Cave explorers have discovered what is now Australia's deepest known cave.
A group of explorers discovered a 401-meter-deep cave, which they named Delta Variant, in Tasmania's Niggly-Growling Swallet cave system in the Junee-Florentine karst zone on Saturday.
The Niggly Cave, its predecessor, has surpassed it by about four meters.
Delta Variant is causing a stir among explorer communities after a 14-hour descent that took many months to prepare for.
But for experts such as myself, who study the interaction between groundwater and rocks (even in caves), this is a different kind of fascination.
This information allows us to understand natural processes and how the Earth's climate has evolved over millions of years.
As exciting as Delta Variant may be in an Australian context, it is perhaps just an appetizer into the wider world of caves; the largest known cave, located in Georgia, extends more than 2.2 kilometers into the earth.
What exactly do these massive geologic structures do exactly under our feet?
What are the origins of caves?
Caves arise when flowing water slowly dissolves rock over a long period. They arise in certain geological formations called "karst," which includes structures made of limestone, marble, and dolomite.
Little fossilized microorganisms, shell fragments, and other debris that accumulated over millions of years make Karst.
Small marine mammals leave behind their 'calcareous' shells made of calcium carbonate long after they die. Corals are also made of this material, as are other species of fauna with skeletons.
This calcareous sediment builds up into relatively soft geological structures. As water flows down through crevices in the rock, it continuously dissolves the rock to slowly form a cave system.
Unlike much harder igneous rocks (such as granite), calcareous rocks dissolve when in contact with water that is naturally acidic.
When rain falls from the sky, it picks up carbon dioxide from the atmosphere and soils along the way, making it acidic. The more acidic the water, the faster it will erode karst material.
As you can see, cave formation can become quite complicated: the physical composition of the rock, the pH of the water, the level of drainage, and the overall geological setting all influence what sort of cave will be formed.
In geology, there's a lot of spatial guesswork. It's akin to going into the deepest layers of a cake, where you may not discover the same thing in all directions.
Stalagmites and stalactites
Caves are very valuable from a research viewpoint because they contain cave deposits (or'speleothems') such as stalagmites and stalactites. These are sometimes tiny things that point up from cave floors, or that droop from the ceilings, or that form beautiful flowstones.
Cave deposits are formed when water flows through the cave. Like trees, they contain growth rings (or layers) that may be viewed. They may also include other chemical signatures the water contained, which might reveal events that occurred at the time of their formation.
Although they may not seem like much, we may use these deposits to unravel previous clues about Earth's climate.
And since they're a function of rock and water's interaction during cave formation, we can generally expect to see them in most caves.
What depth can we go?
Descending deep into a cave system is no small feat. Your phone is non-receiptible, the area is extremely dark, and you're usually relying on a guide line to lead back out.
Explorers may find there are many dead ends, and accurately mapping the space requires effort and great spatial exploration skills.
While cave systems are usually stable (shallow caves can in theory collapse and form sinkholes, but this is very rare), there is always danger.
As you ascend into darkness, you might encounter tricky maneuvers, twisting, and swaying in a variety of uncomfortable ways.
As you descend, the air pressure does not change to a dangerous extent, but other gases such as methane, ammonia, and hydrogen sulfide can sometimes pool and pose a danger to your life.
Despite all of the above, cave exploration is still an activity that people continue to do, and it is of great benefit to researchers in many sub-fields of geology.
Despite our advances, there are still nooks and crannies that we can't access, after all, as humans.
I'm sure there are small spaces, too small for us to explore, that lead to far greater or deeper systems than we've ever discovered.
Gabriel C Rau, Lecturer in Hydrogeology, University of Newcastle.
The Conversation published this article on its original webpage.