The Cave of Swallows, also called Cave of the Swallows (Spanish: Sótano de las Golondrinas), is an open air pit cave in the Municipality of Aquismón, San Luis Potosí, Mexico. The elliptical mouth, on a slope of karst, is 49 by 62 meters wide and is undercut around all its perimeter, further widening to a room approximately 303 by 135 meters wide.  The floor of the cave is a 333-meter freefall drop from the lowest side of the opening, with a 370-meter drop from the highest side,  making it the largest known cave shaft in the world, the second deepest pit in Mexico and perhaps the 11th deepest in the world.  A skyscraper such as New York City’s Chrysler Building could easily fit wholly within it.

 

 

 

 

 

Opened up by water erosion in a fault on an impermeable limestone plain and with a roughly conical shape, the cave has been known to the local Huastec people since ancient times. The first documented exploration was on 27 December 1966 by T. R. Evans, Charles Borland and Randy Sterns.

Temperatures in the cave are low. Vegetation grows thickly at the mouth, where rains can cause waterfalls cascading into the cave.  The cave floor is covered with a thick layer of debris and guano on which “millipedes, insects, snakes, and scorpions” live.  There is also a narrow sinkhole in a fault of lower Cretaceous limestone which goes down at least a further 512 m.

 

 

These people rappel down to the floor of the cave where the scorpions and deadly snakes are waiting.  Why?

And then there are the crazy thrill seekers who want to parachute down into the cave where the scorpions and deadly snakes are waiting.  Why?  Why?

The cave is a popular vertical caving destination. The high side of the mouth is covered with heavy foliage, so cavers most often fix their ropes on the low side, where bolts have been fixed into the rock and the area is clear of obstructions.  Rappelling to the floor takes about twenty minutes, in which time abseil equipment and rope can heat up to hazardous levels. Climbing back out may take from forty minutes to more than two hours. A person without a parachute would take almost ten seconds to freefall from the mouth to the floor, hence the pit is also popular with extreme sporting enthusiasts for BASE jumping.  An average-sized hot air balloon has been navigated through the 160-foot (49 m) wide opening and landed on the floor below.  Base jumpers can get out in about 10 minutes via an extraction rope.

It is estimated that the earth’s surface is struck by about 500 meteorites a year, but only about 5 or 6 are large enough to be detected by weather radar instruments or their fragments recovered. Large collisions that leave discernable impact craters are thankfully, extremely rare events, that occur in intervals of thousands of years on average. For instance, stony asteroids of size 100 meter in diameter strike earth every 5,200 years on average. Such a collision would create a crater 1.2 km across and release energy equivalent to 3.8 mega-ton of TNT, or about a thousand times more powerful than the combined energy of both the Hiroshima and Nagasaki explosions. Larger collisions involving asteroids 1km in diameter are even rarer (every 500,000 years), and collisions with 5km objects are rarer still (once every twenty million years). The last known impact of an object of 10 km in size was the dinosaur killer that happened 66 million years ago.

 

Barringer Crater in Arizona, the US, is the most famous impact crater.

To date there are 188 confirmed impact craters on earth, but most of them are barely recognizable. Only a handful of them have escaped erosion and weathering or show the classic features that result from a large meteorite striking the earth. Here are 16 impact craters that provide the most stunning visuals.

Barringer Crater

The Barringer Crater near Winslow in the northern Arizona desert of the United States, is not only the most beautiful and one of the best preserved impact craters on Earth, its discovery was a turning point in geological science. Before Daniel Barringer conclusively proved that the crater was created by a meteor impact and not by volcanism, geologists didn’t believe meteorites played any role in terrestrial geology. Even craters on the moon were attributed to volcanoes. Since Barringer’s discovery, numerous impact craters have been identified around the world. It is now widely accepted that meteor impacts have significantly shaped the earth’s geological and biological history — from the origin of water, extinction of dinosaurs to origin of life itself.

The Barringer crater is about 1,200 meters in diameter, 170 meters deep and is surrounded by a rim that rises 45 meter above the surrounding plains. It was formed 50,000 years ago.

 

Pingualuit Crater

The Pingualuit Crater is located in Quebec, in Canada. It has a diameter of 3.44 km and was probably formed by an impact roughly 1.4 million years ago. The crater rises 160 meters above the surrounding tundra and is 400 meters deep. A 267 meters deep body of water fills the depression, forming one of the deepest lakes in North America. The lake also holds some of the purest fresh water in the world, and has great visibility at 35 meters.

