2808 feet, a rapid contrast in rock type

Today we processed rock core to a depth of 2758 ft, and received more at the end of the day that stretched down to 2808 ft.

The image above shows about 1.5 ft of rock from two consecutive trays that make up a single run of core.  The tray on the left has loose, baked soil and broken fragments of ʻaʻa clinker.  The tray on the right contains the massive interior of the same ʻaʻa flow.  Within this 10-foot run, the recovered core changes from some of the least cohesive material we have drilled to some of the most cohesive over only a few feet of depth.  This illustrates a challenge of drilling through a basaltic shield volcano: Although the rock can be drilled relatively easily, there are many abrupt changes in cohesion and internal resistance to stress that require the driller to make rapid adjustments in order to keep drilling smoothly.