Bernard BrunhesDiscovered rocks in France in 1906 with reversed magnetic polarity

Cretaceous ‘superchron’

Pacific Antarctic ridge

Schematic model

Drummond Matthews (left) and Fred VineCambridge University

Magnetic anomaliesover the ReykjanesRidge (S. of Iceland) from Vine & Matthews(1963).

Positive anomalies arecolored, negative onesare white.

Magnetic anomalypatterns acquired by the oceanic crust, while it formed during the Gilbert Reversed Chron (top) and afterwards (fromVine & Matthews,1963)

Gauss

Matuyama

Brunhes (today)

Gilbert

Juan de Fuca East Pacific Rise

observed

mirror image

model

Relative spreading rates

Blanco fracture zone

Alfred Wegener

Wegener’s map(1910). Note the distortion of India.

Map made witha computer(1965).

The meaning of an “apparent” polarwander path (APWP).

S. Keith Runcorn(1922 – 1995)

Computer-generatedfit of the Atlantic-bordering continents(Bullard et al., 1965),minimizing gaps and overlaps.

Ages of the Ocean floor determined from magnetic anomalies (~ 1990)

Late Cretaceous (~85 Ma) map of the world (Scotese, 1981)

www.scotese.com

Magnetic field during reversals

Geodynamo simulations (Glatzmaier and Roberts, 1996)

Inner core

Outer core

High fluid velocity intangent cylinder

Magnetic field lines

Close up of inner core