THE EARTHTIME NETWORK: DEVELOPING A HIGH-RESOLUTION CALIBRATION OF EARTH HISTORY

Much of what we know about biological evolution, episodes of severe climate change, and the evolution of our oceans and atmospheres is recorded in the geological record. However, geological records in any one geographical area are incomplete. Thus, to establish a detailed history of the planet we must integrate records from across the entire planet using a combination of the fossil record, proxy stratigraphy and the dating of rocks (geochronology). Our ability to determine the age of rocks has improved dramatically over the past twenty years and calculated uncertainties have been reduced from about 1% to 0.1 %. With increased precision has come the opportunity to explore very small differences in time and small but systematic differences between laboratories and different geochronological techniques. These differences by no means threaten the validity of the techniques but are a consequence of a level of precision never thought possible. EARTHTIME is an a community-based, international, effort with the goal of high-resolution “sequencing” of at least the last 800 million years of earth history in the next decade.

We present two examples of this approach as the best way to illustrate the EARTHTIME concept to students: 1) the Ediacaran and Cambrian Periods, global glaciations and the origin of animals; 2) the transition from ‘ice house' to ‘hot house' during the Pennsylvanian to Permian. In both of these examples the detailed integration of geochronology, proxy stratigraphy, and paleontology has produced a high-resolution temporal framework, permitting new insights into rates of biological evolution, correlation with environmental effects, and evaluation of global vs. local signals. EARTHTIME is an excellent forum for educating students about using geochronology to solve problems that range from rates of biological evolution to rates of climate change.