[00:00.84]D Volcanoes and earthquakes [00:03.57]are even more dangerous than in the past [00:06.34]as around half the world's population now [00:08.95]lives in cities. [00:10.41]There are more than 500 active [00:12.79]and semi-active volcanoes, [00:14.61]about fifty of which erupt each year, [00:16.96]and more than 500 million people [00:19.24]now live within the range [00:21.16]of a volcanic eruption. [00:23.54]An even greater number live at risk, [00:25.98]in some degree, from earthquakes [00:28.05]which have taken a toll [00:29.36]of more than 1.6 million [00:31.45]lives in the last hundred years. [00:35.82]E All the betting [00:37.68]from the disaster professionals [00:39.11]in that things will get worse. [00:41.53]Professor Hou Ming, of Beijing University, [00:43.99]is a volcanologist who has been warning [00:46.34]for years that the world has not seen the worst [00:48.83]nature can do. [00:50.43]The worst eruption in human history [00:52.31]was probably Mt Tambora in 1815,in Indonesia. [00:57.86]It pumped so much dust into the air [01:00.18]that it effectively cancelled the following [01:02.09]summer in Europe and America. [01:04.50]But geographial evidence shows [01:06.33]that 73,000 years ago [01:08.31]there was a much greater eruption. [01:10.64]"It reduced temperatures by maybe 6C [01:14.89]in some places and the whole planet [01:17.28]was plunged into winter for years. [01:19.83]And there are about two of these events [01:22.09]every 100,000 years..." [01:23.55]