Bare Bluff is a rhyolitic shallow intrusive (perhaps sills according to Cornwall, 1954) with steep slopes facing S. The rhyolite has small quartz and feldspar phenocrysts. The Keweenaw Fault is located near the waterline.  It crosses on and offshore in several spots both east and west of the Bluff. In the shallow water the well-bedded Jacobsville layers can be observed and the fault traces seen, especially on calm water days. Kayaks or canoes are ideal for observing these fault locations, and the area is part of the Keweenaw Water Trail.