Key facts
- Fact 01
Milford Sound is a fiord: a valley carved by glaciers and later flooded by the sea, DOC says.
- Fact 02
DOC calls sound a general, non-technical term for a more or less narrow branch of the sea.
- Fact 03
Fiordland has fourteen fiords, from Milford Sound/Piopiotahi in the north to Preservation Inlet in the south, DOC says.
- Fact 04
Milford Sound is the only one of Fiordland National Park's 14 fiords reachable by road, Destination Fiordland says.
- Fact 05
Milford Sound stretches 16 km to the open sea and is 265 m deep in places, DOC says.
Milford Sound is a fiord. The Department of Conservation describes New Zealand's fiords as steep-sided valleys once excavated by glaciers that the sea now partly fills, and it describes the Milford Sound area as a rugged landscape carved by glacial ice. Destination Fiordland calls Milford Sound Piopiotahi a steep, narrow, glacially carved valley.
During the ice ages, DOC says, Fiordland's glaciers flowed out to meet the sea and ground the land into steep-sided, U-shaped valleys. The ice was so thick that the bases of the larger glaciers sat below sea level, so when the climate warmed and the glaciers retreated inland, the valleys flooded with meltwater and the rising sea. Milford Sound stretches 16 km to the open sea and is 265 m deep in places.
So why the name? Most of New Zealand's fiords are named as sounds, DOC says, including Milford Sound, Doubtful Sound and Tamatea/Dusky Sound, and sound is a general, non-technical term for a more or less narrow branch of the sea. Destination Fiordland says both terms are correct: fiord is the geological term for an ice-carved landscape flooded by water, and sound is the geographical term for a large ocean inlet.
Milford Sound is not New Zealand's only fiord, either. DOC counts fourteen in Fiordland, some reaching up to 40 km inland, from Milford Sound/Piopiotahi in the north to Preservation Inlet in the south. Destination Fiordland says Milford Sound is the only one of them you can reach by road.
The English name came from a Welsh sealing captain, John Grono, who named it after his birthplace, Milford Haven, DOC says. The Māori name, Piopiotahi, comes from the piopio, a native thrush that is now probably extinct.
Our Milford Sound planner covers the road day from Queenstown, and our scenic flight guide covers flying in.
Questions visitors are asking
Is Milford Sound a fiord or a sound?
Both. Milford Sound is a fiord, a valley carved by glaciers and later flooded by the sea, DOC says. Sound is a general, non-technical term for a narrow branch of the sea, and Destination Fiordland says both terms are correct: fiord is the geological term, and sound is the geographical one.
Is Milford Sound New Zealand's only fiord?
No. DOC counts fourteen fiords in Fiordland National Park, some reaching up to 40 km inland, from Milford Sound/Piopiotahi in the north to Preservation Inlet in the south. Doubtful Sound is another of them. Milford Sound is the only one of the fourteen you can reach by road, Destination Fiordland says.
How was Milford Sound formed?
During the ice ages, Fiordland's glaciers flowed out to the sea and carved steep-sided, U-shaped valleys, DOC says. The bases of the larger glaciers sat below sea level, so when the climate warmed and the ice retreated, the valleys flooded with meltwater and the rising sea. Milford Sound is 265 m deep in places.
Why is it called Milford Sound?
A Welsh sealing captain, John Grono, named it after his birthplace, Milford Haven, DOC says. Most of New Zealand's fiords carry the name sound, a general term for a narrow branch of the sea. The Māori name, Piopiotahi, comes from the piopio, a native thrush that DOC says is now probably extinct.