Why is the concentraion of water so low in basaltic lava at mid-ocean ridges and the water content much higher in andesite magma at subduction zones? If possible, link the two questions in your answer!
127746
It has to do with the amoungt of silica (SiO2) present in the magma.  Andesitic magma is very viscous, and very explosive, which is a function of the amount of silica.  The greater the percentage of silica, the more viscous the magma is.  With higher levels of silica present, and always high amounts of hydrogen, the possibility to create water under extreme conditions (eruption) has a greater potential with the Andesitic magma because of the greater supply of silica.  The greater supply of silica is linked to subduction zones because a large part of the melt is continental crust which is much higher in silica than oceanic crust.\n\nSo, the concentration of water is low in Basaltic Magma because the concentration of silica is also low.  That is also why Basaltic Lava flows instead of exploding.
277425
there is a hot core in the center of the earth, this escapes from fissures in the earths crust,finding its way up and out of the earth surface through fractures in the platelets. on these platelets the lava flows and when cooled becomes rock hard. when this happens in a volcano type of environment the pressure builds up over time, and the result is the "Blowing of the top/side" of the volcano, causing molten lava to flow, often causing damage to human, and plant life, that is around the base of the volcano..
443380
The Earth is formed of several layers that have very different physical and chemical properties. The outer layer, which averages about 70 kilometers in thickness, consists of about a dozen large, irregularly shaped plates that slide over, under and past each other on top of the partly molten inner layer. Most earthquakes occur at the boundaries where the plates meet. In fact, the locations of earthquakes and the kinds of ruptures they produce help scientists define the plate boundaries. \nThere are three types of plate boundaries: spreading zones, transform faults, and subduction zones. At spreading zones, molten rock rises, pushing two plates apart and adding new material at their edges. Most spreading zones are found in oceans; for example, the North American and Eurasian plates are spreading apart along the mid-Atlantic ridge. Spreading zones usually have earthquakes at shallow depths (within 30 kilometers of the surface).  \n\nTransform faults are found where plates slide past one another. An example of a transform-fault plate boundary is the San Andreas fault, along the coast of California and northwestern Mexico. Earthquakes at transform faults tend to occur at shallow depths and form fairly straight linear patterns. \n\nSubduction zones are found where one plate overrides, or subducts, another, pushing it downward into the mantle where it melts. An example of a subduction-zone plate boundary is found along the northwest coast of the United States, western Canada, and southern Alaska and the Aleutian Islands. Subduction zones are characterized by deep-ocean trenches, shallow to deep earthquakes, and mountain ranges containing active volcanoes.\n\nEarthquakes can also occur within plates, although plate-boundary earthquakes are much more common. Less than 10 percent of all earthquakes occur within plate interiors. As plates continue to move and plate boundaries change over geologic time, weakened boundary regions become part of the interiors of the plates. These zones of weakness within the continents can cause earthquakes in response to stresses that originate at the edges of the plate or in the deeper crust. The New Madrid earthquakes of 1811-1812 and the 1886 Charleston earthquake occurred within the North American plate.
430633
When two plates collide, they BOTH begin to go under a bit.  However, when a continental, and an oceanic plate collide, the oceanic plate ends up going under more.  Why?\n\nFor one thing, the continental plate is up higher than the oceanic plate to begin with.  After all, continental plates are always above sea level, and oceanic plates are always below sea level.  With the advantage of heighth, the continental plate usually pushes the oceanic plate below.\n\nFor another thing, the continental plate is thicker than the oceanic plate, and therefore is going to be harder to crumple, squish, or flatten.\n\nAlso, the oceanic plate is already under an enormous downward pressure from all of the ocean on top of it.\n\nAdditionally, continental plates are lighter.  They were formed by materials on the primordial earth that had floated to the surface, while oceanic plates are formed out of the magma from the center of the earth, which was below the continental plates because it was heavier at the time the plates were forming.\n\nAnd finally, wet rocks are a great deal softer than drier rocks, so the continental plate is harder to bend or break than the oceanic plate, which is soaked all the way through.
