If the theory is true (and evidence is piling up that it is), several million years ago an impact somewhere off the southern coast of Africa resulted in the first island in the Hawaiian chain -- a volcano that erupted in the area now known as French Frigate Shoals until it formed land above sea level.
Yet no scientists are looking for an impact crater in the ocean offshore of southern Africa to explain Hawaii's volcanic hot spot, which I find rather odd.
Does that take drift into account? A programme I watched on the Galapagos said that although they were formed by volcanoes, the natural drift meant that older islands were no longer over the volcano. This also allowed for the creation of new islands (the Galapagos chain is still growing.)
The mystery of the dinosaur extinction was finally solved by the discovery of a huge asteroid impact crater off the Yucatan peninsula of Mexico.
I think solved is a bit too certain. But scientists do believe this is the most likely theory at the present time, or so I gather from the programmes I've seen. Also, does this mean there is a volcano in the Indian Ocean, exactly opposite the Yucatan Peninsula? Not arguing here, just asking because I'm curious. I make the antipodal area to be near Indonesia. Hmm, curious.
Re the 1918 flu pandemic, for a while it was believed that this was what was colloquically called 'swine flu', having passed from birds through swine to humans. Now it is believed that this virus passed directly from birds to humans. The current bird flu is classified as H5N1; the 1918 pandemic was strain H1N1. Maybe the birds caught alien flu and passed it to us. After Daphne duMaurier's story, I'll believe anything about the varmints!