Definition of Relationship of Supercontinents, Lower Mantle Convection, and the Geoid

Some models for the formation and dispersal of supercontinents

suggest a link between mantle convection, heat flow,

and the supercontinent cycle. Stationary supercontinents

insulate the mantle causing it to heat up, because the cooling

effects of subduction and seafloor spreading are absent. As

the mantle then heats up, convective upwelling is initiated,

causing dynamic and isostatic uplift of the continent, injection

of melts into the continental crust, and extensive crustal

melting. These crustal melts are widespread in the interiors of

some reconstructed supercontinents, such as the Proterozoic

anorogenic granites in interior North America, which were

situated in the center of the supercontinent of Rodinia when

they formed between one billion and 800 million years ago.

After intrusion of the anorogenic magmas, the lithosphere

is weakened and can be more easily driven apart by

divergent flow in the asthenosphere. Thermal effects in the

lower mantle lag behind surface motions. So, the present

Atlantic geoid high and associated hot spots represent a

“memory” of heating beneath Pangea. Likewise, the circum

Pangea subduction zones may have a memory in a global ring

of geoid lows.

Other models for relationships between supercontinents

and mantle convection suggest that supercontinents may also

result from mantle convection patterns. Continental fragments

may be swept toward convective downwellings, where

they reaggregate as supercontinents.

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