A huge (68x39x23) monolith of natural obsidian. What to do with it?

(This map also currently has 65 dwarves on it. It was made with a pop cap of 50. If you have a pop cap above 65, you may get quite a few dwarves immigrating in.)

Original forum post: http://www.bay12games.com/forum/index.php?topic=27763.0

In addition to the obsidian monolith, this is a 3x3 area that contains magma, flux, an underground river, HFS, and sand. It does not have an aquifer, bauxite, giant cave spiders, or a large supply of iron (aside from goblins). More details on the wiki at https://www.dwarffortresswiki.org/index.php/Pregenerated_Worlds#The_Barbs_of_Zeal