by: David C. Twichell1, VeeAnn A. Cross1, Valerie F.
Deborah R. Hutchinson1, William J. Winters1, and Patrick
1 U.S. Geological Survey, 384 Woods Hole Road, Woods Hole, MA 02543-1598
2 U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025
Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.