Weathering - ✅✅ -the physical breakdown (disintegration) and chemical alteration
(decomposition) of rock at Earth's surface
Mass Wasting - ✅✅-the transfer of rock and soil downslope under the influence of
gravity
Erosion - ✅✅-the physical removal of material by mobile agents such as water,
wind, or ice
Mechanical Weathering - ✅✅ -Physical forces break rocks into smaller pieces
without altering rock's mineral composition
Chemical Weathering - ✅✅-Chemical transformation of rock into one or more new
compounds
Frost Wedging - ✅✅-Caused by expansion of water when it freezes in cracks in
rocks (expands by 9%)
Repeated freezing and thawing causes expansion of cracks in rocks, resulting in
eventual fragmentation of rock
Unloading - ✅✅-Process is called Sheeting
Reduction in pressure as rocks are exposed by erosion allows rocks to expand
Causes outer portions of rocks to break along concentric slabs
Can create an exfoliation dome
Exfoliation Dome - ✅✅
-Large and smooth rounded domes formed due to
unloading and expansion of rocks
Biologic Activity - ✅✅-Growing plant roots can wedge rocks apart, similar to frost
wedging
Biological activity and decay creates acids which can dissolve rocks
Dissolution - ✅✅-A chemical process in which a solid is completely dissolved into
ions by an acid
,Oxidation - ✅✅-Any reaction where an element loses electrons
Often effects iron bearing minerals (i.e. mafic minerals)
Causes rust colored weathering of iron bearing rocks
Hydrolysis - ✅✅-A chemical process in which a H + ion replaces other cations in a
mineral
Requires acidic conditions (i.e. free H+ ions)
Example: alteration of feldspars to clay
"Bauxite" Al(OH) 3 (the ore for Aluminum) - ✅✅ -Under extreme chemical
weathering conditions (e.g. the tropics), hydrolysis can remove nearly all of the
available cations, leaving behind only
Rates of Weathering - ✅✅-Composition
Climate
Particle size or Fractures
Types of Mechanical Weathering - ✅✅-Frost Wedging
Unloading
Biological Activity
Types of Chemical Weathering - ✅✅-Dissolution
Oxidation
Hydrolysis
✅✅
Why are minerals that form at the highest temperatures chemically unstable under
atmospheric conditions? - -Minerals that form at highest temperatures have the
fewest Silica-Oxygen tetrahedra (i.e. are Silica poor)
, Mineral Composition - ✅✅ -The fewer Silica tetrahedra bonds needed to be broken,
the more easily a mineral is chemically weathered
Mafic Rate of Weathering? - ✅✅-Few covalent bonds thus easily weathered
Felsic Rate of Weathering - ✅✅-More covalent bonds thus harder to weather
What does Quartz Weather into? - ✅✅-Quartz grains
What do Fledspars Weather into? - ✅✅-Clay minerals
What does Amphibole Weather into? - ✅✅-Clay Minerals
Limonite
Hematite
What does Olivine Weather into? - ✅✅-Limonite
Hematite
Climate Influences on Weathering - ✅✅ -The wetter and hotter the climate, the
greater the role of chemical weathering
The colder and dryer the climate, the greater the role of mechanical weathering
Particle Size Influences on Weathering - ✅✅-More surface area exposed to
weathering = faster weathering
smaller pieces are easier to weather (more exposure to weathering)
Differential Weathering - ✅✅-Different lithologies weather at different rates
Regolith (Soil) - ✅✅ -A layer of rock and mineral fragments produced by weathering
covering most of the earth
Soil - ✅✅-A combination of minerals, organic material, water, and air
~50% minerals and organic material
~50% pore space filled with air and water
Parent Material - ✅✅-Source of weathered material that soils develop from
Affects rate of weathering and soil fertility
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