Saturday 15 November 2014

Writer's Resource: Underground, Caves and Cavern Systems

   I did a fair bit of research for a recent book on the underground, caves and cavern systems, and I found that a lot of the information I wanted was spread around in a variety of places, so I decided it might be a good idea to collect up all of this information in one place for other writers to use.
   I've not gathered up too much detail - if there's something you want more info on, such as karst formations, this information is much more easily found. Instead I've limited it to the basics. So unless a character is an expert in their underground surroundings, what I've given you here will be more than enough to work with.


Formation of Caves, Caverns and Systems
   The most common type of cave and cavern systems is limestone, and as well as being the most abundant, they are also the longest and deepest in the world. The limestone is worn away over time by water soaking through from the surface and by underground rivers. Rain picks up carbon dioxide in the air and forms a weak solution of carbonic acid which wears away the soluable limestone and creates caves. The limestone can be deposited elsewhere in the cave as the water flows or soaks. These are solutional caves (caves formed by an acid solution wearing away the rock; some solutional caves are also worn away by sulfuric acid instead, such as Lechuguilla).

Cave Features
   Many caves and caverns have certain formational features, known to cavers and professionals as speleothems, and the most likely to come to your mind are stalactites and stalagmites. First of all, how to remember the difference: I follow Stephen Fry's example: tights hang down. Stalactites hang from the ceiling, whereas stalagmites form on the ground. As long as you know one, you know the other.
   These are formed by water rich in dissolved limestone drop from the ceiling. Tiny deposits of the limestone is left behind when the water drips away, and over time more and more of it builds up to form spires on the ceiling (not always sharp or even conical). But while these are forming, the water that drips onto the ground still has some dissolved limestone in it, and that limestone gets left on the ground. Over time that too can build up and form an up-ward pointing spire. When a stalactite and stalagmite meet they form a column which thickens over time as limestone-rich water runs over it, depositing minerals as it goes.

   There are many other types of speleothems, however, my favourite are cave pearls - smooth, polished stone spheres that cluster together and look like pearls, which are formed in a similar way to real pearls: a grain of sand, for example (a 'nucleus'), is surrounded by a layer of calcite which is deposited in the same manner as a stalactite is formed, but forms a cave pearl when water is moving too vigorously around it to form a stalagmite. They're usually found in shallow pools of water - it's that water which is responsible for making them so smooth and round.

   Here we have an example of stalactites & stalagmites (1), a pool of water and a column (2)

   An example of cave drapery - another form of speleothem which are wider, flatter sorts of stalactites which look to a degree like curtains.

   A flow sheet, which form of cave walls and floors where there is no opportunity for the dissolved limestone to form in one concentrated area. They often look like frozen water.


   To say the least, it's dark. In fact, it's black. No daylight gets into caves and caverns unless they're at the entrance. All the light you see in photographs (for there has to be light for photographs) are either from camera flash, torches, or pre-set lights in show caves (caves that have been adjusted so that the flooring is smooth enough for children to walk over safely and is open to the public for a fee). There is no natural light in caves - at least not as we know it, but more on that later.
   So your characters will need to bring their own light, and you must consider, of course, how far that light reaches and the shadows that will be cast around them.

   The temperature underground is consistant, and it barely changes all year round. In the winter, a cave is generally warmer than the outside, while in the summer it is cooler than the outside. As I said, it's consistant, but it's still quite cold. As a result of the consistant temperatures in caves and caverns, they're sometimes used to mature cheese, such as Gough's Cave in Somerset's Cheddar Gorge.

   For the most part, caves and caverns are silent. You might hear running water if you're close enough, the movements of small animals if they are plenty enough - such as insects and bats - and perhaps the sound of the wind, though it's uncommon for it to be loud enough to hear. More likely you'll feel the slightest breeze.

   Rivers, waterfalls, streams and lakes are not uncommon, and neither is complete flooding. Inland caves will usually feature freshwater unless they open out into the sea, as can happen with very long cave systems, and in this case the two waters don't mix, so much and exist alongside eachother. Or rather on top of eachother. Excessive rainfall can affect flooding, too.
   Because of the consistently cold temperatures underground, the water in caves is very, very cold. As a result, hypothermia is a real threat. Cotton absorbs and holds the most water, so is particularly dangerous, so it's wise to bring a change of clothes or two if someone must enter the water. If there are no change of clothes available, wringing the clothing out as much as they can and letting their body heat dry them will do, but they'll have to huddle together and minimise direct contact with the cold ground with blankets and such. Keeping active can help against hypothermia, even if it's just walking on the spot.


