Xenoarchaeologists in World of Fire find an underground city under their dig site and decide to break through the still-functioning energy barrier put around it. This stirs up the xenophobic, paranoid security system, which kills them all, then people landing on the world to investigate, then ships flying in orbit overhead...
In a Yoko Tsuno story, where the (mostly) peaceful aliens the Vineans live under Earth's crust, an oil drill damages one of their conduits that happened to be transporting lava. Troubles ensue for drillers and Vineans alike as this means there is now lava flowing close to a pocket of natural gas.
Garfield: During a Sunday strip (circa 1996), Odie was shown digging in the backyard for a place to bury a bone; he went sooo deep, that Garfield, who stood watching nearby, was totally freaked out when he saw a giant alligator crawl out of the hole and went away, which meant that Odie had at the very least reached sewer level.
FoxTrot: One of Jason Fox's ideas for "How Disney could improve its movies" went like this:
Dwarves: We dig-dig-dig and dig-dig-dig and mine the whole day through... Grumpy: Balrog!
The title creatures in The Boogens were initially released due to gold mining in the 20's. After sixty years the attacks restart when the mining starts again.
Appears in The Descent Part 2. Apparently, many years before the events of the film a mining operation dug just too deep.
The eponymous creatures in the Sy Fy Channel Original MovieMongolian Death Worm are unearthed by an oil company drilling in the deserts of Mongolia.
Implied to be the source of Perfection's Graboid infestation in Tremors 4, in which Wild West miners uncover "dirt dragon" eggs and unwittingly allow them to revive.
Reptilicus was unleashed by first drilling too deep, then foolishly digging after what they'd drilled into.
Ghosts of Mars a mining crew in Mars dug deep and unleashed the ghosts who possessed everyone at the site.
Lone Wolf: An immortal monster called Shom'zaa was kept imprisoned by the special ore in the rock around it. Very, very valuable ore. Which was dug up by dwarves, thus releasing the ancient evil (which happened to be a servant of the Big Bad from the elder days), which set about destroying the dwarves' underground kingdom.
In the Fighting Fantasy book Portal of Evil, which is set during a gold rush, miners unwittingly uncovered an Artifact of Doom in the form of an ancient portal to a Lost World. The portal is sentient and causes those to pass through to transform into zombie-like slaves to its will. Or prehistoric mammals. Or dinosaurs.
The Lord of the Rings: The Balrog was found when the Dwarves of Moria "delved too greedily and too deep." It wasSealed Evil in a Can, but then they woke it up, and it wiped out their kingdom. And according to Gandalf, there are even worse things further down than that...
In Desperation by Stephen King, Chinese Miners dig too deep and uncover the dwelling of Tak, a sadistic, insane, body-snatching horror from beyond our world. This event also triggers the plot of the King-as-Richard-Bachman The Regulators (an AU version of Desperation).
Ciaphas Cain example: a Necron base was discovered under a Prometheum Foundry. The Foundry was placed there deliberately to dig them up "accidentally."
Another Necron base was found in an asteroid mine. Cain suspected, but as there were also tyranids attacking the asteroid, they got the blame for the deaths of the miners. It seems likely the 'nids actually arrived after just about all the humans were dead.
The same thing happened in the Space Marine novel The Fall of Damos. The Adeptus Mechnicus dug up necron ruins, collected artifacts and did not tell anyone else about it. Some time later the awakened necrons slaughtered most of the human population and were only halted by the Ultramarines.
Subverted in The Last Continent, where a well-digger remarks that if they dig much deeper, they'll give an elephant a nasty surprise. The Discworld, of course, is balanced on the backs of four huge turtle-riding elephants. In the same novel, an opal miner uncovers the Luggage — not technically evil, but no-one stuck around to check.
In the Simon R. Green novel Blue Moon Rising the inhabitants of a mining town Dug Too Deep just as the Big Bad awakened. By the time the heros get there it is far, far too late for anything except revenge.
Streams of Silver by R. A. Salvatore: manages to combine both Moria and The Hobbit, because the dwarves dug too deep, opening a passage to the Underdark that allowed access to a shadow dragon named Shimmergloom who drove them from their home.
