Massive volcanic eruptions have helped shaped the face of the Earth for centuries, with various types of terrain, nature units and even bodies of water taking on their geological features as a result of an exploding peak.
A new study conducted by the University of Edinburgh, however, suggests that discharges from volcanos could also affect the flow of water in major river systems by causing a shortage of rainfall in different regions.
In a study featured in the journal Nature Geoscience, Edinburgh researchers Gabriele Hegerl and Carley Iles discovered that the ash and debris typically shot up into the atmosphere by exploding volcanos often trigger a naturally occurring screen that blocks out the sun and alters the flow of water of some of the primary river systems in the world.
This occurrence was seen in the Nile, Congo and Amazon rivers, wherein water volumes were reduced by as much as 10 percent following major volcanic eruptions during the course of the 20th century that shot millions of tons of debris into the sky.
Iles said that it was already known that eruptions of volcanos significantly impact the amount of rainfall in the world, but it was not yet clear as to what extent these occurrences affect the flow of water in rivers.
Hegerl and Iles studied the yearly water flow of 50 rivers in different parts of the world and compared them with the occurrence of primary volcanic eruptions, from the explosion of the Krakatoa in 1883 to that of Mount Pinatubo in 1991.
Some of the river systems examined had records dating back to the 19th century, which allowed the researchers to take into account data from earlier volcanic explosions as well.
The researchers found that a year or two following eruptions where in large amounts of debris were released into the atmosphere, the flow of water in tropical rivers considerably dropped.
"As well as affecting river flow and rainfall, volcanic eruptions have a cooling effect on climate," Iles said.
"All of these impacts come about because volcanoes inject particles -- sulfate aerosols -- high up into the atmosphere, and these spread out and reflect sunlight back out into space."
Water flow in some sub-tropical areas, however, increased as a result of a disruption in the atmospheric circulation patterns. Some of the regions affected by this water flow increase include the south-west United States and areas in South America.
Hegerl and Iles note that predicting how changes in the water flow of rivers affect people is a direct process.
The Amazon River, for example, is found in a lightly populated region, which is why the reduction of water flow may not have a significant impact.
The Nile River, on the other hand, is vastly depended on by large human populations, so a reduction in its water flow could have a more visible impact than that of the Amazon.
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