Plants and Animals
   There is life underground, though it might be sparse. Plants, however, are difficult to find. They would need both a source of light and a source of water to grow, though not necessarily soil - certain moss, for example, don't require soil. But while plants are one of the basic beginnings to a food chain, they're not the only beginning. Waste that flows from the surface through unpercolated rivers (rivers that don't get filtered through the rock itself before reaching the cavern system) can carry food with it, such as tiny animals, small fish, dead animals, plant waste and so on, albeit on a small scale. But sometimes this is enough. But there is also bacteria that feed on acids. The aptly named 'snottites' (what you're picturing is more or less accurate) are colonies of single-celled bacteria that feed off of sulfuric acid. 
   Troglophiles are animals that use cave entrances to escape the outside weather and temperature, seeking heat in the winter and cool in the summer, and sometimes for safety, too. These animals are usually found near entrances - not necessarily entrances we could fit through, however. As long as there is a short and direct route from cave to surface, you can find them there. Such animals include newts, frogs, snakes and salamanders, and small mammals such as foxes, wolves, raccoons and so on. There may be much larger mammals, too - even elephants have been known to seek shelter in some African caves. Insects include scorpions, cave crickets, cockroaches, moths, etc.
   Then there are the troglobites, the animals that live only in caves, never venturing out. These are the more interesting creatures as they've adapted to a life without light and little food. The most common of these adaptations are a loss of eyes - if there's no light, there's nothing to see, so there's no need for eyes - a loss of pigment - and if nothing can see you, you don't need to blend in, and you don't need to look threatening - and elongated appendages. They also generally don't eat often, and have very slow metabolisms to save their energy, but when a meal comes by, they can't afford to miss it. Such troglobites include, specifically, the Texas blind salamander, the Kauaʻi cave wolf spider, and blindfish.
   There are also some rather unique evolutionary traits for cave-dwellers, such as glowworms (troglophiles). In the Waitomo (Māori for water hole) Caves in New Zealand there's the famous Glowworm Grotto, a small cave that is part of the cavern system wherein hundreds of glowworms live. They spin a line of silk which they cover in their mucus to catch anything that passes by, such as moths and mosquitos, and use their lights as a lure - the insects fly higher and closer to their lines, or 'snares' because their collective lights can cause an insect with poor eyesight to believe it looks like the night sky, and that they're outdoors. It's a truly beautiful sight, despite the worms, mucus and mosquitos, as you can see below:

    Animals are a versatile subject, however. Writing fantasy means you can really play around with them, but you have to consider their environment, too. Instead of being blind, they could have giant eyes that detect the slightest of lights - but that would mean that there would have to be the slightest of lights present and consistant in your cave system, or at least in the area they live. This would mean that the need for camouflage and threatening colours would become relevant again. Their size will also depend on how they feed, and if their food source is abundant.

Effects of Being Underground

   Being underground can easily cause claustrophobia. Claustrophobia is the fear of having no escape, or being enclosed in small spaces, so being unable to get out of a cave or cavern quickly and easily can lead to panic attacks which in turn can lead to hasty decisions and subsequently injuries. Caves and caverns of a single system won't usually vary very much in appearance - all the rock will have the same colouring, possibly the same roughness or smoothness, and lots of similar features as they'd all been worn in by the same cause, and to someone prone to such attacks, the surroundings will seem even more identical than to someone keeping a cool head and taking note of their surroundings.
   Along with claustrophobia, tensions will rise. It could be that no one in the party would suffer obvious claustrophobia, but they might all suffer some small degree of it and become quite irritable. Or if just one person shows obvious signs of it, that can be enough to stress everyone else out.
   Underground there's no daylight, either, which throws your body out of whack. Melatonin is the chemical that is heavily responsible for your circadian rhythm - your 24 hour 'body clock' - and is quite dependant on light. Melatonin levels are low during the day when there's a lot of light reaching your retina, and high in the evening and higher at night when the light dims and vanishes. When melatonin starts to increase, it chemcially causes drowsiness and lowers the body temperature to encourage and aid sleep. Underground there is no natural light (camp fires don't count because they don't emit enough 'blue light' like the sun), and as a result the levels of melatonin will probably be quite high a lot of the time. This means that everyone will be quite cold and sleepy more often than not, and we all know that when we're tired we can get a bit moody, especially if it's constant tiredness. Let's not also forget that natural light can boost moods, so being away from natural light will also contribute to foul tempers.

