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Landscapes are shaped by turning rocks into…
sediments
What are sediments?
fragments of pre-existing rocks
What is physical weathering?
breaking rocks into smaller pieces
What is chemical weathering?
changing the chemistry of the rocks
True or False: physical and chemical weathering act in concert (simultaneously)
true
Smaller pieces of weathered rock —> ?
more reactions (some surface area is exposed to chemical weathering, but it increases as the reactions increase)
The weaker the rock is, the…
easier it is to break
Examples of Wedging (physical weathering)
frost forcing small cracks wider, mineral grains forcing small cracks wider, roots forcing small cracks wider
Unloading (physical weathering)
releasing stress and causing expansion; occurs spontaneously
Exfoliation
occurs everywhere (ex. fractures parallel to the surface)
Examples of Dissolution (chemical weathering)
water dissolving salt, water getting into fractures of rock and dissolving the rock, rainfall dissolving the atmospheric CO2 creates natural acidity
Weak Acid + Limestone = ?
weathered rock
Oxidation (chemical weathering)
turns soluble Fe2+ into insoluble Fe3+ / removes iron from the solution
Hydrolysis (chemical weathering)
ions replaced by hydrogen: KAlSi3O8 + H2O → HALSi3O8 + K+ + OH- ; feldspar weathered along cleavage planes
What is spheroidal weathering?
combining physical and chemical weathering
Process of Spheroidal Weathering
1 - water penetrates extensively jointed rock; 2 - chemical weathering decomposes minerals and enlarges joints; 3 - rocks are attacked more on corners and edges and take on a spherical shape
What is weathering susceptibility?
a function of the: properties of the original rock, climate, presence or absence of soil and vegetation, and length of exposure
The minerals that form first will be…
the ones that weather first
True or False: minerals and rocks weather at the same rate
false
Rocks that resist weathering also resist…
erosion
What is a talus?
a slope of rock fragments
What is the middle ground made up of?
lithosphere (inorganic) and biosphere (organic); 50% pores and 50% solids
What is mineral matter known as?
regolith
What is organic matter known as?
humus
What is soil made of?
components of the physical and chemical weathering of rocks (quartz, clays, iron oxides)
What are soil profiles?
slices into the ground that show the differing soil horizons (horizons vary in size and not all may be present)
Process of Rain Going Into the Ground
rain enters ground —> plant debris accumulates —> worms churn —> microbes and fungi metabolize —> roots weather minerals —> downward-percolating water transports ions and clay —> Iions and clay accumulate
Order of Soil Horizons
O, A, E, B, C, U, unweathered parent material
O Horizon
loose and partly decayed organic matter
A Horizon
mineral matter mixed with some humus
E Horizon
zone of eluviation and leaching
B Horizon
accumulation of clay transported from above
C Horizon
partially altered parent material
Thicker soil develops on…
flat terrain
Thinner soil is on…
steep slope because of erosion
Transported soil can be developed on…
unconsolidated stream deposits
High Temperature + High Precipitation = ?
high vegetation
The tropics have the ________ soils, desert regions have the ________ soils.
thickest; thinnest
As more trees/plants grow, the _ _______ gets thicker, which in turn makes the other horizons much deeper.
O Horizon
