Quicksand Sucks

Everything About Fiction You Never Wanted to Know.

"What is it that's not exactly water, and it ain't exactly earth?"

Quicksand is a common and deadly element of jungle and desert terrain, and its most dangerous feature is its ability to suck people and animals down and drown them in a malevolent blend of sand and water. Although most victims blunder blindly into quicksand, it sometimes seems that the merest touch of an extremity is enough to pull the unwary into its muddy and all-consuming depths like iron filings to a magnet.

In truth, quicksand (while real) isn't terribly common, and exerts none of its movie counterpart's mythical "sucking" power. In fact, real quicksand is so dense that you can't sink in it; the usual advice for someone who finds themselves caught in deep quicksand is to simply relax and float on their back. While animals and people do die in quicksand, it's almost never from the sand or drowning—it's from exposure or dehydration after exhausting themselves struggling against the sand - with the right combination of sand, clay, water, and salt, it is nearly impossible to escape the stuff without help. Also it is possible to struggle badly enough in a panic that you actually do drag yourself down instead of up. Survival guides stress the importance of staying still if this starts to happen.

Okay, if you are weighed down by something you can't remove, you could sink, but that would even happen in boring, old regular water.

Real quicksand requires water. Writers are traditionally unfettered by such technicalities, placing them in the desert or away from a river or any apparent source of water, although a hidden spring could in theory create quicksand in surprising places. In live action, budget and set-design constraints sometimes lead to a "quicksand pit" barely large enough to hold the actor.

Although not always strictly "sand", tidal flats (mudflats) have mud which is actually closer to the danger portrayed in fiction as quicksand. The tide regularly refreshes the surface and smooth implies solid to people. Viscosity decreases after an initial stress. More to the point, being a tidal flat, it's a case where people actually ARE at risk for their lives, since tides have this funny way of coming back in after going out. There are tidal flats which have seen so many deaths the locals are tired of watching stupid people die, but it's not wholly clear how much that is getting stuck in one specific spot versus getting trapped some distance from dry ground on slow-to-traverse terrain or attempting to wait on an insecure bit of slightly higher ground as the tide comes in around you.

Originally a movie serial and B-film device, this trope has been carried over to television by way of programs that mimicked or paid homage to those films, or to pulp fiction in general. Then it also moved to Video Games. This trope is pretty much a Discredited Trope nowadays, although the Shifting Sand Land of video games is still allowed to play it straight, as a gameplay challenge if nothing else.

See also Sand Is Water, Mucking in the Mud, Swamps Are Evil, and Bubblegloop Swamp... Also compare Black Holes Suck because both black holes and quicksand are portrayed in media as pulling in anything nearby whereas both only consume things which have gotten too close in the first place.

Examples of Quicksand Sucks include:

Anime and Manga

  • Mikan and a friend of hers encounter this in episode 3 of Gakuen Alice.
  • A scene of this happens in episode 5 of Deltora Quest.
  • A scene of this happens in episode 8 of a forgotten anime known as Fortune Quest L.
  • Sir Crocodile's "Desert Girasole" attack in One Piece involves him using his sand-controlling powers to create a giant whirlpool of quicksand. He does explain, however, that he's tapping into an underground water source to do this, and he's never seen doing it outside of a desert.


Comic Books

  • In one Spider-Man comic, Spidey is facing Kraven the Hunter in the jungles of Africa. Kraven uses a blowdart to drug Spider-man, making him lose most of his strength and his spidey-sense, then tricks him into falling into quicksand.


Fan Works

  • One entry into a Miniatures forum about what to do when you have nothing but standard bearers in your army is to plant the standards in a sandtrap; the enemy will waste a lot of time to "avoid the quicksand".


