Re: Where is quicksand found in the US?

Quicksand is found in many parts of the US.  Places that I am familiar 
with include New Jersey, the coast of North Carolina, and many areas in the 
Southeast (particularly Florida).
     In general, however, quicksand can occur anywhere where two conditions 
are satisfied: sand and a source of rising water.  The sand can come from 
bedrock, alluvial (river) deposits, glacial deposits, or beaches.  The 
water usually comes from springs or other types of groundwater flow.  
Basically, you need sufficient hydraulic pressure on the water to drive it 
up into the sandy deposit.  Really flat areas tend not to have quicksand 
because there isn't sufficient pressure to force the water to form springs 
while steep areas tend to generate runoff that forms rivers.  Quicksand can 
often be found in areas of rolling topography where the subsurface material 
can transmit water (limestone and dolostone do this well).  As I'm sure you 
may have read or seen, quicksand can also form in swampy or wet areas, 
especially if that swamp is fed by springs.
     Another interesting way that quicksand or even "quicksoil" can form is 
during earthquakes.  In the same way that rising water can agitate sand 
grains to cause the sand to lose it cohesion, vibrations in an earthquake 
can shake up wet sand or soil, causing it to become liquid.  A particularly 
vivid example of this is thought to have occurred in Port Royal, Jamaica in 
1692 (see the article by Kruszelnicki below).  Buildings and people were 
sucked under the earth as the sandy spit where the town was located 
liquefied.
     If you want to know more about quicksand, I suggest you locate the 
following articles:

"Quicksand" by Gerard Matthes in the June 1953 issue of Scientific 
American, page 97.

"The Earth Did Swallow Them Up" by Karl Kruszelnicki in the December 
21/28th issue of New Scientist pages 27-29.