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 rockErosion 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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