In our quest for natural resources, humans have dug very, very deep into the Earth. We haven't raised a Balrog yet, but we've accidentally lit pit fires that burn for decades, and we've caused earthquakes. Here are some insane pictures of the deepest pits we've ever dug.

The Kola Superdeep Borehole in the Pechengsky District, Kola Peninsula, Russia, the result of a Soviet scientific drilling project between 1970 and 2005. The deepest borehole, named SG-3, reached in 1989 is 40,230 ft (12,262 metres) deep.

Here's what lurks inside the world's deepest pitsS

The drilling was stopped in 1992 due to higher-than-expected temperatures (180 °C/356 °F instead of 100 °C/212 °F). The project was closed in 2005 because of lack of funding. All of the equipment was scrapped and the site is abandoned since 2008.

Here's what lurks inside the world's deepest pitsS

(via Wikimedia Commons)

The world's deepest mine, the TauTona gold mine in Carletonville, South Africa with its maximum depth of 2.4 mi (3.9 km), reached in 2008.

Here's what lurks inside the world's deepest pitsS

(via AngloGold)

The KTB super deep borehole, the result of the German Continental Deep Drilling Program near Windischeschenbach, Germany. The 9,101 m (29859 ft or 5.655 mi) deep hole was drilled between 1990 and 1994, and the temperature was more than 500 °F (260 °C) down there.

Here's what lurks inside the world's deepest pitsS

Here's what lurks inside the world's deepest pits

(via Earthscrust and Wikimedia Commons)

The Bingham Canyon Mine, also known as the Kennecott Copper Mine, southwest of Salt Lake City, Utah. The now 107-year-old mine has a 0.6 miles (970 m) deep, 2.5 miles (4 km) wide pit.

Here's what lurks inside the world's deepest pitsS

Here's what lurks inside the world's deepest pitsS

Here's what lurks inside the world's deepest pitsS

Here's what lurks inside the world's deepest pitsS

(via Google Maps and aibob)

The 570 m (1870 ft) deep Fimiston Open Pit (or Super Pit), a gold mine off the Goldfields Highway, Western Australia

Here's what lurks inside the world's deepest pitsS

(via SuperPit)

The Tiber Oil Field in the Gulf of Mexico, a deepwater offshore oil field with a 10,685 m (25,056) deep well under 1,260 m (4,130 ft) of water, drilled in 2009. Its total depth is 11,945 m (39190 ft).

Here's what lurks inside the world's deepest pitsS

(Illustration by Chris Graythen/Getty Images)

Chuquicamata (or Chuqui), outside of Calama, Chile. Its 850 metres (2,790 ft) deep pit is the second deepest after Bingham Canyon Mine.

Here's what lurks inside the world's deepest pitsSHere's what lurks inside the world's deepest pitsS

Here's what lurks inside the world's deepest pitsS

(via Google Maps, Robin Nystrom and Codelco)

The Door To Hell, or Darvaza, in the middle of the Karakum Desert, Turkmenistan

Here's what lurks inside the world's deepest pitsS

A drilling rig was set up here by Soviet geologists in 1971 and started operations, but the ground collapsed into a wide crater and the rig disappeared. A huge amount of methane gases was released, so the scientists decided to burn it off. They thought it would only take a few days, but the methane has been burning since then.

(via Wikimedia Commons/Tormod Sandtorv)

The Berkeley Pit, a former open pit copper mine in Butte, Montana. It's filled to a depth of 900 ft (270m) with acidic water and contains some dangerous chemicals like arsenic, sulfuric acid and cadmium, among others.

Here's what lurks inside the world's deepest pitsSHere's what lurks inside the world's deepest pits

(via Wikimedia Commons and PitWatch)

The Big Hole (or the Kimberley Diamond Mine) in Kimberley, South Africa, excavated by hand between 1871 and 1914. It has a surface of 17 hectares (42 acres) and a width of 1519 ft (463 m). It had a depth of 787 ft (240 m), but partially infilled with debris, so it's 705 ft (215 m) deep now.

Here's what lurks inside the world's deepest pitsSHere's what lurks inside the world's deepest pitsS

(via Wikimedia Commons)

The Mir mine, a former diamond mine (1957-2011) in Mirny, Eastern Siberia, Russia. The airspace above the 1,722 ft (525 m) deep pit is closed for helicopter because some of them were sucked in by the air flow.

Here's what lurks inside the world's deepest pitsS

Here's what lurks inside the world's deepest pitsS

(via Wikimedia Commons and Galaktika)

Nevada National Security Site, 65 miles northwest of Las Vegas, Nevada. Nuclear testing began in January 1951.

Here's what lurks inside the world's deepest pitsS

The site contains more than 1,100 buildings, 400 miles (640 km) of paved and 300 miles (480 km) unpaved roads.

Here's what lurks inside the world's deepest pitsS

(via Google Maps)

The deepest hand-dug well in the world, in Woodingdean, East Sussex, England.

Here's what lurks inside the world's deepest pitsS

It was dug between 1858 and 1862, and its depth is 1,285 ft (392 m).

(Illustration via Wikimedia Commons)

Bonus: The Sudbury Neutrino Observatory, the world's deepest physics laboratory, 6,800 feet (2,07 km) underground in the still operating Creighton Mine, Sudbury, Ontario, Canada. It was used between 1999 and 2006 to detect solar neutrinos through their interactions with a tank of heavy water.

Here's what lurks inside the world's deepest pitsS

(via Wikimedia Commons and SNO)