Rick s Cafe in Jamaica Keith Fairbrother Erosion

Rick's Cafe in Jamaica Keith Fairbrother

Erosion Door County, WI Lizzy Schneider

Erosion Timna Valley, Israel Naamah Azoulay

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING DISSOLUTION Water removes ions or ion groups from a rock or mineral and carries them away. Precipitate later when water evaporates. Due to the bipolar nature of water molecules, ions become dissolved and are transported in solution.

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING DISSOLUTION Halite Na+ is attracted to OH- side of water molecules Cl- is attracted to the H+ side of water molecules Water can also react with another compound to form an acid. H 2 O + CO 2 H 2 CO 3 (Carbonic acid) The acid can then decompose minerals. H 2 CO 3 + Ca. CO 3 Calcite Ca+2 + 2 HCO 3 - (Bicarbonate) Removed by erosion

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING DISSOLUTION Dissolution is the process by which caves are formed. Calcite is dissolved, Ca+2 and HCO 3 - end up in the ocean. Then removed from the ocean by marine organisms in the production of skeletal material.

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING OXIDATION Positive ions in minerals combine with oxygen to produce oxides. 4 Fe+3 + 3 O 2 2 Fe 2 O 3 (hematite) If the reaction takes place in water, limonite (Fe. OOH) is produced. Collectively called RUST.

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING OXIDATION Also affects other metals such as copper.

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING OXIDATION Oxidation has the same result with iron-rich rocks and minerals. Affects olivine, pyroxenes, amphiboles, gabbros and basalts.

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING HYDROLYSIS H+ and OH- ions in water displace other ions in a mineral structure producing a new mineral. Feldspars are readily changed by hydrolysis. 2 KAl. Si 3 O 8 + 2 H+ + 9 H 2 O Orthoclase Feldspar Al 2 Si 2 O 5(OH)4 + 4 H 4 Si. O 4 + 2 K+ Kaolinite Silicic Acid

WEATHERING and the BREAKDOWN of ROCKS CHEMICAL WEATHERING HYDROLYSIS Hydrolysis of orthoclase, other feldspars and mafic minerals produces clays and clay minerals. Clays become incorporated in soils or wash to the sea by erosion. Dissolved materials produced can cement sedimentary grains Or, be utilized by plants (K+).

So…… What are the factors that influence CHEMICAL WEATHERING?

WEATHERING and the BREAKDOWN of ROCKS FACTORS THAT INFLUENCE CHEMICAL WEATHERING CLIMATE Water drives all three reactions discussed. Heat also speeds reactions. Warm, humid climates are most suitable for chemical weathering reactions. Warm, humid climates also tend to have more plants. When plants die, decomposition increases the production of organic acids and increases chemical weathering.

WEATHERING and the BREAKDOWN of ROCKS FACTORS THAT INFLUENCE CHEMICAL WEATHERING LIVING ORGANISMS Mix up soil exposing more material to surface for weathering reactions.

WEATHERING and the BREAKDOWN of ROCKS FACTORS THAT INFLUENCE CHEMICAL WEATHERING TIME The longer a rock or mineral is exposed to weathering the more weathering takes place.

WEATHERING and the BREAKDOWN of ROCKS FACTORS THAT INFLUENCE CHEMICAL WEATHERING MINERAL COMPOSITION The effect of chemical weathering in rocks is related to the stability of the minerals in the rock. Since most rock-forming minerals are silicates, the strength of the bonds between the silica tetrahedra influences how they are weathered. The more silicon-oxygen bonds between the tetrahedra, the more resistant to weathering is the mineral.

WEATHERING and the BREAKDOWN of ROCKS

WEATHERING and the BREAKDOWN of ROCKS PRODUCTS OF CHEMICAL WEATHERING Or…. What’s left after dissolution, oxidation and hydrolysis. Clay Minerals Produced by hydration of feldspars and mafic minerals (olivine, pyroxenes, and amphiboles).

WEATHERING and the BREAKDOWN of ROCKS PRODUCTS OF CHEMICAL WEATHERING CLAY MINERALS Type of clay formed depends on climatic conditions during hydrolysis. Kaolinite forms in warm, humid climates. Smectite forms in cool, dry climates. Uses of clay minerals: Agricultural fertilizers Lubricants in oil drilling Bricks and cement Paper production Cat litter Kaopectate Filtering impurities from beer and wine

WEATHERING and the BREAKDOWN of ROCKS PRODUCTS OF CHEMICAL WEATHERING METAL ORES Aluminum Forms from chemical weathering of feldsparrich rocks in warm, humid climates. Leads to the concentration of aluminum in Bauxite (Al 2 O 3. n. H 2 O).

WEATHERING and the BREAKDOWN of ROCKS PRODUCTS OF CHEMICAL WEATHERING SPHERIODAL WEATHERING Mechanical weathering breaks up rocks into smaller pieces. Chemical weathering rounds off corners.

WEATHERING and the BREAKDOWN of ROCKS SOILS AND SOIL FORMATION Mechanical and chemical weathering of sediment and pre-existing bedrock below produces REGOLITH is all the material above the bedrock. SOIL is the upper part (up to a few meters) of regolith that supports plant life. Soil contains both mineral and organic matter (decaying vegetation). Soil also contains air and water.

WEATHERING and the BREAKDOWN of ROCKS SOILS AND SOIL FORMATION REGOLITH

WEATHERING and the BREAKDOWN of ROCKS SOILS AND SOIL FORMATION SOIL

WEATHERING and the BREAKDOWN of ROCKS INFLUENCES ON SOIL FORMATION PARENT MATERIAL The bedrock or sediment from which soil forms. Influences nutrient richness of the soil. Quartz-rich sandstone Basalt

WEATHERING and the BREAKDOWN of ROCKS INFLUENCES ON SOIL FORMATION CLIMATE Precipitation and temperature influence soil formation. Influences the rate of chemical weathering. Also influences plant growth. Soil formation is most rapid in warm, moist climates.

WEATHERING and the BREAKDOWN of ROCKS INFLUENCES ON SOIL FORMATION TOPOGRAPHY Physical features of the landscape. Influences the availability of water. Influences the rate of soil accumulation. Steep slope vs. gentle slope

WEATHERING and the BREAKDOWN of ROCKS INFLUENCES ON SOIL FORMATION VEGETATION Contributes organic matter to soil. Produces CO 2 and O 2 involved in chemical weathering. Plants contribute H+ that helps weather soils. Aids in hydrolysis Degrades feldspars and other minerals into clay minerals. Clays increase nutrient supply to plants.

WEATHERING and the BREAKDOWN of ROCKS INFLUENCES ON SOIL FORMATION TIME The longer the time Earth materials are weathered, the thicker the soil produced.