Plate Motion
and Hot Spots
Plumes of hot material rise through the
mantle and penetrate the lithosphere at more than 100 places on Earth.
These hot spots are sites of persistent volcanic activity (e.g.,
Hawaii).
Some coincide with present day divergent plate boundaries (e.g.,
Iceland), but many do not.
Hot spots within plates may produce strings
of volcanoes that form as the lithosphere drifts over them. The volcanoes
are only active when directly over the hot spot,
but die out as the lithosphere (or hot spot) moves.
Hotspots may be initiated by subducted
material gathering at a boundary layer (e.g., the upper/lower mantle
boundary at 660 km or the core-mantle boundary).
The lab manual states that the positions of these hot spots is fixed and
that because they are fixed, plate motions can be calculated.
However, for interested parties, see this paper that was published in Science in 2003 that shows that the Hawaiian
hot spot has not remained fixed.
