•Sedimentary Rocks

Question 1

What is weathering?

Answer 1

The disintegration or decomposition of insitu rock at or near the earth’s surface by mechanical breakdown and chemical alteration

Question 2

What is mechanical/ physical weathering?

Answer 2

The in situ disintegration of rock due to the development of stress within the rock caused by changing weather

Question 3

What is chemical weathering?

Answer 3

The decomposition of rock due to the chemical reaction of rock minerals with weakly acidic rock

Question 4

What is frost weathering?

What rocks are affected?

What are the products?

Answer 4

Caused by the expansion of ice within rock. Water freezes into ice causing a 10% volume increase which causes stress

Happens in all rock but especially in porous and fractured rock

Created frost shattered, angular rock degree called scree or talus

Question 5

What is insolation weathering?

What rocks are affected?

What are the products?

Answer 5

Caused by the daily expansion of rock exposed to the suns heat

Happens in all rock but especially those with dark colours

Angular rock debree fragments called scree or talus

Question 6

What is hydrolysis?

What rocks are affected?

What are the products?

Answer 6

Water reacts with Feldspar and causes decomposition

Affects any rock containing Feldspar e.g Granite

Creates Clay and Salt

Question 7

What is carbonation?

What rocks are affected?

What are the products?

Answer 7

Water reacts with limestone and causes the limestone to change into soluble calcium bicarbonate

Affects limestone

Creates calcium bicarbonate (shells)

Question 8

What is oxidation?

What rocks are affected?

What are the products?

Answer 8

Minerals containing Fe react with oxygen and turn into ferrous iron oxide I.e rust

Affects all rock containing iron ( mafic)

Created rust

Question 9

What is solution weathering?

What rocks are affected?

What are the products?

Answer 9

Rocks dissolve in the prescence of water

Affect natural salts and limestone

Creates salt

Question 10

What is erosion?

Answer 10

The wearing down of transported debris because of inter-particle collisions

Question 11

What is traction?

Answer 11

rounded particles are rolled by force of flowing water

Question 12

What is saltation?

Answer 12

Series of hops caused by a sudden increase in energy (flat)

Question 13

What is flocculation?

Answer 13

Salt in sea water ensures electrical charge causing clay particles attracting them together so they become bigger and sink

Question 14

Grain sizes

Answer 14

Coarse >2mm
Medium 0.06- 2mm
Fine <0.06

Question 15

Sorting

Answer 15

Poorly sorted
Moderately well sorted
Well sorted

Question 16

Powers roundness chart

Answer 16

Very angular 
Angular 
Sub angular 
Sub rounded 
Rounded 
Well rounded

Question 17

Cements

Answer 17

Iron oxide= red= desert

Calcite= fizzes= beach from shells

Silica= grey/yellow= river environments

Question 19

Conglomerate

Answer 19

Coarse
Poorly sorted
Sub angular/ sub rounded

Shingle beach

Sand

Question 20

Breccia

Answer 20

Coarse
Poor
Sub angular/ angular

Alluvial fan

Sand and large particles

Question 21

Greywacke (sandstone)

Answer 21

Fine- medium
Moderate
Sub-rounded

Undersea Mudflow
Turbidity currents

Mudmatrix and sand

Question 22

Arkose (sandstone)

Answer 22

Medium-coarse
Moderate
Sub-angular

Flood plane
Braided river

Quartz and feldspar

Question 23

Orthoquartzite (sandstone)

Answer 23

Medium grained
Well sorted
Rounded

Sand beach

Quartz

Question 24

Bioclastic limestone

Answer 24

Medium-coarse
Poorly sorted

Warm tropical seas and beaches

Fossilised shells
Mixture mud
Sparry calcite crystals

Question 25

Chalk

Answer 25

Fine grain
Well sorted

Warm
Deep sea
Still water

Cocolith (zoo plankton)
Micrite mud

Question 26

Oolitic limestone

Answer 26

Medium grained
Well sorted

Tropical beaches
Wave action moved a shell or sand nucleus over the beach micrite mud sticks to it

Ooliths
Soft micrite mud
Sparry calcite crystals

Question 27

Normal bedding

Answer 27

Layer caused by a single pulse of sedimentation

Less than 1cm thick is called a laminae
Separated by lamination planes

Question 28

Ripples and dunes

Answer 28

<10cm ripples
>10cm dunes
Asymmetric

Question 29

Cross bedding

Answer 29

Inclined foreset beds
Climbing ripples

> 5m deserts
0.5-5m shallow marine
0.1-0.5m rivers
<0.1 beach

Lee
Stoss
Foreset

Question 30

Graded bedding

Answer 30

Decrease in grain size from bottom upwards

Rapid deposition

Question 31

Dessication cracks

Answer 31

Surface of sediment drys, contracts and cracks

Polygonal pattern

Question 32

Sole structures

Answer 32

Convex irregularities found on the underside of a bed of sandstone

Question 33

Flute cast

Answer 33

Bulges that occur on the base of turbidite deposits

Turbidity current of up to 100mph creates a blast wave and scours out the soft sea bed
The scouts are infilled by sand/mud

Question 34

Tool marks

Answer 34

Impact scares created by hard tools (stone or fossil fragments) as it is swept over soft sediment.

Turbidity current of up to 30mph carrying a shell that creates an impact impression or tool mark which is then infilled

Question 35

What is a groove Mark?

Answer 35

A linear ridge on the base of a sandstone bed that if formed by the infilling of a groove cut into underlying rock

Turbidity current of up to 100mph carrying a large stone digs into the soft sediment
Cuts a groove into the sediment which is later infilled

Question 36

Load cast

Answer 36

Bulbous loves that penetrate downwards into the rock. Heavier saturated sand sinks into soft rock beneath

Creates flame structures

Question 37

What is a mature rock?

Answer 37

Stable rock that has undergone chemical breakdown during transportation

Question 38

What is an immature rock?

Answer 38

A rock that was deposited before weathering and erosion so contains unstable components such as rocks containing feldspars

Question 39

Shale

Answer 39

Fine grained
Well sorted
Shape- N/A

Deep sea