October 19, 2009 at 6:02 am (dragonflies and damselflies, geology)
Tags: bedrock, dolomite, Niagara formation, Bruce Peninsula, Hines emerald, Somatochlora hineana, dolomite prairie
by Carl Strang
Bedrock is the kind of stone found closest to the surface at a particular point on the Earth. In DuPage County our bedrock is a sedimentary rock of Silurian age called dolomite, and it belongs to the Niagara formation. A bit over 400 million years ago this part of North America was a reef-dotted shallow part of the world ocean. Over a period of millions of years, precipitates and microscopic shells, along with some larger life forms, settled to the bottom of the sea and built up a layer of sediment that later solidified into limestone, or calcium carbonate. Later, some of the calcium became replaced with magnesium atoms, changing the rock enough chemically that it was less soluble, and worthy of a new name, dolomite.
DuPage County is part of a ring of Niagara formation bedrock that extends up the west coast of Lake Michigan, forms Wisconsin’s Door Peninsula and the southern boundary of the U.P., wraps around the Canadian side of Lake Huron to divide the main lake from Georgian Bay, continues south to form the Bruce Peninsula jutting into southern Lake Huron, and eventually wraps around northern Ohio and Indiana back into northeast Illinois. Niagara Falls pours over an erosion-resistant edge of this formation, which also has outliers in Missouri and Iowa.
A few years ago I drove around Lake Huron. One of my stops was the tip of the Bruce Peninsula. There, the bedrock is at the surface. It’s possible to get a sense of what our landscape might look like in northeast Illinois if it were not covered by glacial deposits. Instead of being surfaced with crushed dolomite, our trails might run over the raw rock.
A trip to the beach would look quite different.
We might find cliffs.
Though dolomite is not as subject to solution and cave formation as limestone, sea caves might occur where waves pound the shore.
We might even find structures like the “flowerpots” that stand on Flowerpot Island off the Bruce Peninsula tip.
But as it is, there are few places in northeast Illinois where the bedrock reaches the surface.
For example, the dolomite prairies near the Des Plaines River offer rare habitat for the federally endangered Hines emerald, a dragonfly that can live only where Niagara formation dolomite provides the right water chemistry for its crayfish-tunnel-dwelling larvae.
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September 25, 2009 at 6:22 am (birds, botany, geology, insects (other), plant-eating insects, reptiles and amphibians)
Tags: aspen, beauty, Bombus impatiens, Bombus ternarius, bumblebee, false hemlock looper moth, Michigan, Muskallonge Lake State Park, Nepytia canosaria, pileated woodpecker, smooth green snake, Tahquamenon Falls, Upper Peninsula, Whitefish Point
by Carl Strang
In this final chapter of my Michigan vacation account, I will bring together assorted observations of other animals and sights. None of this truly counts as inquiry, except that travel and the exposure it gives us to new places leads us to make comparisons with our familiar environment. Such comparisons often lead to questions and inquiries on down the line.
At Muskallonge Lake, after completing my investigation at the beach, I went for a walk along the state park’s trails.
There were spectacular views of Lake Superior from elevated points, and flocks of migrating songbirds to investigate.
Tahquamenon Falls State Park is named for various waterfalls along the Tahquamenon River. Especially spectacular are the upper falls.
After a summer in which I made good progress in my knowledge of Illinois bumblebees, I was interested to find that in that part of the U.P., as back home, only one common species of short-tongued, generalist bumblebee is active at this point in the season. Here it’s Bombus impatiens; at the tip of the U.P. it was the beautifully marked Bombus ternarius.
B. ternarius is a northern species that does not extend its range down to Illinois.
One of the more charismatic birds that one hears and, sometimes, sees in the north woods is the pileated woodpecker. Here is a tree that has been well worked by that species.
Beauty on a smaller scale, which provided a reminder of the season in transition, took the form of this aspen leaf lying on a trail.
I spent most of my time at Whitefish Point. Here is a small scene I found especially compelling.
As I walked out from the point to the parking lot for the final time, I found an enchanting little animal crossing the trail.
Smooth green snakes occur in many places, but are so well camouflaged that we seldom have the good fortune to see them.
On my final morning at the Tahquamenon Falls campground, I found that a large number of moths had been drawn to the restroom building’s lights.
These were nearly all males of the same species, emerging all at once.
Nepytia canosaria, the false hemlock looper moth, is a common northern species whose larvae feed on a wide range of coniferous species including firs, hemlock, pines and spruces.
