Weathering Flashcards
Chemical Weathering
Wet, humid conditions. Rocks decay or dissolve as chem composition is altered
Mechanical weathering
Areas of extreme temp, Rock is physically broken down into smaller pieces, chem comp NOT altered
Biological Weathering
Breakdown of rock by action of plants and animals
Factors that affect rate of weathering
- Rock type
- Surface A
- Climate
- Vegetation
- Human Activity
Rock type
Rocks containing soft minerals, such as calcite or iron, weather more rapidly than others with hard minerals like quartz
Surface Area
Rocks with larger s.a weather faster than smaller s.a
Climate
High levels of precipitation and larger temp ranges accelerate w
Vegetation
Bare surfaces are weathered faster than surfaces with veg.
Human Activity
Pollution speeds up weathering, gases, fossil fuels, acid rain, dissolves minerals
Freeze Thaw Action Pt. 1
Mountainous areas, temps fluctuate ^ and ↓ freezing point of 💧, 🏞️ have more precip due to relief rainfall + snowfall.
Freeze thaw action Pt. 2
E.g Croagh Patrick
Water gathers in joints of rocks, freezes when temps drop ↓ 🥶. 💦 Becomes 🧊, it’s volume expands approx 9% , widening the joint, daytime, rising temps melt the 🧊. Freeze thaw is repeated, cracks slowly increase, cracks, sharp rocks called scree move downslope under influence of gravity
Exfoliation (Onion)
E.g Sahara
Hot desert regions, diurnal temperature range (big diff, day and night) , Sunshine brings very high temps, outer layer gets really hot, expands, no clouds at night, heat escapes, temp drops, cool and contract, repeats and exerts stress eventually causing it to crack, thin layer peels away
Salt crystalisation
E.g California Coastline
Dry climates + salt solutions, coastal, salt seep into joint, high temp causes evaporation, leaving crystals behind, crystals expand putting pressure on rock, breaks down, honeycomb effect
Pressure Release
E.g Granite in Wicklow
Snow, ice, soil or rock cover underlying layer of rock, then removed,
1. Weathering removed schust and slate in Wicklow lying on granite
2. Pressure exerted on granite released, able to expand
3. Created stresses on the rock which eventually fractured in sheets
4. Over time, rock broke away along line of fractures
Processes and Landforms: Denudation
The collective name for the weathering and erosion of rocks on the earth’s surface
P & L: Erosion
When rocks are broken down and they’re then transported to new location by agent that broke it down.
Underground features formed in karst regions
- Carbonation (Carbonic acid dissolves calcium carbonate)
- Percolation (Calcium bicarbonate moves through joints and B. Planes)
- Evaporation (Water and co2 evaporates)
- Deposition (Calcite is deposited)
Stalactites
Grow downwards, calcium bicarbonate and grit solidified
Stalagmites
Soluble calcium bicarbonate falls from stalactites, forms stalagmite going upwards
Pillars
Columns that form when stalagmites and stalactites grow and join together
Curtains
Calcite deposits from continuous narrow structure hanging roof of the cave grow down with age.
Caves and caverns
Caves are underground passages, caverns are underground chambers found in karst regions
E.g Aillwee Caves
How they’re formed
Erosive action of underground streams, solution, Hydraulic action and abrasion
