GEOG 1114 1st Edition Lecture 22Outline of Last Lecture -Structure of the Earth-Composition of the Crust-Types of rocks -Rock cycleOutline of Current Lecture - Landforms- Internal vs. external- Geological time- Crustal rearrangement- Plate Tectonics- Types of boundariesCurrent Lecture LandformsTopography - surface configuration of EarthLandform - individual topographic feature of any sizeGeomorphology - study of landformsRelief - difference in elevation between highest and lowest pointsStructure - nature, arrangement and orientation of landforms (slope) The Result of Two Opposing Forces: Internal vs. ExternalThese 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 plasticPlate Tectonics – theory of lithospheric plate movementsVulcanism – movement of magma from interior of earth to surfaceDiastrophism – 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 chemicalMass Wasting: downslope movement of broken material due to gravity (rock fall, rock slide)Erosion: extensive and distinct removal of fragmented rock Geologic Time Vastness/ MagnitudeEarth 4.6 billion years old processes are very slow Results are high magnitudeNew 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 crustAddition of material causes crust to sinkRemoval of material causes crust to rise againPlate Tectonics: Theory of crustal rearrangement based on the moment of continent-sized lithospheric plates.The Breakup of PangaeaSuper 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 SpreadingNew 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 oceanAs 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 PlatesLithosphere 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 spreading7 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 centersNew crustal material is introducedOccur at mid-ocean ridges centers; magma rises from the asthenosphere to form new ocean floorSpreading that occurs within a continent produces a continental “rift” such as the Great Rift Valley of East AfricaConvergent BoundariesPlates come together in three ways:Oceanic plate converging on Continental Plate Results in Subduction Very deep earthquakes are possibleDescending 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. AmericaOceanic Plate converging on Oceanic Plate Results in SubductionVery deep earthquakes are possibleProduces a deep ocean trench and a chain of volcanic islands known as an Island ArcAleutian Islands in AlaskaContinental Crust converges on Continental CrustNo SubductionUplift of mountains resultsHimalayasThe 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