Mount Ruapehu: Getty
A volcano that featured in The Lord of the Rings movies in New Zealand is in danger of erupting as pressure builds in a subterranean vent, experts said on Monday.
Hikers have been warned to avoid the summit of Mount Ruapehu, with the Department of Conservation (DOC) saying temperature readings indicate there could be a "significant eruption" from New Zealand's largest volcano.
According to the Independent Online, DOC volcanic risk manager Harry Keys told Radio New Zealand: "The current situation can't continue, Ruapehu is so active that the temperatures have been going up and down a lot.
"They generally haven't gone up as we've expected for some weeks now and sooner or later that situation will be rectified, either in a small, relatively passive way, or with a significant eruption."
The Daily Telegraph reports that the official monitoring body GNS Science said the temperature a few hundred metres below a lake in the crater of the North Island mountain was estimated at 800 degrees Celsius (1,472 Fahrenheit) but the temperature at the lake itself was just 20C (68F).
It said this indicated a vent was partially blocked, leading to increased pressure that made eruptions more likely "over the next weeks to months".
Director Peter Jackson used Mount Ruapehu and the neighbouring Mount Ngauruhoe to depict Mount Doom in The Lord of the Rings movies.
The 2,797-metre (9,177-foot) mountain last erupted in 2007, sending a lahar - a fast-moving stream of mud and debris - down the mountain but causing no injuries.
In 1953, a massive lahar from the mountain caused New Zealand's worst rail disaster when it washed away a bridge at Tangiwai and a passenger train plunged into the Whangaehu River, claiming 151 lives.
According to AFP, another nearby volcano, Mount Tongariro, erupted in August this year, sending a plume of ash 20,000 feet (6,100 metres) into the atmosphere, showering the North Island and disrupting domestic air travel.
Ruapehu is one of the world's most active volcanoes and the largest active volcano in New Zealand. It is the highest point in the North Island and includes three major peaks: Tahurangi (2,797m), Te Heuheu (2,755m) and Paretetaitonga (2,751m). The deep, active crater is between the peaks and fills with a crater lake between major eruptions.
Ruapehu began erupting at least 250,000 years ago. In recorded history, major eruptions have been about 50 years apart, in 1895, 1945 and 1995–1996. Minor eruptions are frequent, with at least 60 since 1945. Some of the minor eruptions in the 1970s generated small ash falls and lahars (mudflows) that damaged skifields.
The 1945 eruption emptied the crater lake and dammed the outlet with tephra. The crater slowly refilled with water, until on 24 December 1953 the tephra dam collapsed causing the aforementioned lahar in the Whangaehu River.
The lahar caused the Tangiwai disaster, and its loss of 151 lives, when the Tangiwai railway bridge across the Whangaehu River collapsed while the lahar was in full flood, just before an express train crossed it.
It was already known that the river had partially undermined one of the bridge piers and the lahar finished the job, causing the bridge to collapse. Although warned of the collapsed bridge, the train driver was unable to stop the train in time and six of the carriages fell into the river.
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