Film

  • Fondly parodied in the book and movie The Princess Bride, which featured a super-quicksand called "lightning sand," which is dangerous because its grains are so small that you fall straight through it.
    • At least as dangerous (in the novel, at any rate) is the way the stuff gets into your lungs.
  • While it may be a magical plant rather than quicksand, the devil's snare in the film version of Harry Potter and the Sorcerer's Philosopher's Stone fits the functional parts of the trope perfectly. When it grabs the heroes and starts crushing them, Hermione remembers that devil's snare only reacts to panicked movement, so she and Harry relax, slipping through the plant's vines. Ron, on the other hand, is so freaked out that he keeps flailing around and will obviously get strangled. Hermione manages to remember another weakness of devil's snare and uses it to free him.
  • The live-action film version of The Jungle Book starring Jason Scott Lee had this happen to a villain. He even explicitly states "It's sucking me down!" while struggling.
  • In The Mummy, a biplane sinks into a pit of quicksand... in the middle of a desert. The protagonists stand atop a dune and solemnly watch it sink. The sequence takes so long that it's hard to tell if it's Lampshading its own absurdity or just deathly oblivious to it.
    • The same thing happened in Mad Max: Beyond Thunderdome, at least the desert-quicksand part.
      • It wasn't really quicksand, more of a sand pit, but it still sucked them in.
      • It's supposed to be a pothole with sand packed on top of it.
  • Indiana Jones and the Kingdom of the Crystal Skull provides a Hand Wave for the inaccurate depiction by having Indy explain that what he and Marion are sinking into is not actually quicksand, but some sort of collapsing dry sand pit.
  • Tank Girl. A non-liquid version: the dust/sand covering the Rippers' subgates.
  • In the film Lawrence of Arabia, Lawrence has two young servant boys, Daud and Farraj. Daud falls into quicksand, and Lawrence and Farraj try to save him, but fail. In real life, Daud died of hypothermia.[1]
    • Hypothermia in Arabia, no less. Desert nights are very, very, very cold.
  • In Pure Luck, Martin Short's extremely unlucky character manages to walk into a quicksand pit in the California desert.
  • In The Brave Little Toaster, Kirby and the others trying to pull him out get sucked into a mud pit in a swamp that acts much the same way.
  • The Neverending Story contains a particularly charming scene in which Atreyu's horse Artax sinks to his death in quicksand in the Swamp of Sadness. It is explained, however, that Artax' sinking was not due to quicksand, but sadness.
  • A cave in The Scorpion King featured this.
  • One of the policemen in Kekexili: Mountain Patrol dies from this.
  • In the climax of House of Frankenstein, the finally powered up Frankenstein's Monster grabs the Mad Scientist and evades the local Angry Mob and walks straight to the nearest quicksand pit where it sinks with the scientist. Nice job.
  • One of the Sheriff's attempted duels in Hot Lead and Cold Feet ends with him sinking in quicksand brought about by heavy rains.
  • The Hallelujah Trail: The opening narration tells you that there is going to be a disaster at Quicksand Bottoms.
  • A pit appears early in Blazing Saddles; other than the fact that it shows up in the middle of an arid desert, it's actually a pretty accurate representation.
  • Averted in Once Upon a Forest. The quail firmly belive this trope, leaving one poor bastard who gets stuck in the mud to die. Luckily for him, the party comes through and the Smart Guy has them build a lever device to pry him out.

Literature

  • Nick Cave's novel And The Ass Saw The Angel uses this as a framing device. The narrator recounts his story while sinking into a bog. The unlikelihood of this contingency is easy to swallow compared to some of the other stuff we're asked to believe, or asked not to believe.
  • During a stint of being Reassigned to Antarctica Miles Vorkosigan runs across a nasty arctic version called a "Permofrost Inversion Zone"; this appears to be solid ground, but has the potentially lethal property of unexpectedly thawing into a gooey sea of mud. Miles manages to sink an entire "scat-cat" (a kind of arctic all-terrain jeep) in one after he parks on top of it rather than try to drive back to base at night, and very nearly dies because he chained his tent to it.
  • In the Known Space stories of Larry Niven some areas of Mars have sand that is so fine that it essentially is a liquid and people can sink in it.
  • Many older science fiction stories portrayed the Moon as having areas very fine dust that functioned like quicksand, A Fall of Moondust by Arthur C. Clarke being a good example.
  • In The Takers (a modern Two Fisted Tale-homage by Jerry Ahern) the protagonist and his Plucky Girl get caught in quicksand while wading through a swamp on a Caribbean island.
  • Occurs in Book 7 of The Hardy Boys Casefiles, Deathgame. Joe starts sinking in the quicksand and knows enough to float on it, but then has to force himself to sink below the surface to hide from his attacker. The caked mud later serves him as improvised camouflage.
  • The Hound of the Baskervilles uses the swamp version, which is dangerous to enter if if you know the way, and nigh impossible to traverse without a guide.
  • In one of the smaller, chapter Dinotopia books, Magnolia and Paddlefoot, her dinosaur companion, get mired in quicksand. However, the author has done their research—Magnolia and Paddlefoot are experts about water, so they simply lie flat and float. Eventually a boy and his Triceratops come along and give them a hand out.
  • The Shivering Sand in The Moonstone by Wilkie Collins. Dangerous, but not an impossible trap. It's used by a certain character to hide an incriminating piece of evidence, using a locked box and a chain, and to commit suicide.
  • The Neverending Story contains a particularly charming scene in which Atreyu's Sapient Steed Artax sinks to his death in quicksand in the Swamp of Sadness. It is explained, however, that Artax' sinking was not due to quicksand, but sadness.
  • In Dream Park, when Griffin enters the South Seas Treasure Game as an alternate, the party finds him trapped waist-deep in quicksand.


