Posts in the Nature Category

Mapping the Driftless Area

· Posted by Joshua in Maps, Nature

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My home is the Driftless Area — a landscape of rugged hills and coulees that unfolds in steep contrast to the plains of the surrounding Midwest. I’ve long wanted a good map of the area’s unique topography, but this desire has been hard to satisfy. The Driftless Area is flung across the borders of Iowa, Illinois, Minnesota, and Wisconsin, so no individual state map covers the whole region. Moreover, while there are a handful of maps out there centered on the Driftless Area, none that I’ve seen show quite what I want. There was just one solution: I would have to make a map of my own. I have no formal training in GIS or cartography, but maps have fascinated me since childhood, and there is no better excuse than ignorance for learning something new. It took some time, but at long last I’ve made the map I’d been looking for.

Map of the Driftless Area

The Making of the Region

The Driftless Area takes its name because it is comparatively free of glacial “drift,” the silt and stone carried elsewhere by ice age glaciers. Though prehistoric ice sheets passed the Driftless Area on all sides, this region mostly escaped the scouring glaciation that flattened the neighboring countryside. As a result, the Driftless Area exhibits a more timeworn terrain, visible on the preceding map as a swath of rough relief stretching from northwest to southeast. For all its hills, the area is not mountainous — its highest elevation, at West Blue Mound in Wisconsin, is only 1,719 feet above sea level. In fact, the Driftless Area was built up from sediment in a shallow Paleozoic seabed. Ever since the region rose out of the sea hundreds of millions of years ago, streams have been eroding deep, fractal-like drainage channels into the land, creating its present rough surface.1

A Map shows that the Wisconsin Glaciation skirted the Driftless Area to the East; the Illinoian Glaciation passed it on the north and south, and the Pre-Illinoian Glaciation cut across the far north and western part of the Driftless Area
Limit of Glaciation around the Driftless Area during the Quaternary Ice Age. This map is based on U.S. Geological Survey Geologic Investigations Series I-2789, “Surficial Deposits and Materials in the Eastern and Central United States,” by David S. Fullerton, Charles A. Bush, and Jean N. Pennell (2004).

During the last 2.5 million years, ice sheets repeatedly advanced and retreated around the Driftless Area. The accompanying map shows the estimated limits of these glacial advances. The most recent glacial maximum, called the Late Wisconsin, can be mapped with great accuracy. In the Late Wisconsin period, ice sheets spanned from Canada to southern Ohio, leaving behind the lakes, drumlins, and moraines that characterize the geography of eastern and northern Wisconsin. Glaciers in this period did not penetrate the Driftless Area, however. Earlier glacial periods are more difficult to map with precision, but it seems clear that the Illinoian Glaciation also passed around the Driftless Area. On the other hand, geologists have unearthed scattered Pre-Illinoian glacial deposits in the western and far northern portions of the Driftless Area. By definition, Pre-Illinoian glaciation took place at least 310,000 years ago. The ice that once encroached into the Driftless Area probably came even earlier — the magnetic polarity of the region’s glacial deposits indicate that they were formed more than 790,000 years before present. As a result, evidence of that early glaciation has had time to mostly erode away.2

The erosion of the Driftless Area was exacerbated by cataclysmic floods that followed each glacial period. During the last glacial phase, meltwater pooled along the northeast periphery of the region, where a combination of ice and hills held back Glacial Lake Wisconsin. The lake created a broad, sandy bed that remains visible today as flat expanse of lowlands across the central part of the state. When this prehistoric lake overcame its constraints, it unleashed floods that eroded the present valleys of the Black River and the Lower Wisconsin River. Similar outpourings of glacial meltwater molded the Chippewa River and Mississippi River valleys. The last retreat of glaciers from Wisconsin between 14,000 and 10,000 years ago established these rivers in their present courses, leaving the Driftless Area essentially in its modern form just as the first humans made their way into the landscape.3

The Making of the Map

Map of the Mississippi River Valley at Trempealeau
Map Detail showing the Mississippi River Valley at Trempealeau. The river cut a section of bluffs away from the others, forming “Trempealeau Mountain” and Perrot State Park in Wisconsin

I wanted my map of the Driftless Area to reveal at a glance the shape of the natural landscape. Human development and labels were less important, as I can find road maps from Yahoo! and Google, and in any case, the cultural features of the Driftless Area tend to rise from their natural surroundings. River valleys such as the Mississippi and Wisconsin doubled as arteries of trade and transportation. Alluvial terraces became building sites for towns and cities like Winona, La Crosse, and Prairie du Chien. Stretches of highland like Military Ridge became thoroughfares linking upland settlements, and prominent features like the Blue Mounds and Trempealeau mountain have long served as landmarks for passersby. A map that makes these natural features visible will therefore expose the foundations of human geography in the region.

