GEOG 203 1st Edition Lecture 16 Outline of Last Lecture I Review for quiz II Terrain evolution III Preparation for exam 2 Outline of Current Lecture I Terrain evolution a Terrain evolution as a concept b Role of tectonics in terrain evolution c Role of denudation in terrain evolution d Tectonics vs climate in terrain evolution e Mass wasting as a geomorphic concept Current Lecture 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 Terrain evolution Terrain evolution as a concept o Models of terrain evolution used to explain processes of terrain changes William Morris Davis one of founders as geomorphology as a modern discipline Davis class model of terrain evolution Explained uplift occurring followed by youth maturity old age of terrain Problems with Davis model but explains how landscapes develop over time Davis model is not the only model that exists to explain terrain evolution Role of tectonics in terrain evolution o Rock folds form through plate collisions o Causes tears in the rock faults o Anticline upfold in rocks when continents interact o Syncline downfold in rocks o The features of rock under the surface is not enough to entirely explain the terrain Davis saw this and the importance of denudation o Horst upfaulted block o Graben downfaulted block o Bolson span in between one ridge to the next Role of denudation in terrain evolution o Denudation means all the processes that degrade or strip the landscape over time o Weathering in the first step in denudation Weathering if the breaking down of rock Physical weathering ex Breaking off of rock from a landform Cold climates are likely to lead to physical weathering Water in the cracks of rock freeze and thaw many times and over time began to break the rock Chemical weathering ex Iron and oxygen react to form rust Common for chemical weathering to occur in limestone bedrock producing karst terrain Ex Tower Karst in China Denudation under differential weathering Interaction of denudation with underlying rock Tectonics vs climate in terrain evolution o Himalaya mountains o Isostasy concept as plates are less dense than the mantel underneath the crust is floating on denser material that is fluid If something pushes down on the crust in pushes the mantle down just as the mantle can rise if the crust rises Erosion results in a lifting of the mountains since the erosion would lead to less weight pushing down the crust Mass wasting as a geomorphic process o Slope forces Gravity Friction and cohesion o Relative strength of these forces determine whether a slope is stable Ex angle of repose and a pile of sand Sand will naturally fall on a slope and adjust to become in equilibrium o Material weathered and eroded by the force of gravity is deposited as colluvium o Mass movement classes Rockfall talus slope rapid and dry Rockslides avalanches wet