High‐resolution Remotely Operated Vehicle (ROV) mapping of a slow‐spreading ridge: Mid‐Atlantic Ridge 45°N

Abstract

[1] Axial volcanic ridges (AVRs) are found on most slow-spreading mid-ocean ridges and are thought to be the main locus of volcanism there. In this study we present high-resolution mapping of a typical, well-defined AVR on the Mid-Atlantic Ridge at 45 N. The AVR is characterized by "hummocky terrain," composed typically of hummocks with pillowed or elongate pillowed flanks with pillowed or lobate lava flow summits, often with small haystacks sitting on their highest points. The AVR is surrounded by several areas of "flat seafloor," composed of lobate and sheet lava flows. The spatial and morphological differences between these areas indicate different eruption processes operating on and off the AVR. Volcanic fissures are found all around and on the AVR, although those with the greatest horizontal displacement are found on the ridge crest and flat seafloor. Clusters of fissures may represent volcanic vents. Extremely detailed comparisons of sediment coverage and examination of contact relations around the AVR suggest that many of the areas of flat seafloor are of a similar age or younger than the hummocky terrain of the AVR. Additionally, all the lavas surveyed have similar degrees of sediment cover, suggesting that the AVR was either built or resurfaced in the same 50 ka time frame as the flat seafloor.

Volcanism and hydrothermalism on a hotspot–influenced ridge: Comparing Reykjanes Peninsula and Reykjanes Ridge, Iceland

“…hummocky terrain) can coexist and simultaneously erupt on one AVR at approximately the same time. A similar situation has been observed on an AVR located at 45°N on the MAR (Yeo and Searle, 2013).…”

Reconstructing lava flow emplacement processes at the hot spot‐affected Galápagos Spreading Center, 95°W and 92°W

“…Within the MOR neovolcanic zone, a corridor along the spreading axis where most eruptive activity is concentrated, the uppermost layer of oceanic crust is constructed as a series of overlapping lava flows, each with variable morphological properties that provide clues to the mechanisms and timescales of lava emplacement. Previous studies of MOR lava morphology [e.g., Ballard et al ., ; Crane and Ballard ; Fox et al ., ; Kurras et al ., ; Engels et al ., ; Cann and Smith , ; Soule et al ., ; Fundis et al ., ; Yeo and Searle , ] have used photographic data from submersibles and deep‐towed cameras along with multibeam bathymetry and/or side‐scan backscatter imagery to examine lava flow morphologies. However, these phototransects cover <1% of the area in the neovolcanic zone—insufficient coverage for a representative view of lava morphology distribution.…”

Emplacement of submarine lava flow fields: A geomorphological model from the Niños eruption at the Galápagos Spreading Center

“…Like the GSC 95°W, volcanic eruptions at slow spreading MORs are characterized by lower effusion rates and larger eruption volumes [e.g., Smith and Cann , ; Sinton et al ., ]. At the Mid‐Atlantic Ridge (MAR), the primary locus of volcanism appears to be hundreds of individual circular volcanoes (“hummocks”) scattered across the floor of the axial rift valley and along axial volcanic ridges (AVRs) [e.g., Searle et al ., ; Yeo et al ., ; Yeo and Searle , ]. Sets of isolated, but cogenetic, mounds, and hummocks at the MAR and other slow spreading ridges are likely to be emplaced through preeruptive flow focusing (e.g., Dulces at GSC 92°W; Frijoles at GSC 95°W), and linear hummocky ridges are likely to be emplaced through fissure eruptions that quickly localize into multiple segments or point‐source vents (e.g., Gusanos at GSC 95°W).…”