EARTH’S PROCESSES
EARTH’S PROCESSES • Africa & South America Fit Video • Super Volcano As Seen From Montana Simulation • Blast Zone Map • Ash bed map from previous Yellowstone eruptions
ALFRED WEGENER • German scientist • Noticed in the early 1900’s that some continents seemed to fit together as a puzzle • Wegener hypothesized that these continents were once a great land mass or supercontinent called Pangea • 200 million years ago the super continent broke into pieces that drifted over the surface of the Earth. • He couldn’t explain how the pieces moved. • Continents shared rocks, minerals, fossils
PANGEA https://image.slidesharecdn.com/pangea-120222003341-phpapp01/95/pangea-20-728.jpg?cb=1329871490 http://eatrio.net/wp-content/uploads/2013/01/4.-73896956-60a5-41e6-b0ba-55d4942856e7.gif
PLATE TECTONICS • Earth’s plates are in constant, slow motion • Between 2.5 and 15 cm per year! • Since you’ve been alive, plates have moved more than 180 centimeters!!! • Theory of plate tectonics states that Earth’s surface is made of pieces called plates and move over the upper layers. • T op of plate = continental or oceanic crust • Bottom of plate = rigid layer of earth’s mantle • T ogether they make up the Lithosphere • The process continues as the current earth/volcano hot spots of the world reflect the edges of the moving plates atop which the continents sit.
PLATE TECTONICS • Geologists came to the conclusion in the 1960’s that the Earth’s lithosphere was broken up into about 12 large pieces called plates that are moving relative to one another. • The lithosphere floats upon the asthenosphere (upper mantle). • Continental crust is less dense than oceanic crust. • Continental crust is composed of granite. • Oceanic crust is composed of basalt.
SEAFLOOR SPREADING • Harry Hess uses sonar data to get maps of the seafloor. • Found the MOR – mid Atlantic ridge • Produced by sea floor spreading • Magma forced upward because of its low density • Causes crust to crack and form twin mountain ranges with a rift valley in between. https://qph.ec.quoracdn.net/main-qimg-bf29631fa40ceca53d2e243892efd355-c
EVIDENCE OF SEAFLOOR SPREADING 1. Ages of sediments and rocks. • Sediment near the continents are old at the bottom and younger at top. • Layers near the MOR are only of recent age. • Oldest rocks on continents are ~ 400 billion yrs. • Seafloor rocks are , 200 million yrs. https://i.ytimg.com/vi/DZL5GWaLviY/hqdefault.jpg
EVIDENCE OF SEAFLOOR SPREADING 2. Magnetic Polarity of Rocks • some rocks have iron • When rocks form the iron minerals line up along the current magnetic field. • When rocks harden the magnetic orientation is “locked” • Magnetic field reverses direction • Seafloor shows rock bands with reversed polarities https://study.com/cimages/multimages/16/640px-Oceanic.Stripe.Magnetic.Anomalies.Scheme.svg.png
TYPES OF STRESS • 3 Types of Stress: tension, compression and shearing. • Tension: Pulls apart. Thins out crust. • Compression: Pulls apart. Shortens and thickens crust. Squeezes rock. • Shearing: Rocks slip past each other. https://earthquake.usgs.gov/learn/glossary/images/stress_types.gif
TYPES OF PLATE BOUNDARIES • Divergent Boundaries • Convergent Boundaries • Transform Plate Boundaries
DIVERGENT PLATE BOUNDARIES • Tension stress • 2 plates move apart • Magma rises between, spreads out and cools • Forms new oceanic crust • Exist as rift valleys http://www.cotf.edu/ete/images/modules/msese/earthsysflr/EFPlateP3.gif
DIVERGENT PLATE BOUNDARY • The Atlantic Ocean is getting larger as the Western Hemisphere moves away from Europe and Asia while the Pacific Ocean is becoming smaller. This is occurring because the North and South American plates are moving westward. • The Mid – Atlantic Ridge http://faculty.montgomerycollege.edu/gyouth/FP_examples/student_examples/connor_peace/atlantic-ridge.jpg
DIVERGENT BOUNDARY • A satellite view of the Sinai Peninsula shows two arms of the Red Sea spreading ridge, exposed on land. • This is the northern extension of Africa’s Great Rift Valley.
CONVERGENT PLATE BOUNDARY • Compression Stress • Plates come together and collide • Continental plate + oceanic plate • Oceanic plate + oceanic plate • Continental plate + continental plate • Creates mountains, trenches, volcanoes, earthquakes, tsunamis http://www.cotf.edu/ete/images/modules/msese/earthsysflr/EFPlateP2.gif
SUBDUCTION ZONE • A subduction zone is a convergent boundary where two tectonic plates collide. • Less dense thick continental plate moves towards a denser, thin oceanic plate. • Oceanic plate is forced down under the continental plate. • Volcanic arcs parallel these zones • Has a deep sea trench that parallel too.
