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Home page Solar and galactic influences Climate change Sea level change Continental drift Volcanic activity Asteroid impact Pathogens Other species
For most of us, volcanoes are spectacles seen on television or referred to in books. There are about 1500 active volcanoes today of which about 80 are under the sea.  You will notice that most of the active volcanoes occur where plates are colliding and resistance creates high pressure.  The environmental damage caused by volcanoes is not limited to local lava flows and the widespread distribution of ash, but the emission of several toxic chemicals can have long-term global effects. The massive Toba volcanic eruption26 in Sumatra about 73,000 years ago was so catastrophic that it may have caused a reduction of 5ºC in the average global temperature for several years and have initiated an ice age. Ash from the huge explosion was deposited 15cm thick over the whole of India and much of South East Asia. Parts of Malaysia were covered by nine metres of ash. Very few animals would have survived this and many species may have become extinct. It is believed that the world human population of the time was reduced by 60% to about 10,000 to 20,000 individuals by this disaster.
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