Photo credit: NASA

Wolfe Creek Crater

This well-preserved meteorite impact crater is located in the flat plains of the northeastern edge of the Great Sandy Desert in Western Australia, some 150 km south of the town of Halls Creek. It measures roughly 880 meters in diameter, and the mostly flat crater floor sits some 55 meters below the crater rim and some 25 meters below the sand plain outside of the crater. At the crater’s center, the ground rises slightly. Here grows some surprisingly large trees that draw moisture from the crater’s water reserves that remain after summer rains.

The crater was formed 300,000 years ago.

Photo credit: unknown

 

Amguid Crater

Amguid crater is located in a remote and inaccessible region of southwestern Algeria. The crater is about 500 meters across and 65 meters deep, but the actual depth has not been measured as the crater is partly filled with a wind blown sand. The central part of Amguid crater is flat and covered with aeolian silts. These silts refract the light due to which the crater appears white when viewed from space.

The crater is thought to have been formed less than 100,000 years ago but older than 10,000 years.

Photo credit: NASA

 

Lonar Crater

Lonar crater is located in a small Indian village of Lonar in Maharashtra. The crater was formed about 52,000 years ago when a gigantic chunk of rock crashed into this place creating a hole 1.8km wide and 150m deep. Over time perennial streams transformed the crater into a lake.

 

Gosse’s Bluff

Gosse’s Bluff is located in the southern Northern Territory, near the center of Australia, about 175 km west of Alice Springs. The crater is thought to have formed by the impact of an asteroid or comet approximately 142 million years ago. The original crater rim was 22 km across but has been eroded away. The 180 meters high, 5 km diameter structure that is visible now is the eroded remains of the crater’s central uplift.

Photo credit: Yann Arthus-Bertrand

 

Tenoumer Crater

This crater is located Mauritania, in the western Sahara Desert. It’s a near perfect circle of diameter 1.9 km with a rim 100 meters high. The age of the crater is estimated to be between 10,000 and 30,000 years.

 

Tswaing Crater

Tswaing crater is in South Africa, 40 km to the north-west of Pretoria. The crater is 1.13 km in diameter and 100 meters deep with an estimated age of 220,000 ± 52,000 years. Surface springs, ground water and rain water have filled the crater and turned it into a lake rich with dissolved carbonates and sodium chlorides which was harvested until 1956.

Photo credit: M J Gaylard

 

Roter Kamm

Roter Kamm in Namib Desert is 2.5 km in diameter and is 130 meters deep, but appears like a very shallow depression because the floor is covered with 100 meters of sand. It was formed between 4 and 5 million years ago.

 

 

Manicouagan crater

The Manicouagan Crater in Québec, Canada, is one of the oldest known impact craters and is the largest ‘visible’ impact crater on Earth. It is thought to have been caused by the impact of a 5 km diameter meteorite about 215.5 million years ago. The crater is a multiple-ring structure about 100 km across, with a 70 km diameter inner ring, which is now the Manicouagan Reservoir.

Photo credit: NASA

 

Shoemaker Crater

The Shoemaker crater is situated in arid central Western Australia, about 100 km north-northeast of Wiluna. The crater has a central circular region of uplifted Archaean Granite (Teague Granite) about 12 km in diameter, surrounded by a downwarped ring of sedimentary rocks with traces of a rim about 30 km in diameter. The age of the crater is uncertain.

Photo credit: NASA

 

Mt. Fuji is an active volcano. If it blows the people in this town will have to run very fast.  But the view is amazing.

In the spring of 2009, British scientist Jonathan Sims was a member of the first expedition to enter Hang Son Doong, or “mountain river cave,” in a remote part of central Vietnam. Hidden in rugged Phong Nha-Ke Bang National Park near the border with Laos, the cave is part of a network of 150 or so caves, many still not surveyed, in the Annamite Mountains.

There’s a jungle inside Vietnam’s mammoth cavern. A skyscraper could fit too. And the end is out of sight.

 

A giant cave column swagged in flowstone towers over explorers swimming through the depths of Hang Ken, one of 20 new caves discovered last year in Vietnam.

A half-mile block of 40-story buildings could fit inside this lit stretch of Hang Son Doong, which may be the world’s biggest subterranean passage.

Mist sweeps past the hills of Phong Nha-Ke Bang National Park, its 330 square miles set aside in 2001 to protect one of Asia’s largest cave systems. During the Vietnam War, North Vietnamese soldiers hid in caves from U.S. air strikes. Bomb craters now serve as fishponds.

Going underground, expedition members enter Hang En, a cave tunneled out by the Rao Thuong River. Dwindling to a series of ponds during the dry months, the river can rise almost 300 feet during the flood season, covering the rocks where cavers stand.

Like a petrified waterfall, a cascade of fluted limestone, greened by algae, stops awestruck cavers in their tracks. They’re near the exit of Hang En.

