Sedimentary Rocks 2

Question 1

What is frost weathering?

Answer 1

Ice gets in the joints of rocks and freezes

Creates scree/ talus

Question 2

What 3 factors increase frost weathering?

Answer 2

Climate- more intense where temperatures oscillates around 0 degrees

Moisture- more effective in wet climates

Structure- more likely on structurally weak rocks

Question 3

What is insolation weathering?

Answer 3

The mechanical disintegration of rock due to the daily expansion and contraction of surfaces

Creates scree/ talus

Question 4

What increases insolation weathering?

Answer 4

Where there is a large diurnal range

Dark surfaces

Different minerals (inter granular stress)

Question 5

What is hydrolysis?

Answer 5

The decomposition of alkali Feldspar through reaction with water

Affects any rock containing Feldspar

Creates clay and salt

Question 6

What is solution weathering?

Answer 6

When a mineral can dissolve in water

Affects rocks with natural salts and limestones

Produces salts

Question 7

What is carbonation?

Answer 7

Breakdown of a mineral due to reaction with carbonic acid

Affects limestone

Creates calcium bicarbonate/ shells

Question 8

What is oxidation?

Answer 8

Where an element reacts with oxygen and looses an electron

Affects all rocks containing iron

Creates rust

Question 9

What is erosion?

Answer 9

When material is loosened and dissolved by the mechanical and chemical action of water, ice and wind

Question 10

What is abrasion?

Answer 10

Wearing away of rock and debris by the grinding action of moving rock

Question 11

What is attrition?

Answer 11

The wearing down of transported debris due to inter-particle collisions

Question 12

Where is mature sediment found?

Answer 12

Beach
Desert
Turbidity current

Question 13

Where is immature sediment found?

Answer 13

Alluvial fan
Floodplane
Turbidity current

Question 14

Texture of a rock in an alluvial fan?

Answer 14

Coarse grained

Angular

Poor sorted

Immature

Breccia

Formed via rapid deposition from depris laden floods

Question 15

What happens in normal conditions on an upper river catchment?

Answer 15

Low flow regime

River is relatively shallow and slow
Deposits sand to form small dunes and ripples

Question 16

What happens in flood conditions at an upper catchment river?

Answer 16

Water depth is high and fast

River is highly erosive and carved out new channels

As it begins to wane, coarse then medium grains can be deposited

Question 17

Describe a low flow rock

Answer 17

Medium-coarse

Sub angular

Moderate sorting

Immature

Arkose

Question 18

Describe a high flow rock

Answer 18

Coarse

Angular

Poorly sorted

Mature

Conglomerate

Question 19

What is a typical intertidal sand deposit at a low tide river channel?

Answer 19

Orthoquartzite?

Question 20

What is a typical intertidal mud deposited at high tide in a low energy slackwater environment?

Answer 20

Mudstone/shale

Question 21

Describe a symmetrical ripple

Answer 21

Has equal slopes

Created by waves

Question 22

Describe an asymmetrical dune

Answer 22

Has a gentler slope and a steeper slope

By wind or water

Question 23

What ripple is found at an intertidal river channel?

Why?

Answer 23

An asymmetrical

Currents can only travel one way (uni-directional flow)

Question 24

What ripple is found at an intertidal sandflat?

Answer 24

A symmetrical

The currents travel up and down a beach so are oscillating currents (bi-directional flow)

Question 25

Describe a desert rock

What structures may prove its location?

Answer 25

Medium grained
Well sorted
Well rounded

Desiccation cracks
Large scale cross bedding
Frosted/scratched sand grains

Question 26

What are turbidity currents?

Answer 26

Undersea flows of muddy debris and water

Question 27

Where do turbidity currents occur?

Answer 27

On over steepened delta fronts that have become unstable due to deposition during flooding

At the edge of continental shelves where thick sequences of rocks have accumulated