Miners uncover a dragon in Elizabeth Bear's story "Orm the Beautiful".
Annerton Pit by Peter Dickinson: According to local legends, miners working in the Annerton pit unleashed something deep underground that killed almost all of them.
In the Culture science fiction novel Matter by Iain M. Banks, an industrial civilization living inside an artificial world digs up an ancient alien artifact. To communicate with it they get help from a more advanced alien civilization that think the artifact is a member of the species that built the world. Actually it turns out the be their enemy. After waking up it promptly nukes the site of the dig along with a mining town of a hundred thousand people and flies off to the core of the world to make enough antimatter to blow it up.
Tendrils by Harry Adam Knight has geologists drill right into an Eldritch Abomination. Consumption of random people ensues, understandably. And even before said Eldritch Abomination began consuming people, whatever it was inside of contained a huge quantity of extremely corrosive acid which became a gusher from the well — with many people close by.
The terrible thing in Galaxy of Fear: Spore is deep within an asteroid rather than a planet, at the bottom of an old space slug tunnel, but miners still find it. And decide, upon finding a sealed door and terrified-looking statues, to go in anyway because what if there was something valuable there? The Ithorians who'd sealed it up had put up clearer and more explicit warnings, but something had removed them.
Clive Barker's Rawhead Rex. Granted, he wasn't buried very deep.
In Vernor Vinge's A Fire Upon the Deep, data-archaeologists dig too deeply into an ancient digital archive and unleash the Blight, a sort of godlike computer virus that eats minds.
Subverted in the Star Trek: The Original Series episode "The Devil in the Dark". A monster starts attacking a group of miners after they enter a new level. It turns out to be a Mama Bearprotecting her eggs (silicon nodules), which were being destroyed by the mining operation. Fortunately, she's a very reasonable Mama Bear and Kirk and Spock are able to resolve the situation with a mutually agreeable compromise.
In "The Impossible Planet" and "The Satan Pit". The title of the latter should explain it all...
A drill to tap a new fuel source in "Inferno" instead unleashes a substance that transforms people into bloodthirsty beasts, and causes the destruction of a parallel world the Doctor is trapped on for the duration of the serial.
Subverted in the two-parter "The Hungry Earth"/"Cold Blood" — the Silurians they dig up are (mostly) not hostile towards humans, but are simply trying to defend themselves against the drill, which threatens to destroy their life support systems. They're quite willing to negotiate peace with the humans. Unfortunately, Fantastic Racism on both sides prevent the negotiations from succeeding.
On Lexx, an Asteroid Miner scouting a test shaft in a small planetoid is possessed by an alien essence, which proceeds to Body Surf while building a 20,000-planet theocracy around itself.
On LOST, the group of scientists known as the Dharma Initiative uncovered an electro-magnetic hot spot by drilling into the ground, causing a disaster that would result in a hatch being built with a button that would have to be pushed every 108 minutes in order to keep things from going to crap, the failure to push said button eventually causing the crash of Oceanic flight 815.
Used a few times on The X-Files, usually with geologists whose explorations unleash a hibernating Monster of the Week. Another episode, in which loggers sawed too deep into a really ancient tree and released a swarm of killer bugs, could be considered a variant.
The Outer Limits (1995) episode "From Within" has a group of miners blast into an ancient cave containing a dinosaur fossil and a crapload of worms that quickly infest the miners and, shortly after, the whole town. Luckily, they hate light and need salt to survive.
In Babylon 5, the Shadows buried their ships scattered around the galaxy after the last war. Archaelogical expeditions stumbled upon several of them, usually with disastrous consequences.
Superman and the Mole People , which aired as part of The Adventures of Superman had a mine that allowed underground beings to come into our world. Kinda inverted though since they were only trying to defend themselves when they attacked and Supes points this out.
In the Fringe episode "What Lies Below", a sample unearthed from an oil dig contains a prehistoric virus that controls its victims into spreading the disease, before slaughtering them. One of its hosts infects an entire office building, including Peter. It is only cured after realizing the volcanic ash that killed the dinosaurs also eradicated the virus, necessitating a dose of sulfur into the building's duct system.
