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Engel’s Science on a shoestring © Simonized SCORIA CONE Volcanoes at Destructive Boundaries: 1. Plates move together or apart because of convection . currents 2. Heavier (Denser) oceanic plate is sub-ducted. 3. Friction between the plates and heat from the interior causes the subducting plate to melt. 4. Melting of the plate creates molten magma. 5. This magma is less dense than its surrounding rock and is erupted at the surface through a weakness in the crust, creating a volcano. 6. Volcanoes at convergent boundaries tend to be explosive due to the build up of pressure and gases. Straight sides with steep slopes; large summit crater, about 1,000 ft Basalt tephra; occasionally andesitic Strombolian SHIELD VOLCANO Very gentle slopes; convex upward Basalt lava flows Hawaiian- about 200-27,000ft STRATOVOLCANO 5-15,000 ft Highly variable; alternating basaltic to rhyolitic lavas and tephra andesite composition variable; alternating basaltic to rhyolitic lavas and tephra with an overall andesite composition Gentle lower slopes, but steep upper slopes; concave upward; small summit crater Volcanoes at Constructive Boundaries: 1. Plates move away from each (divergent) other due to convection currents 2. This creates a weakness or a ‘gap’ in the crust. 3. Magma is able to rise to plug the gap forming lava flows and submarine volcanoes. 4. As magma continues to build up above the surface of the ocean, volcanic islands (such as Hawaii) may form. 5. Eruptions at constructive boundaries tend to be gentle with little pressure build up. 1 Open the following link and answer the questions that follow. http://www.pbs.org/wnet/savageearth/animations/volcanoes/main.html 1. Under the volcano cone is the ___________ chamber that hold molten magma. 2. The explosive escape of the gases from the magma causes a violent ______________________. 3. Because the fragments of rock and ash are heavier than air and may not mix with enough air to remain high aloft, they may surge down the sides of the volcano as dangerous "__________________________flows." Open the following link and answer the questions that follow. http://www.pbs.org/wnet/savageearth/animations/index.html 4. A stratovolcano is made out of _____________ of ash and lava from previous eruptions. 5. Magma is lighter or less dense than solid ________________. 6. Once magma reaches the surface it is called _________________. Open the following links and answer the questions that follow. http://www.classzone.com/books/earth_science/terc/content/investigations/es0810/es0810page01.cfm 7. Which island is made of at least three volcanoes? _______________ 8.On which island is Pearl Harbor located? _________________ http://www.classzone.com/books/earth_science/terc/content/investigations/es0810/es0810page03.cfm 9. What is the Lithosphere floating on? _________________ 10. Where are the extinct volcanoes found? ________________________ ______________________________________________________________ 11. Where are the active one(s) found? ________________________________ ______________________________________________________________ http://www.classzone.com/books/earth_science/terc/content/investigations/es0810/es0810page07.cfm 12. Where is Yellowstone National Park located? _________________ 13. What can you use as proof that there is a hotspot under Yellowstone? ___________________________________________________ Bonus http://www.classzone.com/books/earth_science/terc/content/investigations/es0810/es0810page08.cfm What is the rate of plate motion under Yellowstone for the last 600,000 years? _________________ 2 Using dichotomous keys to determine the type of rock (Go to the wet side of the lab now!) Igneous rock was once melted and cooled to form a solid. The faster the rock cools, the smaller the crystals in the rock. When rock cools very inside the earth slowly we call it intrusive. The crystals that form grow to large sizes like the granite in our lab desk tops. When rocks cool quickly, near or even at the surface of the earth we call it extrusive and the crystal size or grain is sometimes so small as not to be visible to the human eye. Some rocks that cool vary fast have no crystals structure at all. In some cases as the rocks burst to the surface gasses expand under the reduced pressure to form pockets of gas like Swiss cheese and reduce the density of the rock. Rock type Crystal size Intrusive Coarse (Larger than sand sized) Extrusive Fine (smaller than sandsized) Extrusive Extrusive Felsic (Aluminum) Low Light colored or red hued Element Composition Density Color Mafic (Iron and Magnesium) High Dark-colored or green hued Granite Gabbro Rhyolite Basalt Obsidian (Nearly same chemical makeup as Granite) Obsidian is called natural or volcanic glass because of atomic structure to glass. Color-black, red brown or gray Fractures curved structures. Volcanic glass that has many holes, so many sometimes it floats on water. Colorwhite, gray, grayish brown. Pumice (Nearly same chemical makeup as Granite) Igneous rock can be put in categories based on their color and crystal size. Below is a data table that lists some colors and crystal sizes. Data Table Crystal size Color Rock Name Large Generally pink 23. Large Black 24. Smaller than sand sized Blackish green 25. Smaller than sand sized Generally light colored 26. 3 27. List two intrusive rocks _____________________ and ________________________ 28. Did both of these types of rocks cool quickly or slowly? _____________________ 29. How do you know? _____________________________________________________ 30. Do all extrusive igneous rocks contain crystals? ___________________________________ _________________________________________________________________________ 31. Give two in this lab that do not ____________________ and ______________________ 32. Why do some igneous rocks have bubble holes? _______________________________ 33. Give two extrusive igneous rock that contain crystals, ________________and ______________________ 34. Obsidian and Granite have most of the same elements. How are they different? ______________________________________________________________________________ _____________________________________________________________________________ 35. What is the name of the igneous rock that has a blackish green color and cooled deep below the earth’s surface? ____________________________ 4 Volcanoes at Destructive Boundaries: 1. Plates move together or apart because of __________________ currents. 2. Heavier (______________) oceanic plates are ____________________. 3. _______________ between the plates and _______________ from the interior causes the subducting plate to melt. 4. Melting of the plate creates ___________________ _____________________. 5. Magma is less dense than its surrounding rock and is erupted at the surface through a weakness in the crust, creating a ______________________. 6. Volcanoes at convergent boundaries tend to be _________________ due to the build up of ____________________________and __________________________. Volcanoes at Constructive Boundaries: 1. Plates ________________________________________ (divergent) due to convection currents. 2. This creates a weakness or a ‘____________’ in the crust. 3. ____________________ is able to rise to plug the gap forming lava flows and submarine volcanoes. 4. As magma continues to build up above the surface of the ocean, __________________ islands (such as ___________________________________) may form. 5. Eruptions at constructive boundaries tend to be _________________________ with little __________________________ build up. 5 http://www.bbc.co.uk/sn/tvradio/programmes/supervolcano/flash/supervolcano.shtml Click on this site and watch the seismograph- Go to Seismic Signals Label all the continents- http://kids.earth.nasa.gov/archive/pangaea/Pangaea_game.html http://www.geology.sdsu.edu/how_volcanoes_work/ http://www.volcanolive.com/volcanolive.html http://volcano.wr.usgs.gov/vhpstatus.php 6