NW United States Gravity Maps

This map covers some very interesting geological/geophysical provinces. The highest levels of the geoid are found in a region centered onthe Yellowstone Caldera. Geoid highs generally indicate regions of excess mass, unaccounted for by a homogeneous ellipsoid, which acts as the reference surface (and solid) upon which the geoid (and anomalous potential) refers. Local lows in the geoid are seen in the Columbia River valley and in the Seattle/Tacoma area. A small SW trending geoid "ridge" can be seen in an area corresponding to Mt. Rainier.

Gravity anomaly maps feature more localized variations in the intensity of gravity. Again, we see gravity anomaly highs associated with mountain ranges and with the Yellowston Caldera/magma chamber. Particularly strong positive gravity anomalies appear to be associated with the Uinta Mountains in Utah and the Rocky Mountains on the border between Alberta and British Columbia.

Gravity anomaly lows are seen just offshore and in regional lows mildly correlated with basins across land masses. The Columbia River basin is particularly notable, as are the Snake River basin in Idaho and the Great Salt Lake region in Utah, all of which exhibit gravity anomaly lows.

Created: July 13, 2008
Last Updated: July 13, 2008