p.s.y.a.
2006-07-10 12:21:09 · 6 answers · asked by cindy 1 in Science & Mathematics ➔ Earth Sciences & Geology
The time for a rock to complete the rock cycle varies a lot depending of the tectonic environment you are analyzing, and in many cases it is never completed. This is a good thing or we will have no information of rocks that are too old. This is exactly what happens to the oceanic crust which is continuously "recycled" and we do not have oceanic crust older than the Jurassic...
But let's make some simplifications and assumptions. Let's start with a volcanic eruption in the Andes. Volcanic rocks are easily eroded and it can be transported by rivers or a glacial to the ocean, this may take several millions years, but lets assume that it was a very explosive event so it happen instantly and it was quickly sedimented into the oceanic trench. Then lets assume it is quickly incorporated into a subducting oceanic crust (a big assumption, but possible) that is moving fast, let's say 10 mm/year. During this time the rock is buried and affected by different degrees of regional metamorphism after the oceanic crust has moved about 200 km, or about 20 million years. It is going to be right below the active magmatic arc and it can be fractured and incorporated into the ascending magma. It will be slowly digested by the new magma until erupts again as a volcanic rock and thus completing the cycle. So, in other words, the rock cycle as stated in this example would take at least 20 million years to complete. It would take a lot longer, if you start with a different setting. For example if this original eruption went to end up into Amazons river in Brazil, it will be sedimented and it will stay as a sedimentary rock for hundreds of millions years, it may eventually metamorphose, but you have to wait until a next Pangea and is very likely that it will never be an igneous rock again.
2006-07-10 13:16:40 · answer #1 · answered by Scientist13905 3 · 3⤊ 0⤋
Your question is too vague. There are many pathways through the rock cycle, and no single rock is required to somehow pass through them all. Besides, rocks are constantly being cycled through the various pathways all the time.
Figure that the oceanic plates move at about the same rate as your fingernails grow, and you can try and estimate some of the pathways from there...
Good luck
2006-07-10 12:34:44 · answer #2 · answered by stevenB 4 · 1⤊ 1⤋
sediment cycling is dependent on location and is much to complex for a simple answer. But by conservation of matter, all matter is reused unles it is converted into energy (per Einstien) And in what form do you want your material to be when you start. If you assume rocks are to start off molten then deep mantle rocks do not take long at all to recycle to a melted semiplastic state. If you are talking about carbonate rock they never return to a state where they never started (limestone is not chemically stable at high temperatures and the CO2 outgasses.)
2006-07-19 07:06:55 · answer #3 · answered by Chewie 3 · 0⤊ 0⤋
basically, the rock cycle only contains 3 stages (igneous, sedimentary & metamorphic), & they may rotate. It'll take longer (maybe hundreds to thousands of yrs during the process of heat & pressure, heat & biological weathering. However, it be much easier during the stages of mechanical & chemical weathering.)
from igneous to metamorphic:heat & pressure
sedimentary to metamorphic: heat & pressure
metamorphic to igneous: heat
sedimentart to igneous: heat
igneous to sedimentary: weathering & compaction
metamorphic to sedimentary: weathering & compaction
Weathering & compaction means terrible weathers (biological weathering)--erosions, storms & many many more which could make a hard igneous rock into sedimentary rock (a bit like sand). U can imagine that hundreds of yrs it'll take. Also we have mechanical weathering & chemical weathering.
heat comes from the core (& outer core) 'coz that's the hotest U can get. The heat comes out when volcanoes erupt. The process of heating will happen more quickly when a volcano erupts--unstable.
Pressure comes from almost everywhere. But high pressure comes from the moving Pangea tectonic plates.
2006-07-10 12:50:55 · answer #4 · answered by Louisa 4 · 0⤊ 0⤋
What type of rock? As you requested: I support my ansewerl?
2006-07-10 18:45:47 · answer #5 · answered by crytimestwo 1 · 0⤊ 0⤋
millions of years according to http://www.carleton.edu/departments/geol/DaveSTELLA/Rock%20Cycle/rock_cycle.htm 2nd paragraph under the picture
2006-07-10 12:36:44 · answer #6 · answered by metronome 5 · 0⤊ 0⤋