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September 23, 2009 at 6:26 am (geology)
Tags: Agawa, bedrock, Canadian shield, continental glacier, glacier, granite, Green Bay lobe, greenstone, hematite, Illinois Beach State Park, Lake Maxinkuckee, Lake Michigan lobe, Muskallonge Lake State Park, Upper Peninsula, Whitefish Point
by Carl Strang
A second goal of my trip to Michigan’s Upper Peninsula last week was to investigate further the stones left by the most recent continental glacier. As I outlined in an earlier series of posts, my vacation trip last year was a pilgrimage into Canada to trace the route of the Lake Michigan lobe of that glacier, which is responsible for the deposits which cover the land in the northeast corner of Illinois. The turquoise line in the map below follows the route I think that lobe followed.
I studied the various categories of bedrock northeast of Lake Superior, chunks of which were picked up by the glacier and now reside where that powerful river of ice left them when it melted away. I found that there appeared to be commonalities in the stones left as drift along the Lake Michigan lobe’s route in Canada, on the Upper Peninsula of Michigan, and in northeast Illinois. Stones northwest of that route in Canada seemed different, and I was curious to see if those differences might hold farther south along the route of the Green Bay lobe, which is the one immediately west of the Lake Michigan lobe. I chose to visit Muskallonge Lake State Park, on the U.P.’s north shore, approximately in the center of the Green Bay lobe’s route, so that I could compare the beach stones there to those at Whitefish Point, at the U.P.’s tip, which was on the route of the Lake Michigan lobe.
It was a foggy day, but a few people were there. Some were gathering stones, a practice which might bias the results.
For instance, it seemed to me that beach stones at Canada’s Agawa Bay, along the Green Bay route, included an unusual number of red granites and greenstones. If these are selectively removed by visitors, the remaining stones might not represent what had been there originally. I certainly found greenstones, and in the following photo two appear.
However, there were very few compared to Agawa Bay. Here is a typical aggregation of Muskallonge stones, representing the Green Bay lobe.
Here is a corresponding photo for Whitefish Point, along the Lake Michigan lobe’s route.
While to my eye there did seem to be more reds and a few more greens at Muskallonge, and a few more grays and browns at Whitefish point, I don’t think the differences would hold up in a proper sampling procedure and statistical analysis. Furthermore, when I bring in a photo from Illinois Beach State Park (below), I am hard pressed to say that it is closer to one U.P. site or the other.
Nevertheless, the two years’ travel and study were enjoyable, and I learned a lot especially from studying the Canadian bedrock. The glacial drift may not provide additional support for the route map shown above, but the scratches on bedrock indicated by the little arrows in the geologists’ original map certainly are consistent with the turquoise line I added after last year’s trip.
Incidentally, there were places at Muskallonge Lake where there were deposits of black sands, I suspect composed of hematite like I found at Lake Maxinkuckee last winter.
The next installation from this trip will be more biological.
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April 5, 2009 at 12:19 pm (geology, methods)
Tags: beach, Culver, cyanobacteria, glacier, hematite, Illinois Beach State Park, iron, iron formation, Lake Maxinkuckee, magnetite, Saginaw lobe, stromatolite
by Carl Strang
Yesterday I described my return to check on a seedling growing near the town park at Culver, Indiana. On the way to the seedling I noticed a black line of material that had been sorted out from the beach sand at the edge of Lake Maxinkuckee.
I don’t remember seeing this at Culver, before, but it reminds me of similar deposits at Illinois Beach State Park that are of finely ground iron minerals. Here’s a close-up of the Culver stripe.
I had no trouble finding a bottle cap in the litter along the lake edge. Sad, that, but it provided the tool I needed. I used it to scoop up some of the black material and carry it back home.
Notice how the mainly quartz sand is revealed beneath the thin layer of black particles. The next stage was to dry out my sample, then see if it would respond to a magnet. My hypothesis was that it would prove to be magnetite or hematite, both black iron minerals, possibly from chunks of banded iron formation in Canada that were picked up by the glacier, deposited in Culver, broken into tiny pieces by glacial and/or wave action, and finally distributed along the beach.
The black powder was strongly attracted to a magnet. Here is the sample after I poured it onto a white card and dragged a magnet beneath it. The sand was left behind.
A close-up shows the particles aligning themselves with the magnetic field.
The particles were not themselves magnetic; they didn’t stick to iron. So, I conclude that they are not magnetite but rather bits of hematite, an iron mineral very common in banded iron formations, and deposited billions of years ago in Canada (in this case; Culver is on the route of the glacier’s Saginaw lobe). During the early days of life on Earth, oxygen was increasing in the atmosphere through the work of stromatolite-forming, photosynthetic cyanobacteria in shallow seas. Iron was abundant, dissolved in the water, but it reacted with the oxygen to form the hematite, which precipitated out to produce iron formation deposits that in recent times have been our important sources of iron ore.
