Sedimentary Rocks 2 Flashcards
(27 cards)
What is frost weathering?
Ice gets in the joints of rocks and freezes
Creates scree/ talus
What 3 factors increase frost weathering?
Climate- more intense where temperatures oscillates around 0 degrees
Moisture- more effective in wet climates
Structure- more likely on structurally weak rocks
What is insolation weathering?
The mechanical disintegration of rock due to the daily expansion and contraction of surfaces
Creates scree/ talus
What increases insolation weathering?
Where there is a large diurnal range
Dark surfaces
Different minerals (inter granular stress)
What is hydrolysis?
The decomposition of alkali Feldspar through reaction with water
Affects any rock containing Feldspar
Creates clay and salt
What is solution weathering?
When a mineral can dissolve in water
Affects rocks with natural salts and limestones
Produces salts
What is carbonation?
Breakdown of a mineral due to reaction with carbonic acid
Affects limestone
Creates calcium bicarbonate/ shells
What is oxidation?
Where an element reacts with oxygen and looses an electron
Affects all rocks containing iron
Creates rust
What is erosion?
When material is loosened and dissolved by the mechanical and chemical action of water, ice and wind
What is abrasion?
Wearing away of rock and debris by the grinding action of moving rock
What is attrition?
The wearing down of transported debris due to inter-particle collisions
Where is mature sediment found?
Beach
Desert
Turbidity current
Where is immature sediment found?
Alluvial fan
Floodplane
Turbidity current
Texture of a rock in an alluvial fan?
Coarse grained
Angular
Poor sorted
Immature
Breccia
Formed via rapid deposition from depris laden floods
What happens in normal conditions on an upper river catchment?
Low flow regime
River is relatively shallow and slow
Deposits sand to form small dunes and ripples
What happens in flood conditions at an upper catchment river?
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
Describe a low flow rock
Medium-coarse
Sub angular
Moderate sorting
Immature
Arkose
Describe a high flow rock
Coarse
Angular
Poorly sorted
Mature
Conglomerate
What is a typical intertidal sand deposit at a low tide river channel?
Orthoquartzite?
What is a typical intertidal mud deposited at high tide in a low energy slackwater environment?
Mudstone/shale
Describe a symmetrical ripple
Has equal slopes
Created by waves
Describe an asymmetrical dune
Has a gentler slope and a steeper slope
By wind or water
What ripple is found at an intertidal river channel?
Why?
An asymmetrical
Currents can only travel one way (uni-directional flow)
What ripple is found at an intertidal sandflat?
A symmetrical
The currents travel up and down a beach so are oscillating currents (bi-directional flow)
