The online class I'm taking is now shifting towards the rock cycle, and one of my classmates posted something about glaciers. This made me start pondering about what would happen on icy bodies such as Pluto and Titan. The rocks types of igneous, sedimentary, and metamorphic might be carried out by different types of ice! ("Ice" = H_2O, CO_2, or CH_4 methane) To make matters even more interesting, on Titan they've suggested methane rivers - in other words, when the body heats up, the ice changes to liquid and perhaps vapor, so that the "ice cycle" is realy an intermixed "rock cycle" and "water cycle."
Try and wrap your head around that one! :)