On May 18, 1980, a major volcanic eruption occurred on Mount St Helens in the US state of Washington. The blast, which measured 5 on the Volcanic Explosively Index, has been declared as the most disastrous volcanic eruption in modern US history. An eruption column rose 80,000 feet into the atmosphere and deposited ash in 11 states.

At least 57 people were killed and hundreds of square miles were reduced to wasteland, causing over $1billion (£770million) in damage.

However, many residents did not know the volcano had erupted until it was too late, it was revealed during a bombshell documentary.

Amazon Prime’s “Mega Disaster: It’s Happened Before, It Will Happen Again” series revealed how a “silent zone” prevented locals from having any idea their lives were at risk.

Geophysicist Keith Ronnholm revealed on the 2006 series: “I was reading a book in my car, when I heard some people yelling and looked over to the mountain.

“The entire north side of the mountain was sliding down.