Day 4 (on Day 5): the East Pacific Rise

What you're looking at is a shaded three-dimensional perspective of a section of the East Pacific Rise (EPR), where new oceanic crust is actively being produced, and the distinction between the Pacific and Cocos plate is set (for our journey at least).  The freshly exhumed rock, from the mantle, is very hot; but, eventually it cools to a point where it records the magnetic field around it (look up the Curie temperature).  Using this information, we are able to tell a story about the history of the crust over a very broad scale (hundreds of kilometers in some cases!), which is why I mentioned the San Andreas fault a few days ago.  Soon enough we'll be using this kind of information to describe the history of the crust (microplate interaction, faulting, etc.) in the vicinity of Panama, so stay tuned.

On a more important note: I just realized (reading my title) that I may have a future in geo-poetry.  Well, probably not, but at least I just made up the term for it - I think I'll start a Wikipedia page...

-Andy

Day two, part two.

As Brad mentioned previously, things are settling in a bit in many ways (mostly in our work/eat/sleep routine), but we're also coming upon some interesting geomorphology: Inactive spreading ridges.  At the moment, we're transiting between the Rosanna and Rosa ridges - two in a system of seven en-echelon ridge/transform zones off the coast of Baja California Sur.  We are, as I write, recording the magnetic field associated with the oceanic crust, which, when combined with precise laboratory dating of rock specimens, tells us about the history of such ridges.   Previous studies have found that these ridges were active producing new oceanic crust from approximately 12 to 6 million years ago, and are interpreted as excellent evidence of microplate capture, a theory which helps explain, for example, the development of the San Andreas fault hundreds of kilometers away. 

Andy