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Alfred Wegener ( Alfred Wegener (VAYG-uh-nur) Continental drift –the claim that all of the continents were once together, forming one large continent called Pangaea. (All land) Alfred Wegener German scientist (weather man) came up with the idea
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Continental drift-Fact or fiction? Support/ Evidence Continents seem to fit together Fossil record seems to match Rock structures match –Rock ages match Changes in climates –Glacier debris Opposition/ problems What Continental drift couldn’t answer! How can the continents move? –No mechanism to make them move –Ocean crust is to hard for the continents to move through
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Continental Drift Possible mechanism?
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Clicker question The term given by Alfred Wegener, which means “ all land”. a)Eurasia b)Panthalassa c)Pangaea d)Continentolossal
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Modern Evidence Plate Tectonic theory Mid-Ocean ridges & Sea floor spreading Mid-Ocean ridge –Large under water mountain range, with a deep valley down the center –Ocean floor was moving, Why not continents? Sea floor spreading –new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge
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Modern Evidence Plate Tectonic theory Paleomagnetism Study of Earth’s magnetic field through rocks and minerals Shown by different magnetic properties preserved in the rock record Magnetic poles reverse N S, S N Cause/ Mechanism Convection –Hot magma rises cool magma sinks –Causes movement within the mantle
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What scientists discovered that there is a cycle in which the continents move. –Supercontinent cycle: continents come together and break apart –Wegener’s Pangaea
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Breaking up “it’s not you it’s me” During the mesozoic era Pangaea began to split up. Sniff sniff so sad –When it did it formed two separate continents named Laurasia and Gondwanaland.
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Clicker question How much does the Earth weigh (mass) in pounds? 13, 227,735, 700, 000, 000, 000, 000, 000 lbs.(13 octillion, 227septillion,735 sextillion 700 quintillion pounds)
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Plate tectonics theory There are 52 tectonic plates. –14 major plates –38 minor plates So what is going on at all these plates? The theory that the earth’s lithosphere is divided into plates that move on the Asthenosphere. ASK THIS How many plates are there Mr. Hernandez?
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The Crust (Lithosphere) Oceanic: more dense and younger –5 10 km thick Continental: Older less dense material made from recycling of Oceanic crust –15 80km thick
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Earth’s layers Mantle: Thickest layer; made of two parts Lower mantle Solid Upper mantle/ Asthenosphere “Putty like” and flows even though it is solid rock (very hot and under a lot of pressure) Moho- –(Mohorovic discontinuity) –Boundary that separates the mantle from the crust. Earth quakes waves speed up.
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Earth’s layers Lithosphere- –Crust: Oceanic Continental –Thinnest layer (5- 70km) –Even thinner when underneath the ocean. 1. 1.The wrapper –Crust 2. 2.Moho -Waxy part of wrapper 3. 3.Mantle- Shell –Upper and lower 4. 4.Core- tootsie roll –Outer liquid –Inner solid
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How do we know? Seismic waves caused by earth quakes –Waves travel at different speeds through different mediums. (a medium is the material a wave travels through) – Primary (P) waves: Travels fast through liquid, solid, gas –Secondary (S) waves: Solids only and slower
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Earth’s layers Moho- –(Mohorovic discontinuity) –Boundary that separates the mantle from the crust. Earth quakes waves speed up. Moho must be more dense
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Lithosphere vs Asthenosphere
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Types of plate boundaries 1.Divergent –Pulling apart –Ex. Mid-Atlantic ridge Great rift Valley Africa
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Types of plate boundaries 3.Transform Boundary –One plate slides past another Ex. San Andreas fault –Causes earthquakes in California
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Types of plate boundaries 2.Convergent (push) –Two plates crashing into each other Three types of plate collisions –Ocean-Continent –Ocean-Ocean –Continent--Continent
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When will California fall off of the United States? NEVER !!!
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Types of plate boundaries Ocean to Continental –Ocean plate is more dense subducts under continental plate. Ex. Alaska island arc
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Types of plate boundaries –Ocean-Ocean Two oceanic plates collide Ex. –Marianas trench 1,600 miles long,43 miles wide, 36,200ft deep –Island arcs (volcanoes)
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Types of plate boundaries 2.Continent-Continent –Two continental plates crashing into each other –Himalayan mountains. Formed by this grow an inch a year
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Clicker question What will most likely form at a oceanic and continental plate convergence? a)Non-geologically active volcanoes b)Craters c)Hot spots d)Composite volcanoes
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Tectonic plates Major: Pacific North American South American Eurasian African Indo-Australian Antarctican Minor: Juan de Fuca Coco's plate Nazca Caribbean
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I.Igneous rocks are rocks that from molten material (magma/lava). A. Extrusive igneous rocks are formed when molten rock (lava) cools above ground. Usually they are formed after the material has been erupted by a volcano. 1.This molten material cools quickly. 2.No crystals are visible to the eye.
