Mount Ruapehu on New Zealand's north island is showing signs that it's about to erupt, scientists have warned. The snow-capped volcano was used as one of the backdrops for those punishing Mount Doom scenes in Peter Jackson's Return of the King, and, if seismic activity is anything to go by, the Dark Lord Sauron has been pretty restless of late.
On Wednesday, the volcano alert level for the mountain was raised to Level 2 (moderate to heightened unrest), and the aviation colour code changed from green to yellow, with authorities warning climbers and hikers to avoid the 2-kilometre area surrounding the volcanic crater.
"There are more signs of life at the volcano," volcanologist Brad Scott from GNS Science told National Geographic. "Recent visits to the volcano have confirmed an increase in the output of volcanic gas."
On top of the gas, a swarm of tremors were recorded on the mountain in April, and the crater's lake has been steadily rising in temperature since last month, increasing from 25 degrees Celsius (77 degrees Fahrenheit) to 46 degrees Celsius (115 degrees Fahrenheit).
That doesn't mean the volcano is definitely about to erupt - the crater lake goes through a lot of these natural heating and cooling cycles. Since 2010, eight of these cycles have been recorded, and none of them have been associated with eruptions (three Level 2 alerts were issued during that time).
"One of the common factors of the crater lake is it heats up and cools down. Typically those cycles last between nine and 14 months," Scott told the press. "When there's unrest that doesn't always lead to an eruption. It can show more signs of life and then go back to a quieter state."
But the combination of the gas and seismic activity with the temperature rise is enough to keep people a safe distance from the crater.
The good news is there's not too much to worry about if the volcano does erupt - Ruapehu is the most active volcano on the north island of New Zealand and has erupted at least 60 times since 1945, with the majority of those eruptions being minor.
The last time it went off was in 2007, with only one injury being reported from the incident - a hiker in the area got his leg trapped under a rock.
That's because the volcano is situated in the heart of Tongariro National Park, so unless people are nearby there's not too much of a threat. According to Hall, the greatest risk from the volcano is a 'lahar', which is a mudflow often caused when a crater wall collapses.
Air travel might also be affected, as we've seen in the past with the eruption of Mount Etna last year, and the Eyjafjallajökull eruption back in 2010.
Researchers from Geonet - the national agency that monitors New Zealand's geological threats - will continue to monitor the region closely over the next few weeks, so we'll hopefully get plenty of warning if and when that does happen.
In the meantime let's hope all those Lord of the Rings fans listen to authorities and stay clear of the area.
Note for those who are curious: most of those wide-angle shots of Mount Doom were computer generated for the film (sorry, no Eye of Sauron here) but a lot of the close-up Mordor scenes were filmed on the hissing, jagged slopes of Mount Ruapehu. Other Mount Doom scenes were filmed on New Zealand's Mount Ngauruhoe.