Adjective
geoidal (not comparable)
Relating to, or shaped like a geoid
Accretion occurs over geoidal lows that can be caused by avalanche slabs or the downgoing limbs of convection cells. Source: Internet
The plates will be moved towards a geoidal low perhaps where the slab avalanche occurred and pushed away from the geoidal high that can be caused by the plumes or superplumes. Source: Internet