Weathering

Weathering 1

• Terms that describe processes that break down rock in earth's surface.
• Two main classes of weathering process.

• Mechanical

• tear rocks apart by physically destroying them.
• physically fracture or pull rocks apart at large(outcrops, cliffs) scale or small(prying individual mineral grains apart.
• produces smaller fragments with no change in chemicals.
• Weathering processes
• frost wedging
• exfoliation
• thermal expansion
• contraction
• crystal growth
• tree root growth
• abrasion.
• Frost wedging
• Wedging- a fracture(crack) in a rock provides ice with a lot of leverage.
• Temperature go low - upper surface of water freezes first because it is in contact with air.
• The ice cannot expand upward because the surface is already frozen solid.
• So, the ice exerts force outward on the rock as it grows.
• Freeze/thaw
• freezing can wedge the fracture open tiny amount.
• So, it takes many cycles of freezing and thawing with filling the fracture each time to break a piece of rock.
• Exfoliation
• term that describes peeling layers.
• sheets of rock fall aoff from bar rock
• The sheets of rock that fell out from the bare rock are called exfoliation slabs.
• rocks break off due to erosion and it is called "unloading"
• and the water can be entered then frost wedging can process.
• The most common rock igneous rock such as granite.
• exfoliation occurs mostly in mountain regions.
• Thermal Expansion
• crystals of rock also expands when they are repeated heat and be cooled.
• But this expansion and a contraction can loosen grains of a rock and enough to cause weathering.
• Rocks are poor conductors of heat.
• Grain by grain breakage maks this a slow process.
• Crystal Growth
• salt crystals grows in rock fractures or small porse between sedimentary grains causes rock to break.
• This happens when the slalty water gets into the rocks and later evaporate.
• Tree roots
• Wedging phenomenon
• Caused by tree
• grow in the fracture
• stress break rock
• Abrasion
• simply mechanism of rocks breaking or wearing down by the direct actons of rocks.
• Rock falling down the cliff-the rock break into pecies.

• Chemical   

• break down rocks atom by atom.
• chemical reactions.
• water- carries charged atoms or molecules.
• chemical weathering process
• Dissolution
• Oxidation
• Hydrolysis

• Climate and weathering

• Intimately involved in the processes of weathering.
• Hot & wet climate condition - chemical weathering.
• Cold - Physical weathering.
• Dry region- slower weathering.
• "Rain shadow" produces when air mass dries out and mountains and plains receive less water.

Weathering 2

• 3 types of weathering
• Physical
• Physical changes such as temperature, freezing and thawing, and the effects of wind, rain and waves.
• Temperature changes
• Hot -expands
• Cold - contracts
• This repeat, the rock cracks and fall off.
• Wind rain and waves.
• Wind-blows tiny sands against the rock.
• Rain, wave- wear the rock for long period of time.
• Freeze/Thaw
• If the water freezes in the crack, the ice expands and make the crack fall.
• Chemical- wear by chemical
• Biological- wear by plants and animal.
• Erosion:  Movement of the broken pieces of rock going away from the site of weathering.
• Transport: Rivers and streams move pieces of rock.