Gg Power Point 12 Soils

Front 1

Weathering

Back 1

The effects of the physical and chemical environment on the decomposition of rocks

- Igneous rocks form at high temperatures and the constituent minerals reflect the conditions of formation. The minerals are not necessarily stable at surface conditions, long after they cooled.
- Weathering can be thought of as an attempt by rocks to attain physical and chemical equilibrium with the surface environment.
- Most igneous minerals are not stable on Earth’s surface. Given time most will decompose. With the addition of extra energy (heat or mechanical energy) reactions will proceed sooner, rather than later

Front 2

Chemical and Physical Weathering
Factors that affect the efficiency of physical weathering

Hot and wet is hardest on rocks

Back 2

1. Topography and relief
e.g., falling down hill; pounding by waves
2. Climate
Especially temperature, and diurnal variations
3. Original structure
Porosity and permeability are especially important

Front 3

3 Factors involved in Chemical Weathering

Back 3

1.Original Composition
- Some substances are more resistant to alteration than others.
- In Hawai‘i, glass and olivine are the least stable substances
2. Physical Environment (see above)
3. Chemical and Biological Environment
- Microbial activity is important in all weathering processes
- Most rain water and ground water in Hawai‘i is acidic

Front 4

what are the 2 The End-Product of Weathering is Soil

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Soils can be generally divided into two main types:
1. Residual soils form by weathering in place by the breakdown of rocks beneath them

2. Transported soils have been brought in by wind or streams, and may be unrelated to rocks beneath them.

note: In Hawai‘i:
Most Hawaiian soils are residual.
Transported soils are restricted to outwash from streams (alluvial fans)

Front 5

Residual soil formation by spheroidal weathering

shows weathering

Back 5

Weathering begins along permeable fractures in the outcrop.
Progressive weathering leaves rounded cores of less-weathered rock

Front 6

Soil Classification and respective abundances in Hawai‘i
LOOK AT SLIDE 7 TO MEMORIZE DIIFERNT TYPES OF SOIL

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Front 7

Inceptisols

Back 7

(24 % of state land area)
the most abundant soil type in Hawai‘i, a fairly immature soil type.

Front 8

Histosols

Back 8

(14 % of state land area)
Rich in organics (= good stuff). Rainforest floors, almost entirely restricted to Big Island

Front 9

Oxisols (5 % of state land area)

Back 9

These are the soils that used to be called laterites.
Depleted in nutrients (leached out from prolonged weathering)
Potential commercial source of bauxite (an ore of aluminum)
Major sugar cane and pineapple growing areas, mainly because of gentle slopes. (require massive use of fertilizers)
Oxisols dominate de-vegetated areas

Front 10

Ultisols (2.5 % of state land area)

Back 10

Clay-rich soils, mainly windward areas

Front 11

Molisols

Back 11

2.3 % of state land area)
Moderately organic-rich soils, mainly in grassland areas
Good stuff for growing (Kula, Kahuku, Hale‘iwa, Kekaha, Waimea)

Front 12

5 soil types in hawaii in Hawaii

Back 12

Inceptisols, Histosols, Oxisols, Ultisols, Molisols