New Zealand volcano explodes

(ROUGH CUT ONLY - NO REPORTER NARRATION)

Aerial videos show thick grey ashes blanketing part of New Zealand's central North Island.

Mount Tongariro roared to life after being dormant for 115 years, spewing boulders and spreading ash cloud on Monday night (August 6).

Flights to and from provincial destinations, including renowned tourist spot Rotorua, were delayed or cancelled and local highways were closed for a time, but no other damage or injuries were reported.

Craters on Mount Tongariro, one of the three volcanic peaks in the central North Island, exploded with bright flashes and thunderous booms.

Volcanologists said the scale of the eruption was unexpected.

And the spew of rocks was caused by pressure build-up of volcanic gases, since seismic activity had increased in recent weeks.

The last time Mount Tongariro erupted was in 1897, ending a decades-long period of intermittent activity.