Gassed to Extinction!
The world's largest mass extinction was probably caused by poisonous volcanic gas, according to research published in the journal Geology revealing vital clues about the mass extinction at the end of the Permian period, 250 million years ago, when mammal-like reptiles known as synapsids roamed the earth.
Many scientists had previously thought that an asteroid hitting the earth or a deep-sea methane release had caused the extinction, which obliterated more than two-thirds of reptile and amphibian families.
The chemistry of the rocks reveals that although the sugar molecules were found in marine sediments, they derived from land, supporting the theory that massive soil erosion caused them to end up in the sea.
Soil materials in the oceans would have blocked out light and soaked up oxygen. Analysis of rock chemistry suggests that after the soil crisis on land, the marine ecosystem succumbed to the stresses of environmental change and oceanic life faltered, completing a global catastrophe.
Dr Mark Sephton, from Imperial College London's Department of Earth Sciences and Engineering and lead author of the research, said: "The cause of the end Permian extinction has been highly controversial. We show that the terrestrial ecosystem was the first to suffer. The continent-wide nature of the event implies that it was caused by something in the atmosphere. The unique chemical data indicates that something fast and catastrophic happened on land."
Prof Henk Visscher of Utrecht University, also part of the research team, commented: "Similar to the 'Dead Zone' nowadays spreading in the Gulf of Mexico, the soil crisis could have caused a worldwide expanse of uninhabitable low-oxygen conditions in shallow marine waters. So what began on land ended in the sea. It seems there was no place to hide at this time of great dying."
Dr Sephton believes that lessons can be learned in the present day from the damage caused by the end Permian extinction: "Land degradation is a worsening global problem thanks to human activity and soil erosion has caused the loss of a third of arable land over the last forty years. 35% of the Earth's land is now soil-free. Identifying the nature of the end Permian soil crisis may help us understand what is in store for us in the years ahead," he said.
The research was carried out by an international team of scientists from the United Kingdom, the Netherlands and the United States..
College of London
Fire Mountains of the West
The Cascade And Mono Lake Volcanoes
by Stephen L. Harris
Mountain Press Publishing Company, 2005
This popular science text profiles the active volcanoes of the Pacific Coast, from Mammoth Mountain in northern California to Mount Meager in southern British Columbia.
Following introductory chapters on plate tectonics, glaciation, and recent research findings, the volcanoes are described in successive chapters, detailing the hazards their future eruptions pose to lives and property.
"The discovery and dating of newly recognized deposits reveals that most of the volcanoes have erupted far more often -- and with more far-reaching effects -- than was previously recognized," writes Stephen L. Harris in the introduction to this third edition.
Studies of the physical deposits from eruptions and avalanches reveals that some volcanoes, like Mount Rainier, have been active for more than a half million years. Others, like Mount St. Helens, are only tens of thousands of years old.
"Because they erupt infrequently in terms of a single human lifetime, many people living near them tend to ignore the volcanoes' deadly potential," Harris points out.
While this book emphasizes
the dangers of volcanoes, it also encourages exploration and
of these mountains with directions on how to visit them by car or on
The book includes maps, some photos and a glossary of geologic terms.
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