Hello and thank you for downloading witness on the BBC World Service with me for Hana Hiva.

Today we're going back to June the 15th, 1991,

where one of the largest volcanic eruptions of recent times occurred at Mount Pinatubo in the Philippines.

The volcano had been threatening to explode for several days.

Mount Pinatubo on the Philippines is continuing to pour out clouds of ash and steam, and there may be another

violent explosion soon.

In early June 1991, Mount Pinatubo, just 90 kilometers north of the Philippines capital, Manila, had begun

a series of eruptions.

This morning's explosion, which had been threatening all week, could be the first of many. Experts say pressure is

building again and another bigger eruption could follow soon. One of those experts

was John Hewitt, a volcanologist working for the US Geological Survey who'd been sent to the Philippines

to help monitor the volcano just a few weeks earlier.

When you arrived in the Philippines, were you apprehensive?

I was apprehensive because in the three weeks that

are the first three members of our team had been there we learned enough about

the volcano to be concerned. Mount Pinatubo had lain dormant for over 600 years and the first sign that it might be

restless had come on the 2nd of April 1991 when an explosion opened a line of steaming vents along the mountainside.

This was a volcano that basically blew itself apart every time it erupted and

erupted large volumes of ash and pumice producing phenomena that we know as

pyroclastic flows. These are incandescently hot surges or avalanches of

rock and ash that move at 100 kilometers an hour and literally

destroy and incinerate everything that they encounter.

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