Geology of the Fjords

Sixty percent of our land mass, including the Southern Alps, is made up of Greywacke. Greywacke is recycled Granite and ours is from somewhere unknown within Gondwanaland. Fiordland is one of very few places in New Zealand free of Greywacke, or choss as it is colloquially known.

In Fiordland igneous rock 99 to 385 million years old, originating from the Median Batholith of Gondwanaland and formed deep within the Earth's crust, is exposed due to tectonic uplift. The Homer Tunnel, Mount Tutoko and Mitre Peak are all carved from metamorphosed granite or orthogneiss. The hardness of the rock has preserved the steep angular shapes carved by glaciation during the last 2 million years.

Milford Sound, which is the first of Fiordland's many fiord's is 400m deep in places. It is covered by 4 to 6 meters of fresh water, which is why the forest grows to the high tide mark. Also in Fiordland is Lake Hauroko which at 463 meters deep is New Zealand's deepest lake. Lake Te Anau is the second largest lake in New Zealand, 417 meters deep. It has 3 spectacular and seldom visited fresh water fiord's of its own.


Explore with the Milford Sound Guide

View of Milford Sound from Gertrude Saddle