Volcanos

  Geol 105 presentation notes on plate tectonic relationship with the volcanoes:      Plate tectonic in correlations@ volcanoes formed nearby plate boundaries. 

Volcanoes formed near Mid‐oceanic ridge:    The mantle phase of athesophere, where mantle convection and partial melting  take place  The convection which is largely motivated the magnetic and self circulation nature, by providing push and pull forces for plates.  All plates on earth are fragmentized and have a floating nature.  The crash between two different plated that have different density, usually  oceanic crust subduct under the continental crust, provided the mantle phase  with supplies of land crust.  Partial melting began to take place when plate subducted to certain level. Water followed the subduction zone into the boundary, which the helped the  magma to speed up the melting process.  The newly magma add up to the content of the tank of magma convection and  provides pressure within the magma system. 

With the pressure, the magma was compressed in such a proportion that it  burst thought the line of weakness into the lithosphere. Then it breaks thought to the lithosphere in within and filled with sills and dikes.  The magma that finally that goes all the way to the ground became lava.  The accumulation of lava formed the layers which became part of the volcano.  The lava interacted with the surrounding environment and became other type  of rocks.  The volcano that formed in the ocean will form basaltic rock due the intense  cooling environment. Where if it formed on land, it tend to have more carbonate composition.  Other then always moving along as plate boundaries change with movement,  hotspot does not move along as plate advance  The Hawaiian archipelago is constantly formed by the moving plate, which the  hotspot of it has been constant against the recycling process. 

 

Chemical Processes in Volcano Most of chemical processes in volcanoes occur in Magma Magma in the "chamber" evolves over time into chemicalcompositions which result in different forms of rock It is too hot within the chamber itself for rock to crystallize but on subsequent eruptions, lava which pours out of the chamber is composed of different material. Types of Magma Basaltic Magma -- 50% silica Initial magma Forms from partial melting of the mantle High in iron, magnesium Olivine - Mg2SiO4 to Fe2SiO4 Pyroxene -Ca(Mg,Fe,Al)(Al,Si)2O6 Plagioclase - CaAlSi3O8 to NaAlSi3O8 Andesitic Magma -- 60% silica

Forms from partial melting of mantle and or oceanic crust in the presence of water (reduces the melting temperature and thus the mineralogy and composition are different). Plagioclase - CaAlSi3O8 to NaAlSi3O8 Amphibole - NaCa2(Mg,Fe,Al)5(Si,Al)8O22(OH)2 Muscovite/Biotite - KAl2(Si3Al)O10(OH)2 Quartz - SiO2 Some chemicalprocesses Dehydration melting of peridotite and fractional crystallization Melting of subducted slab containing sediments Magma mixing between felsic rhyolitic and mafic basaltic magmas in an intermediate reservoir prior to emplacement or eruption.
Granitic Magma -- 70% silica Forms at depth within the lithosphere as they rise they lose water (as steam), and raises the temperature at which theycrystallize

Rich in silica, sodium, aluminum, and potassium Potash Feldspar - KAlSi3O8 Quartz - SiO2 Muscovite/Biotite - KAl2(Si3Al)O10(OH)2 Amphibole - NaCa2(Mg,Fe,Al)5(Si,Al)8O22(OH)2
Types of volcano Volcanoes are often classified by the size of activities and the materials, and it is important for us to know the types of eruption because it relates to the evolution of a volcanic land form andenvironment around the volcanoes. Generally, there are two kinds of main eruptions; explosive and effusive eruption. Explosive eruptions usually involve magma that is stickier and has more gas content. Effusive eruptions involve basaltic magma that is less sticky and contents less gas, so this type of eruption occurs quietly. There are many types of eruptions;...