The Gorillaz song "Fire Coming Out of the Monkey's Head".
"The Strangefolk, they coveted the jewels in these caves above all things, and soon they began to mine the mountain...as the Strangefolk mined deeper and deeper into the mountain, holes began to appear, bringing with them a cold and bitter wind that chilled the very soul...And then came a sound. Distant first, it grew into castrophany so immense it could be heard far away in space. There were no screams. There was no time. The mountain called Monkey had spoken."
Merlin by Doug McArthur and Kathy Mar tells this from the other side:
It's not so dark in the cave tonight Just over here there's a crack of light Tomorrow is the day I heard the voices coming through the wall They're digging for a brand new shopping mall...
Werewolf: The Apocalypse has the example of the White Howlers, a warrior tribe of the Garou who often proved their mettle by traveling into both the dark places of the earth and the Umbra, fighting whatever forces of the Wyrm they found. Such history of diving led them deep into Malfeas, the Wyrm's domain, and exposing them to its corrupting influence. Eventually, the tribe was wiped out entirely, with the survivors being subjugated into the Black Spiral Dancers that rose in their place.
Cold Fear, a knock-off of Resident Evil, revolves around a tanker and later a drilling platform infested by re-animating parasitic terrors from the deep, unleashed by the drilling platform delving into the wrong place.
The Penumbra series heavily implied this in Overture but outright stated so in Black Plague that the source of all the deaths and strange creatures was the Tuuurngait, an otherworldly hive mind alien creature which shared its knowledge with the Inuits until humans became corrupt. The Turungait then dug into the earth and remained peacefully sealed away until it was disturbed first accidentally by miners, then intentionally by The Archaic
The entire premise of third person shooter series Gears of War revolves around the government mining the crap out of resources and unleashing a horrible plague of locusts. The locusts in this case aren't small bugs that mercilessly devour crops: they're pale man-sized monsters. And in Gears of War 3 from the trailer we learn that there is something far worse than the locusts living underneath.
Freelancer. Explorers visiting the Omicron Major system awoke theNomads which possessed them, hitched a ride to human space, and tried to exterminate us.
Halo: Combat Evolved The Covenant are responsible for unleashing the Flood after exploring Halo's secrets. As the Monitor explains "their kind seems most persistent in accessing restricted areas". They do it again in Halo 2, with even worse results.
Tales of Phantasia. Part of the game sees you access the abandoned Morlia Mineshaft, recently discovered. When you travel to the future, you can access the end once more and go even further, to the Dwarven Ruins—the game's optional dungeon.
In its prequel, Tales of Symphonia, there is a closed off tunnel in the Toize Valley mine, which is hinted to lead to Morlia.
Tales of the Abyss: The miners of Akzeriuth dug deep enough that they released the miasma from beneath the Outer Lands, kickstarting its Scored destruction.
In Dwarf Fortress, mining to the very bottom of the map (which frequently involves passing caverns filled with hostile creatures and finding a way to get through a magma ocean or three) will result in you breaking through into Hell itself.
Hell Science has been taken to its logical conclusion at last with the fortress Swordthunders: the glowing pits were sealed, hell was completely walled off, and used to grow strawberries. Then it was flooded with magma.
In the computer game Temple Of Apshai (1979), part of the backstory was that greedy people tried to excavate the buried temple of the Apshaians, releasing the evils hidden inside.
Legend of Mana has two of these: the mine in Gato Grotto and the Ulkan Mines.
In Sonic Unleashed a monster is sealed in the core of the planet, prompting Eggman to crack open the Earth's crust in order to set it free.
Absolute Zero has a mining operation on Europa unearthing (Er? Something like that) a buried race of belligerent aliens that immediately attack. With nothing else to use, the colony repurposes mining tools into weaponry.
Ditto Dead Space, except the mining operation just unearthed an artifact that turns corpses into belligerent aliens.
