A mysterious 110-meter deep "rabbit hole" is hidden in Alaska, and no one knows how this enigmatic pit came to be (photo included).

The Savonoski Crater is a perfectly round hole approximately 500 meters wide and about 110 meters deep, located in Katmai National Park in Alaska. Scientists first observed it over half a century ago, yet they have been unable to explain how it came to be, according to Live Science.

For years, researchers have attempted to uncover what might have led to the formation of this mysterious structure — unfortunately, no definitive answer has been found. Fortunately, some conclusions have been drawn: the enigmatic hole in Alaska is neither a supernatural phenomenon nor an extraterrestrial creation.

As stated in a 1978 article by a team from the University of Alaska Fairbanks, the crater is partially filled with water due to precipitation and melting snow. Interestingly, from a bird's-eye view, the Savonoski Crater appears to have been formed by a meteorite impact. It is worth noting that impact craters are typically round and deep, making Savonoski fit that description perfectly; however, scientists have yet to find evidence of a cosmic stone falling in this area.

During the 1960s and 70s, researchers conducted extensive investigations for signs of meteoritic material or other impact debris within the crater. The results of such studies would have confirmed an impact-related origin for the crater. The researchers also found no fragments of rock around the crater that would indicate the meteorite had dispersed material away from its point of impact.

On the other hand, scientists believe the crater could be a volcanic maar — a depression formed when magma rises from deep within the Earth's crust and reaches the groundwater level. The penetrating magma heats the water to boiling point, generating steam that creates such immense pressure underground that an explosion eventually occurs.

Researchers note that volcanic maars often leave wide craters that fill with groundwater. For instance, it is known that the 100-meter eastern Ukinrek maar in Alaska formed during a 10-day eruption in 1977; since then, the crater has frequently filled with water.

At the same time, there are no known volcanic landforms in close proximity to the Savonoski Crater, and there are no signs of a magma source beneath the hole, according to studies from the 1960s and 1970s. Thus, the potential volcanic origin of the crater remains a mystery.

Scientists have yet to unravel the secret of the crater's formation, but they believe it is either a meteorite crater or a volcanic maar; however, a definitive answer will only come after much more extensive research.

It is known that the mysterious crater has survived at least one glaciation event since its formation — it was engulfed by an ice sheet when glaciers last covered the southwestern part of Alaska between 23,000 and 14,700 years ago. This glaciation, scientists believe, obliterated all obvious evidence of the crater's origin. Nevertheless, researchers hope that clues may still be hidden within the crater, should they ever decide to drill into its center.