Just wanted to share a few images I've taken of Mink Bay at Rock Point over the past few weeks.
One of the more intense storms of the summer. Sudden gusts up to 40mph brought in sheets of rain for about 30 minutes. This was about 5 minutes before it hit
Heiligenschein (German for 'holy light'), that halo of light around radiating out from my head's shadow
Looking out towards the causeway
Been awhile since I posted anything here. I went canoeing a couple weeks ago and spotted a bizarre underwater formation just off the cliffs of the northwest edge of Marble Island in Colchester. It was undoubtedly construct by someone - a square shape with rounded edges about 12' in diameter, with a break in the rocks - an opening? - facing out from shore west towards the bay. It was constructed of dolostone boulders each about the size of a basketball.
A closer look at the object
The water level is already near its annual low (declines throughout summer into the fall, then begins to climb as leaves fall and evapotranspiration shuts down. Of course trends are also contingent on lake freezing over, precipitation, and warm winter days) and even with the lake at record low levels, the person would have had to have been about 7 feet under water. An impressive feat. The question of why they built it is another matter. Not really sure, it's just below and awesome rock that stands above the water by quite a bit. There were a few fishing hooks/line around on the shore so maybe this was built as bait to lure fish in? Maybe just for fun? Maybe a solar sculpture? Not really sure. It's totally inaccessible other than to a couple of private landowners and boats.
What: Sam and went out to the lake yesterday to check in on the progress of the lake freezing over. Boy oh boy did it look frozen all the way across! With the continued cold weather the lake just might be crossable this winter! This would be the first time since 2007. Lake Champlain won't be the only large lake to freeze across. Looks like Superior is on the same trajectory (news story here)!!!
In the afternoon there were people playing hockey out on the ice (specks in bottom left of above photo). Later that evening Jon and I ran out to the light house and followed snowmobile trails. So at least as fall as the break wall, the ice is solidly frozen.
What: When we first arrived at the Thrust Fault, looking north to Apple Tree Bay it appeared as though the bay hadn't frozen entirely on the other side of the bay. In the picture above you can notice the thin strip of darker area that's reflecting the houses and trees in it. I've often noticed this effect when looking across the lake at NY, where the thin strip of land closest to the lake often appears twice as thick, as though in reflection. I'd always kind of unthinkingly attributed this to simply being a reflection of the horizon in the water.
But when we climbed up to the top of the point and changed our perspective, it became quite clear that the bay was indeed completely frozen over and the "reflection" wasn't simply a reflection (the surface of the ice is super rough and not reflective. What was it then?
I had also noticed a thin rippling effect in the air while looking out across the lake. It reminded me of my childhood in Southern California. I loved watching those heat waves dance up off the pavement - the phenomenon of a distorted horizon when looking down a long road in the middle of the desert. As a child I remember seeing the ripples on the road, but I don't remember the reflective quality. I was more than surprised to see those with mid-day temperatures hovering around 0.
I remembered looking into this in regards to the lake a couple of summers ago, but had forgotten the details so wanted a good refresher. The cause of the effect is the same in the winter as in the summer, as the ripples are indeed caused by heat, but it's actually relative heat. The effect, known as an inferior mirage occur when the surface is much warmer than air directly above it. The gradient needs to be about 5degrees per meter (normal atmospheric change is about 1degree of cooling for each 100m you travel up in elevation). While the lake is frozen, it's not super thick ice in parts so the warm water temperature (about 35) heats up the air right above the ice while the ambient temperature was frigid (about 8 on that day). So sufficient temperature gradient to cause the optical illusion!
The refraction occurs only at shallow angles, so as soon as we changed our vantage by going up to the point (as in the photo above), the mirage disappeared and we were left wondering when the rest of the lake would freeze over already!!
What: Winter always makes me remember how I forget about the winter when it's summer. It's hard reconciling the stunted, gnarled growth of the silver maples and white cedars that grow along the edge while sitting on the shore, my feet gently washed by the warm waters lapping up under a lazy summer sun.
But being out during the winter, when spray whipped against the low hanging leaves and branches and supersatured "foggy" air right above the lake freezes into tight icicles, gives clue as to the real limiting factors for planst growing next to the edge. The sacrifice for all that sun is a 2" rind of ice that snaps branches and scouring icy winds that peel away bark.
