 Weathering: breaking down of rocks, soil and minerals as well as artificial materials through contact with the Earth's atmosphere, organisms and water. Two basic types  Physical/mechanical  Chemical

 Frost/Ice wedging Water seeps into open spaces and freezes. Expansion of water wedges and cracks material Breaks at distinct angles

 Exfoliation also known as unloading, overlying materials (not necessarily rocks) are removed (by erosion, or other processes) which causes underlying rocks to expand and fracture parallel to the surface

 Plant roots seedlings sprouting in a crevice and plant roots exert physical pressure Provide a pathway for water and chemical infiltration. Paper beats rock 

 Abrasion mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. moving particles dislodge loose and weak debris from the side of the rock.

Clicker Which type of Physical weathering occurred in the picture below? a)Frost/ice wedging b)abrasion c)Exfoliation d)Plant roots Timer Times up!

 Oxidation: Materials react with Oxygen from atmosphere or water (H 2 O) Most common Iron (Fe) “rusting”

 Hydrolysis(water): Materials react with water to form new material Water dissolves rock Chemicals in water react

 Dissolution: Acid dissolved in water dissolves rock Reactions carbon dioxide + water → carbonic acid CO 2 + H 2 O → H 2 CO 3 carbonic acid + calcium carbonate → calcium bicarbonate H 2 CO 3 + CaCO 3 → Ca(HCO 3 ) 2

 Plant Acids: Some plants produce weak acids that seep into rocks and dissolve certain minerals Examples : Lichens and Mosses

Question What type of chemical weathering process produces corrosion and iron oxide? Oxidation Timer Times up!

ROCK COMPOSITIONCLIMATE  Rocks are made of minerals Tougher the mineral the slower the weathering  Surface area More area exposed to weathering forces, faster the weathering  Very cold( no change) Slow weathering Polar regions  Dry and Hot Slow weathering Desert regions  Moderate (warm summer/cold winter) Fast weathering Temperate regions

Clicker While doing a standard pH test on uncontaminated rain water, you observe a pH of 5, this result indicates that: a)Rain water is slightly more basic/alkaline b)Rain water is neutral c)You made an error d)Rain water is acidic Timer Times up!

 pH concentration “power of Hydrogen”  Lower pH = more H+ ion (acidic)  Higher pH= less H+ more OH- ion (basic or alkaline)  1 x 10 – pH =Concentration

 1 x =.003  1 x = / = times more concentrated  Or = =10000

 Bedrock: Solid un-weathered rock below the surface  Regolith: layer of loose, weathered material covering solid rock.(bedrock)

 Minerals 54% weathered rock Rocks are made of minerals  Water 25% water  Gases 25% Air  Humus (organic matter): 5% organic material

 Explain the relationship between weathering and soil formation. Weathering and erosion make soil

 Soil profile: Cross section, shows layers top to bottom O. Organic materials A. Topsoil (organic material) B. Subsoil minerals collect C. Regolith R. bedrock

Clicker Soil is formed as a result of which of the following: a)Weathering of rocks and minerals b)Decaying of plants and animals c)Microorganisms adding Nitrogen d)All of the above Timer Times up!

 Tropical climate: Rain and High temperatures cause thick infertile soils to develop.  Desert: Low precipitation causes thin soil  Arctic: Slow weathering creates thin soil