It has long been speculated whether the global climate can be influenced by volcanic activity. While the short-term (on the scales of years) cooling effects of very large explosive eruptions are well-known, it has proven difficult to assess whether the longterm global cooling trend starting 3.2 million years ago and the subsequent Pleistocene (<2.6 million years ago) ice cycles may have been influenced by volcanism or vice versa. The major problem in testing such connectivity is the lack of time-precise volcanic records that with the tracers of long-term climate evolution.

In this project, we tested whether the marine fallout ash beds that form following highly explosive, cataclysmic eruption of arc volcanoes can be used to for testing causal links between arc volcanism and climate. Large explosive eruptions of subaerial arc volcanoes produce abundance volcanic ash (fragmented volcanic particles < 2 mm) that are transported by stratospheric winds far into the ocean basins and deposited in as centimeter thick beds volcanic ash in the non-volcanic sediments. Marine ash beds can readily be dated by standard methods of sediment dating, and thus can provide temporally well resolved and time-precise history of volcanic source area, which can be directly linked with the marine sedimentary record of climate change.

We studied the ash bed series contained in Plio/Pleistocene sediments of three sites (881, 882 and 884) drilled by the Oceanic Drilling Program (ODP) outboard the Kurile/Kamchatka volcanic arc in the northwest Pacific. The composition of the ash beds clearly identifies the ash provenance from the Kurile/Kamchatka volcanic arc. Their compositional constancy through time does not provides a cause for the sudden, at least sevenfold increase of the tephra bed frequency at the Plio/Pleistocene boundary, nor for the subsequent frequency variation of the tephra beds in the Pleistocene. Instead, the changes in tephra bed frequencies can be related to the rapid expansion of the Northern Hemisphere ice sheets just prior to the Plio/Pleistocene boundary, and to the variability of the global ice volumes. The latter is in turn is modulated by the variance of periodic changes of insolation that Earth undergoes in its path around the sun, and which drive Plio/Pleistocene climate evolution. Thus, we conclude that increase in the global ice volume and that subsequent waxing and waning of ice sheets accelerate the Kurile/Kamchatka arc volcanism when the widespread glaciations start. As the volcanic output increase, so must increase the arc output of climatically active volatiles and the flux of volcanic particles to the ocean-atmosphere system, which in turn may lead to feedbacks that could enhance the Plio/Pleistocene climate cycles.

The project provided a summer internship for female minority college student, and research opportunity for two minority undergraduate students who worked on closely related projects. In collaboration with a retired high-school teacher, two lectures were presented in the Earth2Class (E2C) outreach program that aims at K-12 teachers and students with the goal to integrate cutting edge research in to the K-12 classroom. Educational posters about explosive volcanism were presented at the 2021 meeting of the Geological Society of America and the 2022 AGU Fall Meeting and an exhibit on volcanism with hands-on experience was presented for the Public at Lamont Open House. The project fostered national collaboration with researchers at Miami University, in Oxford, Ohio) and international collaboration with researchers in Mexico, Taiwan and Australia. The projects contributed to the career of a female career researcher with a disability, and of an early-career scientist at Lamont.

Last Modified: 04/09/2024
Modified by: Susanne M Straub