Test 2 - Weathering, Soils, Sedimentary and Metamorphic Rocks Flashcards
What is weathering? What does it do? What does it lead to? (4 points)
(1) Weathering is a surficial process.
(2) It breaks down rock into loose particles
- Creates sediment, soil and dissolved ions in H20
- Changes physical and chemical characteristics of rocks
(3) Weathering leads to development of sediment and sedimentary rock
- Major Earth material @ surface
- Minor in total Earth crust
What are the two types of weathering? Compare them. Can they occur together?
(1) Mechanical weathering and chemical weathering. Mechanical weathering is more physical, focusing on physical disintegration without chemical change; whereas, chemical is well.. chemical, focusing on rock decomposition due to exposure to water and gases into atmosphere.
(2) Mechanical and chemical weathering usually occur together.
Do materials weather at the same rate or at a different rate? Is weathering progressive or not? Does weathering increase or decrease toward the surface? Does increased surface area lead to more weathering?
(1) Materials weather at different rates.
(2) Weathering is progressive.
(3) Weathering increases toward the surface.
(4) Increased surface area does lead to more weathering.
What are the major types of mechanical weathering? (5 points)
Frost action, pressure release, plant growth, burrowing animals, temp. changes: expansion and contraction.
What is frost action? What does it create?
(1) Frost action, otherwise called the freeze-thaw cycle, is the most effective form of mechanical weathering.
(2) Frost action creates boulders.
What is pressure release? How do rocks act during pressure release?
(1) Pressure release is another effective form of mechanical weathering.
(2) During pressure release, rocks break apart along joints and exfoliate. Exfoliation breaks rocks apart in sheets.
Where will mechanical weathering be intense and why?
Mechanical weathering will be intense in cool, abundant water and steep slopes. In cool, abundant water, freezing/thawing assists weathering and on steep slopes, gravity assists weathering. (Gravity can be considered a mechanical process.)
What is chemical weathering? What happens during it? Which conditions are preferred?
(1) Chemical weathering is also called rock decomposition.
(2) Rocks react with H2O and air to produce new chemical products, making new minerals and ions in solution.
(3) Many of these reactions prefer warm, wet conditions.
Why is equilibrium important during chemical weathering?
Equlibrium ensures mineral stability. If minerals are removed from equilibrium, they can break down. E.g. breakdown of granite boulders, pitted limestone, weathered monuments.
Where is oxygen found?
When oxygen combines with other elements what process is occuring?
What is created when oxygen and iron is present?
When alumininum and iron is present?
(1) Oxygen is found abundantly in the atmosphere.
(2) Oxidation is occuring.
(3) Fe-oxide and Fe-hydroxide minerals are produced.
(4) Al-oxide minerals are produced.
What is carbonic acid?
What form does it take on Earth?
What does it aid?
(1) Carbonic acid is essentially CO2 dissolved in H2O, and is an abundant but weak acid.
(2) Often, carbonic acid takes the form of acid rain (2-4 on pH scale) or it can be water percolating through soil.
(3) Carbonic acid aids in dissolution (dissolving of minerals) and hydrolysis (the breakdown of rocks from water).
Name the minerals in order of decreasing weathering rate and increasing stability.
Halite, calcite, olivine, Ca-plagioclase, pyroxene, amphibole, Na-plagioclase, biotite, k-feldspar, muscovite, clays, quartz, aluminum oxide, iron oxide.
What is solution weathering?
The complete dissolution of minerals via chemical weathering.
How does solution weathering affect calcite?
Where do the ions from weathering go?
(1) CaCO3, from caves, becomes discoloured; marble and limestone statues/monuments are dissolved as well.
(2) Products of weathering are carried as dissolved ions by rivers into the ocean. Approximately 4 billion tons per year.
How does solution weathering affect quartz?
What happens to the ions from weathering?
How susceptible is quartz to chemical weathering?
(1) Quartz dissolves into smaller particles of quartz and silica ions.
(2) Common cement in sedimentary rock is formed through the dissolution of quartz by solution weathering.
(3) Quartz is the LEAST susceptible rock forming mineral to chemical weathering, due to the strength of the bonds in its crystal framework.
