It's likely that you have eaten a peanut butter and jelly sandwich. But do you understand the significance of the PB&J in the world of GEOLOGY? Probably not....unless of course you are a geologist. Here I present:
The Top Five Greatest Lessons of the PB&J Sandwich to the Field of Geology.
1) SUSTENANCE: Many a grad student has spent long durations of time far far away from civilization searching for that unit-of-pillow-basalt-to-prove-that-ophiloites-extend-further-into-the-pacific-northwest-than-previously-thought. The trouble comes as, what the fuck to eat out there? Luckily the PB&J is light weight, has a good calorie count and maybe most importantly CHEAP. I know as a grad student I had no pay and was frequently deep in the Maine woods looking for more damn schist on an empty belly. PB&J saved me more than once.
2) HYDROGEOLOGY: The main lesson that comes right to mind when talking about a good PB&J is related to hydrogeology and proper construction of the PB&J. Peant Butter acts as a very impervious barrier between 'watery' jelly and porus bread. Any PB&J worth its weight will be constructed in this manner: bread, peanut butter, jelly, peanut butter, bread. Whereby the peanut butter retains the jelly, keeping it from soaking the bread. It's just common sense people. The peanut butter also tends to act as a seal, keeping the jelly in, when the sandwich is bitten into. No Mess.
3) TECTONICS: Many a PB&Js sitting side by side on a flat table have been mashed into one another demonstrating mountain building processes. The jelly can even look like the lava of and erupting volcano. *haha*
4) SEDIMENTARY: The Law of Superposition is no where better illustrated than in the construction of the PB&J. (See #2) Alt Link. Chuncky peanut butter can even stand in as a conglomerate or melange.
5) STRUCTURAL GEOLOGY: Cut a PB&J in half and faulting can be demonstrated, sinistral, dextral, reverse normal. Fold it up, syncline. Fold it down, anticline (pic right-->). Fold it and flip it, recumbent fold. BLAM!
There you have it. This is by no means a definitive list and I encourage you to add your best peanut butter and jelly sandwich stories.