After deciding on an emphasis for my map, I needed to collect the geospatial data and software needed to make it. I was able to complete the map with public domain data from U.S. government agencies. To process this data, I relied exclusively on free open source software. GRASS (with GDAL and OCR) did the heavy work of rendering my data sources into graphical map layers, while Inkscape and GIMP aided me with further graphic editing and layer compositing — all on a GNU/Linux operating system.

Land elevation formed the basis for my map. I downloaded local elevation data from the National Elevation Dataset (NED) maintained by the United States Geological Survey. The NED is a raster or grid of elevation measurements spaced at every 1 arc second (1/360th of a degree, or approximately 30 meters) across the entire contiguous United States (other levels of detail, such as measurements at every 1/3 arc second, are also available). I used GRASS to map these elevation measurements in three ways. First, I defined a different color to mark each elevation level — rising from green lowlands to brown uplands. This is a cartographic technique known as “hypsometric tinting,” and it serves to fill the map with color while making it easy to compare the height of distant locations at a glance. Second, I instructed GRASS to draw simulated shadows behind rises of elevation, creating a classic “shaded relief” map. This provides a three-dimensional illusion of the rise and fall of terrain. Finally, in addition to traditional relief shading, I also utilized GRASS to draw subtle “slope shading,” making steeper areas appear slightly darker than flat areas. This outlines hillsides even at angles that standard shaded relief would miss.

As I created these three elevation layers, I also needed GRASS to project my renderings onto a plain — the earth is round, but maps are flat. There is no perfect way to depict the spherical surface of our planet in two dimensions, and as a result cartographers have designed countless map projections that compromise shape or scale in different ways to make the best approximations for different needs. I used the transverse Mercator projection for my map of the Driftless Area, as that projection is ideal for mapping small regions that are longest from north to south. Below are samples of my three elevation renderings — hypsometric tinting, shaded relief, and slope shading — each as a transverse Mercator projection:

Three elevation maps showing hypsometric tinting, relief shading, and slope shading

After mapping elevation, I added a few more elements. Streams are responsible for the erosion that created the Driftless Area’s topography, so I wanted to show water features in as much detail as possible. I was able to obtain outlines of streams and waterbodies from the USGS National Hydrography Dataset and the U.S. Census Bureau’s TIGER mapping service. I also downloaded state and county boundary definitions from the Census Bureau. Although I left out other human features on my map, I included boundaries to serve as a location reference and enable easy comparisons with maps that emphasize man-made features. As before, I rendered both the water features and boundaries as a transverse Mercator projection using GRASS. I then turned to Inkscape to color and pattern each set of features, creating the maps below:

Three vector maps showing water features, county boundaries, and state borders

A Poster of the Driftless Area Map lays spread on an outdoor table, with the landscape of the Driftless Area visible in the background.
The printed Driftless Area Poster outside in the Driftless Area

When I had at last prepared each layer of the final map — state and county boundaries, water bodies, and three renderings of elevation — I used GIMP to stack the layers together. The resulting composite map was shown at the start of this article.

I still was not done. It was not enough merely to pan across the map on my computer screen — the only way to study the whole region in detail would be to order a large format print of the map. A print would need to be as polished and informative as possible, so I went back to the USGS for more data and used GRASS and GIMP to create a map of local glaciation (included in part one of the article) as well as a locator map based on the contiguous United States. I inset these additions onto the main map for added reference value in the final printed version. Finally, I embellished the map with photographs showing four seasons of Driftless Area natural scenery. I sent the design away to be printed, and in a few days, I had the map in my hands as a 24 by 36 inch poster.

How to Get a Copy

This map was made to be shared. You can get the 24 by 36 inch print for yourself by ordering the Driftless Area Map Poster from Zazzle. I wouldn’t hawk the poster if it wasn’t absolutely the best way to see the map in all its detail. A portion of your purchase also helps keep this website alive and free of outside advertising.

