1. Mrs. NeistadtPhysical Science Chapter 29VOLCANO TYPES

2. VOLCANO REVIEWReview Questions:1. On what kind of plate boundaries do volcanoes appear?2. What is the difference between magma and lava? 3. THREE TYPES OF VOLCANOES: *There are three types of volcanoes: *Shield Volcano *Cinder cone Volcano *Stratovolcano 4. *WHY DO WE HAVE DIFFERENT TYPES OFVOLCANOES? The process of magma formation is differentat each type of plate boundary. Therefore, the composition of magma differsin each tectonic setting. *Tectonic settings determine the types ofvolcanoes that form and the types oferuptions that take place. 5. *SHIELD VOLCANO Form from manylayers of runny lava. Very wide, not toosteep. Biggest type ofvolcanoes Tallest mountain inthe world is MaunaKea (measures fromsea floor to top) non explosiveeruptions 6. MAUNA KEA, HAWAII 7. TECTONIC SETTING (LOCATIONS)Darwin, ashieldvolcano intheGalapagosIslands.Shield-type volcanoes are almost exclusively located in an oceanicsetting, in the middle of oceanic basins or as isolated islands,typically somewhat distant from continental shorelines. 8. MORPHOLOGY (SHAPE and SIZE)Fernandina,a shieldvolcano intheGalapagosIslands.Shield volcanoes tend to have very gentle (low-angle) slopes,sometimes referred to as the overturned soupbowl profile.Although not as visually dramatic as stratovolcanoes, they aregenerally much larger, particularly in diameter. 9. ACTIVITY Continued;San Martin,a smallshieldvolcano offthe coast ofBaja,California.These volcanoes can form during single long-term effusive eruptionsand remain active for tens to hundreds of thousands of years. Duringtheir lifespans, dormant intervals may also last thousands to tens ofthousands of years. 10. *CINDER CONE VOLCANO Smallest type of volcano Most common Made from pyroclastic material (materialshot out of a volcano) Form a large crater Explosive! 11. PARICUTIN, MEXICO 12. CINDER CONESCinder cones, also known as scoria cones, represent the smallest typeof volcano, rarely exceeding ~1000 ft in height. They are entirelycomposed of pyroclastic materials (volcanic ash). They are quitecommon and associated with both composite or shield volcanoes.They typically occur on the flanks (sides) of these volcanoes wheresecondary vents or fissures have opened up. Scoria cone near the summit of Mauna Kea, Hawaii.La Poruna, ChileSunset crater, Arizona 13. CINDER CONESA small cinder cone (~225m high, ~200m in diameter) located onBarren Island, a part of the Andaman Islands chain situated justnorth of Indonesia. 14. CINDER CONESKwohl Butte cinder cone is one of a chain of small cones trendingsouth of Mt. Bachelor (a composite volcano) in the Cascade range ofOregon. It is ~ 12,000 years old. 15. CINDER CONESThe Cerro Negro cinder cone represents one of Nicaraguas youngestvolcanoes. It was born in April of 1850 and has grown to a height of250 m. 16. PARICUTIN, MEXICO 17. *STRATOVOLCANO OR COMPOSITE VOLCANO: Eruptions alternate between explosive andnon-explosive. Sometimes they have runny lava layers,other times the have pyroclastic materialsform layers. Have a wide base and steep sides. Have a crater Mount Fuji 18. MOUNT FUJI 19. MORPHOLOGY (SHAPE and SIZE)Mayon, themost activecompositevolcano inthePhilippines.Stratovolcanoes are what most people associate with the wordvolcano. These towering peaks rise hundreds to several thousandmeters above their surroundings, often visually dominating thelandscape around them. They tend to be steep-sloped. 20. MORPHOLOGY (SHAPE and SIZE) Continued;Niragongo,an activecompositevolcanolocated onthe borderof Rwandaand Zaire,East Africa.The relatively steep profile of stratovolcanoes are due to their rockmakeup. They are formed of stratified layers of both viscous lavaflows and fragmental material (volcanic ash). 