Paleo Slide Set: The Ice Ages
A 10m-piston core being raised to the deck of the Hudson.

Milankovitch's theory would be resurrected once again, however, this time from the depths 
of the world's oceans. Beginning in the 1960s and continuing to the present day, scientists 
have found overwhelming support for the Milankovitch theory in long cores such as this one 
extracted from the ocean floor. These oceanographic studies have two major advantages over 
the studies of terrestrial glacial deposits done in the 1950s that seemed to refute the 
Milankovitch theory. First of all, ocean cores provide a much more continuous record 
of glaciation than terrestrial deposits do. The reason for this being that subsequent 
waves of glaciation often erased or altered traces of earlier glacial and interglacial periods. 
Secondly, by the late 1960s, sediment cores pulled from the oceans could be dated with relative 
confidence as far back as 650,000 yr. BP. In contrast, radiocarbon dating becomes much less 
accurate on materials over 40,000 yr. old. Thus, the initial land-based studies that claimed 
to provide chronologies for glaciation over the past 80,000 years relied heavily on some 
very tenuous dates.

Photo Credits:
Anne Jennings
INSTAAR, University of Colorado, Boulder