   The ground is far from even - far from even. In fact for half the time you're likely to be scrambling over rocks, and it would be all too easy to break a bone, twist an ankle and fall down narrow cracks. In Lechuguilla in New Mexico it took over 100 expert cavers 3 days to retrieve someone who'd broken an ankle, and in Riesending Cave in Germany, it took over 700 people to get out another man with a similar injury. So simply put, injury is fairly likely, and if there are no experts in caves or underground worlds with your characters, injury is even more likely.
   Caves can also be flooded over time, and these flooded caves can be anywhere from metres to miles long - over 300 miles of underwater passageways have been mapped in the Yucatan Peninsula in Mexico, and Ox Bel Ha is almost 150 miles long - and sometimes, if fresh water meets salt water, it can be deceiving to the eyes, as salt water is heavier than fresh water which leads the salt water to slip beneath the fresh. Salt water isn't as clear as fresh water, either, so the separation of the two can create the illusion of air, which is certainly dangerous if free-diving (diving on one breath, carrying no breathing apparatus). While it would be much harder to break an ankle or fall off of something while swimming, there are other dangers, such as 'squeezes' - narrow gaps that you can squeeze through though you run the risk of damaging yourself or your oxygen tanks, and if you get stuck you'll either run out of air quicker in your panic, or, if free diving, will perhaps inhale in a panic.
   The water is also quite cold, so if someone were to stay in it for too long they could get hypothermia quite easily, and the water can also weaken the rock, wearing it away over time, and as a result ledges can give way beneath people which will, obviously, result in injury.
   Small unventilated caves can become gas chambers which fill in time with extremely toxic gases like carbon dioxide, carbon monoxide, sulfur dioxide, ammonia, methane and others. Sulfur dioxide and ammonia in particular are extremely water-soluable, meaning that they create acids upon contact with water - this includes bodily fluid and as a result it can be irritating to the eyes and lungs, especially when in great concentration. These two also have pungent smell - sulfur dioxide smells of rotten eggs; ammonia smells like urine.

   Disorientation is easy in a cave system, as tunnels wind off everywhere and areas, as mentioned before, all look the same to untrained eyes. And so string is often used to both map their route and measure the length of cave systems. It's quite a simple method, but it's one still used today.
   First aid should always be on hand, the most basic of which would be bandages, clean cloths, clean water, alcohol and material for splints. Painkillers would also be good, but, of course, it depends on the advancement of your world (you'd forgotten this was a writing rescource put together by a fantasy writer, hadn't you?).

Other types of caves

Limestone Caves
   Limestone caves are the most common, largest and deepest of all cave types, so it's likely that it would be a limestone cave that characters would either stumble across or be forced to pass through. They're formed over thousands of years by water wearing away the rock - usually it's rain water mixing with carbon dioxide to form a weak solution of carbonic acid, or occasionally it's rain water mixing with hydrogen sulfide in the earth, creating a weak solution of sulfuric acid which eats the rock away in the same manner. Limestone caves are rich in speleothems.
Search 'limestone caves' on Google images for visual examples.

Lava Caves
   Lava caves or lava tubes are generally tubular in shape (I bet you didn't see that coming). They're created by lava flow, where the outer layer of the lava will harden and cool, but the inside is still molten and continues to flow. The caves/tubes are formed when that still-molten lava flows right out of its hardened casing and leaves an empty passage way. These are, of course, found in regions with both active and extinct volcanoes, but they usually lack speleothems, except perhaps a few stalactites created by hardened lava that dripped from the ceiling. They also have a tendancy to lead nowhere.
Search 'lava caves' or 'lava tubes' on Google images for visual examples.

