Geo. 101 – 1st Edition Lecture 11 Outline of Last Lecture I. VolcanismII. Eruption: Why?Outline of Current Lecture I. OverviewII. Weathering a. Physicalb. ChemicalCurrent LectureOverview:- 75% of the land surface is composed of sedimentary rocko Provides soil for growing food and forestso Sculpts and modifies the land (responsible for hills, cliffs etc.)- Weathering: The process by which rocks are broken down at the earth’s surface.- Erosion: The process that moves pieces of rock and deposits them elsewhere.o Wind, Water, Ice, Gravity- What controls weathering?o Rock Properties: Hardness, composition, solubility, zones of weaknesso Climate: Wide variations in temperature and moisture accelerate weatheringo Soil and Vegetation: Exposes rock to variations in moisture and chemistryo Length of Exposure- Weathering and Erosion both generate sedimentsWeathering:- Physical: fractures rock, breaks material into smaller pieces- Chemical: converts minerals and rocks into altered solid, solutions and precipitates – only occurs to those materials exposed to “weather”.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Physical Weathering:o Mechanical or Physical weathering breaks material into smaller pieces creating more surface area for chemical weathering to work on.o Frost wedging, roots, exfoliation (sheeting) Exfoliation: the process of pressure pushing sheets of rock away from each other (popping up, pushing out).- Chemical Weathering:o Water is naturally acidic (slightly)o Weathering Processes: Hydrolysis: the reaction of any substance with water – Gains water. Oxidation: a mineral reacts with oxygen to make a different product. Dissolution: minerals dissolved by water or acids.o By-Product of weathering = soilso Soil forming factors: Climate- Temperature and Precipitationo Higher temperature and more rainfall means more weathering and thinner soils Time- Longer time = thicker soil Plants/Animals- Organic matter- Needs moisture! Slope- If too steep, little/no soil – increased