GeoSphere

New Zealand

Geology Photo of the Week #36

The highlighted photo for this week comes from my last trip to New Zealand for the AMS12 conference a few years ago. They were taken at the end of a hiking trail in the Mount Cook area, it is behind the clouds looking straight ahead but you can kind of make out some small glaciers in the distance. However, the interesting stuff is all in the foreground.

These pictures highlight two really interesting phenomena. The first is the massive pile of gravel in the middle of the picture. It is called the Mueller Lateral Moraine and is a great example of a very recently formed glacial feature. Lateral moraines form as big gravel piles along the edges of a glacier, in this case, the Mueller Glacier, which has receded out of the picture.

The Mueller lateral moraine at the Mt. Cook glacier on New Zealand’s south island. (Photo: Matt Herod)

The second cool feature of this image is the water. At first glance, it may just look like muddy water, but there is more to it than that. If you look closer you can see there is some ridiculously blue water in the picture as well. The picture below shows it much more clearly.

(Photo: Matt Herod)

Some cool blue water courtesy of rock flour. (Photo: Matt Herod)

Pretty cool looking water eh?! But, why is it so blue? The colour comes from a substance called rock flour. Rock flour is extremely fine grained sediment that is formed underneath a glacier by erosive action of basal sliding, freeze-thaw or meltwater erosion. The particles are so small that they don’t sink rapidly like a larger stone would, they stay suspended in the water column and change its colour from turquoise blue to milky white, all of which can be seen in this photo. One very interesting thing about this photo is the colour gradients that can be seen and the mixing of the blue stream with the milky pond. You can see the trailers of blue water entering and flowing into the pond and then gradually being diluted with the white water. Also, some little pools of water are super blue, while others are more pale, I imagine this has something to do with the amount of suspended sediment. I don’t really know, but it sure is interesting! Another strange thing is that I would have expected the streams to be white and the ponds to be blue. I am not sure why this inversion is taking place so if anyone has a suggestion I’d love to hear it! Maybe it has something to do with how cloudy it was, I’m not sure. Normally, in when rock flour laden stream enter a lake the lake is blue and the streams are white. Both colours are due to the suspended rock flour, but the colours are inverted here and I don’t know why….

The moraine and the mixing ponds (Photo: Matt Herod)

The moraine and the mixing ponds (Photo: Matt Herod)

By the way, I am starting to run out of photos for this weekly series! I need to get out in the field more, but sadly I am trapped in the lab for most of this summer doing data collection. Therefore, if you have any photos you would like to see highlighted in the photo of the week let me know in the comments below, along with your email, and we can set something up. Otherwise, I’ll have to start posting pictures of plants soon!

Cheers,

Matt

Geology Photo of the Week #13 – Nov 25-Dec 1

So the 13th photo of the week is this sweet as pic of boiling mud from New Zealand’s North Island. Both photos were taken by me in July of 2009. I had to stand at the ready for quite a while to try and get good pictures of the bubbles bursting and there were many failed attempts. On the whole I think I did pretty well.

(Photo: Matt Herod)

(Photo: Matt Herod)

Hope you like them! By the way, stay tuned for some an awesome guest post later this week.

Cheers,

Matt

Geology Photo of the Week #9 – Oct 21-27

Check out this wicked awesome rock!!

This awesome formation is aptly known as “Split Apple Rock”. It is probably one of the more unique rock formations that I have seen. It is located in Abel Tasman National Park in New Zealand’s South Island. As the with the Pancake Rocks post a few weeks ago I was in the area for a conference and was touring around afterwards. Split Apple Rock is composed of granite.

The theory on its formation is an interesting one. From what I have been able to discover online, which is very limited,  the consensus is that this formation had a glacial origin and that it formed due to freeze-thaw fracturing, although I am not sure that this fully explains it. I realize that this area was glaciated, however, I would think erosion by sea spray on an already existing fracture could make something like this too. If you know more about this rock please comment or simply state your opinion!! Meanwhile, enjoy the pictures.

Cheers,

Matt

Geology Photo of the Week #7 – Oct 7-13

Sorry this post is a bit late…the Thanksgiving holiday was Monday, class this morning and then hockey! Anyway,  for the 7th edition of Photo of the Week we travel to the Pancake Rocks, in Punakaiki on the west coast of New Zealand’s South Island. I was there in 2011 for a conference in Wellington and went travelling around afterwards.  One of my stops was here. The Pancake Rocks are made of 30 million year old limestone that is very finely laminated. The daily pounding of the surf has led to the amazing convoluted structures in the picture. As to the formation of the Pancake Rocks themselves I cannot find a definitive answer…some sources claim that they are interbedded lime mud and coarser material. Others state that they contain stylolites. Unfortunately, I don’t remember from my own visit which is the case…although I feel like I would remember if it were stylolites so I am inclined to believe the bedding view. Plus the beds seem too regularly spaced for stylolites.  Does anyone else have a definitive answer?

Thanks for reading and let me know which hypothesis you support for the formation of the bedding.

Cheers,

Matt

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