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When it rains, where does the water go? Well for one, a lot of rainwater will funnel its way off roads and impermeable surfaces and will make its way into storm sewers. Another path might be directly into rivers and lakes. Or, rainwater might get soaked up by soil where it will then infiltrate into the ground and replenish aquifers. But just how deep does this rainwater infiltrate?
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According to new research, rainwater can penetrate below the Earth’s fractured upper crust – which is at least eight miles below the Earth’s surface!
It had been thought that surface water could not penetrate the ductile crust – where temperatures of more than 300°C and high pressures cause rocks to flex and flow rather than fracture – but researchers have now found fluids derived from rainwater at these levels.
The research could have major implications for our understanding of earthquakes and the generation of valuable mineral deposits.
Fluids in the Earth’s crust can weaken rocks and may help to initiate earthquakes along locked fault lines. They also concentrate valuable metals such as gold. The new findings suggest that rainwater may be responsible for controlling these important processes, even deep in the Earth.
Researchers from the University of Southampton, GNS Science (New Zealand), the University of Otago, and the Scottish Universities Environmental Research Centre studied geothermal fluids and mineral veins from the Southern Alps of New Zealand, where the collision of two tectonic plates forces deeper layers of the earth closer to the surface.
The team looked into the origin of the fluids, how hot they were and to what extent they had reacted with rocks 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,” says University of Southampton researcher Catriona D. Menzies. “We have analysed these waters and minerals to identify where the fluids deep in the crust came from … 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.”
Read the study at ScienceDirect.
Read more at EurkeAlert!
Rain image via Shutterstock.
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