why at the super CONDUCTOR magmatic the magmatic field is so high?
361293
Do you mean "magnetic"?????
833924
I think volcanic exhalatives formed from molten material rocks under great heat and pressure.
29120
Here is a chart of various estimates of the mantle's composition that have been made:\nhttp://www.mpch-mainz.mpg.de/~jesnow/Ozeanboden/2004/Lecture4/Composition.html\n\nThe answer in terms of minerals is (I quote) "The uppermost mantle is comprised of a peridotite with about 60% olivine 30% enstatite 6% clinopyroxene, 2% plagioclase and 2% spinel. At slightly greater depth, the plagioclase disappears and is replaced by spinel and clinopyroxene. Deeper still, garnet appears." from the above site. \n\nThe other thing you should realize is that while the earth's mantle may be 'plastic' it is not molten. From Wikipedia: "Although these temperatures far exceed the melting points of the mantle rocks at the surface, particularly in deeper ranges, they are almost exclusively solid. The enormous lithostatic pressure exerted on the mantle prevents them from melting."  From: http://en.wikipedia.org/wiki/Mantle_%28geology%29\n\nMagma coming from volcanoes actually originates in the asthenosphere, which is above the mantle.
752200
1.the molten mixture of rock-forming subtances, gases,and water deep in earths mantleis called magma .\n2.the ring of fire is a belt of volcanoes around the rim of the pacific ocean.\n3.the more Silica that the magma contains, the thicker the magma is.\n4.An eruption happens when an explosive erruption hurls ash,cinder,bombs,and gases out of a volcano. \n5.in a process called smeltin, an ore is melted to separate the use full metal from other elements from the ore.\n6.the property of density is the mass of the minral sample per unit volume.
905674
There are mainly 2 broad classes of magma, rhyolitic and basaltic. Due to the chemical characters(more mg and fe) of the basaltic magma, it is denser but less viscous than the acidic (rhyolic) magma.  The rhyoltic lava due to its excess silica content are highly viscous and due to this reason after eruption from the plate collision site(normally we find volcanic eruption where an ocenic plate subducts beneath a continental plate though there are another kind of volcanic site called hotspot volcano which can be anywhere regardless of the plate position)it mounts up significantly but the basaltic lave flows downslope and  cannot mount up ( eg Deccan Trap in India and the whole ocean crust).  So we find the volcanoes are mainly made up of rhyolitic lava.
51754
mafic magma - about 1100 Celcius\nintermediate magma - about 1000 Celcius\nfelsic magma - about 800 Celcius
244145
Not exactly pressure.  Tectonic plates under the Earth's crust are constantly in motion.  When they collide, mountains are formed.  These mountains become volcanoes when the tectonic plates hit each other and then move further apart, therefore creating a direct channel to the molten core of the earth.  When the molten material builds up it shoots up the hole of a volcano.
1175553
This would be false.\n\nIt has to do w/ convection currents in the mantle. This is the driving force behind plate tectonics.\n\nConvection currents are caused by uneven heating of molten rock in the mantle. As magma rises toward the crust, it becomes cooler & will then sink. As it sinks it will become hotter again causing a current to form.\n\nThis current actually moves the lithospheric plates. In some places where the lithospheric plates are broken they may be subducted but in others they will not. In this case (continental/continental boundaries) neither will be subducted. They will crumple up & deform. Many mountain ranges have been formed through continental/continental crust deformation.
819640
The most common place to find shield volcanoes is over hotspots (such as Hawai'i, the Galapagos, etc.). This is because hotspot magmas are almost always hot basalts and therefore the erupted lavas have low viscosities. Low viscosity lavas cannot be piled up very steeply so they form shield volcanoes.\nSubduction-zone magmas are almost always cooler and they are higher in silica, both qualities that make the lavas more viscous. These magmas are able to pile up into steep domes and additionally make the volcanoes more explosive so that they have a greater percentage of ash. This makes the volcanoes steep strato-cones instead of shields. It isn't impossible to find shield volcanoes along lines of arc volcanoes (for example Masaya in Nicaragua), but it is rare.
