Hi All. Something Chris posted the other day got me to thinking (hate doing that as it gives me a headache) on the causes of some quakes. I remembered something that Dr. Mark Zoback had said.

His theory about past glaciers may be an answer to some of the inner continent quakes, but most certainly not all of them. Take Care…Don in creepy town

The ghost of past glaciers may still rattle the American Midwest. During the last ice age 20,000 years ago, a gigantic ice sheet invaded North America, weighing down the hard upper crust of the continent for millions of years. Eventually, the glaciers melted. Freed from the heavy pressure of the ice sheet, North America slowly rose. This glacial rebound continues even today and triggers quakes in the New Madrid fault zone in Missouri, Kentucky, Arkansas and Tennessee, says Stanford geophysicist Mark Zoback.

• Dr. Mark Zoback