Lecture 17 Flashcards
Mineral
Naturally occurring inorganic compound with a characteristic crystal structure.
EX: quartz, SiO2; crystal structure is a hexagon.
Intrusive igneous
Solidified below surface. Slow cooling - bigger crystals.
Extrusive igneous
Solidified at surface. Fast cooling - small crystals.
Clastic sedimentary rocks
Made of particles (clasts), mostly of other rocks.
Shale - siltstone - mudstone - sandstone - conglomerate.
Exception; clastic limestone (made of skeletons/shells of living things).
Chemical sedimentary rocks
Material dissolved in water become solid (precipitates), accumulates and forms rock.
Evaporites
Becomes solid when water evaporates (rock salt, gypsum).
Organic sedimentary rocks
Formerly living tissue.
EX: coal; plant remains buried in swamp and modified over time.
Metamorphic rocks
One rock changed into another by heat and/or pressure.
New minerals.
Regional metamorphism
Deeply buried rock under high pressure and heat.
Contact metamorphism
Contact with magma
Rock cycle
Rock material changes from one form to another.
SEE CHART.
Chemical weathering
Alteration of minerals.
Water is important in some kinds of chemical weathering; wetter environments typically have more than dry ones.
Temperature also important; warmer = faster chemical reactions.
Chemical stability
How easily a mineral is altered.
EX: quartz; very stable. Olivine; relatively unstable.
Solution
Minerals dissolved in acidic water.
EX: limestone is most common.
Hydrolysis
Water broken up, hydrogen ions replace metals in minerals. Created clay minerals (new mineral, very stable).
Oxidation
Modifies iron and aluminum to produce oxides (like rust). Red soils to do oxidation.
Oxides are new mineral and are stable.
End products of chemical weathering
Stable minerals (like quartz), oxides, clay minerals, soluble ions (soluble ions leave, others remain as parent matter of soils).
Physical weathering
Breaking down of rocks into peaces.
Based on internal or external forces.
Internal expansion
Intrusive igneous rocks formed at higher pressure than at the surface, so expand when they get to surface.
Exfoliation
Example of internal expansion.
When outer layer of granite/rock flakes off.
Frost action
Water freezes in cracks, exerts force on rock.
Number of freeze/thaw cycles are important.
Salt crystal growth
Salt crystals form when salty water evaporates.
Igneous rocks
Formed by cooling of magma.
Classified by mineral content and texture (crystal size).
Sedimentary rocks
Material accumulates and solidifies.