523806
viscous felsic or high silica magmas
1150478
It's widely believed in the scientific community that the earth has a liquid mantle (that's where magma/lava comes from) and a solid super-hot iron core.  Good luck digging through that.
228826
It's because as the slab descends, it stays fairly cold (because rock doesn't conduct heat very well!), and the pressure increases.  As the pressure increases, certain minerals change their shape to more compact arrangments, typically losing water and other "volatiles" (this is called slab dehydration).  When these volatiles are lost, they move upwards into the overlying "mantle wedge", where they lower the melting point of the rock.  It's from here that magmas arise.  The reason for the 100km or so distance from the zone of subduction is due to the slab "dehydration" not occuring until a certain depth, and because the slab typically descends at an angle of ~60deg
129623
The dynamo theory (that the earth is maganetic) is actually due to the fact that the outer crust is molten iron.  This iron is moving around inside the earth at very high temperatures.  Physics tells us that moving metals will create  a magnetic field.  This is why we have the magnetic field around the earth.
975488
When plates are diverging they are pulling apart and magma can come up from under the crust to fill the gap. This can create mid-ocean ridges, like the Mid-Atlantic Ridge, which is an underwater mountain range that runs about the whole length in the center of the Atlantic ocean.
563621
yes i won 1st place last week on how does density affect the movement of magma? i can give u the whole project nd what to do just email me my email is my display name at yahoo nd im in 8th grade nd they might even put my board in the metropalitan museum of art
846532
There are several processes in Plate Tectonics that cause volcanism, but they result in two main types of volcanism.\n\nVolcanism in subduction is caused by volitals, like H2O, CO2. These are carried down by the plate, mainly in the form of weak minerals. These minerals break down with pressure and temperature into stronger minerals that don't contain water and carbon dioxide. The leftover gases and liquids travel into the mantle (the mantle wedge) and hydrate the mantle, causing melting. The melt rises and then... volcano!\n\nThe other main cause is from rising mantle material, which forms decompression melting. Basically, hot mantle is kept from melting by the pressure of the earth at depth. When this material rises, the pressure drops much faster than the temperature, and thus it partially melts. This mainly occurs at divergent boundaries and hot spots, which are areas in plate tectonics that have rising materials or spreading.\n\nBy the way, as far as scientists know, the largest ever was the 27.8 Ma eruption of the Fish Canyon Tuff at La Garita in Colorado, estimated at 3,000 - 5,000 cubic km.\n\nTambora in 1815 was the largest in recorded history, 100 cubic km.
24742
There are volcanoes because of the interaction between multiple plate boundaries which causes the magma in the upper mantle (from beneath the crustal lithosphere) to rise, erupt and form lava at the surface.  \n\nVolcanoes tend to occur at either subduction zones, rifts or at hot spots.  Subduction zones are located at convergent oceanic/oceanic or oceanic/continental plate boundaries, where the denser oceanic crust sinks into the mantle beneath the other plate.  The minerals in the subducted slab dehydrates through metamorphic processes, which releases fluids to the mantle wedge to produce the melt (magma), which erupts to form volcanoes.  \n\nFor rifts, during the early stages of continental rifting (where continents are pulled apart because of extensional forces), volcanic activity can occur because crustal extension can allow magma to rise and intrude further up the crust.  Therefore, volcanic activity can occur in such situations.  eg: East African Rift. \n\nIn mid oceanic ridges, the divergent motion of oceanic plates allows mantle material to rise from below.  This tends to form a submarine ridge rather than a volcano.\n\nHowever, volcanoes can occur within the plate.  These are usually called hotspots, where a plume (a plume of anomalously hot magma) rise from deep within the mantle (probably as deep as the core-mantle boundary) to the surface.  These are stationary and therefore, it can leave a trail of volcanoes as the lithospheric plates move over the mantle.  Eg: Hawaii-Emperor seamount chain.