Milford Sound (or Fiord)

Sunday, December 13, 2009     Dunedin, New Zealand

Yesterday, Saturday, we cruised through the famous Milford Sound and the Dusky Sound.  The weather in the morning was overcast, foggy, and raining, so I don't have any photos of Milford Sound  - - lousy weather for photography.  I do have some nice pictures of the Dusky Sound, further south, but they're still in the camera.  I'll post a couple of them in a few days.

We learned that there is a difference between a sound and a fiord, and that the "sounds" on the western side of the South Island are misnamed.  They are actually fiords, just like in Norway.  A sound is a flooded river valley, which happens when sea level rises and/or the river valley subsides.  River valleys are characteristically V-shaped, with walls that do not exceed about 35-40 degrees in steepness.  This is what the solids mechanics engineers call the "maximum angle of repose".  Fiords, on the other hand, were carved by glaciers during one of the recent ice ages.  They are characterized by a U-shaped cross-section, with potentially very steep or sheer cliffs toward the top, and by the presence of "hanging valleys", the truncated end of a former tributary river which has been cut off by the erosion of the advancing main glacier flow.  This results in spectacular waterfalls as the stream runs out of riverbed and plummets over the edge of the sheer cliff face.  The New Zealish "sounds" are actually glacial fiords.