Breaking off the weathered surface of lavas in the Clear Lake Volcanic Field to sample the fresh, unaltered cores
Detailed Description
Geologists often break off the weathered surfaces of rocks in the field to get at the fresh, clean cores. This makes it easier to see the original mineralogy of the rock in question without oxidation, alteration, or other environmental impacts. USGS photo by D. Blatter.
Sources/Usage
Public Domain.