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Building the Adirondacks, one theory at a time

"More recent rock-dating data suggests there's a longer, slower rise going on-maybe starting 130 million years ago," Kelly said. "Yet the edges of the mountain dome appear younger. But even with that said, why are these mountains rising so far from a plate boundary? Maybe Yngvar's hot-spot theory will prove to be as good an explanation as any other. Maybe there's a plume of magma stuck to the bottom of the continental plate? We just don't know."

In the late 1990s, Kelly said, a research team from Rensselaer Polytechnic Instituteconducted a global positioning system (GPS) study of the High Peaks region to see if the Adirondacks were rising rapidly. The team camped out and collected data for 72 hours. They discovered they couldn't get a reliable answer-they couldn't compare their data to existing data, including pioneer Adirondacker Verplank Colvin's survey data of the 1870s, because of various errors. So the RPIfield trip didn't amount to much. Using the 1990s data, RPI researchers plan to recheck the GPS results in 10 years.

Regardless, Kelly backed up some of his late colleague's claims-

•The Adirondacks are not "old" by standards of deep geological time (however, they are composed of very ancient, metamorphosed sedimentary and igneous rocks).

•Dr. Isachsen believed the Adirondacks started forming 5-10 million years ago; Dr. Kelly believes they are older-up to 130 million years old.

•The Adirondacks appear to be growing, but probably not at a rate faster than the Alps as claimed during the 1990s (1 millimeter per year).

•The Adirondacks are not a product of Ice Age rebound.

Kelly said many domical mountains are associated with hot spots. But in some cases, as seen on other planets, huge asteroid impacts can create dome mountains.

In Africa several dome mountains are erupting lava. Isachsen believed lava might someday break through the rocks of the Adirondacks. It won't happen-if it happens at all-for millions of years in the future, Kelly said.

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