how does a metamorfic rock form ??? by heat anh pressure or wat????
141648
It is formed by heat pressure
210093
Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing substance called magma. Because it is lighter than the solid rock around it, magma rises and collects in magma chambers. Eventually some of the magma pushes through vents and fissures in the Earth's surface. A volcanic eruption occurs! Magma that has erupted is called lava. \n\nalso\n\nWhen rock inside the Earth becomes hot enough it melts.\nThis molten rock, or magma, is less dense than the surrounding\nsolid rock.  Just as an object that is less dense than\nwater will float on water, the relatively low density of\nthe magma causes it to rise to the surface of the Earth.\n \nIf the magma contains water and dissolved gasses, when\nthe magma reaches the surface the water and dissolved\ngasses will suddenly expand into steam and gas, causing\na violent eruption.  This is like shaking a coke\ncan and then popping the tab.
393590
Well, sedimentary has "sediment" in it. You know, the yucky mud stuff on the bottom of a river or stream. That's what sedimentary rocks are made of.\n\nIgneous looks like ignite, which is to start a fire. Volcanoes have red-hot magma in them, and that's what igneous rocks are formed from.\n\nA metamorphosis is a change from being one thing to being something else (like a caterpillar becoming a butterfly.) Metamorphic rocks are formed when other rocks are transformed by heat and pressure deep withing the earth's crust. \n\nI know you probably wanted some kind of clever mnemonic device, but in this case all you have to do is remember the meanings of three common words.
73951
In order for volcanoes to form, there has to be some way for magma to form and pool up.  The "ripping" of plates at spreading zones, and the melting of a subducted plate in subduction zones, can both result in a pool of molten rock.  But there's nothing to cause this to happen at a transform fault, just two plates passing by each other.
870655
Magma, or molten rock located beneath the earth's surface, cools upon reaching the surface to form the crust. This crust is moved away from the location of upwelling by thermal convection currents in the semi-plastic mantle. The crust is then resorbed back into the mantle upon meeting another, less dense (more buoyant) crust. \n\nThere are two types of crust: oceanic and continental. Each are made from different minerals, resulting in oceanic crust being 'heavier' (denser) and thus sinking below the 'lighter' (less dense) continental crust at convergent boundaries. The earth's crust is in a state of constant motion (or, in some places, no motion, but a building up of energy) called plate tectonics. \n\nSee the wikipedia link below for more details. Hope that helped.
858820
Some rocks are formed from magma (lava) that comes from deep in the earth. THose rocks never have fossils because, hey, they were like, 2000 degrees and anything close to them was burned totally. \n\nSome rocks were formed from deposits at the bottom of ponds, rivers, mud flats along the ocean, and in the shallow ocean. Those kinds of rocks (shale, limestone) can have lots of fossils. Let's say that you had a pond at the end of a river where it meets the sea. Lots of dead stuff could float down the river and get caught in the mud. Then it would gradually get covered by more mud. After thousands or millions of years the mud would be really thick. It would be formed into rocks with the remains of the dead animals in it. Bingo. That's a fossil. \n\nThere are lots of grat books about fossils. Check it out at your local library. And most places in the USA there are rocks near you where you could go and dig up your own fossils. That would be cool.
887609
the rock starts as magma turns into igneous then to sedimentary the metamorphic....extreamly siplified but i think u get the point\nheres what a more complex on looks like\nhttp://geologyonline.museum.state.il.us/tools/lessons/6.4/rockcycle.gif
86122
I was taught in school that it is due to radioactive decay of elements in the core.  That is pure bullcrap.  If it were true, every time a volcano exploded, there would be radioactive toxins spread out across the world.  Others say gravity pushing on the substances create heat and liquification of earth.  This may be somewhat true.  If you put a piece of solid ice in a chamber and put extreme pressure on it, it turns to liquid.  There must be some other source of internal heat generation though.  I have never found a satisfactory answer to date.  I really don't think anyone knows, just like gravity is still a big mystery.
404441
It depents on the gem, of course.  Most of the ones people think of as gems, such as diamonds, sapphires &c., form as high-temperature, high-pressure phases in deep molten rock.  They don't necessarily take a long time to crystallize either.  These phases aren't stable in cooler melts, though,  so the problem is to quickly get them to the surface from their formation depths.  Some volcanic eruptions do this.  Diamonds have to come all the way from the mantle to near the surface in minutes.\n\nOther gems can form near or at the surface.  Opal, for instance, is formed by precipitation of silica from groundwater.
