Thanks for the info.
I wonder if it was related to solar activity. Do these episodes correlate with sun-spots?
I’m not sure about the dates, but its generally believed that the first English settlers arrived just after the native population had drastically declined. I always understood that this was due to disease, but it seems the drought might have been a factor.
The solar sunspot cycles are 11 years for half a cycle. A full cycle is about 22 or 23 years. The 80 year cycle seems to be linked to the basic sun spot cycle in the sense of having a similar cause but a longer periodicity.
I've found the 80 year cycle to be useful in working backwards to 1492 to see if there could have been a drought going on somewhere in America. A 70 year cycle is probably more consistent with the hanta virus problems. There you need some good weather for a few years to enable the pine nuts to grow to feed the rodents that carry hanta virus. Then all H breaks out! Notice, that takes place WITHIN the 80 year cycle. That's because that cycle, although tracing drought occurrence, is not perfect ~ we don't always have a Great Drought, and we don't always have a smaller drought. It's a period of less than normal rainfall over an enormous part of the continent ~ if it's a Great Drought. There are almost always hotspots within the cycle and it looks like Virginia was a hotspot ~ like Oklahoma was a hotspot in the 1930s Great Drought.
There's an even longer cycle that we know of inferentially. That's where it gets colder in the Northern regions. The traditional lifestyle there is herding animals. Colder weather is dry weather, and grazing lands become scarce so the nomads move South and invade some otherwise civilized place.
They may stay in the area hundreds of years and then when the climate warms up they move back North!
Pretty clearly that's not going to happen these days but it was predictive of the Mongols conquering China and India, and less obviously, of the movement of Turkish speaking Buddhists North out of India all the way to Siberia, and then on to the conquest of Korea and the initiation of a 900 year civil war in Japan!
The Turks have been showing up in both Eastern and Western India for thousands of years ~ apparently driven to do that by climate change.