The fall of the Nerubian Empire is attributed to this. This underground empire of anthropomorphic spiders waged war against the Undead sent by the Lich King. As they lost land, they dug deeper until they reached the zone of influence of Yogg-Saron. Beset from two sides, the Nerubian Empire collapsed. It's a shame really. They had a real shot at ending the Undead Scourge before it took off.
The corruption of Netharion has a similar reason. As the Earth-Warder, his workplace was very literally the depths of the Earth. It is commonly believed that over the course of his work, he came across the prison of an Old God and was put under the collective influence of three Old Gods (the aforementioned Yogg-Saron was one of them). The rest is history.
A partial example is the failed World Tree Vordrassil. The roots plunged deep into the soil and reached Yogg-Saron's prison; his corruption flowed upward through the tree and remains present even after its destruction.
Gnomeregan is the best example. The gnomes were tunneling out more earth for their city, minding their own business, and bam! Troggs everywhere!
There's an excavation site in the Southern Barrens with a dwarf standing in front of a collapsed tunnel. If you talk to her, she tells you that they dug too deep and found... something. And then she lets you know that you better start praying to whatever you believe in that the cave-in was enough to keep it down there.
In the Blasted Lands, one of the most demon-populated areas in Azeroth, Alliance miners dug too deep and found... A demon! They got absolutely terrified. The Horde questgiver who tasks people to kill the demon, finds it rather hilarious.
You, the player, can do this in Pandaria while excavating Pandaren and Mogu digsites. Every so often when you dig up an archaeology piece a random Sha enemy will appear for you to fight.
There's a daily quest for the Horde's Dominance Offensive that involves a goblin mine. The quest giver starts by telling the player that sometimes they dig too deep and uncover something terrible... then says she's just kidding. They just found some neat ore and need you to collect it.
Taken to new heights in patch 5.4, when Garrosh Hellscream's endless search for artifacts of power turns an entire zone — and one of the most beautiful zones in the game, to boot — from this◊ into this◊. Remember those autumn trees and two mogu statues at the login screen? Yes, those are destroyed too.
In the first game Yeslick's clan was destroyed when their mining unleashed... An underground river. A lot more mundane most of the examples on this page, but no less devastating.
Baldur's Gate II. The player is asked by a svirfneblin (deep gnome) to use a scroll to seal a shaft the little munchkins dug and released something that slept far under the earth. It then turns out the protagonist has to defeat the creature in question before the shaft can be sealed, which turns out to be a demon. A balrogbalor, no less.
Inverted in Dragon Age: Origins where, during the course of the Dalish elf origin, you can find "a strange statue commemorating the emergence of — and short-lived trading partnership with — dwarves who dug too frugally and too shallow and struck elves."
Also played with with the Deep Roads, the Moria of the setting, where the problem wasn't that the dwarves dug too deep, but that the subterranean tunnels were taken over by the darkspawn, who were themselves digging for their old dragon-gods (although a few old dwarven records you can find insist that at first contact the darkspawn were digging up.
Speaking of the Deep Roads, in the sequel, Act 1 consists of Hawke trying to scrounge up both the finances and the necessary materials for an expedition into a "lost thaig (Dwarven city-state) older than anyone's ever seen". Once you get there, it's old alright; so old that it's completely alien, which is shocking since Dwarves are kind of famous for ancestor worship and not having changed their style or culture since what was believed to be the origins of their race. So does it actually predate that? Or was it corrupted and changed after long isolation? Nobody can figure it out, and the old denizens are dead. Or rather, transformed into Rock Wraiths after untold centuries of eating raw lyrim. You do find a nifty idol though! It tends to drive people with already-extreme personalities off the deep end. The already-greed Bartrand locks his own brother and the rest of the party away seconds after taking hold of it, and ends up a gibbering idiot after years of exposure to the incessant whispering. It later ends up in the hands of Knight-Commander Meredith, who goes from a literal Knight Templar to a mage-hating Blood Knight and semi-accidentally sparks off a civil war in Kirkwall due to her abuses.
