Images © Dee Breger Back to November 2002 press release Back to NSF/Science award press release

MONGOLIAN FROST RINGS: Lamont dendrochronologist Gordon Jacoby collected this sample of tree rings from a Siberian pine in Mongolia, which records the years 534-539 C.E. (left to right). The narrow, distorted rings for 536 and 537 indicate a drastic cooling in the northern hemisphere that froze sap in the cells during the growing season. Evidence for this abrupt climate change points to a massive eruption of the volcanic precursor of Krakatoa. Another theory invokes a cosmic impact that possibly triggered the eruption. Magnification ~ 27.6 X