soil and weathering and erosion(Unit #5)

a mixture of weathered rock, organic matter, mineral fragments, water, and air.

soil

The amount of soil that forms and how long it takes to form is influenced by…..

1. climate, 

2. slope of land (flat or steep) 

3. type of rock, 

4. type of vegetation, and 

5. time.

Different layers of soil are called….

horizons

All the horizons of a soil form a…..

soil profile

The top layer of soil/ A horizon

top soil

contains the most humus

a horizon or top soil

A horizon or top soil properties

• The top layer of soil (Topsoil).

• Dark in color because it 

   contains lot of humus.

• Contains smaller sediment,

   bugs, worms, 

   and plant roots.

• It is the most evolved

   layer of soil.  (This means

   it has changed the most.)

most advanced layer

a horizon

b horizon properties

• Located below the A Horizon

• It’s less evolved and lighter 

   in color than the topsoil.

• Contains only a little humus,

   but does have plant roots.

• Contains minerals that have

   leached down from the topsoil.

order of a soil profile

A horizon, B horizon, C horizon, bedrock

properties of c horizon

• Located below the B Horizon

• It is the bottom horizon

   in the soil profile.

• Contains materials leached from 

   the B Horizon

• Consists of partially 

   weathered rock because it is the

   least evolved layer

• Contains no humus

soil is all solid rock

bedrock

leaching

• he process when minerals are dissolved in water and carried down in a soil profile.

can weathering effect man made objects

yes

two types of weathering

mechanical and chemical

types of mechanical weathering

1) ABRASION (2) ROOT PRY 3 ice wedging and exfoliation

which type of weathering does not change the objects chemical composition

mechanical

abrasion

• wears rock down by the rubbing of one object against another.

Ice Wedging

rain fills crack, then freezes, expands and breaks rock apart

Root Pry –

as plants grow in rocks their roots widen the crack and force rock apart.

Exfoliation

layers or sheets of rock gradually break off

what type of weathering changes the chemical composition of the object

chemical weathering

types of chemical weathering

(1) oxidation 2 plant acids 3 cave formation 4 acid rain

caves

groundwater dissolving limestone

Oxidation

iron to iron oxide

Moss

dissolving rock with its acid

hoodoos

pillar rock structures

what effects the rate of weathering

the climate of an area, rock type, topography

in what climates do each type of weathering occur more easily?

• Chemical weathering occurs more easily in warm, moist climates.

• Physical weathering occurs more easily in cool, dry climates.

what type of rock weathers the most easily

sedimentary

what type of topography weathers quicker

Rocks on a steeper slope are more likely to move as a result of gravity

what are causes of soil loss

over grazing , Urban Construction,Farming