Notes on Basic Geology
Notes created & information organization based on the book:
The Dynamic Earth - an introduction to physical geology"
Brian Skinner & Stephen C. Porter   (further book information here)
also look at for additional resource information
Weathering - Page 8

Rate of Soil formation vs. Rate of Loss

The Good news: the rate of soil formation is faster than would be expected if it were related directly to the rate of chemical erosion of bed rock. Soil formation is very fast in the first few years of conversion, but then gradually reaches steady state and slows from then on.

The Bad news: due to deforestation and poor land management by man, the rate of soil loss now far exceeds the rate of new soil creation. The worlds most productive soils are being depleted at the rate of about 7% per decade. At the current rate of loss, about 40% of our total soil will be gone in 70 years.

What can be done?

1.) reduce defoliation
2.) rotate crops
3.) use contour plowing
4.) use terracing
5.) plant in the off season
6.) manage over grazing

Weathering and the Rock Cycle

Plate tectonics are responsible for bringing new rock to the surface. Without new rock, the continents would eventually weather away and all land would be at or near sea level.

The sun provides the energy to move water in its cycles and thus produces the energy for weathering, both physical and chemical.

Most difficult to weather

Easiest to weather

Ferric (Fe+3) Oxide/Hydroxides

Already oxidized


Mg+2, Fe+2 rich
Minimal silica chains

Aluminium Oxide/Hydroxides

Already oxidized
Strong bond to oxygen

Calcium Feldspars

Ca+2 rich - lower percentage silica


Already oxidized
Best Cross linking


Mg+2, Fe+2 rich
No silica chains

Clay minerals

Already weathered

Carbonates (Calcite)

100% soluble with acid !


Better cross linking of silica - already hydrated


100% soluble !

Potassium Feldspar

Some cross linking of silica - better percentage silica


100% soluble !


Better cross linking of silica - already hydrated

Sodium Feldspar

Some cross linking of silica - better percentage silica


Some cross linking of silica

More Silica polymerization
(More or higher shared oxygen)

Less silica polymerization
Fewer shared oxygen

Already contains stabilized water or
hydrolysis product

Weak bonds to oxygen

Fewer ions can be oxidized

Ions in lower oxidation states