Sedimentary Rocks Flashcards
What is Chemical Weathering?
Rocks decompose when the chemical structure of their minerals breaks down.
Produce ions that are removed in a solution leaving an insoluble residue.
What are examples of Chemical Weathering?
Carbonation and Hydrolysis
What is Carbonation?
CO2 reacts with rainwater in the soil to form carbonic acid making the groundwater more acidic than rainwater.
What is Hydrolysis?
Reaction between water and silicate minerals. Hydrogen ions from water and carbonic acid react with mineral ions.
What is Frost Shattering?
Water enters cracks and joints and freezes and expands. This exerts pressure on the rock until it fails and fractures.
What is Exfoliation?
When sheets of rock split off due to differential expansion and contraction of minerals during heating and cooling.
What is a clast?
A fragment of broken rock produced by erosion.
What is root action?
Causes the weathering of rocks by wedging action of plant roots.
How is weathered material transported?
Gravity
Wind
Rivers
Ice
Sea
What is abrasion?
Wearing away of earth’s surface due to wind, water or ice dragging sediment across surfaces.
What is attrition?
The wearing down of sediment grains due to collisions with other grains in transport.
What is solution?
Transport of ions dissolved in water such as K, Ca, Na
What is saltation?
Transport of material by bouncing
What is suspension?
Transport of material in water or air without touching earths surface.
What is traction?
Transport of material by sliding along the surface.
What is mineral maturity?
A measure of the extent of rocks being weathered and being destroyed by attrition
What happens as mineralogical maturity increases?
Increase in textural maturity, one chemically stable mineral, rounded uniform grains.
Wind transport sediment characteristics
Fine to medium grain size
All quartz composition
Well rounded
Very well sorted as easy to carry
High energy environment
Ice transport sediment characteristics
Very coarse (boulders) to very fine (clay)
Varied composition
Angular/Sub-angular roundness
Very poorly sorted, material in every seive
Low energy environment
River transport sediment characteristics
Coarse near source to fine
Quartz and mica with rock frags
Angular near source, sub-angular/rounded downstream
Wide range of sediment size in sieve
High energy environment
Beach transport sediment characteristics
Medium sand
Nearly all quartz some shell and rock fragments
Sub-rounded/rounded
Moderately sorted with sediment in few sieves
High energy
Gravity transport sediment characteristics
Very coarse (boulders) to very fine (soil creep)
Varied composition
Angular to very angular roundness
Very poorly sorted
Diagenesis
Physical and chemical processes change sediments into rocks at low pressures or near the earth’s surface
