What geological concept or idea did you hear about that you had no notion of before (and likely surprised you in some way).
I have a few ideas for my own topic, but I would be interested in what people have to say about this. Some things we think are obvious and just know about other people have never heard of.
The deadline for this is February 18th. Please post all your submissions in the comments section. And don't forget to get your submission in for Accretionary Wedge #30 which is due January 28th.