Not Your Grandfathers Mining Industry, Nova Scotia, Canada

Fraggle Rock was a children’s TV show, not a geological formation, but it was partly inspired by geology!

Fraggle Rock

The show was about four types of creatures - Fraggles, Doozers, Gorgs and Silly Creatures - who lived in a cave and shared a water source (a lake that was created by a leaking radiator in the home above).

The Fraggles’ cave was inspired by Bermuda's Crystal Caves, according to the show’s creators.

In 1907, two twelve-year-olds found a hole in the ground while searching for a lost cricket ball. The hole revealed the Crystal Caves, some of the many caves in Bermuda’s bedrock that have become significant tourist attractions.

Limestone is the main type of bedrock in Bermuda. It is a relatively soft rock that is easily-eroded by flowing water breaking it down (similar to how streams/rivers carve valleys), or calmer water dissolving the limestone.

As sea levels have risen and fallen through various ice ages, Bermuda’s cave systems have repeatedly transitioned from being completely or mostly filled with water to being mostly filled with air. Sea levels are lower during ice ages because so much water is frozen in glaciers, and sea levels rise as glaciers melt and water returns to the sea.

Bermuda Crystal Cave

During periods when they were mostly filled with air, stalactites (which hang from the ceiling) and stalagmites (which point upwards from the ground) have formed in Bermuda’s caves.

When water flows down through the ground and into a cave, it dissolves a mineral called calcite, a major component of limestone, and carries it through cracks in a cave’s ceiling. The dripping water leaves behind traces of calcite, which slowly builds up on the ceiling until a stalactite forms, hanging down like an icicle.

Water that drips from a stalactite leaves more calcite in a pile on the cave floor, which builds up and forms a cone-like stalagmite. That’s why stalactites and stalagmites are usually found together.

You will sometimes see pictures of caves that are filled with water but have stalactites and stalagmites in them. Because of how stalactites and stalagmites form – in caves mostly filled with air - we know that such caves were not always filled with water.

Head crystal caves Bermuda

The water in the Crystal Caves is a combination of sea and fresh water. The caves are connected to the sea through subterranean passages, and the Caves’ water level rises and falls with the tide.

The first tourist to enter the Crystal Caves was American author Mark Twain in 1908. Twain wrote books such as The Adventures of Huckleberry Finn and The Adventures of Tom Sawyer.

Most caves in Nova Scotia are in gypsum bedrock, but the process by which they form is basically the same as how Bermuda’s limestone caves formed: water erodes the gypsum, which is also a soft rock. This process also leads to Nova Scotia’s many naturally-occurring sinkholes. Groundwater erodes the rock, leaving an underground cavern. Eventually, the weight of the rock and earth above the cavern causes it to cave in and creates the sinkhole. (Learn more about sinkholes at https://www.facebook.com/MiningNS/posts/4000853439941759).

Apple TV is rebooting Fraggle Rock, which first aired in the 1980s, and is shooting new episodes in Calgary.