Navigating an algae-skinned maze, expedition organizers Deb and Howard Limbert lead the way across a sculpted cavescape in Hang Son Doong. Ribs form as calcite-rich water overflows pools.

“It sounded like a roaring train,” said “Sweeny” Sewell, describing the noise a second before a waterfall exploded into Hang Son Doong through the Watch Out for Dinosaurs doline, or sinkhole opening. A rare dry-season downpour produced the thundering runoff. Were the cavers scared of drowning? “Maybe if it were a smaller cave,” said expedition leader Howard Limbert, “but not here.”

A jungle inside a cave? A roof collapse long ago in Hang Son Doong let in light; plants thickly followed. As “Sweeny” Sewell climbs to the surface, hikers struggle through the wryly named Garden of Edam.

The Darvaza gas crater, known locally as the “Door to Hell” or ”Gates of Hell”, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since 1971. The diameter of the crater is 69 metres (226 ft), and its depth is 30 metres (98 ft).
The crater is a popular tourist attraction. Since 2009, 50,000 tourists have visited the site. The gas crater has a total area of 5,350 m2. The surrounding area is also popular for wild desert camping.

The gas crater is located near the village of Derweze, also known as Darzava. It is in the middle of the Karakum Desert, about 260 kilometres (160 mi) north of Ashgabat, the capital of Turkmenistan. The gas reserve found here is one of the largest in the world. The name “Door to Hell” was given to the field by the locals, referring to the fire, boiling mud, and orange flames in the large crater, which has a diameter of 70 metres (230 ft). The hot spots range over an area with a width of 60 metres (200 ft) and to a depth of about 20 metres (66 ft).

According to Turkmen geologist Anatoly Bushmakin, the site was identified by Soviet engineers in 1971. It was originally thought to be a substantial oil field site. The engineers set up a drilling rig and operations to assess the quantity of oil available at the site. Soon after the preliminary survey found a natural gas pocket, the ground beneath the drilling rig and camp collapsed into a wide crater and was buried.
Expecting dangerous releases of poisonous gases from the cavern into nearby towns, the engineers thought it best to burn the gas off. It was estimated that the gas would burn out within a few weeks, but it has instead continued to burn for more than four decades.

In April 2010, the president of Turkmenistan, Gurbanguly Berdimuhamedow, visited the site and ordered that the hole should be closed. In 2013, he declared the part of the Karakum Desert with the crater a nature reserve.

The crater was featured in a Die Trying episode titled “Crater of Fire”. Explorer George Kourounis became the first person to ever set foot at the bottom, gathering samples of extremophile microorganisms. The episode was broadcast on the National Geographic Channel on July 16, 2014.

 

Camping on the edge of the “Gates of Hell”

Copper mine, Bingham Canyon, Utah

 

 

 

 

Darvaza, The burning gates of Turkmenistan

 

 

 

Chuquicamata copper mine, Chile

 

 

 

Diavik diamond mine, Canada

 

 

 

Sink hole in Guatemala, a consequence of tropical storm Agatha

 

 

 

Kimberley big hole, South Africa

 

 

 

Mirny diamond mine, Siberia, Russia

 

 

 

Ronda is a town in the Spanish province of Málaga. It is located about 105 km (65 mi) west of the city of Málaga, within the autonomous community of Andalusia. Its population is about 35,000 inhabitants.

It now is one of the towns and villages that is included in the Sierra de las Nieves Natural Park.

Ronda is situated in a mountainous area about 750 m (2,460 ft) above mean sea level. The Guadalevín River runs through the city, dividing it in two and carving out the steep, 100-plus-meter-deep El Tajo canyon above which the city perches. The Spanish fir (Abies pinsapo) is endemic to the mountains surrounding Ronda.

Workers refurbishing a platform overlooking the iconic Nazca Lines in Peru could not believe their eyes when they stumbled upon a massive drawing of a cat that had been etched into a hillside thousands of years ago. According to a press release from the Peruvian Ministry of Culture announcing the remarkable discovery, “the figure was scarcely visible and was about to disappear, because it’s situated on quite a steep slope that’s prone to the effects of natural erosion.”

Fortunately, upon finding the feline, experts set about clearing and restoring the drawing, which measures 120 feet long and is believed to have been created around 200 BC to 100 BC. “With this discovery, once again, the rich and varied cultural legacy that the area harbors is revealed,” marveled the Peruvian Ministry of Culture. The proverbial Nazca cat is the latest in what has been a staggering series of finds made in the region over the last few years, including a whopping 50 previously unseen drawings documented in 2018 by way of a drone survey.