Live-Action TV

  • Tales of the Gold Monkey
  • This trope has been disproved by the MythBusters.
  • Even Power Rangers has used this, a couple times over the years. "Ninja Quest" in season three, and "Fire Heart" in Mystic Force.
  • One episode of The Man Show has a segment advertising fake products. One of those was "Quicksand Kitty Litter," which causes cats that step in it to sink in and drown. Technically, it does what it's advertised to do: free you of the responsibility of cleaning the litter box.
  • In Xena: Warrior Princess, one round with Xena's Evil Counterpart, Callisto, ends with Callisto falling into a just-Callisto-sized patch of quicksand in the middle of the desert that seems to exist just to enable that scene. It was...pretty silly.
  • Larry and Balki get trapped in quicksand on an episode of Perfect Strangers.
  • In Man vs. Wild, Bear Grylls demonstrates how to escape from a quicksand in the middle of the Sahara Desert and prevent health problems as a result from having clay on your skin.
  • In an episode of Lassie, Timmy gets stuck in the swamp version of this.
  • In Sea Patrol 2Dads sinks into a pit, briefly going under before he's fished out by a team member. It's described as 'swamp', not quicksand, but it works the same way and when he falls in he's immediately buried up to his chest.
  • Subverted in an episode of Magnum, P.I.: Rick stumbles in what he believes is quicksand and yells for help; when TC and Magnum arrive, Magnum tells Rick he's in a swamp - "There is no quicksand in Hawaii."
  • The Big Bad in The Wild Wild West's "The Night of the Bottomless Pit," who absolutely hates muck, meets his maker that way.
  • Averted in, of all places, the campy Batman series, where the Riddler's Death Trap involves tricking the Dynamic Duo into posing for a picture on a giant cake which is made of quicksand (long story). Batman warns Robin that the key to surviving quicksand is not to panic, and once this advice help them stay buoyant, he is able to use a rocket-device on their belts to propel them upward and escape.

Music

  • The song "The Legend of Wooley Swamp", by the Charlie Daniels Band, involves quicksand.


Tabletop Games

  • Dungeons & Dragons
    • Supplement I13 Adventure Pack I, adventure "The Weird Woods of Baron Orchid". Several patches occur near a lake.
    • Adventure Q1 Queen of the Demonweb Pits. One of the rooms in Lolth's spider ship has a quicksand floor to trap unwary party members.
    • Adventure OA6 Ronin Challenge. Can be encountered in the Kutuk Valley. Anyone falling in sinks at a rate of 2 feet per minute.
    • Adventure OA7 Test of the Samurai has several patches in the other-dimensional plane of Qui.
  • Several Classic Traveller adventures have this as a possible encounter on alien planets.
    • Twilight's Peak has quicksand as a possible encounter in wetlands on the planet Fulacin. If PCs got into it they would be trapped and sucked down with no chance to save themselves.
    • In the Double Adventure Marooned/Marooned Alone, PCs can encounter dangerous quicksand in the jungles of the planet Pagliacci. If trapped, they'll be sucked under in 4–9 minutes.


