Transcript Slide 1
Roots: Cata = down Caust = to burn Ceed = to yield Ceive = to take Celer = fast Cent = hundred Centr = center Cephalo = head Cerebro = brain Cert = sure catacombs caustic recede receive accelerate centipede egocentric encephalitis cerebral certain MECHANICAL WEATHERING Chemical Weathering MECHANICAL WEATHERING Occurs when physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition. MECHANICAL WEATHERING Three main mechanical weathering forces: Frost Wedging Breaking of rocks intoBiological smaller pieces which provides more surface area for Unloading Activity chemical weathering processes. Talus = large piles of broken rock. Pg. 127 Figure 2 Pg. 127 Figure 3 MECHANICAL WEATHERING Three main mechanical weathering forces: When large masses of igneous rock are Frost exposed from Wedging uplifting and erosion of overlying rocks. Unloading Biological Activity Pg 128 Figure 4 Exfoliation = when outer layers of rock separate and break loose. MECHANICAL WEATHERING Three main mechanical weathering forces: Breaking of rocks into smaller pieces Frost by the actions of plants, burrowing Unloading Wedging animals and humans. Biological Activity Pg. 128 Figure 5 Chemical Weathering Transformation of rock into one or more NEW compounds. Chemical Weathering Water • Most important agent of chemical weathering. • Absorbs gases from air and ground. • Oxygen in water reacts to form oxides (like rust). Silicate Granite Spheroidal Weathering • Weathering Carbon DioxideWeathering in water reacts to form carbonic acid. • Sulfur and Nitrogen oxides in water turn into acids that can erode monuments and structures. Chemical Weathering Water Granite Weathering • Granite is mostly feldspar and quartz. • Carbonic water Silicate acid inSpheroidal Weathering Weathering turns the feldspar into clay. • Quartz is released and washed away. Chemical Weathering • Silicates make up most of Earth’s crust. • Composed of 8 elements . • Sodium, calcium, Granite potassium, and magnesium Water are carried awayWeathering by ground water. • Iron becomes rust. • Aluminum, silicon and oxygen turn to clay. Silicate Weathering Spheroidal Weathering Chemical Weathering Water • When chemical weathering changes both the physical shape and the chemical of Granitecomposition Silicate Spheroidal the rock. Weathering Weathering Weathering • Water rounds corners and edges fastest making them rounded. Pg. 131 Figures A & B RATE OF WEATHERING 1. Physical characteristics of a specific rock (like cracks) influence waterproofing. RATE OF WEATHERING 2. Mineral composition determines a rock’s resistance to weathering. RATE OF WEATHERING 3. Crystal formation determines a rock’s resistance to decomposition. (Olivine crystallizes first and weathers rapidly; Quartz crystallizes last and weathers slowly.) RATE OF WEATHERING 4. Climate (especially temperature and moisture) determines the frequency of freeze-thaw cycles, etc. RATE OF WEATHERING 5. Differential weathering refers to different parts of a rock that may weather at different rates.