Global Ruin

Sorcery

Each player chooses from the lands they control a land of each basic land type, then sacrifices the rest.

2004-10-04:
If a land counts as multiple basic land types, you can choose it for either or for both of those land types.
2010-08-15:
You sacrifice all lands other than the chosen ones. Since you can only choose lands with basic land types, any non-basic lands that don’t have a basic land type (even if they have some other land type, as in the case of Cloudpost) are necessarily going to be sacrificed.