Videogames

  • In the 2D Prince of Persia 2, an early puzzle required you to jump between a set of stone platforms in a displayed but randomly-selected order. Quicksand comes in because the platforms are suspended in it, and if you miss a jump, or jump onto a platform not in the sequence, you're sucked in.
  • Super Mario 64 and its DS remake play this on the "Shifting Sand Land" level with two intensities. One one hand, there is light quicksand where you slowly and steadily sink in; you can eventually free yourself by jumping. On the other hand, there is dark quicksand that instantly sucks you in, thus counting as a bottomless pit.
    • There's also a middle type that sucks Mario in quickly but not instantly. It's the most common type.
    • Of course, quicksand first appeared in the Mario series in Mario 2, probably one of the elements borrowed from its source material Doki Doki Panic. At least one hidden area involved going through quicksand.
    • And again in Super Mario Bros 3 and New Super Mario Bros. Wii.
    • Subverted in Mario Teaches Typing 2. During a cutscene, Mario and Luigi fall through a hole in a bridge and are saved by a pool of quicksand below.
  • Super Metroid's many quicksand pools present no danger at all, because Samus wears a sealed space suit and can't drown. If you don't feel like jumping out, you can sink all the way in and walk around on the bottom. In a few places this allows access to new areas.
  • The Legend of Zelda this is a recurring hazard:
    • The Arbiter Grounds in Twilight Princess has quicksand, including the instant-death type, as a frequent and dangerous obstacle.
    • Ocarina of Time's Haunted Wasteland has a river of no-escape quicksand that you cross by either using the Longshot or the Hover Boots. Once across, you are still in danger of sinking if you stray off the path.
    • Spirit Tracks has quicksand pits in the Sand Temple and parts of the Tower of Spirits.
    • You fight a Moldorm in a pit of quicksand in Links Awakening. You only get sucked downward (to a cave you must traverse to get back to the surface) if you get put in the center of the pit; the rest of the quicksand simply pulls you toward that center.
    • In Skyward Sword, Link can keep from getting sucked into the quicksand of Lanayru Desert if he sprints across it. Also, the Timeshift Stones can change it back into the solid, grass-covered ground it once was Before the Dark Times.
    • A variation is the Bottomless Bogs in Breath of the Wild and Tears of the Kingdom, a mire that can cause Link to drown almost instantly.
  • Subverted in Banjo-Tooie. While there is quicksand in Mayahem Temple and Terrydactyland, it doesn't pull you down, the Dragundas living in it do, then spit you back onto solid ground. The wading boots are used to cross the quicksand. The Dragundas are also in Grunty Industries' toxic waste and polluted water.
  • Used in an absolutely laughable manner in the |Sonic the Hedgehog 2006 game. Wherever sand appears, expect it to be quicksand. And if you fall in? You fall straight through like there's nothing there. In other words, another Bottomless Pit in disguise, much like water in that game.
  • Appears in Toejam and Earl which makes the protagonists start sinking and move slower. The sand also resembles a desert, complete with cacti.
  • Used rather realistically (given the medium) in Sonic 3 and Knuckles. In Sandopolis Zone (and the 2-player mode Desert Palace level), quicksand would slowly pull the character under but it could be escaped by jumping properly. Marble Garden Zone also featured surfaces that acted the same way, but looked like black water.
  • In Mega Man X Command Mission, one character falls into a quicksand trap, which pulls him and his two friends down into it. Which wouldn't make sense in the first place, but made even worse by the fact that all three are super-strong reploids that could have easily pulled themselves out (especially since one was still on firm ground). They even treat it like it's deadly, despite the fact they don't even need to breathe and would, at worst, just be stuck.
  • In Mega Man 10, Commando Man's level has Mega Man rushing through quicksand pits. Although he can move and shoot normally in them, even completely buried, he needs to jump to exit it, and if he's dragged to the bottom of the screen, he dies as if he had fallen in a bottomless pit.
    • 4 has it as well.
  • Ratchet and Clank has the planet Aridia, a desert planet with massive LAKES of quicksand. You can hop out, but only three times before you sink, for whatever reason.
  • It doesn't pose a direct hazard to your player characters, but Corel Prison is described as "a natural prison in the middle of the desert... surrounded entirely by quicksand."
  • Final Fantasy IX has sand whirlpools on the path leading up to Cleyra. Iif you end up in one, you whirl towards the centre, sinking in. Mashing X repeatedly allows you to jump out, failing to do so will land you in a fight with a sand scorpion. The scorpions are presumably causing the whirlpools in order to trap prey.
  • This appears in the Egypt levels of The Lost Vikings. You have to get across by having coconuts drop into the quicksand and landing on the coconuts.
  • The ZX Spectrum game Where Time Stood Still, being a tribute to old movie serials, makes use of lethal quicksand as a hazard.
  • The Nintedo DS game Summon Night: Twin Age has around 60% of different sinky stuff in the game, like "Poison Marshes" and "Desert Quicksand"...
  • There are floors in Hades' Underworld lair (Ancient Greece) and the Medieval Swamp (Medieval Times) that can make you sink down like quicksand and swallow you up if you stay on the floor for too long in the NES game Day Dreamin' Davey.
  • The Death Marshes in Turok 2 have insta-death quicksand.
  • Averted in The Curse of Monkey Island. Guybrush gets trapped in a pool of quicksand, but only up to his waist, and he sinks so slowly that the player has ample time to figure out how to use a balloon, a rock, and a nearby thorn bush to get him out before anything unpleasant happens to him.
  • Adventures of Dino Riki has quicksand whirlpools popping up from the ground.

