Bedrock geology is a vast subject. Of greatest interest to naturalists are ways in which underlying rock types, alignments, fracture patterns, and variable resistance to erosion explain the shape of the land and the distribution of natural communities.
Bedrock geology units are based upon a detailed map-in-progress by USGS, but color coded by 6 broad rock-type families. Expand the legend (>>, upper left) to see them. Notice that granitic types (pink, our highest & most resistant peaks) are mostly back under the icefield. Rocks with highest carbonate content (blue) hosted most of Juneau’s successful mines. For more info on each rock unit, click, and a popup will name the geologic period (capital letters in the code), dominant rocks, and broader rock family