I was hiking today and there was a lot of dirt/sand and it got me thinking there’s all rock eventually break down to dirt given enough time? like if I took a pile of gravel and left it out long enough and came back in amount of years would it literally be a pile of dust at some point if so, how? And sorry one more question if you put that same gravel in a secure covered area where the weather or really anything couldn’t get to it in 1 million years. Would it still look exactly like gravel?
In: Planetary Science
Most rocks are reduced to fragments which are eventually washed into lakes and oceans. This happens for all sorts of reasons – being bashed around in water, ground by moving ice, blasted by sand, changes in temperature, water freezing and thawing and the growth of salt crystals inside the rock. However, there is another process going on – rocks dissolve in rainwater.
This happens most quickly with carbonate rocks, such as limestone and dolomite. There’s a very small amount of carbon dioxide dissolved in rainwater which makes it very slightly acidic, this reacts with the calcium carbonate in limestone to dissolve it and wash it away which is why you get caves in limestone.
There’s a similar process that happens with carbon dioxide and water reacting with the silicates found in most rocks so even the hardest rocks will eventually dissolve in nothing more than rainwater. Over time, the dissolved minerals in water fall out of seawater and form new rocks on the ocean floor which is the most important process that takes carbon dioxide out of the atmosphere over millions of years.
To answer your second question, if you could keep a rock away from rain, wind, water and make sure it was kept at a constant temperature it would last almost indefinitely.
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