CONSTRUCTION AND DECONSTRUCTION OF A SEAMOUNT ON THE GALAPAGOS SPREADING CENTER

Seamounts play an important role in the story of crustal formation, adding considerable mass to the ocean floor. At the Galapagos Spreading Center (GSC), typical mid-ocean ridge processes are complicated by the presence of the Galapagos hotspot. We will examine the morphology and emplacement of “Empanada,” a flat-topped, roughly 1-km-high seamount formed on the axis of the GSC ~200 km west of the Galapagos hotspot. We are using dive video (obtained using the HOV Alvin) and samples to construct a map of Empanada to constrain its construction and erosion through mass wasting. This study will contribute to our understanding of seamount formation processes at mid-ocean ridges, specifically how erosion and construction combine to create the final observed seamount.

Lava-flow morphology and mass-wasting features, such as amphitheater-shaped scarps with talus at the base, will be identified using dive videos of Empanada collected by the R/V Atlantis Expedition 15-63 (AT15-63) crew. The frequency and timing of events is determined from cross-cutting and superposition relations between the mass-wasting chutes and visible lava-flow and talus lobes. This will determine if mass wasting events occurred concurrently during eruption, causing the seamounts to gain and shed material simultaneously.

Current progress includes an ArcGIS basemap of Empanada using Sentry data collected by the R/V Atlantis (AT15-63) crew. This multibeam sonar data has 2 meter spatial resolution and <0.5 meter vertical resolution. Points of interest noted in the dive transcript have been plotted on the base map, showing the relevant dive track. High-definition dive video from the HOV Alvin will provide finer resolution along this track. With the dive video as a refence, we will interpolate mass-wasting scars and lava flows for the portions of Empanda that are not located directly beneath the Alvin dive track.

We plan to present a finalized ArcGIS map of Empanada’s mass-wasting scars and lava flows which shows the temporal relationship between the mass-wasting events and emplacement.