Weathering and soil formation

what causes soil formation?

weathering

weathering

physical and chemical changes that occur in sediments and rock when exposed to the atmosphere and biosphere

why does weathering occur?

because minerals formed deep in earths crust are not stable at earths surface

what is the most stable mineral to weathering?

iron oxides

what is the most susceptible mineral to weathering?

halides

halides

Salt

what do mafic minerals decompose to?

oxides

what do feldspars (granites) decompose to?

clay

what does quarts decompose to?

doesn’t decompose

what does pyroxene degrade to?

iron oxide

list the four methods of mechanical weathering:

freeze-thaw, thermal expansion, organic activity, mechanical abraission

thermal expansion

differential thermal expansion of minerals creates stress in rocks

bedrock

underlying rock of any kind

regolith

a layer of broken pieces of rock and slightly altered rock that overlies the bedrock

soil

a layer of altered mineral material usually mixed with organic matter

How does increased surface area impact weathering?

it increases the surface area for chemical weathering

what type of weathering dominants in colder climates?

physical weathering?

what type of weather dominates in warmer climates?

chemical weathering

how does weathering impact atmospheric CO2?

it decreases it

list the controls of soil formation:

parent material, climate, biosphere, time, topography

O horizon

organic material

A horizon

decayed organic material

E horizon

washes out elements

B horizon

clay, Iron and element accumulation

C horizon

bedrock

permafrost

ground that remains frozen for over two years straight