1. Weathering / Soils

2. Weathering
The process by which natural forces break down rocks

3. Mechanical Weathering
The breaking up of rocks by physical forces
Ice Wedging: water freezing, expanding and splitting rock
Pressure release: (exfoliation) Inside pressure causes rock to expand when overlying burdens are removed
Plant root growth: plant roots expand cracks
Abrasion: wearing down by friction (moving water rubbing rocks against each other)

4. Root growth
Ice Wedging
Exfoliation
Abrasion

5. Chemical Weathering Breakdown of rock by chemical reactions
Dissolving: minerals dissolving in water or weak acids
Rusting: Iron in rocks combining with oxygen to produce rust (iron oxide)

6. Sediment:
Solid materials (rock fragments, minerals, organic remains) that are carried by water or air that settle on the bottom of a water body or ground.

7. Soil
A mixture of weathered rock particles, organic matter, water and air
Humus: decayed plant and animal material

8. Soil Properties Texture: size of particles in soil
Sand: largest, visible, feels gritty
Silt: smaller – microscopic, feels silky
Clay: smallest – microscopic, feels sticky when wet

10. Soil Horizons
A horizon: upper most layer (topsoil) containing the most humus. Darkest layer
B horizon: little humus, brown to reddish brown, contains clay that washes down from A horizon
C horizon: deepest layer, largest least-weathered rock particles, light yellowish brown

12. Properties continued Color: comes from iron compounds and humus
humus – black,
iron – reddish
original rock- yellows or tans
bright colored soils drain well
Pore space: the spaces between particles
Chemistry: pH (acidity) determines how well nutrients dissolve