Not ready to buy the poster? No worries! I’m also giving the map away as a 1280-pixel JPG for screen viewing. It’s not quite the same as having the print for your wall, but it is free. Just right click on
Download the Driftless Area Map and select the “Save” option from your browser’s context menu.

Notes and References:

  1. Robert H. Dott, Jr., and John W. Attig, Roadside Geology of Wisconsin, (Missoula, Montana: Mountain Press Publishing Co., 2004), pp 119-128, 158.
  2. David S Fullerton, Charles A. Bush, and Jean N. Pennel, “Surficial Deposits and Minerals in the Eastern and Central United States (East of 102 Degrees West Longitude),” U.S. Geological Survey Geologic Investgation Series I-2789, (2004). [http://pubs.usgs.gov/imap/i-2789/]; Dott and Attig, pp 131-134.
  3. James Theler and Robert F. Boszhardt, Twelve Millenia: Archaeology of the Upper Mississippi River Valley, (Iowa City: University of Iowa Press, 2003), pp 19-32; 58-68; Dott and Attig, pp 134, 166-179, 199-205.

The Mississippi Flood: Awash In History

· Posted by Joshua in History, Nature

Note: This article documents flooding that occurred in April 2011. As of May, Prairie du Chien is once more dry and green, and all the parks and historic sites mentioned below are now open for visitors.

The Mississippi River surrounds a log house on St. Feriole Island in Prairie du Chien during the Flood of 2011. The Villa Louis mansion is visible perched on a mound in the far background.

The Father of the Waters is reenacting a familiar natural drama at Prairie du Chien, Wisconsin. Swollen by spring rain and melted Minnesota snow, the Mississippi River will carry over 1.5 million gallons of water past town each second during the peak of the Flood of 2011. While the power of the river is awe inspiring, the latest flood is nothing new. At Prairie du Chien, the Mississippi is immersed in history.

An inch or so of water pools in the grass around the foundations of old Fort Crawford
Floodwater began to seep around the foundations of Fort Crawford on Monday, April 11, 2011.
The two-story blockhouse is a replica constructed in the 1930s. The fence surrounds an excavated stone “prison pit” from the fort that has filled with water.

On April 11, 2011, floodwater began to creep across the foundations of Fort Crawford, one of Prairie du Chien’s most significant archaeological sites. Built in 1816, Fort Crawford was a federal military installation intended to secure control of the Upper Mississippi River for the United States. It was also situated on an island in the middle of a floodplain.

One year after Fort Crawford had been built, Major Stephen H. Long made an inspection of the post. “In regard to the eligibility of the site upon which Fort Crawford is erected,” wrote Long, “very little can be said in favor but much against it. … The site has been repeatedly subject to inundation, which is always to be apprehended when excessive floods prevail in the river.”

Major Long’s apprehensions proved well-founded. In 1823 he returned to Fort Crawford along with William Keating, who noted:

The river bank is here so low and flat, that by a swell which took place in the Mississippi the summer before we visited it, the water rose upon the prairie, and entered the parade, which it covered to the depth of three or four feet; it penetrated into all the officers’ and soldiers’ quarters, so as to render it necessary for the garrison to remove from the fort and encamp upon the neighboring heights, where they spent about a month. The waters having subsided, at the end of that time, they returned to their quarters; the old men about the village say that such an inundation may be expected every seven years.

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A Fall Adventure in the Wisconsin Woods…

· Posted by Joshua in Nature

Because I thought, hey, why not post more leaf photos?

Vine-wrapped tree limbs sprawl out in every direction, with leaves ranging from green and yellow to orange and deep red.
I. Lost in the Leaves: Arts and Crafts Wallpaper has nothing on this.

An Oak Tree branches out high overhead, bearing a mosaic of leaves in yellow, orange, and green.
III. Oaks in the Sky: Could I climb one to meet Jack and go looking for giant’s gold?

Bright yellow leaves make a ceiling over the autumn woods.
II. A Golden Canopy: It’s like discovering El Dorado.

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Four Pictures of October

· Posted by Joshua in Nature

Trees burst with fire-orange leaves into the cool blue sky.

