UNIVERSITY OF SOUTH ALABAMA GY 111 Physical Geology Last time before the test we covered 1 Intrusive igneous rocks and the bodies they form 2 Summary diagram of all igneous rock types Lecture 12 Weathering Erosion and Soil Mineral Stability Today s Agenda 1 Mineral Stability 2 Types of weathering Physical Chemical Biological 3 Chemical weathering reactions 4 Soils Web notes 12a weathering Web notes 12b soils Mineral Stability Bowen s Reaction Series Mineral Stability Bowen s Reaction Series First to form most stable at high temperature 1 Mineral Stability Mineral Stability Bowen s Reaction Series Bowen s Reaction Series First to form most stable at high temperature First to form most stable at high temperature Consider what happens when these minerals are exposed at the surface of the Earth low temp low pressure rain fall Last to form most stable at low temperature Mineral Stability Last to form most stable at low temperature Mineral Stability Bowen s Reaction Series Bowen s Reaction Series Least stable at the surface Least stable at the surface Kaolinite clay Most stable at the surface Most stable at the surface Fe Al oxides hematite limonite bauxite Weathering Weathering Weathering the breakdown of rocks at the surface of the Earth There are 3 types of weathering Weathering the breakdown of rocks at the surface of the Earth There are 3 types of weathering 1 Physical mechanical reduction in the size of rock components 2 Weathering Weathering Weathering the breakdown of rocks at the surface of the Earth There are 3 types of weathering Weathering the breakdown of rocks at the surface of the Earth There are 3 types of weathering 1 Physical mechanical reduction in the size of rock components 1 Physical mechanical reduction in the size of rock components 2 Chemical chemicallyinduced changes in the composition of rock 2 Chemical chemicallyinduced changes in the composition of rock 3 Biological a bit of both Physical Weathering Exfoliation sheet weathering of granite by heating cooling cycles Physical Weathering Frost heaving weathering by alternating freeze thaw cycles Physical Weathering Exfoliation sheet weathering of granite by heating cooling cycles also known as spherical weathering Physical Weathering Frost heaving weathering by alternating freeze thaw cycles 3 Physical Weathering Physical weathering increases the surface area of rocks which in turns speeds up chemical weathering Chemical Weathering Chemical weathering is responsible for the deterioration of natural materials some of which are used as building materials http boldt us 4704 2 weathered old tombstone Chemical Weathering Chemical Weathering Chemical weathering occurs in three different ways 1 Dissolution solution 2 Oxidation 3 Hydrolysis http www gly fsu edu salters GLY1000 10Weathering Erosion 10Weathering 20and htm Chemical Weathering 1 Dissolution Solution Chemical Weathering 1 Dissolution Solution 2 Oxidation reaction with oxygen Carbonates 2 Oxidation reaction with oxygen 3 Hydrolysis reaction with water 3 Hydrolysis reaction with water 4 Chemical Weathering Chemical Weathering 1 Dissolution Solution 2 Oxidation reaction with oxygen 3 Hydrolysis reaction with water Soil Soil soil i The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants ii The unconsolidated mineral or organic matter on the surface of the earth that has been subjected to and shows effects of genetic and environmental factors of climate including water and temperature effects and macro and microorganisms conditioned by relief acting on parent material over a period of time A product soil differs from the material from which it is derived in many physical chemical biological and morphological properties and characteristics soil i The unconsolidated mineral or organic material on the immediate surface of the earth that serves as a natural medium for the growth of land plants ii The unconsolidated mineral or organic matter on the surface of the earth that has been subjected to and shows effects of genetic and environmental factors of climate including water and temperature effects and macro and microorganisms conditioned by relief acting on parent material over a period of time A product soil differs from the material from which it is derived in many physical chemical biological and morphological properties and characteristics Soil Soil soil i The unconsolidated mineral or organic material on the immediate surface of the earth soil i The unconsolidated mineral or organic material on the immediate surface of the earth Regolith is broken up bits of rock and chemically altered rock no organic stuff Soil also contains organic material including bacteria We will regard it as being an in situ deposit 5 Soil Profiles Soil Profiles soil profile A vertical section through a soil that shows its horizontal structure e g Soil horizons A B C soil profile A vertical section through a soil that shows its horizontal structure e g Soil horizons O A Zone of Leaching A B Zone of Accumulation C Zone of Altered Bedrock O Topsoil or humus subdivision of A Horizon B C Soil Profiles Types of Soils Soils come in many different flavors but Geology students in GY 111 only have to worry about 3 types A B C Types of Soils Soils come in many different flavors but Geology students in GY 111 only have to worry about 3 types Al aluminium Fer iron Types of Soils Soils come in many different flavors but Geology students in GY 111 only have to worry about 3 types cal calcium carbonate e g calcite 6 Types of Soils Types of Soils Soils come in many different flavors but Geology students in GY 111 only have to worry about 3 types Today s Homework 1 Download and read web lecture 12 Next Tuesday 1 Nothing Fall break Next Thursday 1 Sedimentary Classification and transport 7
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