Rock cycle explanation

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  • Publicado : 14 de octubre de 2010
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Weathering is the breakdown of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological activity. It does not involve the removal of rockmaterial.

There are three types of weathering, physical, chemical and biological.
How is erosion different to weathering?
Erosion is the process by which soil and rock particles are worn away and movedelsewhere by wind, water or ice. Weathering involves no moving agent of transport.

Erosion and Transport
Erosion is the process by which soil and rock particles are worn away and movedelsewhere by gravity, or by a moving transport agent – wind, water or ice.

Transport refers to the processes by which the sediment is moved along – for example, pebbles rolled along a river-bed orsea shore, sand grains whipped up by the wind, salts carried in solution.
How is erosion different to weathering?
Erosion involves removal of solid material by a transporting agent. Weathering isthe breakdown of rock into fragments at the Earth’s surface. No movement is involved in weathering.

Deposition of Sediment
Deposition is the laying down of sediment carried by wind, water, orice. Sediment can be transported as pebbles, sand & mud, or as salts dissolved in water. Salts may later be deposited by organic activity (e.g. as sea-shells) or by evaporation.

Burial and CompactionHow do great thicknesses of sedimentary rocks (see photo) build up, and how does the loose sediment get turned into hard rock?

As layers are piled one upon another, the sediments beneath areburied, sometimes by hundreds of metres of sediment above. The weight of these layers compacts (squashes down) the sediment grains. Minerals deposited from water in the spaces between the sediment grainsgradually cements them together. Compaction and cementation are explained in the next two pages.
The Principle of Superposition:
In a series of rock layers like those in the picture, we see that...
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