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March 2, 2009 at 2:32 am (botany, geology, mammals, methods)
Tags: cotyledon, Culver, deer, ice fishing, Lake Maxinkuckee, seedling, skunk cabbage, tracking
by Carl Strang
Over the weekend I visited my parents back in my home town of Culver, Indiana. It is located in Marshall County, one of the second row of counties south of the Michigan border, and is south of South Bend. The climate there is a little warmer than in northeast Illinois, but not by much. Still, I hoped for signs of spring on a Saturday afternoon walk. I reached the town park.
Whenever I see the Beach Lodge, in my mind’s ear I hear the sounds of pinball machines, the steel balls bouncing off bumpers and ringing bells. I feel the grit of sand and recall memories of summer odors. On this day, though, the beach was empty of sun bathers and swimmers. A couple of deer had come out of the adjacent woods onto the beach on both previous nights, then turned back.
Lake Maxinkuckee still was frozen, though the edges had melted so that in most places there was just a thin skim of new ice. Sand still was piled where the expanding lake ice had bulldozed it earlier.
A single ice fisherman had found a way onto the thicker ice away from shore.
It turned out he had gotten there at the beach. You can see the tracks of his sled on the sand as he sought a place where thicker ice reached the edge (the tracks are highlighted here because I am facing the sun).
Here is where he took his first steps out.
I went on to the woods, which belong to the Culver Military Academy and are known locally as the “Indian Trails” as they contain footpaths connecting the academy to the town. Near the lake is a small swampy area, and there I found the sign of spring I sought: skunk cabbage flowers.
These are renowned for their ability to metabolize enough heat to grow through snow and cold soil, bringing their flowers within reach of insects that are activated by the warmer early spring days. But I also found something unexpected.
A seedling! I couldn’t identify the species, but clearly a seed had sprouted in February. I don’t remember seeing such a thing this far north before, but maybe I just hadn’t paid close enough attention. It wasn’t jewelweed, which can grow in such places but germinates later and has wider cotyledons. Skunk cabbage? I don’t know. I filed it away as another of those mysteries that sit in the back of the mind as inquiries to be attended, perhaps, later.
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February 5, 2009 at 12:07 pm (geology)
Tags: beauty, snow, tracking, wind
by Carl Strang
We have had a lot of snow on the ground for a long time this winter, it seems. There have been periods when little or no new snow is added, but the wind carves and shifts what is there.
Sometimes that provides a moment when one can pause and admire the beautiful patterns that result.
Cardinals are starting to sing. Spring will come. But there is plenty out there to enjoy right now.
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January 3, 2009 at 12:07 pm (geology, mammals)
Tags: beauty, ice, Lake Maxinkuckee, marsh, Mayslake, muskrat
by Carl Strang
There is a little marsh close to Mayslake’s stream. It once drained into that stream, but the drainage channel was plugged years ago, allowing the marsh to keep its feet wet. Here is the marsh early in December.
Here is the same marsh from a slightly different perspective, after flooding from the late December rain and thaw, followed by a freeze.
A lump in the center of the marsh looks tiny in the photo, but appeared to be the size of a muskrat house. I wanted a closer look, but the ice was too thin. Yesterday, however, I passed by there and thought I’d try again. This time the ice was plenty thick.
I had the good fortune to grow up close to a large lake in northern Indiana, called Lake Maxinkuckee. As kids we learned to read ice and to respect it, but also not to fear it. As long as it was at least a couple inches thick, it would support a person. A shallow marsh that has been freezing for a few days has ice that is easy to read. Marshes have submerged vegetation that is decomposing even in winter, and gases are released by that process. As the ice thickens from the top down, bubbles are trapped at the different levels, providing an easy way to see how thick the ice is.
The resulting patterns are beautiful, and I spent a lot of time just admiring them as I slowly made my way around and across the marsh, constantly checking ice thickness as this was an unfamiliar ice sheet. In places the ice was a good 4 inches thick. Here’s a spot where the original ice fractured as a result of the flood, then became embedded in the thicker new ice along with the inevitable bubbles. This is geology happening in the shortest of time frames.
The mound proved to be a muskrat house.
My comments on ice apply only to ice on still waters. Ice on streams, above springs, or at inlets and outlets is dangerous and not to be trusted.
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December 18, 2008 at 12:41 pm (archeology, geology, history (human))
Tags: Civilian Conservation Corps, dolomite, Fullersburg, Fullersburg history
by Carl Strang
Yesterday I introduced the Civilian Conservation Corps chapter in the history of Fullersburg Woods Forest Preserve. Today I want to describe an abandoned CCC trail that awaits exploration by the adventurous.
The area is on the north side of Salt Creek in the western part of the preserve. Except for a narrow strip of land along the stream bank, and the low triangular area downstream from the Rainbow Bridge (the bridge at the western extremity of the preserve), the north side of Salt Creek still was in private hands in the days of the CCC. They apparently dealt with the challenges posed by this low area of flood plain by piling fill, installing concrete culverts, and cutting into the side of the hill (reinforcing above and below with walls of dolomite slabs) to build a two-branched trail.