Sea Caves
   These are caves and caverns created by the pounding of waves against the rock and removing material as they go. They can also be formed by the waves creating and widening a crack in the rock. They're relatively small, averaging 300 metres in length, feature next to no speleothems and require crossing water to reach them. These, too, lead nowhere. If the rock the water is attacking is a narrow stretch jutting out to sea, it's more likely to cause the cave to become a sea arch instead where the water eats the rock away all the way through to the other side. If the top of the arch collapses, which is likely over time from weathering and a lack of base support, you'll be left with sea stacks.
Search 'sea caves' on Google images for visual examples.

Ice Caves 
   Ice caves are formed by ice, of course, and there are two types: glacier and ice.
   Glacier caves are really just glaciers - just ice - that have had water running through the bottom that has gradually worn the ice away to form a cave. These are highly dangerous because of shifting and melting ice. However, these can also be both beautiful and fantastical.
   Ice caves are simply any kind of cave listed above that happens to have ice in it all year round. This ice forms by cold air trapping air and subsequently freezing water within it, and as caves don't really see much of a change in temperature, that air will stay cold all year round. This can mean that you get beautiful ice formations in ordinary caves.
Search 'ice caves' or 'glacier caves' on Google images for visual examples.

Unique Caves
Er Wang Dong cavern system with its own weather.
Lechuguilla and its Chandalier Ballroom, a cavern filled with enormous gypsum crystals.
Deer Cave in Borneo is big enough to fly a jumbo jet through

Further Your Research

Watch Planet Earth's documentary: Caves
   Part of the Planet Earth series, created by the world-renowned BBC Bristol Natural History Unit and narrated by the even greater known David Attenborough, the episode 'Caves' shows different types of cave formations, speleothems, troglobites, troglophiles, flooded caves and cave diving, and the 10-minute 'diary' at the end of how they filmed certain points also hints at the mental pressures and frustrations of being stuck underground for several days straight. As well as slightly more detailed and varied information than what I've provided, it also offers visual examples of the different formations, creatures and darkness, as well as the difference in weight and density of salt water versus fresh water. It's an amazing piece, and the many visual examples can also really help to put the writer in the setting, making it easier to create a cavern system of your own.
   You can buy the box set of the series on Amazon, and I promise it's worth it. There is another wonderful episode on mountains, and the footage used across the entire series is unique to its own, rather than filled with repeats from others.

Watch Wild China's documentary: Heart of the Dragon
   Part of the Wild China series, created once again by the world-renowned BBC Bristol Natrual History Unit, but narrated this time by Bernard Hill (King Théoden; you're welcome), the episode 'Heart of the Dragon' shows unique caves and caverns, none of which are repeats of Planet Earth's 'Caves', as well as creatures and interaction from people, including the temples and a school built within the caverns. This documentary is just as beautiful as Planet Earth, but features elements of Eastern culture at the same time, some of which really sparks the imagination.
   You can buy the complete series on Amazon as well, and as before, I promise you the entire series is worth it. It's filled with so many unique things - including the fact that people in China keep birds as pets, but as they worry that they get lonely, once a week they take their birds outside, hang their cages in a tree, and let them all talk to one another. I love that.

Go to a Show Cave
   There are show caves dotted everywhere. A show cave is typically a natural cave with natural features (if you're concerned that the cave you're considering visiting isn't natural, do a quick search for it online. If it's not real, several geologists will have been quick to point it out), generally with several examples of different speleothems and even sometimes human remains, such as the 9,000 year old skeleton found in Gough Cave, England.
   The only adjustments generally made to make a cave into a show cave is a smoothing of the floor to make it safe to traverse for children and the elderly, steps and railings, electric lighting, and the closing off of unsafe areas. Everything else is generally authentic. Show caves almost always include guided tours, and often have a walkie talkie tour option and informative posts. Show caves are far, far safer than actual caving, with first aid on hand if needed, and the exits are always easy to find. You can see for yourself the stalactites and cave pearls, feel the temperature, and see the uneven walls - though I suggest you not pay too much attention to the ground. A real cave isn't anywhere near as easy to walk across.
   Prices tend to be around £12/$17 per adult, sometimes more, sometimes less, depending on where the cave is, the kind of cave, the cave's features and nearby attractions. They make for a unique experience, a fun day out, and very hands-on research experience - yes, research. Don't forget that part. All of the pictures above (minus the glowworms, of course) I took myself at Cheddar Gorge, Somerset.


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