Our cruise is 36 days long, 34 of which will be on-site at the Puna Ridge, with 2 days required for transit to and from Honolulu. We are using the W.H.O.I. Deep Submergence Labs DSL-120 deep-towed vehicle to obtain side-scan sonar images and fine-scale bathymetry along and across the crest of the Puna Ridge. We are also collecting photographs and video using the ARGO II vehicle. Additionally, we are collecting rock samples at the Puna Ridge for geochemical analyses. All surveying and sampling is navigated within a network of bottom-moored transponders.
Twenty days will be spent surveying with the DSL-120 vehicle. The 20 days include time for deploying and retrieving the transponders. Our survey area runs along the top of the Puna Ridge and is ~8 km wide and 60 km long.The DSL-120 vehicle is towed ~100 m above the seafloor, and provides detailed structural information necessary for us to identify faults and cracks, small volcanic cones, and talus.
ARGO II Vehicle
We are spending a total of 7 days collecting ARGO II photographic images over selected sections of the area mapped by the DSL-120 kHz sonar. The ARGO II photographs will be used to examine the fine-scale morphology of lava flows, and to determine if the lavas are covered by sediment or debris from landslides. The information provided by the ARGO II imagery will help us to select sites suitable for wax coring and dredging.
Wax Coring and Dredging
A total of 7 days are set aside for dredging and rock (wax) coring.
We will sample rocks every 1-2 km along the crest of the ridge. The large number of sample sites (50-60) requires that most of the sampling be done with the wax corer because of its rapid turnaround time (~2 hours per round trip). A wax corer is shown to the right.
In addition to the wax coring (which brings back small pieces of glass), we are dredging 10-15 volcanic features to obtain large pieces of rock.
The samples will be used to determine the composition of the lavas and their crystal content which in turn will tell us about the rock that melted in the interior of the Earth to produce the magma, and what happened to the magma on its way to the surface to erupt as lava. A dredge being brought on board with rocks in it is shown to the left.