Autumn is the most vivid season. That’s clear enough from the colors, but the visuals are just a veneer on what we actually feel. Autumn is the crisp bite in the air each October dawn. It’s the smell of apple pie in the oven, the taste of sweet squash, the loud crunch of leaves crumbling underfoot. You can’t experience October in Wisconsin with a photograph. You have to go out and live it. Who knows what you’ll find…

A Tuft of Deep Red Leaves against the Blue Sky Bones washed up among the leaves beside a small stream. Leaves of every color at the edge of a Wisconsin forest.

Nodding Trillium

· Posted by Joshua in Nature

A white three-petaled flower tilted toward the ground.

Memories of Summer

· Posted by Joshua in Nature

Three lavender Asters blossom out of a tangle of green leaves which rise over a rocky surface.

I went for a walk this morning. It was -6° Fahrenheit. As I’ve stated before, I like the cold. Even so, I couldn’t help but think back longingly to summer as I hurried down State Street, my fingers turning a rather pretty shade of blue. Summer was just a few months ago, but it seems as though it was a different world. We dressed differently, we spent our time differently, we saw entirely different scenes outside our doors. I took the photograph above on August 31. The pretty scene disguises a greater adventure, for to get that shot I had to hike a few miles, climb some tall rocks, and balance awkwardly with one foot on a steep slope, holding my camera overhead at just the right angle to cut past the weeds towards the lovely Asters you see. I realized later that these flowers were everywhere, and that I could have just taken a picture of them in someone’s flowerbed — but summer wouldn’t have been nearly as fun if I’d just stayed home.

The same thought applies to winter. It is easy on these frigid days of January to think back fondly to August, but I can’t honestly say that winter is any less beautiful. Indeed, some places that are rather ugly in summer become quite aesthetic under a freshly fallen layer of snow. I could never spend winter hiding indoors waiting for the warm weather to return, because I would miss too much. Going through winter without admiring the ice and frost would be like passing the summer without appreciating flowers or thunderstorms. The joy of living in a place like Wisconsin is that we get to pass through all these remarkable worlds just by staying put.

Slender ice crystals coat the branches of a tree like feathers.

A Frosty Morning in January

· Posted by Joshua in Nature

Frosted Valley

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The Oak Tree

· Posted by Joshua in Nature

I took a picture of the Oak Tree…

A crooked oak limb with clusters of bright green leaves rises into the clear sky.

…so you can join me in the shade.

Little Things

· Posted by Joshua in Nature

I don’t usually have an issue with not being able to see the forest for the trees. This afternoon, though, even trees seemed hard to find—I was far too preoccupied with the branches. As I walked into the valley, little things, little ordinary things, kept stealing my attention. Here are a few big pictures of the little things I encountered.

I. Young Pears Still Growing on the Tree

It’ll be a fruitful harvest, in every sense of the word. And what could be better to accompany my favorite artisan cheeses?

Small egg-shaped pears hang abundantly alongside the green leaves of a pear tree.

II. Green Acorns at the Foot of an Oak Tree

I wonder if they fell here during one of the storms we had this week?

A pair of unripe acorns are still connected to a twig lying against the rough bark of an oak tree.

III. Yellow Mushrooms in the Moss

I think these are Cantharellus minor—meaning they’re edible—but I don’t trust my mushroom-identifying skills well enough to taste.

Three tiny toadstool-shaped mushrooms rise out of the leafy moss. Two are bright yellow, the other is shriveled and turning brown.

Zooming in on the small stuff was a refreshing change from the panoramas that surround me at my home atop the ridge, and when I did make my way back up the hill, I realized that upon drawing back from these close-ups, the big view seems even larger. Every grand vista from the top of my hill is made up of a million little scenes like these.

April Flowers

· Posted by Joshua in Nature

I had my first wildflower sighting of the season today, just before Easter. It’s good old Caltha palustris, better known as the Marsh Marigold.

Marsh Marigolds

As their name implies, these plants thrive in wet places. These ones were nestled against rocks and logs at the trickling beginnings of a stream on the family farm. Every year I am amazed to find these flowers blossoming almost as soon as the last snow melts, flowering while the trees are still bare, and shedding their petals for the season before the other plants have gotten two inches from the ground. I think I can understand their impatience. As it is I’m bogged down with books and papers for school, but I wish I could join these marigolds in rising out of the muck and catching some early sunshine. Alas—I’ll just have to wait for May, like all the ordinary flowers.