Natural hazard risk at Piopiotahi Milford Sound
Dramatic and ever-changing, Piopiotahi Milford Sound is one of the world's most spectacular and special environments. Its steep, glacier-carved mountains and deep fiord have been shaped by powerful geological forces over millions of years.
The area is exposed to risk from a range of natural hazards. These can occur at any time, and some can happen without warning. Of all the hazards, large earthquakes, landslides and tsunamis pose the greatest risk to people at Piopiotahi Milford Sound.
It is extremely unlikely that one will happen during your visit, especially for a short stay. However, there is a risk and the longer you spend there, the higher it becomes. Once you are there, your safety options are limited it is important you understand the risks before you go.
Earthquakes The Alpine Fault runs almost the entire length of the South Island and crosses the entrance to Piopiotahi Milford Sound. It can generate earthquakes of magnitude 8 or greater, occurring on average every 300 years. There is a 75% chance of this happening in the next 50 years. An earthquake of this size would almost certainly affect the narrow waterway and surrounding area. Find out more at af8.org.nz
Landslides The steep mountains around Piopiotahi Milford Sound are prone to rockfall and landslides. Earthquakes and severe weather can make the cliffs unstable. Bigger landslides could cause a tsunami in the fiord and do pose a risk to life.
Tsunami Less common but of more concern is the potential for a large landslide to fall into the fiord and trigger a tsunami. Landslide-triggered tsunamis are rare. The chance of one occurring during your visit is extremely unlikely. However, they can create large waves and do pose a risk to life.
What to do:
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In an earthquake, DROP, COVER and HOLD until shaking stops.
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If an earthquake feels LONG (1 minute or more) or STRONG (cannot stand up), Get GONE. Move up and away from waterways (the fiord and rivers) as quickly as possible.
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If you see or hear a landslide entering the water, dust clouds, loud rumbling, or splashing, Get GONE. Move up and away from waterways as quickly as possible.