Omission of a single word.
Wonder what caused the Dino extinction? The last geomagnetic reversal was probably a major factor.
Forgive my omission that line should have read:
The last prolonged geomagnetic reversal was probably a major factor.
5:30 in the morning does that to me sometimes.
I'll clarify my train of thought:
At present the earth's magnetic field is weakening. Scientific consensus figures it may disappear to almost nothing within 1000 to 2000 years.
The major fear is that the weak magnetic field will open up the surface of the earth to massive solar radiation.
Scientists also assume the last geomagnetic reversal was probably about 750,000 years ago. The current weakening of our field may be a prelude to that reversal. Little is known about the varying intensity of the magnetic field just prior to such a polarity reversal. I believe that the intensity/ramifications of the reversal may vary based upon the size and power of the field just prior to the reversal.
Imagine a geomagnetic reversal that is preceded by the prolonged weakening of the earth's field - and that the earth spends a few thousand years with a field intensity hovering at 0 gauss. Maybe as much as ten thousand or even twenty thousand years.
The incoming solar radiation for such an extended time period would create both a sterilization effect and a drastic change in climate. Deserts could be formed in areas that were once lush. Universal sterilization of dinosaurs and any other large creature which could not shield itself from the radiation would be a natural side effect.
Then, after the reversal, the field builds slowly up again, ozone builds up and again any surviving (smaller) lifeforms thrive.
In my mind it seems far more realistic an explanation for dino-extinction than a major impact event for which we can find no evidence.