327906
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:)
1119893
No it is not. Oceanic crust is composed primarily of basalt. Basalt is an extrusive igneous rock that cools quickly. Other types of rock commonly found on or beneath the unconsolidated sediments on the ocean floor are sedimentary rocks like sandstone, limestone, and shale. \n\nGranite is found in continental land masses. (Granite is NOT a metamorphic rock.) It is an intrusive igneous rock that must cool very slowly to form granite. \n\nHere is a good explanation with some illustrations:\nhttp://www.athro.com/earth_science/rocks.html
1069472
First of all any rock can undergo ductile formation under the right conditions...\n\n1.) Heat & pressure - if enough heat & pressure are applied as in conditions deep w/in the earth then ductile deformation can occur.\n\n2.) Time - if a rock has pressure applied over long periods of time then ductile deformation can occur. If done over short periods of time a rock may undergo brittle deformation no matter what type of rock it is.\n\nThe question you are asking I believe has to do w/ composition...\n\n3.) Composition - rocks w/ strong internal bonds are more likely to undergo brittle deformation whereas rocks w/ weak bonds will more than likely undergo ductile deformation. Rocks in the former category include igneous such as basalt & granite. Rocks in the latter category would include sedimentary & some types of metamorphic rocks.\n\nRocks such as quartz & feldspars tend to be very brittle whereas ones containing calcite & micas are more ductile.\n\nBased on this, the answer to your question would be dolomite just as the first person said.\n\nWhy? Rhyolite is composed of quartz & feldspar; Chert is made of cryptocrystalline quartz; Quartzite is made up of quartz (SiO2).\n\nDolomite is calcium magnesium carbonate or quite simply put, a carbonate rock. It will be more likely to deform than the other 3.
1056060
Caves form in limestone rock. I believe you are asking about the process. So here it goes...\n\nAs water moves through the ground it becomes slightly acidic due to the decomposition of organic material. The acid formed is a mild carbonic acid.\n\nAs this mildly acidic water reaches the rock it permeates the cracks and crevices. Over time, the acid reacts w/ the limestone (calcium carbonate - CaCO3) & dissolves it.\n\nThe cracks get larger. Over long periods of time these cracks can get extremely large resulting in a cave.\n\nIf a cave gets large enough it will be considered a cavern.\n\nSometimes a cavern will collapse due to the weight of the overlying material. When this happens a sinkhole occurs.\n\nSinkholes can be small or large depending upon the size of the cavern beneath & the area of structural weakness.\n\nSometimes a cavern collapses b/c groundwater is pumped out for local supplies. When this happens, there is no support left holding up the roof of the cavern & it gives way.\n\nFlorida is notorious for the number of sinkholes that occurs there. Of course, Florida has limestone bedrock underlying the entire state so this is bound to happen on a regular basis. Also, Florida's population is growing & so is their need for water.\n\nKarst topography is the term given to areas that are dominated by limestone landforms that were created from dissolution by acidic groundwater.
897192
Schist = cooked mud (i.e. no water left trapped, clay minerals got cooked to less water containing minerals such as micas). How long depends on the thickness of the sedimentary rocks deposited on top of the particular clay layer (pressure helps evacuate water and increases temperature); whether or not there is an external heat source (volcanic activity, magma chamber nearby, metamorphic processes - faults, etc.). SO - time can't be specified unless is a case study, temperature -  between 150 and 200 degrees C. Above 200 c is the schist kingdom in metamorphic rocks.
551728
If you are asking how rocks are formed, there are three main processes: 1) Igneous rocks are formed by the solidification molten magma from deep in the earth; 2) Sedimentary rocks are formed by pressure acting on sand or other small fragments under a body of water or under other rock layers; 3) Metamorphic rocks start as another type, but are changed into a different, often more complex structure or crystalline matrix by the action of pressure, heat, friction, and/or water.
172246
In order to create sedimentary rock from metamorphic rock you would first have to erode the metamorphic rock into sediment, then cement it together.  Pressure and heat will transform sedimentary rock into metamorphic rock, but they will not change metamorphic rock back into sedimentary rock.
459846
Not much water in the form of free liquid water entrapped in pores of the rocks in subducted lithosphere that makes it into the mantle. However, the subducted plate *does* contain a substantial amount of water in the form of hydrous minerals  (e.g., clays, serpentine, amphiboles, chlorite, epidote, micas, etc.) that form by hydrothermal alteration of the oceanic crust, and are present in the overlying sediments (some of which are subducted).\n\nMuch of the water in these hydrous minerals is released when the subducted plate heats up as it is warmed by the hot mantle surrounding the plate, and the hydrous minerals dehydrate (really just a special type of prograde metamorphism).  The water that is released is thought to leave the plate itself and rise (because it is less dense than the rock, and hence bouyant) into the overlying mantle.  Water reduces the temperature at which  silicate rocks begin to melt, and because the mantle overlying the subducted slab is actually hotter than the slab itself, this water can trigger melting in the mantle.  This is why there is almost always a volcanic front above a subduction zone (e.g., the "Pacific ring of fire").  The magma associated with these subduction-zone volcanoes is usually volatile-rich (water and CO2 coming from hydrous minerals and carbonates in the subducted slab), and gives rise to explosive eruptions like Mt. St. Helens, or in a more extreme example, Krakatoa.