Icicles were also abundant on the underside of overhangs. The icicles below had formed on a rock that was about 10' off the shore. I assume they formed as snow melted from above and froze as it dripped off the rock (and out of the sun). Supersaturated air condensed onto the little icicles forming the weird lichen-like flakes clinging to the sides (a secondary feature).
Also of note was the stalagtites on the underbelly of the overthrust. The chunky yellowish rock is the much older Dunham dolostone perched atop the scraggly charcoal-colored Iberville Shale. Both weather pretty easily, but the dolostone, a lightly metamorphosed and then aged limestone, is filled with lots of cracks. Because it's a limestone (made of calcium carbonates), it weathers rather easily under the acidity of rain (if you drop hydrochloric acid on a freshly cut surface it will fizz as the acid reacts with calcium carbonate and releases carbon dioxide). In this section, the deep groves in the rock have been exaggerated by acidity over time and the icicles are forming under one of these fissures.
Along the edge of the cliffs the fissures become breaking points where larger rocks fracture off the cliff and plunge into the water. A dramatic event, to be sure, as the more crumbly shale beneath erodes faster, so the dolostone plummets rather than roles to its resting place in the lake. The picture also shows pretty straight geometric lines. The fractures are older than the erosion by acidity, which just expedites the fracturing process. And in places more distant from the cliffes, the fissures form small to occasionally large caverns, called karst topography. Many of the caves in Vermont are located in these calcium-rich, or calcareous, bedrocks.
What: Over the next week I'll be posting photos from an wonderful wander I took out at Rock Point with Crow's Path intern extraordinaire, Brooke and her friend, Alana. I took the above photo after we watched a bald eagle fly around the point. We caught a glimpse of the eagle about an hour later soaring north over Apple Tree Point (look here for more recent sightings of bald eagles in Burlington).
Ecological notes: Ice crystals in the atmosphere cause all sorts of atmospheric disturbance, resulting in beautiful optical effects (like irridescent swaths carved across high altitude cirrus clouds). According to Storm Dunlap's The Weather Identification Handbook (yup, his name is Storm), these sun halos are quite common, occuring on about 1 out of 3 days in Britain and western Europe. Like all rainbow optical illusions, the phenomenon is created by the refraction (scattering of light) traveling through a medium, in this case ice crystals.
sun halo again here on Lone Rock
Conditions that favor appearance of sun halos:
Thin veil of cirrostratus clouds (cirrostratus clouds are among the more common, but least noticed clouds. In part because they are very thin, and often nondescript, just giving the sky a general "milky" wash).
Incoming warm front (often associated with previous bullet) - where was our warm weather??
Winter in continental regions (as opposed to polar regions) where tiny ice crystals drift through the air.
Sun halos form as little ice, in the shape of hexagonal prisms like the ones below (click here for a chart of snow crystal classification and here for a chart relating crystal type to temperature/vapor supply), drift through the air. Under aerodynamic forces, they tend to fall like as leaves do, with their horizontal axis parallel to the ground, or rather, broader surfaces at the bottom, like the prism on the right. When light that passes through two faces joined at a 60/120o angle (as on the left), light is bent at a 22o angle off the straight line. Scattered light appears to us in the halo offset about a hand length's distance from the sun. When light passes through two faces joined at a 90o angle (as on the right) light is offset by 46o and forms a wide arc around the sun. Since the crystals tend to fall horizontally aligned, it is very rare to see a 46o halo.
22o sun halos are not rare, yet they are rarely observed. The reason this common phenomenon goes unnoticed is that the conditions for creating this phenomenon are bright conditions where the clouds are mostly imperceptible, again, that milky white sky. This was particularly true last Thursday with the salt making the roads whiter and bright white snow reflecting all that sunlight making it hard to see much of anything (and indeed at times I regretted not bringing sunglasses).
I exagerrated the colors to bring out the optical illusion.
I was captivated by the way ice was flowing while out at the Causeway. I wanted each clip to run indefinitely, to be lulled by the lake's monotonous drone of wind and water. Nothing dramatic, just the water's quiet dramatization of winter's cold.
