in-game text: [i][feeling the burn on his back, he shook his fist at the sun, and crawled down into the deep/i]
cave digging enables you to build your own cave. <OBVIOUSLY>
Lp req: 1500
skills enabled: none <that i can think of yet>
required by: cave's <adventure-dig cave>
basically what this does is enable you to dig a cave in a cliff, this could also be done on mountain terrain but it would cost a lot more stamina.
what would happen: a sign post would come up on the tile infront of the desired cave which would be like the opening support it would require: board x8, block x4 nugget of any metal x4, and stone x30 it would also have a soil requirement of 50 however the soil is added to the sign by pressing build, which technically would make you dig, so like always the process would be faster with a shovel.
once the initial opening is built you have an are that is only the size of the tiles that are normally lit< im not sure i worded that right so basically you enter the cave and have that tiny area>
from there you can use your mining skills to eat away at the walls, until you reach a space equal to 4 log cabins in a square, after that its impossible to mine
plz expand on this and tell me about anything ive left out
also it just came to me so im not sure if its in play yet but> could we also have a way to build a minehole within a minehole or cave so we can go deep into the earth and the lower down the more deposits and veins there are> though limit the levels of deepness to like 10 or so.

EDITING TO ANSWER THREAD QUESTIONS:
1: this does not replace mines or caves in any way shape or form. it is given a size of about the log cabin^2 (squared if you didnt guess

that way it is a nice and cosy home for noobs or nomads wanting a camp for a few days but not wanting a house.
to mine from this <for want of a better word> "dell" or "delving", you would have to build a minehole inside the "dell" of course this makes it possible for people to mine your mine, and so jump your outer defences
it would be the same layer as caves and surface mineholes.

to get a mental picture, imagine the rock thingy, embedded on a cliff, that opens up to your cosy home.
p.s i have no idea wether that image works so.
http://www.seatribe.se/roligabilder/somestuff.png
any thing else you want to know??