GSA Today
Volume 28

About the cover:
View down the nearly flat, 500-meter-long Hickory Run boulder field, central Pennsylvania, USA, one of the largest boulder fields in North America. The age and history of such boulder fields are poorly constrained, but recent measurements of cosmogenic nuclides such as ¹⁰Be, ²⁶Al, and ³⁶Cl demonstrate that some fields are very long-lived. See related article, p. 4–10.

doi: 10.1130/GSATG340A.1

© The Geological Society of America, Inc.