5+Volcano+(Part+1)+Definition,+Types+of+Volanoes+and+Birth+or+Death

 **XAVIER SCHOOL HIGH SCHOOL**

SCIENCE ADVANCED CLASS WRITTEN OUTPUT (OUTLINE)  **TOPIC:** Definition, Types of Volcanoes, Birth/Death of a Volcano and Types of Explosions


 * I.** **DEFINITION** of a Volcano
 * A.** A volcano is a hole, deep opening or vent in the Earth’s surface through which molten rock, hot gases and solid material (rocks and ashes) escape from deep in the Earth.
 * 1.** Sometimes, also known as “chimney’s of the Earth.”
 * B.** A volcano is a landform (usually a mountain) where (liquid rock) erupts through the surface of the planet.
 * C.** In simple terms, a volcano is a mountain that opens downward to a pool of molten rock (**magma**) below the surface of the earth.
 * D.** It is a hole in the Earth from which molten rock and gas erupt.
 * E.** Volcanoes usually form along plate bounderies and hotspots.
 * F.** The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology.
 * G.** The study of volcanoes is called volcanology, or sometimes, vulcanology.


 * II.** **PARTS** of a Volcano
 * A.** Magma Chamber
 * 1.** Thick molten magma travels upwards from the mantle and collects in large pockets in the crust where it mixes with gases and water.
 * B.** Central Vent
 * 1.** The main vent or chimney rises from the magma chamber. Magma flows up the vent to erupt on the surface as lava.
 * 2.** A central vent is an opening at the Earth's surface of a volcanic conduit of cylindrical or pipe-like form.
 * C.** Side Vent (Secondary Vent)
 * 1.** Under pressure, this side vent branches off from the central vent and carries lava upwards through cracks in the rocks to ooze out the side of the volcano.
 * D.** Crater
 * 1.** The funnel-shaped opening at the top of the volcano enables lava, ash, gas and steam to erupt.
 * 2.** It is the mouth of the volcano. It always surrounds a volcanic vent.
 * E.** Cone
 * 1.** The cup-shaped cone is built by ash and lava from a number of eruptions.
 * F.** Sill
 * 1.** Magma dosen’t always find a way out to the surface. Some gathers, cppls and vecomes solid between two underground layers of rock in the Athenosphere.
 * 2.** A flat piece of rock formed when magma hardens in a crack in a volcano.
 * G.** Vent
 * 1.** An opening in Earth's surface through which volcanic materials escape.
 * H.** Fissure Eruption
 * 1.** Some magma forces its way upwards through vertical cracks in the rocks, and erupts to the surface.
 * I.** Parasitic Cone (Satellite Cone or Secondary Cone)
 * 1.** A small cone-shaped volcano formed by an accumulation of volcanic debris.
 * J.** Flank
 * 1.** One of the numerous sides of the volcano.
 * K.** Conduit (Pipe)
 * 1.** An underground passage magma travels through, or a passage followed by magma in a volcano.
 * L.** Summit (Apex)
 * 1.** Highest point in a Volcano.
 * M.** Throat
 * 1.** It is the entrance of a volcano. The part of the conduit that ejects lava and volcanic ash.
 * N.** Fumarole
 * 1.** This is the part where gases escape when an eruption happens.

