surface processes;making new rocks

Question 1

give examples of physical weathering

Answer 1

Ice wedging
jointing

Question 2

what structure is a product of ice wedging?

Answer 2

Talus cones; base of cliffs

Question 3

what are the origins of jointing?

Answer 3

Cooling and contraction; columnar joints from lava flow

Expansion after being unloaded; jointed bedding planes from erosion of top layers.

Enlarged by chemical weathering; Limestone dissolved by acid rain

Exfoliation; layers peel off parallel to rock surface

Question 4

What is the importance of jointing?

Answer 4

Groundwater flows through joints.

Question 5

What are some associated processes involved in jointing?

Answer 5

Mineral wedging
Thermal expansion; spalling
Root wedging
Animal activity

Question 6

how does jointing increse chemical weathering?

Answer 6

Chemical weathering acts faster on rocks with exposed surfaces.

Question 7

Give examples of chemical weathering

Answer 7

Dissolution
Hydrolysis
Hydration
Oxidation

Question 8

What are examples of minerals that often fall victim to dissolution?

Answer 8

Salts (halite) and carbonates (calcite)

Question 9

Give an example of a formula for dissolution

Answer 9

Calcite (limestone) + Carbonic acid = Calcium ions + Bicaronate ions

Question 10

What is a common formula for hydrolysis?

Answer 10

Feldspar (granite) + Carbonic Acid + H2O = Kaolinite (clay) + Dissolved ions + Silicic acid

Question 11

What is a real world example of hydrolysis?

Answer 11

St Austell, Cornwall
Feldspar into “china clay”

Question 12

What is a common formula for hydration?

Answer 12

Anyhydrite (crystal) + H2O = Gypsum (plasterboard)

Question 13

What is a common formula for oxidation?

Answer 13

Fe sulphide + O2 + H2O = Fe oxides/hydroxides + sulphur compounds (RUST)

Question 14

What is a rock example of oxidation?

Answer 14

Pyrite “fools gold”

Question 15

What are the main products of weathering?

Answer 15

Dissolved ions
Eroded rock material
new minerals formed
Regolith

Question 16

What are the factors controlling weathering?

Answer 16

Mineral composition
Rock type and texture
climate

Question 17

How does climate affect weathering?

Answer 17

Increasing temp by 10°C doubles rate of chemical weathering.
If annual rainfall is <25cm, weathering is minimal.

Question 18

Is weathering self limited?

Answer 18

Yes; Regolith limits water movement which then limits uplift.

Question 19

What are the importances of weathering?

Answer 19

Formation of sedimentary rocks

Regulates Earths Carbon balance.

Shaping the landscape

Economic mineral deposits.

Question 20

What are the steps to forming a sedimentary rock?

Answer 20

Weathering

Erosion

Transportation

Deposition (sedimentation)

Burial + compaction

Diagenisis

Question 21

What conditions do diagenisis occur in?

Answer 21

Shallow depths and at around 300°C

Question 22

What processes occur in diagenisis?

Answer 22

Compaction; squeezing out water.

Cementation; Precipitation of new minerals.

LITHIFICATION.

Question 23

What is the difference between Porosity and Permeability?

Answer 23

Porosity; Indicates the empty spaces in rocks

Permeability; Ability for fluids to flow through th rock.

BETTER THE SORTING, THE HIGHER THE POROSITY.

Question 24

What are the three types of sedimentary rocks?

Answer 24

Chemical/biochemical; Limestone

Organic; Coal

Clastic; Quartz

Question 25

How are Clastic rocks classified?

Answer 25

Grain size Grain shape Sorting Compositional Maturity

Question 26

What are the general grain sizes of clastic rocks?

Answer 26

Sandstone; 2mm Siltstone; .062mm Claystone; .004mm

Question 27

What are the two major grain shapes?

Answer 27

Breccia (Angular) Conglomerate (Rounded)

Question 28

What is the general trend compositional maturity follows?

Answer 28

Alluvial Fan to River to Beach.

Question 29

Where would mature clasts be found?

Answer 29

Quartz are concentrated in AEOLIAN landscapes (beaches)

Question 30

Where would the major compositional groups of sandstone be found?

Answer 30

Lithic sandstone; A delta Arkose; Alluvial fan Quartz Arenite; Beach Graywacke; Submarine fan