37899
>>>What are all the planets and moons besides earth and Europa that have liquid H20 water on them? \n\n\nAs you point out the three gas giants are all believed to have layers of liquid water. Added t that there are trace droplets of liquid water in the atmosphere of Venus but they don’t last long individually.\n\n>>>>>My astronomy book says Uranus has water on it underneath a massive layer of liquid hydrogen but this can't be right. It says the temperature there is -360 degrees F and water freezes at 32.\n\nThe ‘surface’ temperature is –360oF. Just as the surface temperature of Earth is 80oF. But as you get deeper into the Earth the temperature increases until it is hot enough to melt rock and iron. And in exactly the same way as you get deeper into the centre of a gas giant the temperature increases until you can melt ice. \n\n>>>>>>. Could life exist with the h20 but virtually no solar radiation? Primitive simple life forms I mean.\n\nIf conditions are relatively stable then where primitive simple lifeforms exist, advanced complex lifeforms can exist even more easily.\n\nCould life exist under such conditions? Sure. It wouldn’t be life as we are normally used to it, but it is perfectly plausible. Life on the surface of the Earth today is almost entirely dependent on solar energy only because that is the most efficiently harvested energy source. It allows those organism that use it to outcompete any rivals using alternative energy sources.  But life didn’t start out relying on solar energy, and the vast majority of all life on Earth today doesn’t rely on solar energy.\n\nLife started out harvesting energy directly from the rocks. Those first lifeforms used iron and sulfur for energy, not sunlight. And even today the weight of the bacteria deep underground that  rely exclusively on energy form rocks is far greater than the weight of those organisms that cling to the surface and rely on sunlight.\n\n\nThere is no reason why life on other planets couldn’t survive perfectly well using similar systems of energy harvesting. And the only reason mineral consuming lifeforms never got very complex on earth is because the Earth is volcanically active, which make sit hard for big complex creatures to survive.  On a gas giant at the interface between the atmosphere and the oceans that wouldn’t be a problem, and life could evolve to become as complex as it liked.
160680
Well, the upper mantle, more specifically the asthenosphere, is a plastic- by which I mean solid but able to flow- layer on which all of the crustal plates "float". Therefore, you can say that the asthenosphere is responsible for continental drift, and is thus the direct cause of earthquakes, volcanoes, and all other geologic events on our fair blue planet. Come to think of it, the mantle can be said to be one of the factors that influenced life itself in its long development over the past 3.8 billion years! As the earth's crust cooled, volcanoes-caused by upwellings in the mantle- released carbon dioxide and other compounds into the primordial atmosphere that were used by early life for nourishment. They also released a portion of the water vapor that now exists as a liquid across 2/3 the Earth's surface as water. Therefore, the mantle, in a way, is directly related to the origin of life, and, in turn, human life.
189649
The answer is: D. Volcanoes that have large amounts of silica\n\nHere is the reason why it is D:\n\nMagma that contains high amounts of silica is very viscous. That means it is very thick. Because of its thickness, gases can not escape & will build up behind the magma. When the pressure builds up enough, an explosion occurs. Large chunks of lava rock are thrown from the volcano in all directions. The debris fallout from these types of eruptions is extremely dangerous!\n\nIn 1980, Mt. St. Helens was an explosive composite volcano. Half the mountain was gone in a matter of minutes. The problem with that particular volcano was not the falling rock debris (few people). In fact w/ St. Helens, it was the ash which is small particles of volcanic glass (a.k.a. silica). These minute particles of glass can cut your lungs. Also, people living & camping down below the mountain were caught up in mudflows caused by the melted snowcaps. Also, pyroclastic flows can race down the mountainside at tremendous speeds. Anyone caught in the way would be annihilated.\n\nSea water can cause explosive steam eruptions but this occurs in submarine volcanoes (underwater). No one is around to be in its way.\n\n:)
279961
heh... are you referring to ecological endangered hotspots or hot spots under plates that cause volcanic activity?\n\nThere are... way to many ecological hot spots particularly in tropical areas in South America, Africa and South Asia.\n\nAs for hot spots associated with plate tectonics, there are many I'm sure but the Hawaiian Island chain is probably the biggest and longest.  Yellowstone wouldn't be a hot spot really, it's pretty close to a plate boundary and it's activity I would think is left over from this.  Hot spots are unusual for continental plates.  It seems like many island chains could have been formed by similar hot spots under ocean plates though.
