A key challenge in understanding the Earth system is quantifying the feedback between climate and the solid Earth, which requires long-term time series. One critical time series is the sea level record, which fluctuated between ice ages and warm periods over millions of years. Volcanic activity at mid-ocean ridges (MORs), where 80% of the Earth’s volcanism occurs, is sensitive to changes in the pressure on the ridges, but its response to glacial cycles, causing sea level fluctuations, is largely unknown.
The key hypothesis that we plan to test is if volcanism at mid-ocean ridges has oscillated inversely with climate induced sea level change. During glacial periods, lower sea level (due to storage of seawater in glaciers on land) resulted in less hydrostatic pressure on the ridges, thus there was enhanced pressure-release induced melting of the upper mantle, creating thicker oceanic crust and greater amounts of volcanism and hydrothermal activity at the earth’s surface. During interglacials, sea level is higher, suppressing mantle melting, resulting in thinner newly formed oceanic crust and less volcanic and hydrothermal activity along the ridges.
Models confirm that sea level fluctuations can affect crustal thickness, lava chemistry, and hydrothermal activity at MORs. However, creating high-resolution time series of these variations has been difficult because sediments quickly cover the sea floor as it moves away from the ridge, making direct sampling a challenge. Recent studies and eruptions on mid-ocean ridges (e.g. the eruption on April 29, 2025 at 9.83°N and 104.3°W on the summit of the East Pacific Rise at 2500 m depth) show that glass fragments are formed during MOR eruptions, distributed for kilometres from the eruptive sites, and preserved in nearby carbonate-rich sediments, which can be sampled by gravity coring. These sediments can be precisely dated using oxygen isotope stratigraphy, providing a record of ridge eruptions (from the composition of volcanic glass hosted by the sediments) and hydrothermal activity (trace metals deposited on sediment grains).
Through closely spaced cores collected along transects perpendicular to the ridge axis during multiple research cruises, we aim to create a high-resolution time series of volcanic and hydrothermal activity directly linked to climate records. Using seismic techniques, we will track changes in crustal thickness over time. Our aim is to gather integrated data from slow, intermediate, and fast-spreading ridge segments over the past 1.5 million years in unprecedented detail. These results will allow us to test the influence of glacial cycles on MOR processes and provide the first high-resolution time series of ocean-ridge magmatism, opening a new frontier in scientific exploration.
