A study conducted by a team of researchers from Rice University, University of Tokyo, the University of British Columbia, the California Institute of Technology, Texas A&M University and Pomona College, suggests that the shifts in weather patterns and temperature that have resulted in global warming and cooling over the past 500 million years, are caused by massive volcanic eruptions.
The findings appear in the latest issue of GeoSphere with a lead author Cin-Ty Lee, a Professor of Earth Science in Rice. They show that enormous quantities of greenhouse gases, and carbon dioxide in particular, are released in the atmosphere, because of the high concentrations of the gas trapped in sedimentary rocks like limestone and marble.
According to Lee, around 44% of carbonates by weight is carbon dioxide, which stays locked in the continental crust. It is released when these carbonates interact with magma, a rare case these days since most of the active volcanic activity occurs on island arcs without continental crust.
Each climate cycle being at a greenhouse or an icehouse state lasts between 10 million and 100 million years. The latest icehouse state, for example, lasted 50 million, and was marked by ice at the poles and periods of glacial activity. The warmer greenhouse state is usually characterized by increased carbon dioxide in the atmosphere and an ice-free surface, even at the poles. The last such period on record lasted around 70 million years in the late Cretaceous and the early Paleogene.
The study established that there is a direct link between natural plate tectonics and greenhouse-icehouse oscillations.
Similar study conducted at Rice University looks into the amount of carbon dioxide that have been released by Mount Etna in Sicily in the past. It inspired Lee to examine whether other mountains of this kind have also affected Earth’s climate in a way. The findings go against the conventional theories about the climate cycles. Through of tungsten-rich minerals like scheelite, formed on the margins of volcanic magma chambers, the team established likely areas of occurrences of volcanoes.
Lees idea is still a theory, but it can explain geophysical conditions that have been determining and controlling greenhouse or an icehouse for many millions of years.