To a lesser degree, the Bone Pit Mine is repeatedly beset with infestations of spiders, walking corpses and dragonlings, forcing Hawke as part-owner to step in and save their employees. In Act III, it gets even worse when a High Dragon decides to make its home there.
The miners of Redding seem to be particularly unlucky when it comes to digging, as when they are hired by the Enclave to dig up the remains of the Mariposamilitary base, they are greeted with massive amounts of mutagenic vapors which slowly turn them into brutish super mutants. They kill their Enclave masters and take over the base. Two notable super mutants are created in this mess, Melchior the magician and Frank Horrigan. The Player knows about this because by the time s/he arrives, all the Enclave are either gone or dead, and they left behind graphic holodiscs on their corpses.
In Fallout 3, the Raiders in Springvale Elementary were trying to mine their way into Vault 101, when they ran into a Giant Ant hive.
Presumably the fate of the Dwarves in Arx Fatalis. When you visit their mines in the lowest levels it's discovered that their entire population was destroyed by the Black Beast, an indestructible monster. Seeing as they didn't leave any writings and the Beast ate any survivors, it's hard to say for certain that they unearthed it, but this seems likely.
In Mass Effect 1, a survey team digging on a world that was being terraformed found a cache of Dragon's Teeth, which turned them into Husks. The exact same thing happens in Mass Effect 2, though to miners. The miners at least had the presence of mind to leave an Apocalyptic Log.
DLC for Mass Effect 3 seems to suggest this in the Leviathan trailer and a demo. It involves going deep into a sea rather than the ground, and the devs cheerfully admit to taking inspiration from the Lovecraft mythos.
For quite a while, mining in has risked tunneling into dungeons containing numerous monsters and a monster spawner. The Adventure Update added Abandoned Mineshafts infested with deadly cave spiders and sometimes possessing cave spider spawners, and, in the best fit for this trope, Strongholds: Sprawling maze-like underground complexes that are planned to have boss monsters added in a later update. What they already have is portals to The End, a bizarre reality from which the Endermen originate and ruled over by the Enderdragon.
The deeper one digs, the greater the chances of falling into a magma lake and being incinerated, along with all of your armor and items. This is one reason many consider the number one rule in Minecraft to be never dig down.
Falling into the bottomless abyss under the game world is prevented by a layer of undiggable, indestructible rock ("bedrock" or "adminium"). But sometimes the irregular nature of the layer itself could cause the game engine to miss a spot or two, before an update fixed it.
One update tried to invoke this by allowing monsters to spawn at ever-increasing light levels; near the bedrock layer monsters would spawn in the equivalent of direct sunlight. This proved too brutal for players, and the change was reverted, with Notch saying other methods would need to be used to invoke the trope.
Slimes can spawn below layer 16. (Sea level is around layer 64.)
As you dig ever closer to the bedrock layer, you begin to encounter a curious fog that limits visibility. That fog begins to manifest itself (in a subtle manner) around layer 30, getting slowly worse, and then gets really bad as you approach the bedrock layers (layers 1-4). Ordinary torches and other similar sources of light can't penetrate this fog (they still have the effect of preventing monster spawns and illuminating over a short range; the fog's effect is on the player); the only counter to the fog is direct sunlight (and you have to be standing in that sunlight to get the full effect). This becomes a problem when enemies are about in deep layers; it's very hard to see the enemies until they're very close.
Dig far enough in Terraria and you'll enter the underworld, a place filled with large lava lakes and stuffed with some of the toughest mobs in game. Without special equipment even the rock you came for hurts you.
The game Delve Deeper is all about digging too deep. The best relics and treasure (including mithril) are in the "deep" parts of each map, but so are some of the toughest monsters. If you do happen to dig too deep too quickly then you will quickly be swarmed with goblins and slimes and whatever else.
Phantasy Star Online: Both the Caves and the Mines qualify for this. Really, everything after the forest is digging deeper. You dig so deep that you find the spaceship of the final boss. Each dungeon is deeper and more monstrous that the previous.
Though Samus intervenes (read: blasts their plans to hell) before it can happen, one could interpret this as the direction the Space Pirates were headed in in Metroid Prime with the Phazon Mines.