Web Originals

  • Shows up in Survival of the Fittest, where it's used to kill both Melina Frost and Beth Vandelinder, one getting stuck in the sand long enough to be stabbed, the other being pulled in head first and drowned.
  • This Homestar Runner cartoon involves Homestar making this type of overestimation, as applies to a sandbox crudely labeled "QUiCK SAnD". "If you have any vines or roots you can toss my way, I would be really, really still alive."
  • Ninjai: The Little Ninja has the Big Bad leave people to sink in a "swamp" which, despite being explicitly referred to as quicksand, seems to be a very stick, viscous fluid.


Western Animation

  • Duke falls into a pit of quicksand while escaping from Cobra in an episode of G.I. Joe and goes in over his head in a matter of seconds.
  • Happens in the form of dry desert quicksand The Transformers episode "Countdown to Extinction".
  • Happened to the whole cast of Foster's Home for Imaginary Friends. They were rescued by BEES. A bit perplexing, even if you DO accept imaginary beings springing into life for no explained reason.
    • The ending of the episode implied it was All Just a Dream, with the whole camping trip being imaginary, but, possibly, Your Mind Makes It Real. Not that that makes it any less perplexing, as imagination, despite its life-giving powers in the setting, was never shown to have power to that degree before or since.
  • Max Steel both plays this straight and partially subverts it. In season two, Max and Berto walk in to quicksand and start sinking, having to use a vine to pull themselves out. In season three, Berto and Kat walk in to quicksand; however, Berto says that the human body is lighter and they manage to swim out of it.
  • Happens two different times in Totally Spies!.
  • Crossing the line between Did Not Do the Research and Rule of Cool, the Recycled: the Series of The Little Mermaid had underwater quicksand.
  • Catwoman leaves Batman and Robin in a quicksand Death Trap in the Filmation series episode "The Nine Lives of Batman".
  • Happens with Shareena and Gug in this clip from a Detention episode. Actually, the "quicksand" is just a sinkhole.
  • There were at least two occasions on The Super Mario Bros Super Show where the good guys found themselves getting stuck in quicksand. In a strange mistake in relation to the games, they apparently forgot they had the ability to hop out of the quicksand and needed to be rescued.
  • The Wild Thornberrys subverts this completely, as the "evil swamp" Darwin was so worried about was only about two inches deep. Eliza still lost a shoe, though.
  • The mice run into this a couple of times in the Pinky and The Brain episode "Welcome to the Jungle."
  • Heloise throws a bunch of pandas into a quicksand pit on an episode of Jimmy Two-Shoes. They only approve of the mudbath.
  • A Robot Chicken sketch has a giraffe step into quicksand and, because its tall body takes so long to go down, goes through the five stages of grief as it sinks. The giraffe's life is saved when its feet hit bottom!
  • Subverted harshly in Ed Edd & Eddy's Big Picture Show. Ed and Eddy at first appear to be sinking in quicksand, and appear to die as Edd attempts to save them. However, as Edd mourns their deaths, it turns out it was just a joke that Ed and Eddy played on him. Naturally, Edd gets pissed off at the two and immediately leaves them to return to the cul-de-sac, preferring to be punished by the kids for the scam that backfired and sent them on the run in to first place rather then continue on the journey with Ed and Eddy.
  • Mozenrath's Black Sand in the Disney Aladdin TV series. The heroes didn't even have to step in it, it reached out to suck them in, an act that was, in one episode, disturbingly referred to as eating.
  • In Scooby-Doo on Zombie Island, the gang loses footage of all the paranormal things they witnessed after their camera falls into quicksand.
  • Johnny Bravo: Johnny Bravo ends up stuck in quicksand while marooned on an island. Fortunately, he keeps his shirt on in the situation... so to speak. It was smart of him to call for help though. No point in allowing himself to go under.

