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Module 25: Soils

Rocks Module 25

  • Igneous (fire)
  • Sedimentary (layers)
  • Metamorphic (Kafka rocks, just kidding: changed by heat and pressure)


Igneous= directly from magma, and can be either basalt (low melting point, like our island or oceanic plates) or granite (lighter, what continents are made of)
Granite breaks down into light-colored sand, makes for fertile soil. 
Basalt (like us) can make sand too, but less fertile (e.g. black sand beach).
Sedimentary= just like it sounds, from mud, sand, or dust, usually in layers.
Metamorphic= changed by heat and/or pressure (slate, marble, or coal)

Soil-formed by weathering (chemical or physical) of parent rock
Erosion can be by water or air (wind)
Soil Horizons:



Our Soil Sieve has 4 filters, with 5 layers:
  • mesh 5 = 4 mm
  • mesh 10 = 2 mm
  • mesh 60 = .25 mm
  • mesh 230 = 0.063 mm
Basically, most of what you find is silt and clay...



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