GEOL 101 1nd Edition Lecture 11 Outline of Last Lecture I Cinder Cones II Shield Volcanoes III Other Landforms IV Igneous Activity Outline of Current Lecture I Earth s External Processes II Mechanical Weathering Current Lecture External Processes Definition Processes that occur at or near the earth s surface These processes are powered by energy given off from the sun wind water etc rather than by the internal energy the Earth already has Results in Erosion o Physical removal of material by water wind and ice Weathering o Physical breakdown and chemical alteration of rocks Mass Wasting o Transfer of rock soil down a slope due to gravity Weathering Chemical Chemical transformation of the rocks into a new compound Mechanical Break down of rocks into smaller pieces Three main types of mechanical weathering Frost Wedging 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 o Water seeps into cracks and fractures within a rock o The water freezes and expands then thaws and contracts o Breaks rock Unloading or exfoliated o As overlying rocks are eroded off of igneous plutons the pressure is reduced o As the igneous rocks are exposed at the earth s surface they expand causing fractures to form parallel to the edge of the pluton o Orientation of fractures causes onion layering or sheeting Biological Activity o The breaking apart of rocks by plants and animals o Plant search for water and nutrients and squeeze themselves into cracks o Fungi and lichen produce acids that etch away at the rocks o There are also some bacteria that get their energy by breaking chemical bonds in rocks this is also called chemosynthetic bacteria
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