An excavation team accidentally uncovered a marker on Tartarus which, through a series of events, eventually led to the release of a daemon. Another one opened up the necron catacombs on Kronus. You'd think they'd learn to keep their spades out of the earth.
This is also how the Imperium had their first contact with the Necrons. On the Mining Planet of Damnos it was an ordinary day in the ice mine...until they struck something. Cue tomb scarabs coming up and slaughtering most of the miners, followed by the tombs waking up legions of Necrons and slowly slaughtering their way across the planet until only the capital city of Kellenport is left. Even the Ultramarines couldn't stop them and eventually the planet was destroyed via Exterminatus.
Fate Of The World: The destabilization of methane clathrates, caused by countries drilling too deep to get natural gas, can be a game-ending event. Even a player who does not believe in banning the use of certain resources in Real Life may consider banning clathrates in this game.
The Desert Gold Mine under the Dusty Dunes Desert in Earthbound has the Guardian Diggers, five giant moles, as well as lots of poisonous snakes and spiders.
Only really showing up in Fridge Horror in Tales of the Abyss. Until much later in the game, the world is essentially a floating shell above a layer of poison miasma and bottomless mud. If you dig too deep in this world? You'll go right into the layer of bottomless mud. Fridge Horror when you consider this might have happened in Akzeriuth.
There's a DLC quest where you help fund a mining expedition. Since it's under this trope, they awaken the local equivalent of graveyard zombies and get slaughtered, and you need to clear it out so another team of miners can be sent in. Then it happens again. The third time around, your partner hires mercenaries, but this means that only some of the miners are alive when you get there. The fourth time, you finally kill the Dragon Priest causing all these problems. Your partner's journal implies that unleashing the Priest was his goal all along. The miners were deliberately set up to be sacrifices in the Priest's name.
The above is the most textbook (and memorable) example of this, but really, there are almost too many examples of this to count in the game. Miners tunneling into draugr barrows, miners tunneling into falmer caves, miners tunneling into dwemer ruins... It's a wonder anyone dares to dig at all by this point.
In the backstory to Resident Evil 4, the Las Plagas were discovered this way.
This is what kicks off the whole plot of Shining the Holy Ark as the residents of a mine stumble upon an ancient temple buried into the mountains. The evil spirits locked inside were able to get out through the newly created passageway.
In Ys I and II, the demons were unleashed when the buried Cleria left behind by the Ys civilization was rediscovered by the people of Esteria. This also resulted in the abandonment of the town's mine.
In Star Wars: The Old Republic, a Czerka archaeological team on Tatooine discovered a Rakata mind prison and opened it, allowing the Imprisoned One to infect them and turn them into zombie slaves. Both the Republic and Imperial quest lines involve cleaning up their mess.
"Dear Czerka, please stop discovering horrible ancient things. Love, Kira."
In many balanced scenarios of Dungeon Keeper, digging too much too early is a recipe for disaster, as this usually uncovers zones patrolled or inhabited by powerful and numerous creatures that easily outmatch your puny and untrained forces.
Alpha Prime has a variation where what caused the disaster from digging too deep was exactly what the Company was looking for, and they still wanted it. At the end, they more or less get it, though the ending implies it won't go so well for them after all.
Pokémon X and Y has an Abandoned Mine where Zygarde can be found. According to in-game notes, the mine was abandoned because it excavated a very dangerous monster. It's left up to the player's imagination what, exactly, Zygarde did to terrify them into leaving.
In Betrayal at Krondor, the dwarves in the Mac Mordain Cadal accidentally mined their way into the nest of a Brakk Nurr (Essentially a living rock golem), which naturally started attacking the miners. The party eventually has to fight their way past it to travel under the mountain, as it's blocking the path.
In Digger this is how the story started, and arguably its entire premise. It is however of course deconstructed as unlike the dwarfs of Moria, wombats are Genre Savvy enough to know there are some things in the deeps you leave the hell alone!
In The Noob, the dwarves "dug too deep", and unleashed... level 200 mining bots. So they turned to the tourism industry instead.
