Quicksand on the beach

As a "winter snowbird" I am interested in the quick sand areas along the beach. Several of my friends have had one or both legs buried up to their thighs. (1) What causes this quick sand, (2) How to recognize the area before stepping in it (3) How to get out if no one is around to help. Thanks for any answers.

We had a very similar experience back in 2007 at Watersound. At the time, I had no idea what was going on, but now that Camp Creek Lake has made its way into the gulf way west of where it was last year, I suspect that at the sand sink holes were probably created where the lake had pulled back to a more east outflow. Not sure if one of the coastal lakes were close to where you were or not, but I agree a startling experience to suddenly find yourself (or child) thigh deep in wet sand.

This is a good explanation from "How Stuff Works"





Quicksand is an interesting natural phenomenon -- it is actually solid ground that has been liquefied by a saturation of water. The "quick" refers to how easily the sand shifts when in this semiliquid state.


Quicksand is not a unique type of soil; it is usually just sand or another type of grainy soil. Quicksand is nothing more than a soupy mixture of sand and water. It can occur anywhere under the right conditions, according to Denise Dumouchelle, geologist with the United States Geological Survey (USGS).


Quicksand is created when water saturates an area of loose sand and the ordinary sand is agitated. When the water trapped in the batch of sand can't escape, it creates liquefied soil that can no longer support weight. There are two ways in which sand can become agitated enough to create quicksand:

• Flowing underground water - The force of the upward water flow opposes the force of gravity, causing the granules of sand to be more buoyant.
• Earthquakes - The force of the shaking ground can increase the pressure of shallow groundwater, which liquefies sand and silt deposits. The liquefied surface loses strength, causing buildings or other objects on that surface to sink or fall over.

Vibration tends to enhance the quickness, so what is reasonably solid initially may become soft and then quick, according to Dr. Larry Barron of the New South Wales Geological Survey.


The vibration plus the water barrier reduces the friction between the sand particles and causes the sand to behave like a liquid. To understand quicksand, you have to understand the process of liquefaction. When soil liquefies, as with quicksand, it loses strength and behaves like a viscous liquid rather than a solid, according to the Utah Geological Survey. Liquefaction can cause buildings to sink significantly during earthquakes.



While quicksand can occur in almost any location where water is present, there are certain locations where it's more prevalent. Places where quicksand is most likely to occur include:

• Riverbanks
• Beaches
• Lake shorelines
• Near underground springs
• Marshes

The next time you're at the beach, notice the difference in the sand as you stand on different parts of the beach that have varying levels of moisture. If you stand on the driest part of the beach, the sand holds you up just fine. The friction between the sand particles creates a stable surface to stand on.


If you move closer to the water, you'll notice that the sand that is moderately wet is even more tightly packed than the dry sand. A moderate amount of water creates the capillary attraction that allows sand particles to clump together. This is what allows you to build sand castles.


But beach sand could easily become quicksand if enough water were thrust up through it. If an excessive amount of water flows through the sand, it forces the sand particles apart. This separation of particles causes the ground to loosen, and any mass on the sand will begin to sink through it. In the next section, you will find out how to save yourself if you happen to fall into a pit of quicksand.

Personally, I believe there is a more plausible explanation for this. I've been walking beaches for turtle walk for the 3rd year now and many times when I see a deep hole left near the waters edge, I'll bury the hole with the pile of sand next to it in hopes of saving an unwary jogger or walker from an overextension.

I've stepped in these "quicksand" holes myself. When I've looked around, it's usually been because of a recent hole being filled in, but not packed. When the tide rises to the point that water is flowing through the sand in the recently buried hole, the sand isn't the same consistency of the rest of the beach and doesn't support weight until the tide has had a chance to move sand around and firm up the hole. Thus the loose-quick-sand.

Maybe

I have encountered quicksand on the beach a few times and it is almost always in wet areas on the edge of a lake outflow, of tidal flows or pools where they have been present for awhile to saturate the sand. I have never sunk much above my my knees and after the initial rush it has been a surprising and somewhat amusing experience.

As a "winter snowbird" I am interested in the quick sand areas along the beach. Several of my friends have had one or both legs buried up to their thighs. (1) What causes this quick sand, (2) How to recognize the area before stepping in it (3) How to get out if no one is around to help. Thanks for any answers.

I have encountered this only once -at the outflow of a dune lake that just recently 'busted out' and I did sink all the way up to my thighs!

It was more surprising than scary.

The sand was smooth and looked very solid, no water flowing over it, but it was obviously wet. I think if you are worried about this, then I would recommend staying away from the wet sand at the mouth of an outflowing coastal dune lake.

Thanks, PTYAYA, for bringing this to our attention. I had never heard of quicksand in our area before. Interesting.

Murray, a great post! Where is the second section on how to get out of it?

I would think just sitting down would spread your weight out enough to enable you to lift your legs out of the hole. The holes i remember have been only a foot or so across and easy to find terra firma right next to.

That's a good one, Andy! I've experienced quicksand a few times. I still have a Birkenstock sandal about 3 feet below the surface on the eastern shoreline of Little Redfish Lake. That was my first experience and rather comical, but I was a little p.o.'d about losing a favorite shoe! One other rather amusing experience was when I used to run on the beach in the evening, and somewhere around Gulf Trace/Alligator Lake, I hit quicksand in full jog, and busted by booty as one leg sank down to my knee. After everyone started digging massive fox holes on the beach, I stopped running on the beach after dark.