Heat flow through the eastern Pacific ocean floor

Abstract

A total of 194 new measurements of heat flow through the eastern Pacific Ocean floor are presented. They range in value from essentially zero to 8.04×10−6 cal/cm2 sec. The crest of the east Pacific rise is systematically associated with high values, a strip 200 to 300 km wide at the crest having an average heat flow of about 3×10−6 cal/cm2 sec. Within this strip, the highest values occur in two narrower zones which appear to be approximately parallel and symmetrically oriented to the crest. The source of the high heat flow in each of these zones is probably a region of unusually high temperature a few tens of kilometers wide located about 10 km beneath the ocean floor. One-fourth of all the measurements gave low heat-flow values (≤0.80×10−6 cal/cm2 sec). Two approximately equidimensional regions near the equator and to each side of the rise show generally low heat-flow values. These regions are 2 to 4×10−6 km2 in area, and their average heat flows are about half the normal oceanic value of 1.2 to 1.4×10−6 cal/cm2 sec. In other areas, many of the isolated low heat-flow values are correlated with flat topography which suggests an effect of the local environment; these values are presumably not representative of the regional geothermal heat flow. The systematically distributed variations suggest an origin associated with large-scale thermal convection in the mantle.