The dunes here seem to be right inline with where the crater is supposed to be, and they go way inland: [link|http://maps.google.com/maps?f=q&hl=en&q=madagascar&ie=UTF8&t=k&om=1&z=11&ll=-25.234758,44.520035&spn=0.475155,0.720291|http://maps.google.c...0.475155,0.720291]
Tha 2nd one appears to be volcanic
[link|http://www.kew.org/gis/projects/madagascar/images/simp_geology_very_large.gif|http://www.kew.org/g...gy_very_large.gif]