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Re: Mass Extinction



> I'm just wondering, what is the accuracy of the dating methods used for
> geologic events in the 65 mya timeframe.  Because all you'd need is a .6%
> error in either of the dates and the'd occur at the same time.

Good point. OK, let's throw out all absolute data. There's a place in the 
Deccan where the K-T boundary layer (with iridium and so on) lies in 
intertrappean sediments.

> I remember reading somewhere that if the location is near the opposite
> point 180 degrees from the impact site, the shock waves are refocused at
> that point.

Sure. However, evidence for this from other planets (e. g. the "chaotic 
terrain" on Mercury) occurs only with much bigger craters that Chicxulub. 
Then I don't know if India really was 180° away from Chicxulub... the 
position of India relative to Africa, Madagascar and Asia at that time is 
still in some dispute AFAIK.

> Also If the crust near there was in a weakened state, ie. if
> there were large amounts of magma just under the crust, as there usually is
> in the millenia before a large basalt eruption.  Couldn't a moderate impact
> event weaken the crust above the magma to the point of triggering the
> eruption.

Might work, but probably only if there really already is a lot of magma in 
that place. The lower lithosphere is pretty solid, and a hole/break/... that 
reached the asthenosphere in a tectonically inactive region must have been 
implausibly deep.