Download soils, rocks, and rates.

Soils, Rocks, and Rates
Types of Rocks
IGNEOUS ROCKS
=> Form when magma/lava cools and solidifies.
Sometimes contain valuable deposits.
Magma and lava are made up of silicates
(compounds of S and O) with other small
amounts of Fe, Mg, and K.
When liquid rock cools, the minerals form
crystals.
Igneous rocks are crystalline rocks.
2 types :
1. Intrusive (plutonic) rocks, formed below the
surface.
2. Extrusive (volcanic) rocks, formed on the surface.
SEDIMENTARY ROCKS
=> Formed by sedimentation of material at the
earth’s surface and within bodies of water.
When weathering or erosion breaks down a
rock into loose material.
Transported to the deposition area.
Carried by suspension.
Gradually sinks to the bottom, becomes a
sediment.
Process continues for a LOOONGGG time.
Mud layers are pressed down under the weight
of other sediment.
Lower layers are compacted.
Eventually, they’re pressed together so solidly
they form solid rock.
Different sized particles form different kinds of rocks :
Shale : formed by very small particles. Fine-grained grock
Sandstone : Larger sand-sized grains.
Conglomerate : formed by larger gravel sized particles.
Limestone : Formed under the sea where CaCO3 is squashed tightly to become rocks.
Freestone : can be split in any direction. Good for buildings.
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METAMORPHIC ROCKS
=> Igneous or sedimentary rocks that has metamorphosed and
has changed its structure and form.
Regional Metamorphism
Happens to rocks buried deep underground.
High temp. and pressure operate over larrgee areas.
Large quantities of rocks are metamorphosed.
Contact Metamorphism
Caused when magma comes in contact with other rocks.
Rocks near magma is heated and metamorphosed.
Happen around the edges of hot magma.
ROCK CYCLE
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Geological Time Scale
These are SUPER long compared
to human lifetimes.
Earth’s history is divided into
eras.
Eras divided into periods.
Recent periods divided into
epochs.
Study of rock layers is called
stratigraphy.
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Weathering
Chemical Weathering
=>The process that breaks apart rocks by a chemical
reaction
=>Involves decomposition of rocks by changing their
chemical composition.
Four types of chemical weathering
1.
2.
3.
4.
Oxidation
Hydrolysis
Carbonation
Other Acids
Hydrolysis
Minerals in the rock react with water
Water is the strongest agent of chemical weathering
Dissolves minerals
Mica, Feldspar, Halite and Calcite
Speeds up chemical reactions
Rust forms quicker when exposed to water
Reacts with elements to form acids
Water + carbon dioxide= Carbonic Acid
Water + sulfur = Sulfuric Acid
Water + nitrogen= Nitric Acid
Biological Weathering (Part of Mechanical Weathering)
By Plants :
Using roots to force apart rocks.
Along bedding planes, joints, or cracks
Releasing acids and other chemicals in their lifecycle.
Decomposition of the remains.
By Burrowing Animals :
Breaking up and loosening rocks
Releasing acids and other chemicals in their life-cycle.
Decomposition of the remains.
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Physical Weathering (a.k.a. Mechanical
Weathering)
=>The process of breaking rocks without a chemical
change in the composition of the rock.
=>Involves disintegration of rocks.
Four types of Physical Weathering:
Frost Action
Plant Action
Exfoliation
Abrasion
Frost Action
Weathering of a rock due to alternating freezing and
thawing of water in the cracks of the rock
Water fills in the cracks between a rock
Water freezes
Water expands as it freezes into ice
Expanding of ice makes crack bigger than before
Water thaws and fills in the new bigger crack
Water freezes again making the crack even bigger
Type of weathering responsible for Potholes
Also known as freeze/thaw cycle and ice wedging
Weathering of Rocks - Plant Growth
Weathering of rocks releases salts.
Including Calcium, Nitrates, Phosphates, Potassium.
Needed for plant growth
(That’s why you have N, P, K fertilizers)
Soil
=> Formed from rock debris and organic remains.
=> built up by the action of living things on weathered rocks.
Weathering of rocks produces small particles of various minerals.
Particles of weathered rocks can be colonized by lichens.
Lichens absorb minerals from rocks.
Other organisms such as bacteria, small plants and animals also begin to colonize the
rock.
When they die, bacteria and fungi break down their remains.
Rotted and partly-rotted organic material called humus produced.
Humus mixes with rock particles.
-> Called soil.
Soil Acidity
If the soil is too acidic, N, and P will start forming insoluble compoinds with Ca and
hence can not be absorbed by the plants.
If soil is too acidic, plants can’t grow.
Acid rain may change the soil.
That’s why quicklime or slaked lime is used to reduce soil acidity.
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