I mean, a desert is basically just a huge amount of sand but where does it stop, what is beneath? I googled it and it says there’s groundwater but what does that mean, and (how) is that even possible?
Edit: So, actually the main question I wanted to know is if there’s a exact border between sand and rock, or if the sand just gets denser and denser until it’s rock (but I believe the weight must not be that big), like Saturn or something.
(Yes, I know what a desert is but I specifically need to know about this certain type of desert)
In: 1165
So first off, most deserts aren’t sand. The largest sand desert in the world is the Rub Al Khali on the bottom half of the Arabian peninsula.
As a geologist, I’ve drilled in the area on some geotech projects so I can tell you what that’s like.
Depending on what you’re dealing with, you can have a sharp contact between rock and soil, or something more gradual. Generally, we’d drill in the sand and it would grade into a carbonaceous mudstone. Slowly becoming harder and more cohesive, there was also a fair amount of gypsum.
And yes, we did encounter groundwater on site. You go deep enough anywhere and it’s going to be rock and wet. To be clear, you’re not hitting an underground river or lake (they do exist in some places) but generally groundwater exists in the spaces between the material. In sand, there’s a surprising amount of space that holds water and let’s it move about easily. In clay there is much less space, so you’ll get much less water.
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