Baked soil contact

Today we were kept extremely busy processing rock core down to 700 ft.  The day's core was less fractured than what we typically have been seeing, so the drillers didn't have to pull out short runs or lift the drill string and re-drill cave-in material as often as they have had to recently.

The photo above shows a striking contact between two lava flows.  The upper flow has both large and small vesicles, and some of the large ones show irregular (non-spherical) shapes.  This upper flow has almost no phenocrysts at all.  In contrast, the lower flow has abundant small round vesicles, and is loaded with olivine (click on photo for a larger view).  The material between the flows is soil that accumulated via weathering of the lower flow and then was baked and oxidized when the upper lava flowed over it.  This baking extends down into the upper portion of the lower flow as well.