Real Life

  • Interesting counterpoint: Water with a great deal of gas bubbling through it behaves suitably, in that a human would sink like a rock in it, and subsequently drown. This isn't encountered very often, however, which probably comes down to most writers not doing the research... the only example this contributor can come up with is a pool of this in Metal Gear Solid 2: Sons of Liberty, where its dangers are carefully described by Vamp. Who then, seconds later, starts swimming through it with ease (He does have superpowers). This has been implicated in the loss of ships at sea, because of a subsidence or other event on the seabed which causes a dramatic release of gas. Mythbusters did this one, too, and in Code Geass R2 episode 7, the Black Knights take advantage of this.
    • An example in real life which has taken many lives: The Niagra Falls massive amount of fallen water has the same effect of the aerated water of Metal Gear Solid 2 and has resulted in many people drowning.
    • Another take on this version appeared in an episode of Sea Quest DSV. A French leisure submarine was lost and the SeaQuest was sent to investigate. Their findings? Small underwater caverns were filled with FRESH water, and they caved in like undersea potholes. Rather than aerated water causing the issue, the freshwater mixed with the sea water and desalinated it through dilution. This made the vessels too heavy to remain buoyant in the brackish zone, and they fell to the bottom of the freshwater pockets, unable to escape as their oxygen dwindled.
  • Real life example: Rodolfo Fierro, a General at the service of Francisco Villa died this way. He fell along with his horse and fell to the bottom because of the weight he has carrying (it's said it was gold). He was very well known as a sadistic bastard so his death could be a Karmic Death.
  • The effects of The Princess Bride's "lightning sand" can be mimicked by forcing a burst of air through sand (a phenomenon that happens daily in the Fire Swamps, of course). An object placed on top sinks instantly to the bottom. Fortunately the events required to create this dry quicksand are highly unlikely to occur in nature.
    • This effect was used in one of the 'reality' shows on Discovery a while back. They put an area of sand with perforated pipes in front of a bank door, with brick pavers over the top and a similar larger and deeper one at the exit to the parking lot. When the simulated bank was simulatedly robbed, the air was turned on, he sank to above his knees and was trapped when the air was turned off; the driver of the getaway SUV was sunk in the other one to the point where he couldn't open the door.
  • Large heaps of loose sand can stop a vehicle. In the rare situations this is life or death (when a stranded car in the desert means a stranded driver for instance) and it can be fatal. And in any case, it probably isn't something you wish to explain to your insurance agent.
    • Sometimes, getting stuck in the sand is the desired effect. Some steep roads have sand or piles of other things to give truckers a chance to stop relatively safely in case their brakes fail. Some airports seem to have something similar at the end of the runway in case the plane doesn't stop for some reason.
      • That's why gravel traps are so common at racing circuits. No matter if a car that goes screaming off the tarmac is doing it forwards, backwards or sideways, loose sand and gravel stop it up since the vehicle digs into the gravel, pulling itself in and creating resistance. However, since this also tends to ruin the underbody and wheels of a car, another option that's become popular in recent years is to create a large tarmac runoff area so a driver can recover from a loss of control or error in judgment and quickly rejoin the race. On cars with slicks, especially light ones such as Formula One cars, they're so grippy that gravel traps actually cause more slippage in comparison.
  • An interesting article on the rise and fall of this trope (it's now discredited) can be found here.
    • Alan Davies, incidentally, laments the decline of quicksand in a recent episode of QI.
  • Non-Newtonian fluids behave in a similar way; they are so viscous that if a great deal of force is applied to them in a brief time, they behave like solids, but if the same force is applied slower it will allow it to pass through. It can be very difficult to get something out from being trapped in a pool of a non-Newtonian fluid.
  • Soil liquefaction, a rare phenomenon associated with earthquakes, can cause water-saturated sandy ground to temporarily turn so slippery and unstable that it becomes too weak to support buildings' foundations.