Reading my N encyclopedia I read most of the rivers in Nevada go into Sink Holes.
What is that? No I don’t have an S encylopedia. Is it just a hole in the ground where it dries up?
Why isn’t it a lake?
Simple answer: Water flows downhill. If it can drain into the ground faster than it can flow into the location where it does, it will simply not build up to form a standing body of water – pond, lake, or whatever. Much of Nevada is in the Great Basin, where there is no natural outlet to the ocean, so any streams will either run into lakes or into sinkholes. Remember too that it’s an arid area – so evaporation is not an inconsiderable element to deal with. Most lakes lose a small percentage of the water that flows into them through evaporation – bodies like the Salton Sea, the Great Salt Lake, and the Dead Sea lose most of it that way.
If I understand correctly you are asking what exactly is a sinkhole.
As a Florida native, I saw my fair share of sink holes… though I’m not sure if they are quite the same in Nevada.
In Florida, the ground is primarily limestone, with lots of underground waterways (caves). When the water table drops during a dry season, the underground chambers lose the support of the water, and sometimes will collapse. When this occurs, you have a large pit that feeds straight into the aquafer. Think of it as a spring that doesn’t flow.
There’s a lake in Tallahassee that every 25 years will drain itself through a sinkhole that opens in the middle. Damn thing just flushed like a toilet!
I am just having trouble visualising(sp?) what one would look like. I picture this river and it all going down into a hole like a drain.
By the power of Google image search, here’s a photo of one in Scotland:
http://www.bbc.co.uk/scotland/education/higherstill/uplandlimestone/surface/sinkhole.html
A lot of Nevada is karst topography, too. You have Lehman Caves over on the east end.
Sinkholes can occur in other formations (salt, gypsum), but they are most commonly associated with limestone / dolomite. They are basically like a big funnel in the ground. Water running into them may connect to underground streams in cave systems, or pool at the bottom and seep into the very porous rock formations that caused the sinkhole in the first place.
They can occur quite suddenly as the surface collapses over a dissolved empty space under the ground, and this can obviously be a serious disaster for buildings sitting on the spot.
I remember hearing a geologist give a talk once who was quite humorous on the subject of sinkholes. It seemed the bane of his existence was farmers who thought sinkholes on their land made DANDY trash dumps …
Some background:
http://www.mme.state.va.us/DMR/DOCS/Hazard/sink2.html
A couple pictures:
http://www.gov.nt.ca/RWED/iea/nwt_pics/landscapes/sinkhole.jpg
http://cgpr.ce.vt.edu/photo_album_for_geotech/Erosion%20&%20piping/Karst%20sinkhole/Karst%20-%20Main.html
Take a close look at the scale on that last one - now THAT’S what I call a sinkhole! You can click on it for a larger picture.
I think there’s some confusion on terminology:
The Sinks in Nevada are playa lakes that form in closed basins (no external drainage), as described above by Polycarp. AFAIK, “Sinks” are just a local term for playa lakes.
Sinkholes, however, are Karst (groundwater dissolution) features that form in limestone when caves collapse, as described above by yabob. Streams may or may not flow into these sinkholes–when they do, such streams are termed “disappearing streams”. See also:
That does sound more reasonable, and I second Pantellerite’s point. I originally wondered about the statement myself. I got carried away describing sinkholes, though, since it’s where the discussion was going. Quite possibly, the OP’s encyclopedia was careless in their terminology. You might want to look at a map and contemplate the size of the Carson Sink NE of Fallon.