523989
I researched this as a geology student 20 years ago and has interested me since then.  By researching cores of basalt, they have a pretty good idea what the magnetic field does when it starts to shift but it is somewhat random and slow.  I remember that typically, before the switch in polarization, the poles starts to migrate in a spiral as it is doing now.  It has been an extra long time since the last switch so it is due.  I suspect that it is about to switch (within the next thousand years or so) but no one can say for certain in my opinion.  Apparently there is a period of time (100 years or so) when the field is next to zero in strength.  I saw a show on it recently that demonstrated they have learned a lot since I studied it in school.
139283
Fluids such as water, carbon dioxide, & oxygen (volatiles) are required for retrograde metamorphism to take place.\n\nDuring prograde metamorphism, the water contained within the rock is released during the metamorphic processes of heat & temperature.\n\nBy the time they finally work out & reach the surface (if they even do), they’re usually lacking in any of these volatiles and are said to be “dry” due to the fact that they were driven out at such high temps & pressures.\n\nRetrograde metamorphism requires water & other fluids. That is why is stays that way & doesn't revert back. It needs the fluid factor to revert back to a lower grade.\n\nThe outer surfaces of the rock may weather but it takes a very long time for the entire thing to revert back to the most stable form.\n\n:)
438661
If this all was true, the waters off the EAST coast would be higher, since Earth spins toward the east. \nHowever; even the ocean has areas of higher/lower elevation, according to Topex Dynamic Ocean Topography.\nhttp://seawifs.gsfc.nasa.gov/OCEAN_PLANET/MOVIES/Topex_Dynamic_Ocean_Topography.mpg\nBut there, around NZ, the ocean does not show higher elevation; it's at a normal  level.
670895
The lithosphere (from the Greek for "rocky" sphere) is the solid outermost shell of a rocky planet. On the Earth, the lithosphere includes the crust and the uppermost layer of the mantle (the upper mantle or lower lithosphere) which is joined to the crust.\n\nAs the cooling surface layer of the Earth's convection system, the lithosphere thickens over time. It is fragmented into relatively strong pieces, called tectonic plates (shown in the picture), which move independently relative to one another. This movement of lithospheric plates is described as plate tectonics.\n\nThe distinguishing characteristic of the lithosphere is not composition, but its flow properties. Under the influence of the low-intensity, long-term stresses that drive plate tectonic motions, the lithosphere responds essentially as a rigid shell and thus deforms primarily through brittle failure, whereas the asthenosphere (the layer of the mantle below the lithosphere) is heat-softened and accommodates strain through plastic deformation. Both the crust and upper mantle float on the more plastic asthenosphere. The crust is distinguished from the upper mantle by the change in chemical composition that takes place at the Moho discontinuity.\n\nThere are two types of lithosphere:\n\noceanic lithosphere \ncontinental lithosphere \nOceanic lithosphere is about 70 km thick (but can be as thin as 1.6 km at the mid-ocean ridges), while continental lithosphere is about 150 km thick (and can be considerably thicker at continental collision zones). Oceanic lithosphere consists mainly of mafic and ultramafic rocks and is denser than continental lithosphere, which consists predominantly of felsic rocks. This higher density has the effect that at subduction zones the oceanic plate will invariably sink underneath the continental plate. New oceanic lithosphere is constantly being produced at mid-ocean ridges from mantle material and is recycled back to the mantle at subduction zones. As a result, oceanic lithosphere is much younger than continental lithosphere: the oldest oceanic lithosphere is about 200 million years old, while parts of the continental lithosphere are billions of years old. As oceanic lithosphere grows older, it gets cooler and denser, with the result that if two oceanic plates converge, the older one will subduct below the younger one.\n\nhttp://en.wikipedia.org/wiki/Lithosphere\n\nBoys mature slower than girls so they seem stupid. \n\nGood Luck!
