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Environment

Scientists Find First Evidence That Weather Affects Movement of Tectonic Plates

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What’s the News: Geologists have known for years that tectonic plates affect climate patterns. Now they say that the opposite is also true, finding that intensifying climate events can move tectonic plates. Using models based on known monsoonal and plate movement patterns, geologists say that the Indian Plate has accelerated by about 20% over the past 10 million years. “The significance of this finding lies in recognising for the first time that long-term climate changes have the potential to act as a force and influence the motion of tectonic plates,” Australian National University researcher Giampiero Iaffaldano told COSMOS.

How the Heck:

  • The researchers plugged information from research on monsoonal patterns and the Indian Plate’s movement into a model, which indicated that the monsoonal erosion that has battered the eastern Himalaya Mountains for the past 10 million years erodes enough material to account for the plate’s counter-clockwise rotation. By gradually shaving off rocks from the eastern flank and decreasing crustal thickness, the monsoonal rains essentially lighten the load on the eastern part of the Indian Plate, causing the plate to actually turn (at geological speed).

  • The scientists ruled out the traditional powerhouse behind tectonic movement—mantle convection—because the mantle’s influence works on longer time frames than 10 million years. It doesn’t account, for example, for the Indian Plate’s geologically rapid velocity increase of more than 5 millimeters per year since 3.6 million years ago.

What’s the Context:

  • It’s long been known that tectonic movements have slow but huge effects on long-term climate patterns. As the Indian Plate slammed into the Eurasian Plate, for example, it closed up a sea and built the Himalayan Mountains, changing wind and rain patterns in the process. This study is the first to show the converse.

  • Dubbed the lithosphere, Earth’s outer 60 miles of solid material is split up into pieces called tectonic plates. Over long periods of time, these plates move, mainly due to the forces of churning magma underneath.

  • At present, plates generally move at the same rate that your fingernails grow. In the past, they’ve moved at different rates depending on variations in the forces involved, erosion patterns, and other factors.

  • One major way geologists track plate movement patterns and velocity is by looking at magnetic minerals in age-dated rocks: When igneous rocks cool, the magnetic minerals in them align with the magnetic north pole (which moves over time); as tectonic plates move, the original alignment changes.

  • Recently, scientists have suggested that even the young Earth had tectonic plates and that ancient continental collisions may have provided the air we breathe.

Not So Fast: These geologists are looking at time patterns on the order of millions of years, so you don’t have to worry about global warming causing stronger earthquakes (unless you plan on living that long).

The Future Holds: Next up, the geologists want to see whether climate has a similar effect in other regions, such as the Andes and the Rocky Mountains.

Reference: Giampiero Iaffaldanoa, Laurent Hussonb, and Hans-Peter Bunged. “Monsoon speeds up Indian plate motion.” Earth and Planetary Science Lettersdoi:10.1016/j.epsl.2011.02.026

Image: Wikimedia Commons / USG

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