Sedimentary Rocks and Processes (A2)

Question 1

Define Weathering

Answer 1

The in situ breakdown or decomposition of rocks and minerals through chemical, biological and physical processes

Question 2

Define Erosion

Answer 2

The weathering down of rocks by the mechanical action of transported debris

Question 3

What are two types of physical weathering?

Answer 3

Freeze-thaw, Insolation

Question 4

What are five types of chemical weathering?

Answer 4

Carbonation, Oxidation, Hydration, Hydrolysis, Solution

Question 5

What is a type of biological weathering?

Answer 5

Root growth

Question 6

Define Arenite

Answer 6

A sandstone with less than 15% matric

Question 7

Define Wacke

Answer 7

A sandstone with between 15 and 75% matrix

Question 8

Define Lithic Fragment

Answer 8

A rock fragment

Question 9

Define Facies

Answer 9

An area with a distinctive sediment type

Question 10

What are the four facies in a desert environment?

Answer 10

Scree, Alluvial fan, Aeolian sandstone, Playa lake

Question 11

Define Mesa

Answer 11

A portion of a plateau separated from the main plateau

Question 12

Define Butte

Answer 12

An isolated tower, remnant of a plateau

Question 13

Define Wadi

Answer 13

Dry riverbed eroded by flash flooding

Question 14

Define Sabkha

Answer 14

Evaporate deposits left behind after floodwater in coastal areas/lagoons is evaporated

Question 15

What is the trend in grain size in an alluvial fan?

Answer 15

Courser closer to the source and finer further away

Question 16

What are two factors controlling grain size in an alluvial fan?

Answer 16

The amount of water and The velocity of the water

Question 17

What is the mode of transportation of the grains in an alluvial fan?

Answer 17

Carried as a bed load in water

Question 18

What is the reason for deposition of the grains in an alluvial fan?

Answer 18

Grains are deposited when the water loses velocity

Question 19

What is the mode of transportation of the grains in sand dunes?

Answer 19

Wind

Question 20

What is a sedimentary feature commonly found in sand dunes?

Answer 20

Large scale cross bedding

Question 21

What is the texture of the grains in a sand dune?

Answer 21

Sand sized particles, Well rounded, Well sorted

Question 22

What is a playa lake?

Answer 22

Site of a former or occasional lake

Question 23

What are the four main deposits found in a playa lake?

Answer 23

Calcite, Gypsum, Halite, Magnesium

Question 24

What is the reason for the order of the deposits of a playa lake?

Answer 24

Differing evaporation rates of the deposits mean some come out of solution before others e.g. Magnesium is most soluble so is deposited last

Question 25

How are ripples formed?

Answer 25

High velocity water picks up sand grains on the stoss side of the ripple and a drop in velocity on the lee side causes the grain to be deposited

Question 26

What are two fossils found in a fluvial environment?

Answer 26

Roots from plants will be preserved on the flood plain, Fish in rivers

Question 27

What are three bedforms in a fluvial environment?

Answer 27

Floodplain, Point bar, Channel

Question 28

Define Delta

Answer 28

Formed when a current of water carries sediment into deeper, relatively still water, causing sediment to be deposited

Question 29

What are five features of a delta top?

Answer 29

Channels, Point bar sands, Levees, Distributaries, Fan shaped lobes

Question 30

Define Flocculation

Answer 30

Saltwater is an ionic solution which causes clumping and cohesion of clay particles, increasing size and mass allowing it to settle

Question 31

What is Walther's Law?

Answer 31

Facies that occur next to each other are recorded vertically in sequence

Question 32

Define Prograding Delta

Answer 32

Building out into the sea because sediment brought in is greater than subsidence on the delta

Question 33

What is recorded in the deposits in a prograding delta?

Answer 33

Marine transgression

Question 34

Define Retrograding Delta

Answer 34

Reducing in size because sediment brought in is less than subsidence on the delta

Question 35

What is recorded in the deposits in a retrograding delta?

Answer 35

Marine Transgression

Question 36

Define Isostatic

Answer 36

Local change in sea level related to the loading of the lithosphere by sediment deposited on the delta

Question 37

Define Eustatic

Answer 37

Global changes in sea level linked to periods of glacial/interglacial as well as an increase in mid-ocean ridge activity

Question 38

Define Turbidite

Answer 38

A deposit from the turbidity current

Question 39

Define Turbidity Current

Answer 39

An underwater avalanche

Question 40

Define Bouma Sequence

Answer 40

Idealised sequence of one turbidity event

Question 41

What are two reasons a bouma sequence might be incomplete?

Answer 41

Distance from source, Top layers could be eroded

Question 42

What are five conditions required for limestone formation?

Answer 42

Marine water, Shallow water depth, Warm water temperature, Clear water, Well oxygenated and nutrient rich

Question 43

Define Fringing Reef

Answer 43

Formed around the edge of a small landmass/volcanic island, attached to the land

Question 44

Define Barrier Reef

Answer 44

Reef grows at the same rate as the sea levels rise

Question 45

Define Atoll

Answer 45

Eventually, the island is covered by water, creating an atoll and lagoon

Question 46

Where does chalk form?

Answer 46

In shallow water in the photic zone

Question 47

What are the three steps in chalk formation?

Answer 47

(1) Coccolithophore dies (2) Coccolithophore falls apart, taking a long time to settle to the ocean floor (3) Form usually on continental shelf due to Carbonate Compensation Depth (CCD)

Question 48

Define Carbonate Compensation Depth (CCD)

Answer 48

The depth of water carbonate shells will dissolve back into the water

Question 49

What are the two stages of diagenesis?

Answer 49

Compaction and cementation