randomlittlewriter wrote:How big, on average are cave systems?
When you ask how big cave systems are on average, you could be asking how large the passages are on average or what is the total length of passages on average. If you were to average out all the caves in the world even the ones that are pretty short, then the average passage size would probably be under 5 feet tall by 5 feet wide and the average total length on average would probably be under 1,000 feet of passage. The cave with the largest passage in the world is Son Doong Cave in Vietnam with a passage 3 miles long, 700 feet tall, and 500 feet wide. The cave with the largest total of length of passages is Mammoth Cave in Kentucky with over 400 miles of passage explored so far.
There are some areas of the world that have no caves or hardly any at all so if you narrow the area that you are talking about to a more specific area with lots of caves you could have a higher average. Areas with limestone, volcanic activity, glacial melt, and sea cliffs that are prone to erosion from sea waves are more likely to have caves than other areas for example.
Here is a map of the karst in the United States:
And here is a map of the karst of the world:
randomlittlewriter wrote:How deep do they go?
When you ask how deep they go, you could be asking what is the farthest point from an entrance or what is the elevation difference between the highest point in the cave and the lowest point in the cave. You're not asking about averages so I will just give you the record for the cave that has the farthest point from an entrance and the cave with the largest elevation difference between the highest and lowest point in the cave. The cave with the farthest point from an entrance is Fort Stanton Cave in New Mexico with the farthest point from the entrance being over 12 miles so far. And the cave with the largest elevation difference between the highest point and lowest point in the cave is Krubera-Voronja Cave at 7,208 feet in depth in the disputed territory and partially recognized state of Abkhazia which is claimed by the country of Georgia.
randomlittlewriter wrote:How many rooms are there, usually?
I really don't know if I could make a guess for this. It is different for every cave. You should look into the area of Cappadocia, Turkey on the internet which has a bunch of ancient underground cities including the world's largest underground city of Derinkuyu. Derinkuyu is large enough to have sheltered 20,000 people and was 200 feet deep. It is currently not fully excavated and probably had thousands of rooms.
randomlittlewriter wrote:What's the air quality like? Could you breathe it constantly for a long time? Would you need ventilation? How would you go about getting said ventilation?
Most caves have good air quality but there are some caves where air quality is a problem and it is hard to breathe. The caves where it would be hard to breathe would be the ones that had mining in them in the past that released harmful chemicals from mining. Also, if there is a tight passage that many people are going through it may deplete that passage of oxygen faster than if there were fewer people and it may become hard to breathe in that passage. Most caves you would not need ventilation. Another case where the air quality would be a problem is where there is a large bat colony which produces a lot of bat guano. You don't want to breathe in any of the bat guano because if you did you could get histoplasma which would not be good. For the cases where you need better air quality, you should wear a mask.
Here is a picture of some Brazilian cavers wearing masks to protect themselves from histoplasmosis:
If you want to learn more about the specifics of ventilation, I would suggest that you read up on the Cappadocians and their ideas for ventilation for their underground cities.
randomlittlewriter wrote:How would you deal with getting rid of bats? If you closed off most or all of the entrances would they still find a way in?
First of all, what would be the purpose of getting rid of the bats? I don't see why you would need to get rid of the bats. In most caves, bats are a rare occurrence to see and are usually near the entrance of caves. They usually mind their own business. For most caves, you only see bats in the winter when they are hibernating. There are some caves though where the bats go there during the warmer months for breeding colonies and some caves where the caves are a breeding colony year round for bats like in warmer/tropical areas of the world. If a cave had a lot of bats in it like if it was a breeding colony, it would be pretty difficult to get rid of all the bats. If a cave had just a couple of bats in it then it probably wouldn't be as difficult to get rid of the bats. If you closed off the known entrances that humans can fit through, there may still be entrances that are bat sized and that we don't know about that the bats could go through to get into the cave.
randomlittlewriter wrote:Is it possible for water to flow from another underground area to flow down into another cave like a waterfall? Would that water be clean and drinkable? Would it be possible for water to carry away waste and not have it build up and be really nasty smelling? How deep would that have to go?
Yes, it is possible for water to flow from one cave to another that cannot be humanly accessible from one cave to the other. And yes there are waterfalls in caves. It would depend on the cave that you are talking about as to whether the water would be clean enough to drink. If the cave was high up in the mountains totally away from civilization the water in the cave would be more likely to be safe to drink. If the cave's drainage basin included a lot of farmland then in would be a bad idea to drink the water because there could be cow manure and all sorts of possible pathogens and viruses that could be a problem if you drank that water. If the cave's water is flowing fast, waste would be carried away faster than if the water is flowing slower. If there is a dam of some sort blocking the water's path in the cave such as a log jam, the waste could collect there possibly. It is generally not a good idea to urinate or poop in a cave. It is generally suggested that you pee in a bottle and carry out your waste in bags rather than do your business in a cave. But if you were to do your business in a cave, it is better to do your business in flowing water than in a dry area of a cave where it will pretty much fossilize if no water flows through that area. If you were to do your business in a cave, the deeper you do your business in a cave (where the water is flowing), the better so people are less likely to smell it and it is more likely that the water will wash it away faster.