Many had never heard of Mount Tongariro before Monday night's eruption, but they've likely seen it in the backdrop of Peter Jackson's "The Lord of the Rings" films. Dormant for over 115 years, the towering volcano on New Zealand's North Island came alive, spewing ash more than four miles high and hampering travel both on the ground and in the sky.

Police described the eruption, which occurred around 11:50 p.m. local time, as a series of flashes and explosions followed by a massive cloud of ash that blanketed parts of the North Island in a thick grey film. The eruption is believed to have come from the Te Maari craters on the northern face of the 6,490-foot (1,978m) volcano, which lies within a designated national park.

The ash cloud closed roads and disrupted regional air travel before moving off the coast to the east.

Air New Zealand, the national carrier, resumed many flights to regional airports Tuesday evening after canceling some earlier services in Gisborne, Rotorua, Taupo, Napier and Palmerston North due to the risk of ash. Auckland Airport, however, reported about two dozen domestic flights in and out as being canceled Wednesday morning.

No international flights were affected.

The so-called Desert Road, a stretch of highway linking the political capital, Wellington, with the commercial capital, Auckland, was closed for a time but, according to the New Zealand Transport Agency's website, all state highways in the area reopened Tuesday after the ash cloud blew away, maintenance crews swept the streets and the GNS Science agency downgraded the alert for Mount Tongariro from red to orange.

Many tourists walk through in the area along the Tongariro Alpine Crossing, widely regarded as New Zealand's best one-day hike. Hiking tracks and huts around the mountain, however, have been closed until further notice. Three overnight hikers were safely evacuated from Mangatepopo hut, according the Conservation Department. Ketetahi hut, closer to the Te Maari craters, was damaged by falling debris and the Department's spokesperson, Nic Peet, said visitors could have been injured or killed had they been inside during the eruption.

All other parts of the national park -- save the Tongariro Alpine Crossing and the Tongariro Northern Circuit -- remain open.

Tongariro is one of three volcanoes that rise from the center of the North Island. It sits just north of Mount Ngauruhoe, known by many as Mount Doom for its depiction in the "Lord of the Rings" movies, and Mt. Ruapehu, a popular ski resort in the winter.

All three ski areas on Ruapehu -- Tukino, Turoa and Whakapapa - reported business as usual Tuesday with no ash headed their way.

Though it caused some travel delays, there were no reports of serious damage or injuries in the eruption, according to the Ministry of Civil Defense & Emergency Management.

Government scientists believe the event was driven by steam rather than magma and said they cannot rule out further explosions.

"I wouldn't be surprised if there were more small-scale eruptions," Brad Scott, a volcanologist at GNS Science, told reporters at a news conference Tuesday.

New Zealand is extremely volatile geologically and is no stranger to earthquakes and volcanic eruptions. Yet, Scott said Tongariro "just snuck up on us."

Tongariro's last eruption was in 1897, though Ngauruhoe, which many volcanologists consider a vent of Tongariro, blew in 1975.

On Sunday, scientists observed small eruptions on White Island, an offshore volcano about 110 miles (180 kilometers) north of Tongariro. Both volcanoes are part of the Taupo Volcanic Zone, but scientists believe the events are unrelated.

Both eruptions come less than a month before the two-year anniversary of a magnitude 7 earthquake that struck the South Island city of Christchurch. There have been 10,560 subsequent shakes since then, according to the University of Canterbury, including a large one in February 2011 that killed 185 people and destroyed the historic heart of Christchurch, New Zealand's second-largest city.

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