I have been a bit lax with the photo’s of the week lately. Sorry about that! Here is a nice one from last year’s field season showing a cute little marmot sitting on an erratic with a great vista behind him.
(Photo: Matt Herod)
The little guy stuck around long enough for me to get a close-up. (Photo: Matt Herod)
Cheers,
Matt
This photo is a bit of a change of pace. This past weekend I was at the cottage (Garden Island, just outside of Kingston, Ontario) and was lucky enough to get pretty close to a Northern Water Snake that slithered over our swimming area. It later approached my girlfriend with a fish in his mouth as well…maybe it wanted to share? I dunno.
Of course, this wouldn’t be a photo of the week without geology so the rock that the snake is an Ordovician limestone that is part of the Black River Group. It is fairly fossiliferous and contains lots of large cephalopods and rugose corals.
A mature Northern Water Snake. They darken as they age. (Photo: Matt Herod)
This particular Nerodia sipedon is about 1m in length so a pretty large example. (Photo: Matt Herod)
We also had a massive Bullfrog move into the garden pond. Hope the snake doesn’t get him! (Photo: Matt Herod)
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.
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)
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
This edition of the photo of the week highlights something I feel that I should have explained a long time ago: my banner photo. The banner photo above is more than just a pretty picture. It actually illustrates, very beautifully, a truly interesting phenomenon that can be encountered in Arctic watersheds. I speak of the aufeis, pronounced oh-fyse, which is the giant sheet of ice covering the river. Aufeis form in one of two ways. The first is when an ice dam forms in a river and water piles up behind it and then overflows and freezes upward creating an aufeis. The second is when aufeis occur at points of groundwater discharge into a river. Groundwater, which has a much higher temperature than surface water during the winter can discharge year-round. Therefore, it continues to discharge even when temperatures are well below freezing. However, when it discharges into the frigid temperature of an Arctic winter it rapidly freezes causing the development of an aufeis at the discharge point, which is the case in the pictures below. It is possible to distinguish the two types of formation by analyzing the stable isotopes of 18O and 2H in the ice to determine its source: groundwater or river water.
A beautiful panorama of the Tombstone Mountains and the North Klondike River with an aufeis on it in May 2010. (Photo: Matt Herod)
Getting a closer look at the aufeis. You can start to see the layering within the ice. (Photo: Matt Herod)
A nice pic showing all of the ice layers within the aufeis. In the past these have been samples for their isotopic composition as part of groundwater studies.(Photo: Matt Herod)
These aufeis are relatively small. Only a few sqaure kilometres max. However, they can grow into massive ice bodies. The largest known is at the Moma River, Siberia and is between 70 and 110 km^2 (Clark and Lauriol, 1997).
One of my all time favourite pictures shoing the Tombstone Mountain range in the fall of 2011. On the left you can see the river and all the braided channels that are covered by the aufeis in the pictures above. (Photo: Matt Herod)
Cheers,
Matt
Clark, I. D., & Lauriol, B. (1997). Northern Aufeis of the Firth River Basin, Northern Yukon, Canada: Insights into Permafrost Hydrogeology and Karst. Arctic and Alpine Research, 29(2), 240–252.
