Developments in Brief : Scientist Estimates Appalachians’ Growth

Going back even further in time, a Yale geophysicist has determined that a massive mountain range rose up 400 million years ago in the New England area at a rate more than twice as fast as the Himalayas are growing today.

The ancient range has been weathered down to what is now the Appalachian hills, but Prof. Antonio Lasaga believes that the peaks may once have surpassed Mt. Everest’s 29,000 feet.

He used a method he calls “geospeedometry” to measure the rate of growth. “Geospeedometry reveals the history of heating and cooling that rock formations undergo,” Lasaga said, revealing a pattern similar to tree rings.

“The ancient New England mountains were created by the collision of three continents, North America, Europe and Africa,” he said. “The Himalayas are being formed by the relatively recent collision of India and Asia.

“Geospeedometry gives us an idea about the violence of those collisions,” he said.

Lasaga said the Himalayas are rising at the rate of one millimeter a year, about the thickness of a dime, compared to 2 1/2 millimeters a year for the ancient New England range.

His calculations are based on microscopic studies of garnet stones. “Garnet stones are useful gauges of geospeedometry because they are found everywhere,” he said. “Additionally, they are made of iron and magnesium, and the rate at which these atoms mix when they are heated is relatively slow. As a result, the atoms align in identifiable crystal zones that provide a rock’s thermal history much as tree rings reveal variations in growing conditions.”