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Hydrothermal circulation at mid-ocean ridges drives the exchange of heat and matter from Earth’s interior to the global ocean and supports deep-sea life. Away from the ridge axis, however, the spatial extent of hydrothermal discharge remains enigmatic. Using near-bottom data for a 25-kilometer-long section of the East Pacific Rise between 9°43′N and 9°57′N, we show that considerable hydrothermal flow occurs at variable distances from the ridge axis. Mapping the seafloor and water column along this segment using an autonomous underwater vehicle, we identified 448 candidate hydrothermal chimneys. More than half of them lie outside the axial summit trough, indicating that hydrothermal fluids discharge over a larger area than previously thought. Water column measurements show that >27% of mapped constructs are likely to be venting actively. Our results indicate that widespread active hydrothermal flow occurs over the near-axis region, with important implications for constraining total heat flux along mid-ocean ridges and for identifying previously unexplored benthic habitats. 

Hydrothermal vent temperatures fluctuate in response to transient magmatic and tectonic activity at the axis of mid-ocean ridges (MORs) and modulate energy fluxes from the deep Earth to the ocean. Such fluctuations have thus far only been documented on time scales of minutes to years, because of the scarcity of long, continuous observations. Here, we assemble a ~35-year-long time series of exit fluid temperatures from five hydrothermal vents on the East Pacific Rise axis, between 9°46’-51’N. This dataset reveals a steady increase in maximum venting temperatures atop the central part of the axial magma lens (AML), from ~350 °C to ~390 °C between the 1991–92 and 2005–06 eruptions. Temperatures decreased back to ~350 °C shortly after the 2005–06 eruption and have been rising ever since. We interpret the temperature increase as a result of a steady decrease in upflow zone permeability caused by the steady inflation of the AML compressing the oceanic upper crust. Using laboratory-determined pressure–permeability relations, we estimate crustal pressurization rates of 0.38 MPa/y (1992–2005) and 0.33 MPa/y (post-2006), consistent with geodetic observations from 2009–2011. Decadal fluctuations in hydrothermal vent temperatures likely mimic the rate of AML pressurization, yielding valuable new constraints on the dynamics of magmatic replenishment and eruptions at MORs. Notably, this temperature time series underpinned our forecast of the April 2025 eruption at the study site. 

Abstract Tectonic subsidence, sea level, and paleoclimate reconstructions using marine records rely on accurate decompaction of the sediment column. Over time, increased overburden pressure from burial decreases sediment porosity with depth. The porosity‐depth relationship is lithology‐dependent and can be represented by an exponential function determined by initial porosity at the seafloor and compaction decay length. While site‐specific compaction parameters are useful for most studies, these are often unrepresentative due to an insufficient number of measurements. Existing, commonly applied parameter estimates are based upon a handful of spatially restricted sites and lack meaningful uncertainty constraints. We compiled a global porosity data set consisting of 31,808 moisture and density measurements from 280 scientific ocean drilling sites visited during 60 Integrated Ocean Drilling Program and International Ocean Discovery Program (IODP) expeditions between 2009 and 2024. Using bootstrapping techniques, we resampled and fit porosity measurements 10,000 times using nonlinear least squares to obtain compaction parameters and uncertainties both globally and independently for sites in the Pacific, Atlantic, Indian, and Southern Oceans. Measurements from samples dominated by a single lithology (>75%) were used to obtain lithology‐dependent parameters. Average compaction behavior for marine sediments can be described with an initial porosity of % and a decay length of  m. Our results confirm the lithology‐dependence of these parameters and indicate that sediment compaction behavior is consistent across ocean basins. These globally‐applicable parameters and uncertainties are a valuable resource for evaluating sediment decompaction and will enable error quantification in subsequent analyses of basin evolution and sedimentation. 