2703
There are three types of lava and lava flows: pillow, pahoehoe, and aa. Pillow lavas are volumetrically the most abundant type because they are erupted at ocean ridges and because they make up the submarine portion of seamounts and large intraplate volcanoes, like the Hawaii-Emperor seamount chain. Pahoehoe is the second most abundant type of lava flow.\n\nEruptions under water or ice make pillow lava. Pillow lavas have elongate, interconnected flow lobes that are elliptical or circular in cross-section. \n\n"Pahoehoe" and "aa" are Hawaiian words that describe lava. Pahoehoe lava is characterized by a smooth, billowy, or ropy surface. Pahoehoe flows tend to be relatively thin, from a few inches to a few feet thick. In map-view the flows tend to be narrow and elongate. \n\n    Aa is characterized by a rough, jagged, spinose, and generally clinkery surface. Aa lava flows tend to be relatively thick compared to pahoehoe flows. During the early episodes of the current eruption of Kilauea volcano, aa flows up to 36 feet (11 m) thick surged through the Royal Gardens subdivision at rates as great as 108 ft/min (33 m/min). Pictures in Hawaiian Tour Guide illustrate many of the points noted above.\n\nAll volcanic eruptions produce lava. The lava can take one of two forms: lava flows or pyroclastics. We already described lava flows. Pyroclastics are pieces of lava explosively thrown out of a volcano by the expansion of gas bubbles. Pyroclasts can take many forms depending on the violence of the eruption, type of eruption, and composition of magma/lava. Two types of pyroclasts that I'm sure you are familiar with are ash and cinders. Ash is produced by very violent eruptions that fragment the lava into pieces smaller than 2 mm (0.08 inch). An excellent example of an ash producing eruption is the May 18, 1980, eruption of Mount St. Helens. Cinders are pieces of fragmented lava in the size range of 2-64 mm (0.08-2.56 inches). A good example of an eruption that produced a cinder cone is Paricutin in central Mexico.\n\nLava and pyroclasts have a variety of uses including building or ornamental stone and road material. Volcanic rocks also make an excellent substrate for agriculture.
515315
The 'science guru' is right, but I'll chime in to try and help you wrap your mind around it. \nThe slower magma cools the bigger the crystals in it get. The deeper the magma is in the earth the more it is insulated (like a pizza in one of those pizza delivery bags) and so it cools lots slower the deeper it is.\nThe faster the magma cools the smaller the crystals in it. Since the earth insulates the magma it has to get closer to the surface before it can cool fast enough to have small crystals.\nIf you have two different sizes of crystals then you must have two different rates of cooling.\nThe crystals that can form at higher temps start forming first, of course, and then, when the magma gets pushed up nearer the surface the rest of the material cools quickly into small crystals that surround the larger ones.\nDoes that help?
442464
My guess is dissipation, hydrothermal, volcanic. Just guessing.
109123
Good thinking, unlike some of the answers here. Anything put in or on the water displaces water and makes the water level rise. The ocean is so huge that you could not measure it unless the rock was so large you could not move it.
509038
volcanoes are built when tectonic plates push together, the way mountains are formed. except volcanoes have magma inside of them. the gas and magma inside are under extreme pressure, and this pressure pushes its way through small cracks in the rock, eventually escaping in an eruption of gas that brings lava with it. a lot of people have been killed by eruptions, but i cant tell you how many. the lava takes weeks or months to cool down unless it hit the water, which will cool it in a matter of days.