Rainwater at New Depths: A Cause of Earthquakes?

Rainwater penetrates into the Earth's crust far deeper than experts once thought. Researchers claim that this knowledge has major implications, potentially overturning our understanding of mineral deposits and even earthquakes.

It had long been thought that surface water could never slip past the ductile crust of the Earth, as this portion of the crust boasts incredibly hot temperatures approaching 570 degrees Fahrenheit  (~300 degrees C). The ductile crust also is not known to fracture, as incredible heat and pressure causes rock to flex and flow with changing weights, but without becoming magma.

However, now researchers have detected signs of fluids that should not be there - fluids derived from rainwater.

"When fluids flow through the crust they leave behind deposits of minerals that contain a small amount of water trapped within them," lead researcher Catriona Menzies explained in a statement. "We have analyzed these waters and minerals to identify where the fluids deep in the crust came from."

According to Menzies, rainwater can traditionally flow very deep into the Earth, but only through means of slipping through cracks and fractures in its crust - fractures that also contribute to earthquakes in the long run.

Forced deep down by the immense pressures of mountains from above, this water can build, mounting pressure upon fractured rock until entire sections of the Earth shift to sit more comfortably upon the sub-surface waters.

This phenomenon is not uncommon, and is thought to be one of the primary causes of man-made earthquakes. According to the US Geological Survey contaminated waters from activities like fracking are often pumped far into the Earth, creating "deep wells" far below any aquifers providing water for the world above.

However, recent research has shown that these man-made injections of water are unintentionally shifting the Earth's crust, increasing the likelihood of earthquakes so much that so far this year, Oklahoma has reported more earthquakes than California.

Fluids in the Earth's crusts have been known to weaken rocks, causing earthquakes and even expediting the formation of certain minerals.

According to Menzies and her team, now that it is known that natural rainwater can even slip through the "impenetrable" ductile crust, an understanding of these processes will have to be amended.

The study was published in the August edition of the journal Earth and Planetary Science Letters.