Ch 15 Flashcards
lowering the surface of continent by weathering, mass wasting, and erosion. Disintegration wearing away and removal of rock material.
Denudation
The destiny of weathering
Carrying away by Erosion
Breaking down of rock into smaller components by atmosphere and biotic changes
Mechanical
Biological
Chemical
Weathering
Short distance down slope movement of broken rock material under influence of gravity.
Mass wasting
Extensive/distant removal, transportation deposition of fragmented rocks
Erosion
Weathering and mass wasting work together to ““they fragment the bedrock while weathering reduces the large rock into smaller more numerous units.
Shape the earths surface
The downslope movement of Rock materials that happens in two ways
- An open scar may be left in the surface that was vacated
- An accumulation of debris deposited somewhere downslope from the scar
Mass wasting
Types of weathering which occurs where the lithosphere and atmosphere meet
Mechanical
Chemical
Microscopic openings
Joints/faults/lava vesicles/solution cavities
Openings in rocks
Cracks from stress
Joints
Breaks in bedrock displacement
Faults
Small Holes
Lava vesicles
Holes in calcareous rocks
Solution cavities
Where they are numerous, they are arranged in sets each comprising a series of approximately parallel fractures
Joints
Two prominent sets of these intersect almost at right angles,
Joint system
Large joints or joint sets that extend for long distances and through a considerable thickness of rocks (functions as plain weakness)
Master joints
Physical disintegration of rock but no change in chemical composition / increases the surface area of chemical weathering
Mechanical weathering
Frozen water expands in wedges and breaks rock
Frost wedging
Frost wedging
Salt wedging
Exfoliation
Mechanical weathering
Less intense than frost. Growth of “ crystals in rock openings-granular disintegration. Pries open rocks grain by grain. Breaks snow.
Salt wedging
Day to night (diurnal) changes. Winter to summer. (Seasonal) changes. Expansion when heated and contraction when cooled. Weakens coherence and breaks. Effective on high elevation mountains. Fires as well.
Temperature changes
Curved layers peel off bedrock. -curved and concentric sets of joints»_space; unloading and pressure release. Shells break away in succession like onion. Mainly in granite and related intrusive igneous rock.
Exfoliation
Caused by atmospheric and biotic agents. Decomposition of rock by chemical alteration of its minerals. -enhanced by mechanical. Weakens coherence and loose particles.
Chemical weathering
High rates in warm moist environments like the wet tropics
Low rates in cold lands and deserts
Chemical weathering
Oxidation
Carbonation
Hydrolysis
Types of chemical weathering
When oxygen dissolved in water comes Ono contact w: certain rock minerals the oxygen atoms combine w/atoms of various metallic elements making up the minerals in the rock and form new products. -iron oxide. RUST
Oxidation
Reaction between carbon dioxide in water and carbonate rocks “limestone” to produce soluble product that can be reduced by runoff or percolation. Ex. Rockfall
Carbonation
Chemical union of water w/another form of substance To produce new compound. Softer/weaker
Hydrolysis
Root penetration
Organic acid
Gopher
Burrowing animals
Biological weathering
Influenced by downslope steepness, gravity, angle of repose. Accumulation of weathered material. An facilitators.
Mass wasting
Steepest angle without downslope transfer
Angle of repose
Soil regolith fragmented rock added. undoes balance and friction causing things to go down faster. is called
Accumulation if weathered material
Water and clay
Increase mobility and fluidity of an object up slope, calles
Facilitators
Landslide Slope failure Heavy rains add weight Earthquake Geological weakness (jointing) Rapid downslope movement Large rigid mass (no fluid flow) of weathered rock
Slides
Slope failure as well.
Weathers debris rotates. Water saturation overland. (Concave.)
Slump
Weathering to “” to “”
Mass wasting and erosion
Fully water saturated weathered debris w/high clay fraction soil. Important catalyst
Flow
Slowest moving. Can barely see it happening. We never know when it does. Entire slope included. Particle by particle movement under freezing to thawing conditions.
Creep
A form of creep. Called soil flows he. Surface becomes saturated and heavy surface sags down slope slowly
Solifluction
Big piece of rock
Talus
Small piece of rock
Scree
Dislodged rocks that become come shaped heaps as they collect in sloping
Talus cones
Extremely slow flows of great masses of accumulated talus in rugged mountain areas
Rock glaciers