What: The Jons, Christin, and I headed out to Colchester to walk the Causeway and see what it would like like with all the snow. I was away for most of the cold weather in December and early January and wanted to see what chance the lake might have of freezing over this year. According to NOAA, the water temperature up around Colchester Point is 34degrees, and since freeze overs don't usually occur until the end of January or beginning of February, I'd say it's looking close.
Jon Bond, our intrepid explorer, testing the resilience of the ice
The covering ice Niquette and Mallet's Bay was stunning. With low visibility it seemed like an endless artic desert. The ice was in stark contrast to the other side of the trail, which was almost entirely open. The Causeway, which forms the barrier between Lake Champlain and Niquette and Mallet's Bay, is an old railroad bed constructed 1899 to open up markets in the Great Lakes. The "fill" is actually large chunks of marble, which supports a few limestone loving trees, like basswood and white cedar.
Above shows a the clear difference in habitat between the more exposed lake and the more sheltered bays. Wind and surface turbulence of the water will draw up relatively warmer water from the depths of the lake buffering the lake from freeze. Water movement can also prevent freezing. Lower winds combined with shallowers depths allowed for the bays to freeze of first. The tongue of unfrozen water on the right side of the above image corresponds to where a bridge creates a break in the buffer and has allowed that stretch to remain unfrozen.
With another polar vortex in full swing and hopefully another couple weeks of subfreezing temperatures, we just might get a freeze over and I just might get to run across the lake. I posted last year about lake freeze over events (it hasn't froze over at the widest part - 9.5 miles from Burlington Bay to Corlaer Bay - in 32 of the past 54 years; and 6 of the last 6 years - since I moved here - it hasn't frozen over).
In the distance there was an oddly geometric island (in the photo above, it's just to the left of the island, but in the distance beyond the ice-locked boat). Turns out to be a (see this photo for what it looks like on a very distant beautiful summer day).
What: I hiked up Snake Mountain with Jon and his family yesterday. Looking out at the southern end of Lake Champlain, I was surprised by how the sharp line at the edge of the ice was. The ice seemed to be corralled into the southern bay, perhaps by the harsh northerly wind. The freezing point I think was between Potash Bay in Addison, VT and Mullen Bay near Westport, NY.
The image to the right shows data collected on the lake between 1816. Rectangles on the left side, colored in red, indicate years in which the lake did not freeze over completely at the widest point (from Burlington Bay across the lake about 9 miles to Corlaer Bay; 6 miles if you don't include the 2 bays).
In total, since data collection began, the lake has not frozen over 38 times in the past 197 years. 32 of these are in the last 54 years! While it might be convenient to readily assume that climate change is the culprit, there might be some confounding factors that have also changed over the past 197 years. Things that lower the freezing point of water could include increased:
Turbidity (suspended solids absorb more heat from sunlight)
Wind
Turbulence (like flow in a river)
Concentrations of salt, alcohol or any other substance that has a lower freezing point than water
I don't know for sure if these have any bearing on the fact that the lake is consistently less likely to freeze over, but they are likely a part of the story. I found an article from Feb 15, 1993 in the Daily Gazette about Lake Champlain closing dates (when it freezes over completely). The article states:
"Whether the lake freezes over or not has no effect on the fish and other creatues that live there, said George LaBar, a UVM fisheries biologist. 'The bays are always going to be frozen, those shallow areas are going to freeze over,' and the fish who live in those bays are used to that, he said. A frozen lake doesn't affect teh overall temperature of the lake water, he said. Winters with less ice cover might encourage fish to spawn earlier, he said, which allows the young fish to grow larger."
I really doubt that the lake not freezing over has no effect. I think it probably means something pretty significant for some things and not so much for others. Complex system with complex feedback loops.
What: I don't think I'll ever be able to fully empathize with a mollusk, well at least not with a bivalve. But I do find them terribly fascinating, which isn't a bad start. And like most things, the more I learn and observe them the more I appreciate their quiet existence. While walking the shoreline at Delta Park, I was caught by the odd swirling groves etched into the sand. I had been spending some time trying to figure out how different water currents would manifest in the topography of the underlying sand - in some patches there were long straight furrows like a recently plowed field, while others had overlapping u-shaped mounds consistent in size for a given patch (see end of video for what I mean). I couldn't help but be distracted by the seemingly chaotic lines that the clams had carved across the ripples.
