Rayleigh-Taylor instabilities (with animations)
(H. Schmeling, Institute of Geophysics, Goethe Univsity Frankfurt)

If a dense viscous layer rests on top of a less dense viscous layer, the lower layer will become unstable and form a Rayleigh Taylor instability. It will rise through the overburden in the form of diapirs. Geological examples are salt domes or magmatic diapirs.

This instability is named after the famous physicists Lord Rayleigh and Geoffrey Taylor

As example the figure shows a laboratory experiment by Hemin Koyi (1989, Dissertation, Uppsala) in which a light layer (PDMS,black) was overlain by a denser layer (bouncing putty). The faulted basement (plastillina) was comparably stiff. After centrifuging the buoyant layer becomes unstable and forms a series of diapirs.

The following animations of numerical experiments demonstrate the evolution of a Rayleigh-Taylor instability, and show how different viscosities and boundary conditions  influence the style of the instability and the growth rates.



Case 1: Same viscosities
Free slip
Total model time: 4000 (s)
Char wavelength  = 0.72 (m)
To play the movie, click here (mpeg, 7 Mbyte)

No slip
Total model time: 8000 (s)
Char wavelength  = 0.36 (m)
To play the movie, click here (mpeg, 3.3 Mbyte)

Case 2: Weak (0.01 Pa s) layer 
Free slip
Total model time: 140 (s)
Char wavelength  = 1.92 (m)
To play the movie, click here (mpeg, 4.9 Mbyte)

No slip
Total model time: 250 (s)
Char wavelength  = 1.25 (m)
To play the movie, click here (mpeg, 10.8 Mbyte)

Case 3: Strong (100 Pa s) layer  
Free slip
Total model time: 10 000 (s)
Char wavelength  = 1.1 (m)
To play the movie, click here (mpeg, 6.6 Mbyte)

No slip
Total model time: 30 000 (s)
Char wavelength  = 0.3 (m)
To play the movie, click here ( mpeg, 4.4 Mbyte)





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H. Schmeling, Last modified May 29, 2003