Expedition 301 Overview

Integrated Ocean Drilling Program (IODP) Expedition 301 is part of a multidisciplinary experiment to evaluate the composition, structure, physical properties, chemistry, fluid flow, and biological communities on the east flank of the Juan de Fuca Ridge. The Juan de Fuca Ridge is a seafloor-spreading center located in the Pacific Ocean just off of the northwestern United States and Southern Canada. This area is important to study because at this spreading center new ocean crust is created and the large amounts of seawater flowing through the crustal rocks play a major role in the exchange of elements and minerals between the inside of the Earth and the ocean. Throughout the world’s oceans, the flanks of these ridges are responsible for water flow that is about the same as the total outflow of all rivers in the world combined. They are an important, but poorly understood, part of the Earth’s water and geochemical cycle.

On Expedition 301, scientists plan to: 1) evaluate formation-scale hydrogeologic properties (how the water flows) within the oceanic crust; 2) determine how the water pathways are distributed within an active sub-seafloor hydrothermal system; 3) establish linkages between fluid circulation, alteration, and microbial processes within the oceanic crust; and 4) evaluate the relationships between seismic response and hydrologic anisotropy (variations in properties usually dependant on the orientation of structural features).

During IODP Expedition 301, we will drill two new boreholes into which new sub-seafloor observatories will be installed. In addition, we will replace two existing sub-seafloor observatories, creating a three-dimensional monitoring network. Coring operations will sample the basaltic upper oceanic crust and the overlying sediments to assess the physical, geochemical, and microbiological conditions in a geothermally active area. Experiments will be placed into the boreholes in the basaltic rocks below the sediments to assess the hydrogeologic properties near the new boreholes. An additional basement hole will be drilled nearby during a later expedition. The IODP Expedition 301 monitoring stations will be used in conjunction with this new well to conduct the first controlled, long term cross-hole testing ever attempted in the history of scientific ocean drilling.

Collectively, the combination of laboratory measurements and downhole experiments will allow us to evaluate: 1) the extent to which fluid pathways in oceanic crust are connected vertically and horizontally; 2) the influence of these connections on fluid, chemical, heat, and microbiological processes; and 3) how the hydrologic properties are determined by small, medium, and large scale measurement techniques.

More detailed information about the scientific objectives can be found in the Expedition 301 Scientific Prospectus.