21. ACTIVITY Kamen (left) and Kliucheyskoi, two of Kamchatkas highest composite volcanoes.Due to the viscous nature of the lavas associated with compositevolcanoes, they tend to plug up. If the pressures are great enough,these volcanoes may literally blow their top, and can be quiteviolent and dangerous! 22. ACTIVITY Continued; Colima, Mexicos most active composite volcano.Some stratovolcanoes may form in a few thousand years, but remainactive for tens to hundreds of thousands of years. During theirlifespans, dormant intervals may also last tens of thousands of years. 23. *2 TYPES OF ERUPTIONS *Explosive: volcanoesthat build enoughpressure to blow itstop, sendingpyroclastic materialinto the air. *Non explosive: Buildonly enough pressureto allow lava to rundown its sides. 24. NON EXPLOSIVE ERUPTION Mafic: refers to rocks and magma rich in ironand magnesium. This type of lava that is very runny. As magma nears the surface there is littlepressure, causing gasses escape easily. Magma low in Silica have quiet eruptions 25. EXPLOSIVE ERUPTIONS Felsic: means magma with high silica andfeldspar content. Felsic magma traps water and gas bubbles,which leads to lots of pressure. Silica acts like a cork Explosive eruptions are caused by a build upof high pressure. Convergent zones contain lots of water,therefore have explosive eruptions. 26. *PYROCLASTIC MATERIALS *Material that is thrown into the air during anexplosion. *Volcanic bombs: large blobs of magma thatharden in the air. Lapilli: pebble size rocks Volcanic ash: tiny powder like material 27. *FOUR TYPES OF LAVA Aa: lava that is thick and sharp Pahoehoe: lava that forms thin crust andwrinkles Pillow lava: lava that erupts under water, hasa round shape Blocky lava: cooler, lava that does not travelfar from eruption, jagged when it dries. 28. *AA *lava that is thick and sharp 29. *PAHOEHOE: *lava that forms thincrust and wrinkles 30. *PILLOW LAVA *lava that eruptsunder water, has around shape 31. *BLOCKY LAVA *cooler, lava that doesnot travel far fromeruption, jagged whenit dries. 32. WHY DO COMPOSITE VOLCANOES TEND TO BE EXPLOSIVE AND SHIELD VOLCANOESNON-EXPLOSIVE??1) CHEMISTRY (COMPOSITION) OF LAVA2) LAVA TEMPERATURE COMPOSITE SHIELD- Higher silica content of lavas -Lower silica content of lavasmake them more viscous (thick).make them more fluid (runny).- Lava temperatures are- Lava temperatures are quitegenerally a few hundred degreeshot, ~ 2200oF, making it easiercooler than those of shieldfor these lavas to flow likevolcanoes, making the lavaswater.thicker in consistency. 33. OTHER CHARACTERISTICS ASSOCIATED WITH COMPOSITE AND SHIELDVOLCANOESBoth volcano types commonly contain abundant gases dissolved inthe magma (especially composite-type).GAS EMISSIONS:Water vapor (steam) is the most common gas emitted by a volcano(70-90%). Other common gases include; CO2, CO, SO2, SO, and avariety of other sulfurous (stinky) gases.It is the buildup of gas pressures that commonly cause compositevolcanoes to violently explode when they get plugged up.ASH EMISSIONS:Pyroclastic (means hot particle) eruptions volcanic ash areparticularly common with composite volcanoes and uncommon withshield volcanoes. 34. WHY ARE THESE TWO VOLCANO TYPES (COMPOSITE-SHIELD) SO DIFFERENT???It is most fundamentally tied to the source material from which thesetwo types of volcanoes come from, and this ties back to their tectonicsetting!!!Recall, that composite volcanoes primarily have a continentalsetting, and shield volcanoes have an oceanic setting. 35. THE ROCK CYCLE 36. REVIEW1. What determines the type of volcano found in a particular location?2.What type of lava creates wrinkled lava flows?3. What type(s) of volcanoes have the most explosive eruptions?