Studying episodes of mass extinction and abrupt climate change from the geological past is key for understanding the impact of anthropogenic carbon emissions on global climate and species extinctions in the modern. Most of these past events overlapped with times of huge volcanic activity (millions of times greater than modern eruptions). Because of the impact of comparatively tiny recent eruptions on global weather (eg. the eruption of Pinatubo in 1991), these massive volcanic events have been proposed as the cause of past climate change/extinctions.
The mechanism for linking volcanism with climate/extinctions is based on huge volcanic carbon emissions to the atmosphere, but relies on knowing the timing and volume of erupted lavas with respect to climate/biospheric degradation. To constrain these parameters, we will analyse the osmium-isotope composition of sedimentary records of past climate/extinction events. Osmium (Os) is a trace metal in sediments, where its isotopic composition can be influenced by influx of the element from weathering of lavas. Thus, Os-isotopes can be used in sediments as a proxy of volcanism. The simplicity of the natural Os cycle also means that the changing volume of erupted lavas can be modelled from Os-isotope trends, allowing determination of whether the most voluminous eruptions coincided precisely with times of climate change/extinction. Establishing these relationships will greatly aid understanding of past climate change/extinction events.