a. The tephra is most commonly of lapilli size, although bomb -size fragments and lava spatter may also be present. b. The tephra fragments typically contain abundant gas bubbles (vesicles), giving the lapilli and bombs a cindery (or scoriaceous ) appearance. c. The tephra accumulates as scoria-fall deposits which build up around the vent to form the volcanic edifice. a. the build up of tephra on the downwind flank of the edifice b. elongation of the volcano above an eruptive fissure, c. partial rafting of an outer wall of the volcano due to basalt lava oozing outward from beneath the volcano edifice. a. It is one of several parasitic cones on the northwest flank of Las Pilas volcano. Cerro Negro has erupted more than twenty times since it was born in 1850. b. Its most recent eruptions were in 1992 and 1995. a. This classic stratovolcano shape is exemplified by many well-known stratovolcanoes, such as Mt. Fuji in Japan, Mt. Mayon in the Philippines, and Mt. Agua in Guatemala.
 * III.** **TYPES** of Volcanoes
 * A.** Scoria Cone (Cinder Cones)
 * 1.** This volcano has straight sides with steep slopes and a large summit crater.
 * 2.** Normally is made up of Basalt tephra, but occasionally andesitic.
 * 3.** Scoria cones are the most common type of volcano.
 * 4.** They are also the smallest type, with heights generally less than 300 meters.
 * 5.** They can occur as discrete volcanoes on basaltic lava fields, or as parasitic cones generated by flank eruptions on shield volcanoes and stratovolcanoes.
 * 6.** Scoria cones are composed almost wholly of ejected basaltic tephra.
 * 7.** The edifice has very steep slopes, up to 35 degrees, although older eroded scoria cones typically have gentler slopes, from 15 to 20 degrees.
 * 8.** Unlike the other two main volcano types, scoria cones have straight sides and very large summit craters, with respect to their relatively small edifices.
 * 9.** They are often symmetric, although many are asymmetric due to
 * 10.** Where scoria cones have been breached, they typically reveal red-oxidized interiors.
 * 11.** Scoria cones are generated by Strombolian eruptions, which produce eruptive columns of basalt tephra generally only a few hundred meters high.
 * 12.** Many scoria cones are monogenetic in that they only erupt once, in contrast to shield volcanoes and stratovolcanoes.
 * 13.** An exception is the Cerro Negro volcano in Nicaragua, which is the Earth's most historically active scoria cone.
 * 14.**
 * B.** Shield Volcano
 * 1.** Shield volcanoes are broad, low-profile features with basal diameters that vary from a few kilometers to over 100 kilometers (e.g., the Mauna Loa volcano, Hawaii).
 * 2.** Their heights are typically about 1/20th of their widths.
 * 3.** The lower slopes are often gentle (2-3 degrees), but the middle slopes become steeper (~10 degrees) and then flatten at the summit.
 * 4.** This gives shield volcanoes a flank morphology that is convex in an upward direction.
 * 5.** Their overall broad shapes result from the extrusion of very fluid ( low viscosity ) basalt lava that spreads outward from the summit area, in contrast to the vertical accumulation of airfall tephra around scoria-cone vents, and the build-up of viscous lava and tephra around stratovolcanoes.
 * 6.** Cross-sections through shield volcanoes reveal numerous thin flow units of pahoehoe basalt, typically < 1 m thick.
 * 7.** Pyroclastic deposits are minor, normally less than 1%, and of limited dispersal, generally from flank eruptions associated with parasitic scoria cones, or from rare, localized hydrovolcanic eruptions.
 * 8.** Shield volcanoes are generated by Hawaiian eruptions.
 * 9.** However, there is some variability in their eruptive style, which translates into variations in shield morphology and size.
 * 10.** The almost perfect symmetry and small volume (~15 km3) of Icelandic shields, for example, stands in marked contrast to the elongation and huge volume (thousands of km3) of Hawaiian shields.
 * 11.** These variations are largely attributed to the monogenetic, small-volume, centralized summit eruptions, typical of icelandic shields, and the polygenetic, large-volume, linear fissure eruptions, typical of most hawaiian shields.
 * 12.** Still different are the symmetrical Galapagos shields, which have steep middle slopes (>10 degrees) and flat tops occupied by large and very deep calderas.
 * 13.** These shield types appear to be generated by ring-fracture eruptions, which delineate the sides of the caldera and mark the site of caldera collapse.
 * C.** Stratovolcanoes (Composite Cones)
 * 1.** Stratovolcanoes, also known as composite cones, are the most picturesque and the most deadly of the volcano types.
 * 2.** Their lower slopes are gentle, but they rise steeply near the summit to produce an overall morphology that is concave in an upward direction.
 * 3.** The summit area typically contains a surprisingly small summit crater.
 * 4.** In detail, however, stratovolcano shapes are more variable, primarily because of wide variations in eruptive style and composition. Some may contain several eruptive centers, a caldera, or perhaps an amphitheater as the result of a lateral blast (e.g., Mt. St. Helens ).
 * 5.** Stratovolcanoes have a layered or stratified appearance with alternating lava flows, airfall tephra, pyroclastic flows, volcanic mudflows ( lahars ), and/or debris flows.
 * 6.** The compositional spectrum of these rock types may vary from basalt to rhyolite in a single volcano; however, the overall average composition of stratovolcanoes is andesitic . Many oceanic stratovolcanoes tend to be more mafic than their continental counterparts.
 * 7.** The variability of stratovolcanoes is evident when examining the eruptive history of individual volcanoes.
 * 8.** Mt. Fuji and Mt. Etna, for example, are dominanted by basaltic lava flows, whereas Mt. Rainier is dominated by andesitic lava, Mt. St. Helens by andesitic-to-dacitic pyroclastic material, and Mt. Lassen by dacitic lava domes.
 * 9.** Stratovolcanoes typically form at convergent plate margins, where one plate descends beneath an adjacent plate at the site of a subduction zone.
 * 10.** Examples of subduction-related stratovolcanoes can be found in many places in the world, but they are particularly abundant along the rim of the Pacific Ocean, a region known as Ring of Fire.
 * 11.** In the Americas, the Ring of Fire includes stratovolcanoes forming the Aleutian islands in Alaska, the crest of the Cascade Mountains in the Pacific Northwest, and the high peaks of the Andes Mounains in South America.

