GEOG 1114 1st Edition Lecture 22 Outline of Last Lecture Structure of the Earth Composition of the Crust Types of rocks Rock cycle Outline of Current Lecture Landforms Internal vs external Geological time Crustal rearrangement Plate Tectonics Types of boundaries Current Lecture Landforms Topography surface configuration of Earth Landform individual topographic feature of any size Geomorphology study of landforms Relief difference in elevation between highest and lowest points Structure nature arrangement and orientation of landforms slope The Result of Two Opposing Forces Internal vs External 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 Internal Originate from within the Earth increase relief of land structure Surface disturbance produced by the earth s internal thermal energy Earth s internal heat generates extremely strong processes that result in crustal movements They are generally constructive uplifting building forces that tend to increase the relief of the land surface All of these processes give us a pallet They include Crustal rearrangements earth s crust is plastic Plate Tectonics theory of lithospheric plate movements Vulcanism movement of magma from interior of earth to surface Diastrophism deformation of the earth s crust by folding and uplift bending and breaking of the crust External Originate from sources above the lithosphere such as the atmosphere or oceans decrease relief of land surface Molding of peaks slopes valleys and plains by the work of gravity water wind and ice Denudation Overall effect of external forces which level and lower the continental surface Accomplished by Weathering Breaking up of rock in small components physical and chemical Mass Wasting downslope movement of broken material due to gravity rock fall rock slide Erosion extensive and distinct removal of fragmented rock Geologic Time Vastness Magnitude Earth 4 6 billion years old processes are very slow Results are high magnitude New epoch Anthropocene new epoch based on human effects on the earth geology structure climate water land everything Crustal Rearrangement The arrangement of the continents and oceans are not permanent Crustal movement is explained by Plate Tectonics or Continental Drift as it was first called Isostasy Maintenance of hydrostatic equilibrium of the crust Addition of material causes crust to sink Removal of material causes crust to rise again Plate Tectonics Theory of crustal rearrangement based on the moment of continent sized lithospheric plates The Breakup of Pangaea Super Continent made of up existing continents put together like a jigsaw puzzle once existed around 300 million years ago About 200 million years ago internal forces of the earth became so great that the continents began drifting apart Driving Force Slowly moving convection of heated material within the mantle Sea Floor Spreading New ocean floor is introduced at the mid ocean ridges by rising convection currents and volcanic activity Mid Atlantic Ridge continuous system of ridges that run across the floor of the world ocean As oceanic plates move laterally in response to sea floor spreading they drag the continents along with them Subduction at trenches older lithosphere descends into the asthenosphere where it is recycled Old lithosphere is recycled back down into the mantle near deep oceanic trenches Lithospheric Plates Lithosphere is made up of rigid plates embedded in an underlying plastic asthenosphere They move in response to the conveyor like movement associated with sea floor spreading 7 major plates 7 intermediate plates 12 smaller plates smaller plates are large plates that are being subducted Three types of Contact between plates are possible each producing distinct landforms Divergent Boundaries Plates moving apart from one another often called spreading centers New crustal material is introduced Occur at mid ocean ridges centers magma rises from the asthenosphere to form new ocean floor Spreading that occurs within a continent produces a continental rift such as the Great Rift Valley of East Africa Convergent Boundaries Plates come together in three ways Oceanic plate converging on Continental Plate Results in Subduction Very deep earthquakes are possible Descending plate partially melts procuring magma and volcanic acidity Produces a deep ocean trench with mountain building and volcanic activity just inland Andes along the W coast of S America Oceanic Plate converging on Oceanic Plate Results in Subduction Very deep earthquakes are possible Produces a deep ocean trench and a chain of volcanic islands known as an Island Arc Aleutian Islands in Alaska Continental Crust converges on Continental Crust No Subduction Uplift of mountains results Himalayas The pacific ring of fire Plate boundaries exist all around the pacific rime Primary Subduction zones 75 of all volcanoes lie in the Ring of Fire Transform Boundaries Two boundaries slip past each other laterally Transform faults Neither creates nor destroys crust Commonly produce shallow focus earthquakes San Andreas fault