How do gravity measurements give a date?
I can understand detecting the crater through ice but how do you come up with a date, and If this crater helped to break up a continent where is the other side of the crater?
How do gravity measurements give a date?
Maybe they were able to figure a depth of the crater and base the age on that, in part? I was wondering the same.
They don't but oceanic magnetic stripes do (a recording by the solidifying rock at midocean ridges that records the magnetic field at time of extruding magma solifiying--since the magnetic field flips occasionally, they can be used to tell time). If this crater hit 250 million years ago along the plate boundary, there should be remnants 250 million years along the direction that the plates have moved, in both directions. This means that if you take a measurement of oceanic magnetic stripes you should be 250 million years to the plate boundary from the location of the current crater near Antarctica and another 250 million years to the plate boundary from other debris near Australia.