#speleology

[cleavagearbiter]

My friend rappelling into the Rumble Room, the second largest cave room in the US. During this rappel I was unable to see any of the walls or even the floor except for the last 50 feet. All I could see was the murky darkness surrounding me.

[linseedling]

Which cave animal are YOU????

(Interested in more cave animal facts? Check out my book!)

[rockchomper]

[postingcards]

the bat cave, carlsbad chrome postcard ca. 1960s

[fullyunsourced]

Measuring the Earth's tides with the world's largest geodetic pendulum

Deep in Italy's largest cave, you'll find Italy's largest pair of pendulums. The Grotta Gigante, which creatively means "Giant Cave" is an enormous cavern in northeastern Italy near the border with Slovenia. The main hall is 351 feet high and 430 feet wide. In addition to making it a beautiful tourist attraction, it's home to a rather important and colossal scientific instrument.

Earth tides are something I've mentioned before: The Sun and Moon have an obvious effect on the height of the sea in the form of oceanic tides, but they also stretch and squeeze the land itself. The crust of the Earth is only an average of 22 miles thick, and it's moved up and down by these tidal forces about ten centimeters per day.

In addition to this, the crust is also moved by tectonic forces, which most often you see as earthquakes. After that, you have the ocean tides making an impact too: All that water moving about weighs the earth down and shifts it.

How do you measure these effects? Why, a pendulum, of course! Were it not for these outside impacts, a pendulum should move stably. So with a large enough pendulum to detect the changes in the crust, you can determine what's actually happening.

The next trick is that you also need to avoid interference, such as heavy traffic nearby. The Grotta Gigante turns out to be the perfect location to install a pendulum, and so one was built in 1959. It's a horizontal pendulum, so there's a steel beam weighing about 18,000 kilograms suspended by wires running to the top and bottom of the cavern.

From there, a small mirror is mounted on the beam, and a light aimed at it and reflected onto a sensor can pick up the most minute of movements. So really, what it is is a massive tiltmeter.

The Grotta Gigante horizontal pendulums are an incredibly valuable scientific tool. You can determine the Earth tides by looking for periodic movements, and outliers will be seismic activity. The pendulums have recorded four of the five most powerful earthquakes of the last half-century, including two in Chile. There's a lot of value in having the same instrument measure different events.

As for superlatives... Wikipedia denotes it as the "world's largest geodetic pendulum", but when I looked up the term, I could only find the Grotta Gigante pendulums anyways. So sure, they can have it.

[sxpxrmxrgxr]

[noosphe-re]

Some stones are so porous and pitted that they invite the curious eye to wander deep into their secret spaces. For below their outer crusts you will find an elaborate network of mines and crypts with worn and wasted bedrock riddled with holes and strewn with scaffoldings of rock. Runnels furrow through their seams and ferry silt back through their channels. Here is a place of slow tunnel-building akin to neural network growth: a brain-like subterrain of branching chutes and boreholes. Here are the truncated synapses of the earth's own cortex lacing through the sediments of deep time. Channels chisel thoughts and then smooth them into memories. And, here and there, the ducts link limbs to form larger chambers within the stony matrix. Uncertain tunnels weave past vaults, past chimneys, past domes and past concavities crammed with towers scratched with touchstone signs. Water writes its paean to gravity as it finds its new affinities. So, scored within this rock, we have another proof of Newton's inverse. Another computation worked within the rock, another winding sum of liquid flow, and another fluid thread to guide the eyeless. We float beyond these flooded channels, past barques and caravels of ghosts, and past chambers clogged with bones and piled with feathers.

Paul Prudence, Figured Stones: Exploring the Lithic Imaginary

[useless-catalanfacts]

According to the legend, when the Moorish people felt the danger of the Christian conquest getting near, they hid their treasures in a cave near the El Marinet area, at the feet of the Penyagolosa mountain (Castelló, Valencian Country) and planned their escape.

A Moorish prince volunteered to guard the treasure until the Muslim people returned to the land. The Arab magicians turned him into a bull, which is a noble and fierce animal.

The Christians conquered the lands and heard the story. They hurried to look for the treasure in all the caves, but they never found it. Since the Moorish people could never come back, the bull is still in the cave, guarding the treasure.

People say that, on a calm day, if you listen closely, you can still hear the muffled sounds of the bull, crying for the return of his people.

La Cova Santa ("The Holy Cave") in Vistabella del Maestrat, near the Penyagolosa mountain. Photo by Nacho Gimeno, from De Penyagolosa.

The Catalan Countries, and particularly the areas that were under Islamic rule for longer (the Valencian Country, the southern part of Catalonia, and the Balearic Islands) are full of similar legends about the Moorish people leaving hidden treasures behind, with enchanted magical people guarding them. These legends can be more simple (like this one) or more elaborate with details on how one might retrieve the treasure, if they're ready for the dangerous challenge. Historically, many people have believed these legends, and some have tried to find such treasures. As far as we know, no enchanted treasure has been found... so far.