This is the dramatic moment an avalanche was captured from a helicopter as it thundered down a mountain in New Zealand.

Footage shows a massive wall of snow cascading down the slope during a controlled release carried out by authorities in Milford Sound.

The operation was conducted to safely clear fresh ice from the mountainside, reducing the risk of natural avalanches and protecting motorists on the highway below.

Officials said the road from Te Anau to Milford Sound - a crucial route for locals and tourists - had been closed following days of heavy snowfall.

An avalanche is a sudden, fast-moving mass of snow, ice, and debris that can be triggered by various factors, such as heavy snowfall or an earthquake. Avalanches are extremely dangerous, as they can bury people, vehicles, and entire villages, causing severe injury or death within seconds.

The deadliest avalanche in recorded history occurred in 1970 in Peru, when an avalanche triggered by an earthquake buried the town of Yungay, killing around 22,000 people.