SUBDUCTION ZONES APPEAR AS DEEP OCEANIC TRENCHES. MOST OF THE CONTINENTAL MOUNTAIN BELTS OCCUR WHERE PLATES ARE PRESSING AGAINST ONE ANOTHER.
IN THE CROSS SECTION OF THE EARTH IN THE SOUTHERN HEMISPHERE, THE MAP SHOWS A SUBDUCTION ZONE THAT HAS CREATED THE PERU-CHILE TRENCH AT THE WESTERN EDGE OF SOUTH AMERICAN AND THE ANDES MOUNTAINS ALONG THE WEST COAST OF SOUTH AMERICA.
http://joediv4.weebly.com/uploads/9/7/8/3/9783392/526861118.gif https://i.ytimg.com/vi/BlymeytlMiM/hqdefault.jpg https://i.ytimg.com/vi/JlWaYPHd9mQ/hqdefault.jpg
TRANSFORM PLATE BOUNDARIES • Shearing stress • When 2 plates slide past one another • Horizontal motion • Important when they cut perpendicular to the MOR (mid ocean ridge) http://academic.brooklyn.cuny.edu/geology/grocha/plates/images/transform1.jpg
SAN ANDREAS FAULT • An aerial view shows probably the most familiar meeting of two plates in the United States, the San Andreas fault slicing through the Carrizo Plain in the Temblor Range east of the city of San Luiz Obispo, CA.
VOLCANOES • magma (melted rock inside Earth)rises to the surface where the earth’s plates pull apart (divergent zones) • “holes” in the plates called hotspots • cooler oceanic crust dives underneath continental crust (convergent boundary) forcing magma to rise to the surface http://www.abc.net.au/cm/lb/8996162/data/volcano-illustration-data.jpg
VOLCANOES • Hotspots : active sites where large amounts of magma move to the surface in a column like plume. • Hotspots don’t move much, but the plates above them do! • Under oceanic plate = Hawaiian islands • Under continental = Yellowstone http://www.coolgeography.co.uk/A-level/AQA/Year%2013/Plate%20Tectonics/Plate%20tectonics/Tectonic_Hotspots_map.jpg
EARTHQUAKES • https://www.youtube.com/watch?v=_- CNX9W_KPw • Occur at the boundaries of Earth’s plates • Occur at different depths depending on the type of boundary • Divergent = shallow, narrow zone • Convergent = greater depth, wider zone https://steemitimages.com/0x0/http://static.boredpanda.com/blog/wp-content/uploads/2016/08/italy-earthquake-before-after-fb__700-png.jpg
EARTHQUAKES • Shaking of the Earth caused by massive amounts of energy released when there is sudden movement at a plate boundary along a fault.
ELASTIC REBOUND THEORY • An explanation for how energy is spread during earthquakes. • As rocks on opposite sides of a fault are subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded. • At that time, a sudden movement occurs along the fault, releasing the accumulated energy, and the rocks snap back to their original undeformed shape. http://slideplayer.com/230743/1/images/3/What+is+the+Elastic+Rebound+Theory.jpg
ELASTIC REBOUND THEORY • Focus: Where the earthquake starts Epicenter: Place on Earth directly above the focus Locating Epicenters Video http://www.sliderbase.com/images/referats/489b/(3).PNG
SEISMIC WAVES • Three types of waves • -Primary Waves (P) • -Secondary Waves (S) • -Surface Waves https://d2gne97vdumgn3.cloudfront.net/api/file/wMeeL62TmK6kAbVAG8l4
PRIMARY (P) WAVES • Longitudinal waves that move faster then other waves • Compresses earth’s crust in front of it and stretching the crust in back of it • Alternately compress and expand the material they pass through • Can cause ground to buckle and fracture http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/imgwav/pwave.gif
SECONDARY (S) WAVES • A transverse wave that moves more slowly • Cause materials to shake at right angles to the direction of wave motion • Cause ground to shake up and down and sideways http://3.bp.blogspot.com/-H4_4hbJSWKo/TbV_bKJNpuI/AAAAAAAACCo/Xip3KPNc5Fc/s1600/s-waves.JPG
SURFACE WAVES • Moves only across earth’s surface • Can move ground side to side and damage foundations of buildings • Another type moves like an elliptical. A combination of up and down and back and forth motion. • More destructive than P and S waves. Can cause building to collapse because of their longer wavelength and rolling action http://slideplayer.com/226742/1/images/7/Surface+Waves+Combination+of+transverse+and+longitudinal+waves.jpg
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