Summary for Field Activity Number 1987-033-FA

Alternate Leg ID: 130-1

Area of Operations: Mohns Ridge, Mid-Atlantic Ridge, Norwegian Sea, North Atlantic

Dates: August 02, 1987 to August 20, 1987

Objectives: The neovolcanic zone of a section of the Mohns Ridge will be mapped. Specific interest is to investigate the possibility of hydrothermal activity. If this activity is found, an instrument package will be used to measure the thermodynamic index properties of the venting fluids. If time allows, Vesterisguinnen will be investigated also for hydrothermal activity.

Type of Activity: Sampling
Seismic profiling
Sea floor mapping
Photography

Information to be derived:

Summary: Mohns Ridge is an area of sea-floor spreading and associated volcanic activity (Vogt and others, 1982). As with other mid-ocean ridge systems, the recent or fresh volcanic activity along Mohns Ridge is discontinuous, both temporally and spatially. The question that remains is what are the odds of finding a high-temperature hydrothermal vent on Mohns Ridge? The findings of this cruise suggest that hydrothermal activity has taken place on Mohns Ridge. The presence of temperature anomalies, sediment elutriation structures in rippled, bioturbated sediment, and a water-column density plume suggest that Area 1 was hydrothermally active at the time of this investigation. Although the evidence suggests hydrothermal activity, the existence of a black smoker on Mohns Ridge is not guaranteed by the findings of this cruise. Area 1: 395 sq km SeaMARC data, 106 hrs ARGO pix; Area 2: 5.5 hrs ARGO (bioturbated rippled sediment); Area 3: 275 sq km SeaMARC data, 56.2 hrs ARGO pix, 222 km bathymetry.

USGS Project Number: MIDATLRD

Contact: Bill Schwab (bschwab@usgs.gov)

InfoBank: uses the identifier K-1-87-NA. Visit this site for more information.