Volcanic activity and global change: probable short-term and possible long-term linkages

Article reviews annual to decadal climate response to volcanism; long-term climatic response to volcanism; and recent results from ocean drilling in the North Pacific

The plio-pleistocene history of explosive volcanic activity in north Pacific Island arcs and possible links to regional and global climate change.

Deep-sea sediment recovered by Ocean Drilling Project (ODP) Leg 145 contain the best record yet of explosive volcanic activity over a wide geographical region as well as a record of an intensification of Northern Hemisphere glaciation that occurred at 2.65 Ma. Comparison of this ash record with other ODP sites and with terrestrial records demonstrates the reliability of the ash layer stratigraphy and that this ash record is appropriate to use in an investigation of the effects of explosive, silicic, volcanism on climate. The glacial intensification is recorded in the sediment as an abrupt increase in terrigenous clastic sediment and ice-rafted debris (IRD). The number and thickness of volcanic ash layers increases abruptly in the sediment at the same time. Magnetic susceptibility records show that the climate change occurred rapidly, within 1000--2000 years, too quickly to be a response to tectonic or orbital forcing. The rapid, synchronous, basin-wide climate change suggests that the climate forcing mechanism operated over decades to millennia and was hemispherical in extent. The synchronous increase in volcanism suggests that explosive eruptions may have been the trigger of the glacial onset. Ash layers in marine sediment are often the best preserved record of the explosive history of an arc, because deep-sea sediments are less susceptible to erosion. Volcanic ash layers in deep-sea sediments of the northern Pacific Ocean provide a record of the episodic explosive volcanism in the Kamchatka and Aleutian volcanic arcs, including a major episode that began about 2.65 Ma at both arcs. Mass-accumulation rates (MAR) of volcanic glass and IRD were calculated as a way to determine the stratigraphic relationship between the ash and the IRD. Volcanic glass is used as a proxy for explosive volcanic eruptions and IRD is used as a proxy for glaciation. MAR of both the glass and IRD show a five- to ten-fold increase at 2.65 Ma, with the flux of the glass increasing just prior to the flux of the IRD, again suggesting that explosive eruptions may have been the trigger for the glaciation.Ph.D.Earth SciencesGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/131980/2/9938516.pd

Accumulation rates of volcanic glass and ice-rafted debris in sediments of the North Pacific Ocean

Mass accumulation rates (MAR) of different components of North Pacific deep-sea sediment provide detailed information about the timing of the onset of major Northern Hemisphere glaciation that occurred at 2.65 Ma. An increase in explosive volcanism in the Kamchatka-Kurile and Aleutian arcs occured at this same time, suggesting a link between volcanism and glaciation. Sediments recovered by piston-coring techniques during ODP Leg 145 provide a unique opportunity to undertake a detailed test of this possibility. Here we use volcanic glass as a proxy for explosive volcanism and ice-rafted debris (IRD) as a proxy for glaciation. The MAR of both glass and IRD increase markedly at 2.65 Ma. Further, the flux of the volcanic glass increased just prior the flix of ice-radted material, suggesting that the cooling resulting from explosive volcanic eruptions may have been the ultimate trigger for the mid-Pliocene glacial intensification