Researchers Discover Rainwater at New Depths Below Earth’s Fractured Upper Crust

For the first time, researchers have discovered rainwater at new depths below Earth's fractured upper crust where high temperature and pressure exists.

In this study, researchers at the University of Southampton studied the geothermal fluids and mineral veins from the Southern Alps of New Zealand and found that rainwater can penetrate much below the Earth's crust.  At this place, the collision of two tectonic plates forces deeper layers of the Earth closer to the surface.

Till date, it was believed that surface water do not enter the ductile crust that is considered the strongest part of the Earth's crust. It is a known fact that as you go deeper into the Earth's crust, it gets hotter. The ductile crust temperature is above 300 degree C and also has high pressure due to which the rock flex and flow rather than fracture. 

But in the latest study led by Dr. Catriona Menzies, at this level certain fluids derived from rainwater does exist. This provides a major implication for our understanding of earthquakes as well as understanding the generation of valuable mineral deposits.

The presence of the fluids in the Earth's crust can weaken rocks and also trigger earthquakes along the locked fault lines. They collect precious metals like gold. Based on the finding, the researchers claim that rainwater plays a key role in controlling important processes even deep in the Earth.

They not only focused at the origin of the fluids, but also how hot they were and the extent to which they had reacted with the rocks present deep within the mountain belt.

"When fluids flow through the crust they leave behind deposits of minerals that contain a small amount of water trapped within them," said Postdoctoral Researcher Catriona, who is based at the National Oceanography Centre. "We have analysed these waters and minerals to identify where the fluids deep in the crust came from."

Fluids come from various sources in the crust. In the Southern Alps, the fluids flow upward from a great depth in the crust and due to metamorphic reactions they are emitted from hot rocks. Else rainwater flows down the surface, forced by high mountains above. 

Researcher Catriona said, "We wanted to test the limits of where rainwater may flow in the crust. Although it has been suggested before, our data shows for the first time that rainwater does penetrate into rocks that are too deep and hot to fracture."

They claim that water derived from surface that reach great depths are heated to over 400 degree C and react with crustal rocks. However, with certain tests conducted they successfully established the water's meteoric origin.

The study has been published in Earth and Planetary Science Letters.