation?

Answer 16

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

Question 17

What is precipitate sedimentation?

Answer 17

Solid particles formed out of solution.

Question 18

What group is limestone in?

Answer 18

Carbonate.

Question 19

Ironstones are evaporates, what does this mean?

Answer 19

The ironstones are deposited in a rock by chemical replacement.

Question 20

What do glaciers grind rocks into?

Answer 20

Rock-flour.

Question 21

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

Answer 21

Glaciers.

Question 22

How does salt erode?

Answer 22

Salt crystals expanded by periodic hydration and dehydration.

Question 23

What makes rivers and coasts good at eroding?

Answer 23

The sediment they carry.

Question 24

What are Aeolian processes?

Answer 24

Wind.

Question 25

What kind of erosion makes rounded edges?

Answer 25

Aeolian and chemical.

Question 26

What minerals are stable at the earths surface?

Answer 26

Muscovite, quartz, clay and calcite (sometimes unstable)

Question 27

Minerals that are unstable at the earths surface are?

Answer 27

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

Question 28

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

Answer 28

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

Question 29

How does temperature and humidity effect chemical weathering?

Answer 29

Higher temperature and humidity increases chemical weathering.

Question 30

What do feldspars weather into?

Answer 30

Clay and dissolved ions.

Question 31

What do carbonates weather into?

Answer 31

Carbonic acid and calcium.

Question 32

What minerals are easiest to remove from solution?

Answer 32

Ca, K and Na.

Question 33

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

Answer 33

Mg and Fe2 then Si.

Question 34

What are the hardest minerals to remove from solution?

Answer 34

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

Question 35

What is a regolith?

Answer 35

A mineral not transported after weathering.

Question 36

What do minerals react with?

Answer 36

Temperature, humidity and pH.

Question 37

Rain water is acidic, what is the pH?

Answer 37

pH 6.

Question 38

When organic matter oxidizes what is produced?

Answer 38

Acidity.

Question 39

What is H+

Answer 39

A proton.

Question 40

Is a Low pH acidic or alkaline?

Answer 40

Acidic.

Question 41

What are 5 ways weathered material can be transported?

Answer 41

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

Question 42

What determines the transport mechanism of weathered material?

Answer 42

Grain density, size and current velocity.

Question 43

What does the Hjulstrom diagram show?

Answer 43

Velocity against grain diameter.

Question 44

What is Strokes law?

Answer 44

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.

Question 45

What is saltation?

Answer 45

The bouncing of grains on a riverbed.

Question 46

What is the bedload?

Answer 46

Sediment that rolls along the riverbed.

Question 47

How are sandstones in the UK formed?

Answer 47

Aeolian.

Question 48

Where does ice transport material?

Answer 48

Within, above and below it.

Question 49

What can ice do to material it is transporting?

Answer 49

It can alter it.

Question 50

What kind of sorting is left by ice?

Answer 50

Poor sorting.

Question 51

What is required for deposition?

Answer 51

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

Question 52

What is required for sediments to be preserved?

Answer 52

Deposition rates to exceed erosion rates.

Question 53

What is Flocculation?

Answer 53

Coming out of solution.

Question 54

Do terrestrial environments have a net erosion or net deposition?

Answer 54

Net Erosion.

Question 55

Do marine environments have a net erosion or net deposition?

Answer 55

Net deposition.

Question 56

What is induration?

Answer 56

Hardening/squeezing out water.

Question 57

What is cementation?

Answer 57

Joining of grains.

Question 58

What is the process of diagenesis?

Answer 58

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