PROGRAM TITLE:	Ridge Interdisciplinary Global Experiments (RIDGE)
ACTIVITY STREAM:  	Process, Observe, Data, Model, Assess
SCIENCE ELEMENT:	Solid Earth Processes


SCIENTIFIC MERIT:  The goal of the RIDGE program is to understand the 
physical, chemical, and biological causes and consequences of the energy 
transfer through time and space between the global mid-ocean ridge volcanic 
system and the ocean environment.  Within the Geosciences Directorate the 
RIDGE program is divided between the Global Change initiative and 
Disciplinary Geosciences.  The shorter time scale processes, such as 
hydrothermal circulation, are relevant to global change, whereas, the longer 
time scale processes, such as mid-ocean ridge magmatic processes, are 
considered within Disciplinary Geosciences.  Relative to global change, the 
primary objective of RIDGE is to understand the geological, chemical, 
biological, and physical oceanographic interactions between the oceans and 
hydrothermal circulation of seawater through the ocean crust.  Most of the 
heat loss from the interior of the Earth occurs through the mid-ocean ridge 
system by means of this circulation.  Hydrothermal venting at mid-ocean 
ridges produces a wide variety of important effects in the overlying water 
column, including the formation of turbulent, buoyant plumes, the 
introduction of chemicals and biota, and the modification of deep ocean 
circulation and mixing patterns.  "Megaplumes" of hydrothermal discharge 
into the overlying layers of the ocean suggest that the effects of venting may 
not be confined to the deep ocean.  While megaplumes are expected to be 
episodic, events on the Juan de Fuca Ridge (in the northeast Pacific) in 1986 
and in 1993 suggest that the frequency of the events, and thus the 
accompanying effects, may be higher than expected.  Major RIDGE projects 
aimed at understanding hydrothermal circulation will be conducted on the 
Juan de Fuca Ridge, the East Pacific Rise, and the Mid-Atlantic Ridge.  The 
Juan de Fuca project is a multi-disciplinary, manned and unmanned 
submersible, surface-ship, and laboratory investigation of major vent fields.  
The East Pacific Rise and Mid-Atlantic Ridge projects will determine the 
distribution, relative intensity, and first-order chemical characteristics of 
hydrothermal venting and its relation to ridge morphology, geophysics, 
petrology, biology, and ecology.
STAKEHOLDERS:  The NSF RIDGE program is closely linked with the 
NOAA VENTS program.  RIDGE is also linked with the USGS program of 
deformation studies on the Juan de Fuca Ridge, and ONR studies of "natural 
laboratories" on the East Pacific Rise and the Mid-Atlantic Ridge.  The US 
programs are linked to international mid-ocean ridge research through 
InterRIDGE, which, at this time, is comprised France, Germany, Spain, UK, 
Iceland, Canada, and the US; together with several other associate countries.  
InterRIDGE has been designated a Working Group of the ICSU Scientific 
Committee on Oceanic Research (SCOR).
POLICY RELEVANCE:  The role of hydrothermal circulation on deep-ocean 
circulation, on the chemical mass balance of the oceans, and on the biological 
communities in the ocean basins are only beginning to be understood, and 
the role of the factors in effecting global climate is unknown.
David Epp, Marine Geology and Geophysics Program Associate Program 
Phillip Taylor, Biological Oceanography Program Director