In Sluggy Freelance, the opening narration for Torg's comic book Gunman Stan McKurt vs. the Gates of the City of the Damned begins: "Some archeologists were out five miles west digging around where they shouldn't have. Like dropping a hornets nest in a pail of moonshine. And then lighting the moonshine. They uncovered what they say is "the doors to Hell itself." They ran for their lives and for their souls and one of them hired me, I guess as a way to make amends." It's a bit more complicated, though — the gates are not yet open and, well, there's a Twist Ending that kind of changes the whole thing anyway.
Ruby Quest: The Metal Glen started out as a fairly nice medical facility built on the seafloor. Then one of the administrators heard something whispering to him in the night, urging him to dig the foundations just a litte bit deeper...
The story detailed on Teds Caving Page. A pair of cavers endeavor to widen a softball-sized hole in the wall of a local cave so that the passage beyond can be accessed. This doesnotendwell.
In South Park, BP (later DP) does this. Multiple times. We're sorry.
A lighthearted throw-away gag version in the Donkey Kong Country cartoon. Kaptain Skurvy and his crew are digging for their treasure (in the wrong spot, thanks to Skurvy holding the map wrong), and Green Kroc comments, "If we digs any deeper, we'll sink the island."
One episode of Justice League started with an off shore oil rig releasing some creatures from the Earth's core.
The Deepwater Horizon oil rig exploded a couple months after it finished digging the world's deepest oil well. Coincidence? Well, yes, although not taking proper precautions when drilling that deep was a major factor. Still 560,000 tons of crude oil in the wrong place is definitely evilish.
The famous Yucca Mountain nuclear waste repository is concerned with preventing this. The waste will still be dangerous for ten thousand years, and the warning signs need to be comprehensible for that long. One concern is that even if future generations understand the message "warning! This place will kill you!", they'll dismiss it as a way to scare off the superstitious and assume treasure is buried there. One of the many proposed solutions includes covering the area above the site with a landscape of spikes◊. Another is just attempting to make it as plain and unenticing as possible. (Although the actual plan for waste repositories backed up these crude measures with multiple copies of written documentation all over the site, describing what was buried where, what it was, and why it was dangerous— all written in seven languages, including Navajo. See Expert judgment on markers to deter inadvertent human intrusion into the Waste Isolation Pilot Plant.)
The spike in temperature, at least, was true: they determined the temperature at the bottom of the shaft to be approximately 350 degrees, instead of the expected 212 degrees. This resulted in the project shutting down, since the drill wouldn't be able to take the additional heat. Of course most likely, the temperature spike was caused by heat rising from the earth's mantle or the like.
A Weekly World News story in 1992 elaborated this further into an even stronger example, claiming that it had happened in Alaska and that thirteen oil workers had been horribly killed by a demon that emerged from the hole.
The Sidoarjo Mud Flow. An Indonesian oil and gas company, PT Lapindo Brantas, in its search for natural gas in East Java, created a "Borehole" (a narrow shaft) into the Earth, digging more then 10,000 meters into the ground (a depth no natural gas has ever been found at before). Having ignored sensibility, they decided to ignore the law as well, not using the required protective equipment on the drill. The result? Running a giant drill next to fault lines has consequences, as the poor people of the surrounding villages learned when the drilling erupted a massive mud volcano, making 1.5 million people homeless. The eruption is still going on today, years after the 2006 incident, spewing 88,000 cubic feet of mud every day — and is not expected to stop completely for at least another 25 years. PT Lapindo Brantas was ordered to pay up to $300,000,000 in damages. The higher ups tried to sell the company for $2 to off shore groups in an attempt to avoid responsibility. They were denied.
The Iron Mountain Mine in Northern California. When this location was mined out, they discovered that in addition to rich iron deposits, the mine contained acidophilic archaea that lived off of the rich iron deposits, metabolizing them and producing sulfuric acid as waste. This created extremely toxic hot springs with a pH of less than 1, which drained into other water sources, making the mine one of the most toxic waste sites in the United States of America.