That trail now is so overgrown that navigating it provides something of a challenge, but is easier in winter with vegetation down. The trail does not exactly follow the route indicated on the 1937 map. Walking east from Rainbow Bridge, and looking to the right shortly before today’s trail begins to climb the steep hill (the Tinley Moraine), you can see the old elevated trail route punctuated by a concrete culvert.
That elevated fill is well populated with honeysuckle now, but if you follow it you will find it curves left and soon reaches the edge of Salt Creek. The trail there goes along the edge of the creek in both directions, completely outlining the creek edge of that low piece of ground. Following it east (left) you will cross another concrete culvert,
and eventually reach where the abandoned trail climbs up to rejoin today’s trail. As you do, keeping an eye out for poison ivy and stumbling over the trunks of fallen trees, you will note the stacked dolomite wall that reinforced the stream bank to your right,
and the similar retaining wall built into the hillside to your left.
If you accept this challenge, you will be training your eye to detect old human changes to the landscape. That experience will improve your ability to detect such influences in other places you may choose to explore.
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December 17, 2008 at 12:17 pm (archeology, geology, history (human))
Tags: archeology, Civilian Conservation Corps, dolomite, Fullersburg, Fullersburg history, Hilltop Prairie, Lemont quarries, McDowell, trail shelter
by Carl Strang
Fullersburg Woods Forest Preserve was the site of Civilian Conservation Corps camp #V-1668 in the 1930’s. In 1933, in response to the economic calamity of the Great Depression, Franklin Delano Roosevelt started the CCC in the first two months of his presidency. By the end of that year, two camps had been established on forest preserves in DuPage County, at McDowell and Fullersburg. Young (late teens to early twenties) single men moved into the camps, enrolled for 6 months at a time and could extend to 2 years. The camps were run by the army, but the work was directed by foresters and other specialists. At Fullersburg the camp was located at the present Hilltop Prairie. In 1937, the year before the Fullersburg camp closed, a map was prepared that shows a number of structures that had been built or were under construction.
The CCC built the Visitor Center and other buildings I will highlight in some future posting. Today I want to focus on a series of structures, labeled “Trail Shelters” on the 1937 map and represented there by little black rectangles, that no longer stand.
They are not entirely gone, however. Guided by the map, I went to these locations to see if any traces of the shelters remained. In a couple cases I found lines of dolomite blocks in Salt Creek along its edge, right where the shelters are marked on the map. Apparently the dolomite pieces, a common construction material used by the CCC, were the floors of the small shelters and have collapsed into the creek.
In one case more remains. This one, across from the northeast corner of Willow Island, still is well represented by its relatively intact dolomite stream bank foundation, and a concrete post support at one end. You have to pick your way through the woods off trail to find it.
These rocks, quarried at Lemont, transported to Fullersburg, forming part of structures for a time and now scattered, remain to speak to us of the preserve’s history. They also add structure and chemistry to the microenvironments where they now sit, serving as shelter or obstacles to small animals. From the standpoint of the stones their present locations still are fresh and new compared to the hundreds of millions of years of their existence.
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November 20, 2008 at 12:30 pm (birds, botany, geology)
Tags: aster, beaver, black spruce, blueberry, bunchberry, club moss, honeysuckle, lichen, mastodon dig, paper birch, spider, spruce grouse
by Carl Strang
Though my trip to Canada had as its primary goal an exploration of the route of the Lake Michigan lobe of the Wisconsin glacier, an old wildlifer like me was not going to ignore the vegetative communities and wildlife along the way. I was especially interested in what I would find in the highway loop through Timmins and Hearst, Ontario, as I had never been in that area before. It’s far enough north that I passed a sign marking the watershed for rivers flowing north to the Arctic Ocean and those flowing south.
Potholes Provincial Park along Highway 101 had a little trail going to some beautiful places. The trees along the edge of this photo are black spruces, a tree of special interest because we found a couple cones of this species in the mastodon dig this summer (more on that in future posts). Black spruce was the dominant tree in many places this far north, though it no longer occurs closer to Illinois than central Wisconsin.
Kettle Lakes Provincial Park has a great trail system. Here are some photos showing a segment through paper birch,
another past savanna-spaced pines,
a closeup of lichens and a club moss.
There were edible blueberries,
beautiful bunchberries,
asters still flowering in September
but the changing colors of plants such as these honeysuckles revealing the season.
Signs of animal life included a beaver lodge in every little lake,
dew-highlighted spider webs,
and a spruce grouse.
Tomorrow I’ll conclude with wildlife at Nagagamisis Provincial Park.
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