Abstract Geologic collections play a fundamental role in advancing scientific discoveries, offering rich global archives reaching deep into Earth's past. Realizing the scientific potential of these remarkable resources will require the generation and curation of usable data to facilitate open science and data synthesis efforts. Although core scanners offer an efficient, nondestructive way to acquire cm‐resolution data sets on archived cores, material properties may have been altered over time, making comparisons difficult. To assess the promise of core‐scanner measurements to support studies using decades‐old cores, we scanned the 1961 Project Mohole cores, which were the first cores obtained by deep‐water scientific ocean drilling. We examined cores from the Experimental Mohole Guadalupe site with new X‐ray fluorescence, magnetic susceptibility, and line scan camera measurements, and used the new data to re‐evaluate measurements made up to 64 years ago. We show that new measurements can validate and enhance the original analyses performed on the cores, and that even cores from the dawn of scientific ocean drilling retain valuable information waiting to be retrieved. 

At fast-spreading centers, faults develop within the axial summit trough (AST; 0 to 250 m around the axis) primarily by diking-induced deformation originating from the axial magma lens (AML). The formation of the prominent abyssal-hill-bounding faults beyond the axial high (>2,000 m) is typically associated with the unbending of the lithosphere as it cools and spreads away from the AST. The presence of faults is rarely mapped between these two thermally distinct zones, where the lithosphere is still too hot for the faults to be linked with the process of thermal cooling and outside of the AST where the accretional diking process dominates the ridge axis. Here, we reveal a remarkable vertical alignment between the distinct morphological features of the magma body and the orientation of these faults, by comparison of 3-D seismic imagery and bathymetry data collected at the East Pacific Rise (EPR) 9°50’N. The spatial coincidence and asymmetric nucleation mode of the mapped faults represent the most direct evidence for magmatically induced faulting near the ridge axis, providing pathways for hydrothermalism and magma emplacement, helping to build the crust outside of the AST. The high-resolution seafloor and subsurface images also enable revised tectonic strain estimates, which shows that the near-axis tectonic component of seafloor spreading at the EPR is an order of magnitude smaller than previously thought with close to negligible contribution of lava buried faults to spreading. 

Abstract Oceanic transform faults connect spreading centers and are imprinted with previous tectonic events. However, their tectonic interactions are not well understood due to limited observations. The Discovery transform fault system at 4°S, East Pacific Rise (EPR), represents a young transform system, offering a unique opportunity to study the interplay between faulting and other tectonic events at an early phases of an oceanic transform system. Discovery regularly hostsM5–6 characteristic earthquakes, and the seafloor north of Discovery includes a 35 km‐long rift zone that records a complex history of rifting, faulting and volcanism, suggesting that the transform faults likely interact with regional tectonic activity. We apply a machine‐learning enabled workflow to locate 21,391 earthquakes recorded during a 1‐year ocean bottom seismometer experiment in 2008. Our results indicate that seismicity on the western Discovery fault is separated into seven patches with distinct aseismic and seismic slip modes. Additionally, we observe a patch of off‐fault seismicity near where seafloor abyssal hills intersect the rift zone. This seismicity may have been caused by varying opening rates as spreading rate decreases from north to south in the rift zone. Our findings suggest that the Discovery system is still evolving, and that system equilibrium has not been reached between rifting and faulting. These results reflect the complex yet rarely observed interactions between fault slip, plate rotation, and rifting which are likely ubiquitous at oceanic transform systems. 

North Atlantic Deep Water (NADW), the return flow component of the Atlantic Meridional Overturning Circulation (AMOC), is a major inter-hemispheric ocean water mass with strong climate effects but the evolution of its source components on million-year timescales is poorly known. Today, two major NADW components that flow southward over volcanic ridges to the east and west of Iceland are associated with distinct contourite drift systems that are forming off the coast of Greenland and on the eastern flank of the Reykjanes (mid-Atlantic) Ridge. Here we provide direct records of the early history of this drift sedimentation based on cores collected during International Ocean Discovery Programme (IODP) Expeditions 395C and 395. We find rapid acceleration of drift deposition linked to the eastern component of NADW, known as Iceland–Scotland Overflow Water at 3.6 million years ago (Ma). In contrast, the Denmark Strait Overflow Water feeding the western Eirik Drift has been persistent since the Late Miocene. These observations constrain the long-term evolution of the two NADW components, revealing their contrasting independent histories and allowing their links with climatic events such as Northern Hemisphere cooling at 3.6 Ma, to be assessed.