Chapter 5 Flashcards
Sedimentary Rocks: Soil and Weathering
Weathering
Physical/chemical breakdown of rock at or near the surface of the Earth to produce sediment.
Mass wasting
Transfer of that material downhill under influence of gravity.
Erosion
Sediment movement by water, ice or wind
Deposition
Sediment reaches a location where it accumulates
Lithification
Sediment turns into sedimentary rock
Mechanical weathering
Breaks the rock into smaller pieces by increasing surface area to allow chemical weathering to be more effective
Frost wedging
Water expands by 9% when it freezes and exerts pressure to break rock. Broken rock falls down to form talus.
Sheeting
Granite at the surface breaks into sheets/onion like layers due to pressure release. Temperature cycles create exfoliation domes.
Chemical weathering
Chemical reactions breakdown rock and ends with chemical sediment, ions dissolved in water. Hot and wet environments accelerate process.
Dissolution
- Electrostatic forces allow ions to be removed from solid. Pure water dissolves rock and the presence of a small amount of acid increases the effect.
Oxidation
Iron minerals that will break down when exposed to the atmosphere
Hydrolysis
Hydrogen ions react with and replace positive ions.
Spheroidal weathering
Manifestation of chemical weathering where sharp corners have more surface area per unit volume than flat surfaces. Chemical weathering is faster on corners and produces a smooth shape.
Regolith
Layer of rock and mineral fragments formed by weathering. Unconsolidated material that is mechanically weaker than the bedrock. Very thin, or non-existent in the Arctic and up to 5m thick in mountains. Thickest in sedimentary basins and along major rivers.
Soil
Interface between lithosphere, biosphere, hydrosphere and atmosphere. A combination of minerals and organic material in the upper part of the regolith.