Ecological notes: While walking barefoot through the shallows, we didn't have to worry much about zebra mussels at Delta Park because the substrate is largely sand. Mussels are a subset of clams (see etymology notes below) that have byssal threads that serve to anchor their shells to a solid substrate - no solid substrates, no mussels. Only in a few places, like where we found heaps of downed trees partly submerged in the water, did we find zebra mussels. We did however find an abundance of freshwater clams. I unburied one, then left it with my camera set to take a picture every minute and a half. The time lapse was shot over about an hour and a half. In the first few seconds you can see the animal expel a mess of waste, which appears to be attached by a string.
There behavior still largely mystifies me. With their large rubbery foot the clams slowly reposition themselves along the shoreline - perhaps following changes in wind direction, water depth, or some other factor. Some of their trails were long slow arcs, others overlapping and confused circles. The groves left behind in the wake of their movement created small eddies in which algae settles. Fresher trails appeared as gray fissures bordered with crusty plates of sand fragmented. I checked some of the same trails after about 12 hours and they looked largely in tact, so I'm guessing it takes some stronger currents to breakdown the trails (and that they move really really slowly).
Smaller bivalves burrowed in sediments. Water level is super low right now
Their trails in the sand (hard to see unless you click on image to see a larger version).
Algae settled in old tracks
Where: Delta Park in Colchester (mouth of the Winooski River).
Etymology notes: The term clam is a muddy one to say the least. A clam could be a bivalve (a mollusk with a pair of hinged, clasping shells) that burrows into sediment - as opposed to a mussel, like a zebra mussel, which attaches itself to a substrate like pilings, other bivalves, whales, or just about anything else with a solid surface. Or a clam could be an umbrella term for all bivalve mollusks (a square is always a rectangle, but a rectangle is not always a square like a mussel is always a clam but a clam not always a mussel). When I called ECHO to ask about help identifying freshwater clams, I was corrected: "freshwater mussels," which further confused the matter since I was referring to bivalves that burrow in the sand. Maybe there's a vernacular understanding of "mussels" as any of those freshwater filter feeders.
Other notes: Not sure about the edibility of the mussels, but they seemed an enticing source of food. Mussels themselves are not toxic, but they are filter feeders so you're essentially eating whatever microscopic stuff is floating down the Winooski or hanging out along the edges of Lake Champlain). Plus I'm not sure what species they are. Vermont's Wildlife Action Plan says that of the 18 species of mussels in Vermont, 13 are listed as threatened, of special concern, endangered, or already extinct (a rate on par with national figures). I used a field guide from Connecticut to try and ID these guys, with little luck. There's another publication UVM has that I plan on checking out to try and narrow it down: Fichtel & Smith's The Freshwater mussels of Vermont. Plus, depending on who you talk to, some species can live 75-200 years. I'd feel bad eating something that old.
What: Tonight while driving to Tractor Supply Callan and I stopped at Overlook Park and were treated to a beautiful sunset. The clouds rolling gently over Juniper Island was so simple and beautiful. Big breath in.
Ecological notes: Some things are so beautiful a naturalist type of explanation seems so paltry in comparison. I will say that looking out over the thin layer of clouds sweeping across the lake reminded me of being back in California. Some early morning hikes in the Santa Monica Mountains took me up the hills out of the fog and above the low marine layer. I could look out over the Pacific Ocean and see only the Channel Islands and occasional peaks in the chain of Santa Monica mountains poking their ancient noses above the clouds.
Here's where it gets nerdy: we get those marine layers in Southern California all the time because the water is relatively cool (particularly near Point Conception in Santa Barbara) and the air often significantly warmer. When you get a really warm air mass moving over a relatively cool body of water. The water cools the air nearest the surface, and as it cools it gets denser, effectively getting trapped beneath the warmer, less dense air above. If the air mass cools enough, water vapor will condense out and form clouds (similar to pushing warm air up a mountian - as it rises it cools and forms clouds, which explains why Camel's Hump is always covered in clouds). This cold layer effect is exacerbated when you have a low pressure system that lifts the warm air and makes the trapped cooler layer thicker (as we did tonight). We just had all that rain and the air was warm (67 when I took the photo) so the air was humid to begin with (87% on weather.com), so all the conditions were right for a cool little marine layer.
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.JPG "Sunset with marine layer over Lake Champlain & Juniper Island")
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