the signs say...

This month's accretionary wedge is on geological/geographical signs.

I don't have any geological signs at hand, but one thing that we often encounter in the field are interesting "hazard" signs, such as this one:

Seriously, don't go for a swim. And, um, tsunami.

I don't usually end up going swimming (intentionally) during the course of fieldwork, but falling rocks and/or geologists are always a possibility. So here's an example from the Grand Canyon, complete with "ass over teakettle" graphic.