WHAT MOVES THE PLATES

Roark Franklund

            Plate tectonics is the combination of two hypothesis, continental drift proposed by Alfred Wegener in 1915, and ocean floor spreading proposed in the 1960’s. The basics of plate tectonics is that the lithosphere is divided into plates that can move and interact with each other at their boundaries. That the plates move is observable with modern technology, but the forces and mechanisms that do the moving are not so apparent. Three conventional models to explain the motion are, 1) Ridge push/slab pull, 2) forces of isostasy, and 3) mantle convection. The problem with the models is no one model can explain all the situations at the boundaries, and how exactly the mantle behaves is not understood. We can’t fully image it with technology yet and we use indirect evidence from the various lines of geology such as geochemistry and seismology to infer the mantle dynamics, but these groups don’t always agree.

Describing forces of motion form continental surface expression, (Bokelmann, 2002).

Earths interior structure from (http://pubs.usgs.gov/publications/text/inside.html).

References:

Bokelmann, G.H.R., 2002, Which forces drive North America?: Geology, v.30, no.11,

            p. 1027-1030.

Ellis, S., 1996, Forces driving continental collision: Reconciling indentation and mantle

            Subduction tectonics: Geology, v. 24, no.8, p. 699-702.

Hofmann, A. W., 2003, Just add water: Nature, v. 425, p. 24-25.

Huismans, R.S., Beaumont, C., 2002, Asymmetric lithospheric extension: The role of

            Frictional plastic strain softening inferred from numerical experiments:

            Geology, v. 30, no.3, p. 211-214.

Rowley, D.B., 2002, Rate of plate creation and destruction: 180 Ma to present: Geology,

            v. 114, no. 8, p. 927-933.