a. At the mid-oceanic ridges, two tectonic plates diverge from one another. b. New oceanic crust is being formed by hot molten rock slowly cooling and solidifying. c. The crust is very thin at mid-oceanic ridges due to the pull of the tectonic plates. d. The release of pressure due to the thinning of the crust leads to adiabatic expansion, and the partial melting of the mantle causing volcanism and creating new oceanic crust. e. Most divergent plate boundaries are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor. f. Black smokers or deep sea vents are an example of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland. a. Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. b. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. c. Water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, creating magma. d. This magma tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. e. When it does reach the surface, a volcano is formed. Typical examples for this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. a. Hotspots are not usually located on the ridges of tectonic plates, but above mantle plumes, where the convection of the Earth 's mantle creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth. b. The temperature of the plume causes the crust to melt and form pipes, which can vent magma. c. Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes dormant after a while and a new volcano is then formed as the plate shifts over the hotspot. d. The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hot spot.
 * IV. BIRTH AND DEATH** of a Volcano
 * A. BIRTH** of a Volcano
 * 1.** Divergent Plate Boundaries
 * 2.** Convergent Plate Boundaries
 * 3.** Hotspots
 * B.** **DEATH** of a Volcano
 * 1.** Figuratively, a volcano is dead if it is extinct.

a. Craters are the funnel-shaped hollows or cavities that form at the openings or vents of the volcanoes. b. The simplest craters occur on the top of cones and usually have a diameter of 1 km or less. c. Volcanoes can also form craters at the sides called side vents or secondary vents. a. Calderas are very large craters formed by an exlplosion or massive volcanic eruption. b. In here, the magma chamber empties because it spurts out all the magma it can from the magma chamber, so, the colcano cannot support its weight, so the volcano collapses. c. Calderas are almost 5km in diameter. d. When a volcano is extinct, a caldera can fill with water to form a lake. a. **Magma** is liquid rock inside a volcano. a. **Lava** is liquid rock (magma) that flows out of a volcano. Fresh lava ranges from 1,300° to 2,200° F (700° to 1,200° C) in temperature and glows red hot to white hot as it flows.
 * V.** **WHAT’S THE DIFFERENCE BETWEEN?**
 * A.** Craters and Caldera
 * 1.** Craters
 * 2.** Caldera
 * B.** Lava and Magma
 * 1.** Magma
 * 2.** Lava

