geoidens

Geoidens are a hypothetical geophysical construct used to describe localized, compact mass concentrations beneath a planetary crust that produce measurable distortions of the geoid. They are envisaged as discrete bodies with a higher density than surrounding material, typically with limited lateral extent relative to regional tectonic features. The term blends geo- (Earth) with -id (resembling) and denotes their nature as resident density anomalies.

In modeling gravity fields, geoidens are invoked to explain small-scale undulations in the geoid that persist after accounting for topography and large-scale mantle structure. They may be natural, such as remnants of dense mantle fragments, mineral ore bodies, or structural blocks, or anthropogenic, arising from dense fill or large infrastructure. Their exact size, depth, and density contrast are not uniquely determined from gravity data alone and require joint interpretation with seismic, magnetic, and borehole information.

Detection and study rely on gravimetric surveys, satellite gravity missions, and airborne gravimetry, often combined with seismic imaging to constrain geometry. Inverse modeling treats geoidens as localized sources of gravity anomaly, contributing to residual geoid heights. The concept is primarily a modeling construct rather than an established physical class; it serves to improve explanation of localized geoid variation and to test sensitivity of geoid models.