GSA Today
Volume 33, Issue 7

Cover image

Field photograph from the Sage Hen Flat area, eastern California, USA. Columns show a six-point uncertainty scale — with divisions of no evidence, permissive, suggestive, presumptive, compelling, and certain — as applied to three different observations (attachedness, geometry, and lithology) that geologists make at each outcrop.

© The Geological Society of America, Inc.