This is just a little something I through together in about 10 minutes, although i'm sure someone has made something like it, but it is very efficient. Place redstone for obsidian, don't place for cobblestone. Look at pics above for a better demonstration!!!



Make sure you also check out my adventure map, Lava Land Survival Challenge: http://www.planetminecraft.com/project/lava-land-survival-challenge/



Thanks!!!