Earth System Evolution Research Progress
Since its inception in 1992, the program has made seminal contributions to our understanding of the Earth system. One of its first milestones was a major contribution to the Snowball Earth hypothesis. This proposes that the entire Earth was ice-covered for long periods 600-700 million years ago, that each glacial period lasted for millions of years, and that each ended violently under extreme greenhouse conditions. These climate shocks are thought to have triggered the evolution of multicellular animal life. The hypothesis has opened a whole new field of inquiry that seeks to understand the extreme climatic conditions that can lead to such scenarios.
The program continues to document and explain many critical events in the Earth's history. For example, about 250 million years ago nearly 90% of all life on the planet was wiped out. Program members have investigated many facets of this mysterious period, detailing the extinctions, noting enhanced meteorite activity during this time, and suggesting massive upwelling of toxic hydrogen sulfide as a potential extinction mechanism.
One expanding research focus in the program involves the work of geological biologists (or paeleobiologists) who are adding their expertise to help develop a biological record of the physical and chemical evolution of the Earth.
Other program discoveries have also opened up new areas of study, such as the relationship between earthquakes and climate. The Earth System Evolution program was one of the first groups in the world to show compelling evidence of the long-term effect of climate on tectonic processes. Natural laboratories for these studies include the Alps and the Himalayas. Among other findings, researchers illustrated the complex interplay between uplift, precipitation and sedimentation. They demonstrated that earthquakes are significantly stronger where erosion sediments have covered subduction zones, which are places where one tectonic plate slides underneath another. Since sediments produced by erosion are largely a function of local weather conditions, this research reveals climate’s direct effect on subsequent geological events.
The study of other planets provides another key reference point for study and comparison of geological events. Exoplanetary studies are a new direction for the group; this theme arises from the evolving research interests of many long-term members as well as current research by several new members.
A planetary focus adds breadth to the program's already very integrated investigation of the Earth's evolution and future. The program's other main foci in its current five-year cycle include ice-age dynamics, coupling and feedback among solid earth and Earth surface processes, and interactions among physical, chemical, biological, and climate processes at the Earth surface.