a. Aa Lava b. Block lava c. Pahoehoe a. Volcanic Dust b. Volcanic Ash c. Volcanic Bomb d. Volcanic Block e. Cinder
 * VI.** **Volcanic Materials** Emmitted
 * A.** Magma/Lava
 * 1.** Types/ Colors of Lava
 * a.** Light-colored
 * i.** little water
 * ii.** rich in silica and aluminum
 * iii.** very viscous
 * iv.** forms rhyolite rocks
 * b.** Dark-colored
 * i.** contains a lot of water
 * ii.** rich in iron and magnesium
 * iii.** very fluid
 * iv.** forms basalt rocks
 * 2.** Types of Lava Flow
 * i.** viscous magmas with lava fountaining
 * ii.** rough surface onwards.
 * i.** stronger and thicker than aa lava flows
 * ii.** moves very slowly
 * iii.** has cubic masses with smooth surfaces when it cools down
 * i.** Flows smoothly
 * ii.** solidifies to a smooth surface
 * iii.** ropy or billowy appearance
 * B.** Volcanic Gases
 * 1.** These gases normally include carbon monoxide, sulfur dioxide, hydrogen sulfide, carbon dioxide and many more.
 * C.** Lahar
 * 1.** This is an Indonesian term for a volcanic mudflow.
 * 2.** These lethal mixtures of water and tephra have the consistency of wet concrete, yet they can flow down the slopes of volcanoes or down river valleys at rapid speeds, similar to fast-moving streams of water.
 * 3.** These mud slurries carry debris ranging in size from ash to lapilli, to boulders more than 10 meters in diameter.
 * 4.** Lahars can vary from hot to cold, depending on their mode of genesis. The maximum temperature of a lahar is 100 degrees Centigrade, the boiling temperature of water.
 * 5.** This is normally one of the things people fear the most, because it can burry people alive.
 * 6.** Lahar production can be made faster if there is lots of water. An example would be a typhoon or there are ice and glacier surrounding the place.
 * D.**
 * E.** Pyroclastics
 * 1.** These are hot debris in eruptions.
 * i.** These are as tiny as a grains of flour.
 * i.** These are rock particles about the size of a rice grain.
 * i.** This is a rounded piece of hardened lava.
 * i.** This is a piece of lava that has sharp corners.
 * i.** This is a bubbly rock formed from cooling in the air.

VII. **TYPES** of Volcanic Eruption
 * A.** Hawaiian
 * 1.** Large amounts of runny lava erupt, and produce large, low volcanoes.
 * B.** Peleean
 * 1.** Blocks of thick sticky lava are followed by a burning cloud of ash and gas.
 * C.** Strombolian
 * 1.** Small sticky lava bombs and blocks, ash, gas and glowiong cinvers erupt.
 * D.** Vulcanian
 * 1.** Violent explosions shoot out very thick lava and large lava bombs.
 * E.** Plinian
 * 1.** Cinders, gas and ash erupt great distances into the air.


 * VIII.** **Key** Terms
 * A.** Tephra
 * 1.** A term used to describe any material produced in an explosive volcanic eruption.
 * B.** Andesite
 * 1.** A type of volcanic rock that has small crystals (sometimes too small to see), a gray color, lighter in color when compared to basalt (dark gray to black)
 * C.** Basalt
 * 1.** A dark colored igneous rock (dark color is caused by high amounts of iron and magnesium) with very small minerals, cooled relatively quick


 * Sources:**
 *  Crowley, C. (1996). Volcano. In Travers, B. (ed.), The Gale encyclopedia of Science (Vol.6, pp. 3868-3874). Detroit, MI: Gale
 *  http://www.woodlands-junior.kent.sch.uk/Homework/mountains/volcanoes.htm
 *  http://www.enchantedlearning.com/subjects/volcano/printout.shtml
 *  http://volcano.oregonstate.edu/vwdocs/glossary.html
 *  http://www.msnucleus.org/membership/html/k-6/pt/dictionary/ptdictionary.html
 *  http://www.geology.sdsu.edu/how_volcanoes_work/
 *  http://www.universetoday.com/guide-to-space/earth/parts-of-a-volcano/