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B.Intrusive igneous rocks are formed when molten rock cools below ground. 1.These rocks cool very slowly. 2.There is lots of time for visible crystals to grow
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Clicker question The parent material for all rocks is: a)Quartz b)Magma c)Silica d)Granite
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Igneous rock textures Coarse mineral grains easily visible (grains several mm in size or larger) Granite
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Igneous rock textures Fine mineral grains smaller than 1mm (need hand lens or microscope to see minerals)
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Igneous rock textures Vesicular (Open spaces, bubbles)
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Igneous rock textures Glassy Shiny no visible crystals (looks like glass)
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Felsic VS Mafic Mineral CompositionOver all color of the rock Felsic: light in color –pink, grey, white… Mafic: Dark in color –black, brown, red… Felsic: rich in light minerals feldspar and quartz Mafic: Rich in dark minerals Magnesium and Iron (Ferric)
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Clicker question The size and arrangement of crystalline grains in igneous rock is called a)Luster b)Hardness c)Density d)Texture
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Intrusive rock features a) a)Batholith: Largest intrusions of rock “deep rock” b) b)Laccolith: Intrusion of rock that is parallel to the rock layers “lake of rock” c) c)Dikes: Vertical cross cutting layer of rock d) d)Sills: Parallel sheet of rock
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Volcanoes
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TYPES OF VOLCANOES 1.SHIELD VOLCANOES Mostly made up of lava flows Highly Mafic Ex. Hawaiian islands Hawaii
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Shield Volcanoes Shape: Very large but gentle slopes Composition: Low silica Low gases Eruptive Style: ?
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Types of Volcanoes 2.Cinder cone Volcano – Mostly made of cinders and other fragments Ex. Paricutin in Mexico
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Paricutin volcano in Angahuan, Mexico was born on March 4th 1943. How do we know this? Dionisio Pulido, was plowing his field when he noticed steam coming up from the footprints of the oxen, pulling his plow. Soon, the earth shook and cracks began to form in his field. Dionisio panicked and tried to fill the steaming holes, while his wife called all the villagers to help. As you might have guessed, the volcano was born in spite of their efforts. Luckily, no one was killed. However, the village was eventually covered by lava, sparing only the front and back walls of the cathedral.
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Cinder Cone Volcanoes Shape: Very small but steep slopes Composition: Medium silica High gases Eruptive Style: ?
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Types of Volcanoes 3.Composite Volcanoes (stratovolcano) – Alternating layers of ash and Lava flows Steep sides – Ex. Mt. St Helens Cascade mountain range Mt. Rainier Mt. Pinatubo Mt. Fuji
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May 17,1980
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MAY 18, 1980
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TODAY
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Clicker question Most Hawaiian island volcanoes are gently sloping and experience quieter eruptions of lava that produce basalt. Based on this description, most Hawaiian volcanoes are: A. shield cones B. cinder cones C. composite cones D. fissure eruptions
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Composite Volcanoes Shape: Very large and steep slopes Composition: high silica high gases Eruptive Style: ?
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Volcanoes Fissure eruption –Shape: –Flat; crack in the ground or on the ocean floor –Composition: –Low silica –Low gases –Eruptive Style: ?
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Hot spot Volcanoes -volcanic regions They may be on, near to, or far from tectonic plate boundaries. Ex. Hawaii
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Which Direction is the PACIFIC plate moving towards?
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Hazards
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Clicker question Felsic lava is usually identified by its color and its: a)silica content. b)ropy texture. c)rounded shapes. d)sulfur content.
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Earthquake- Sudden release of energy in the Earth’s crust, occurring at a Fault
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Faults are breaks in the Earth’s crust –Multiple Faults are called Fault Zones
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Three types of Faults 1.Strike slip fault –S–San Andreas 2.Normal Fault 3.Reverse Fault
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Earthquakes are a result of elastic rebound. –fault is locked; stress builds; rocks “bend” –When stress is too high, rocks break –Rocks rebound back to original shapes We call this THE ELASTIC REBOUND THEORY
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Earthquakes The point at which the movement occurs or the center of an Earthquake is called its Focus. The point directly above the Focus at the Surface is known as an Earthquakes EPICENTER
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Energy that is being released from the movement of the tectonic plates, is released IN THE FORM OF vibrations, in other words WAVES. WAVES are measured by an instrument called a seismograph –Measure vibrations of Seismic waves
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Earthquakes have 3 types of waves –B–Body Waves --S waves –S–Surface waves
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Body Waves –P–P-waves: Primary Waves Fastest waves, travels through both solids and liquids First to reach the seismograph Moves rock back and forth in same direction as the wave travels- compression
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P-waves
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Body Waves S-waves –S–Secondary Waves –C–C–C–Can only travel through solids –M–M–M–Moves rock particles side to side, at right angles
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S-waves
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Surface Waves Slowest moving waves –C–Cause the most damage –2–2 types of surface waves Love waves Rayleigh waves
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Love waves –Move side to side –And perpendicular to the wave motion
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Surface Waves Rayleigh waves –Elliptical waves –Similar to water waves
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Locating an epicenter Difference between arrival times of P and S waves –T–T–T–This tells you the distance to the epicenter –N–N–N–Need 3 different stations to find the epicenter –T–T–T–This is called triangulation
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Time-travel graph
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Earthquakes Station P-Wave Arrival (hrs:min:sec) S-Wave Arrival (hrs:min:sec) S-P Lag Time (min:sec) Distance (km) Flagstaff 04:14:1504:18:45 Tucson 04:22:3004:30:00 Reno 04:18:4504:21:15
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Earthquakes Which station A or B is closer to the epicenter of the Earthquake?
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Earthquake Magnitude Seismic Station Epicenter Distance (km) Maximum amplitude of S-wave (mm) St. Louis, MO28050 Springfield, IL6002 Memphis, TN60500
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Earthquake scales –R–R–R–Richter Scale – measures magnitude or energy of earthquake –1–1–1–1-10 Earthquakes are measured by two different scales.
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Earthquake scales Mercalli Scale – – m– m– m– measures intensity of earthquake –I–I–I–Intensity = Damage caused –M–M–M–Measured with Roman Numerals –I–I–I–I – XII (1-12)
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Earthquakes Earthquakes are measured by two different scales. –Richter Scale – measures magnitude or energy of earthquake 1-101-10
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