Around Labor Day (when crowds thin out after the start of school) the Boundary Waters can offer a wonderful experience of warm days and cool nights. With the first frost the number of biting insects is reduced, but by the end of September, careful planning and consultations with local resources is important. A paddler taking a last trip of the year late in the season runs the risk of cold, wet, windy weather and even the possibility of opening up a tent flap to find snow.
In an area as large as the BWCA, weather conditions can vary dramatically. Conditions on and near Lake Superior influence the weather across the eastern portion of the BWCA. Temperatures, rainfall, and wind conditions vary, of course, throughout the BWCAW. The following statistics, recorded in International Falls, MN represent historical estimates for the western region of the Boundary Waters Canoe Area.
The weather plays an important role in any camping trip. Learning to identify basic cloud patterns and read the wind conditions are skills worth nurturing. Packing to accommodate a wide range of weather conditions lessens the chance of enduring an unseasonably cold or wet week that just happens to descend during your scheduled trip dates.
Geology
The BWCAW contains some of the oldest exposed rock in the world, estimated to be as old as 2.7 billion years. It is part of the vast region known as the Canadian Shield, which underlies almost 2 million square miles of eastern Canada and the Lake Superior region of the United States. In Minnesota, this belt of ancient exposed rock extends west from the area of Saganaga Lake on the international border through Ely and International Falls to the northwestern part of the state, where the old rocks disappear beneath younger sedimentary deposits. Included in this expanse of ancient rocks are the metavolcanic Ely Greenstone formation, the metasedimentary Knife Lake Group, and great granitic masses like the Vermilion and the Saganaga batholiths.
Lunch on Basswood Lake
A mountain-building period began about 2.6 billion years ago, during which the rocks became metamorphosed and strongly deformed, and the granites were intruded from below into the older rocks. The rocks that had been formed or altered deep within the earth’s crust became exposed at the surface and were then subjected to erosion.
Inland seas covered what we now call the North Woods. Layers of sedimentary rocks were deposited at the bottom of that enormous sea. Called the Animikie Group, these rocks lie in a belt extending westward along the border lakes from Lake Superior to just south of Saganaga Lake, and then reappearing in the Mesabi Range south of the BWCAW. The Animikie rocks include the Pokegama quartzite, the Biwabik iron formation, and a sequence of shales and sandstones. Flint, too, is found in abundance in the vicinity of Gunflint Lake. Rich deposits of iron ore are scattered throughout northeastern Minnesota, upon which mining communities sprung up in the early 20th century. Iron ore became the economic basis for many communities in northeastern Minnesota and it is still one of the most important industries for the state of Minnesota. Iron ore is so concentrated in some places that it will cause a compass needle to be deflected from magnetic north. Magnetic Lake, in fact, received its name because of just such a phenomenon.
The inland seas had long since disappeared and new mountains had risen on the continent when the great ice sheets of the ice ages advanced from the north to cover northeastern Minnesota, eventually turning this mineral-rich region into the world’s best canoe country. During four major periods of glaciation, which began almost 2 million years ago, the glaciers altered the landscape considerably. Evidence of the last glacial advance and recession (the Wisconsin Glaciation, which occurred from about 100,000 to 10,000 years ago) is everywhere in the Boundary Waters today. Parallel grooves, called striations, are visible on many rock ledges that were scoured by the ice. Glacial debris, from small pebbles to huge boulders, is widespread. Here and there, you will see erratics, large boulders that were carried by the glaciers and left off in new locations when the glaciers melted.
Perhaps the greatest distinction of the border lakes area is the presence of exposed bedrock. This region is unlike the rest of Minnesota, which is almost completely covered by glacial deposits. This domination of exposed bedrock in the Boundary Waters resulted in distinctive patterns of lakes and ridges, which reflect the underlying rock structures. In the eastern third of the region, the lakes form a distinctive linear pattern. Long, narrow lakes give the terrain a notable east-west “grain.” These lakes appear in two major types of rock formations. The lakes on the Duluth Gabbro formation, which is exposed over an area from Duluth north and east to the Canadian border, developed their particular pattern because alternating bands of less resistant rock and more resistant rock are oriented east-west. Erosion removed more of the less resistant rock, creating lake basins. In the area where the Rove Lake formation is exposed—along the international border from Gunflint Lake to Pigeon Point (the very tip of the Arrowhead)—the east-west linear pattern has a different cause. In this area intervening ridges separate the lakes. These ridges are the exposed edges of south-sloping layers of dark igneous rock that was intruded into sedimentary rocks after they were deposited. The north-facing slopes of the ridges are very steep and form escarpments 200–500 feet high. Huge piles of talus blocks cover the lower parts of many escarpments, the result of erosion by the advancing glaciers as they passed transversely over the ridges.
The lakes that appear in the Knife Lake group of rocks show a similar linear pattern, but the trend is northeast-to-southwest. In the rocks associated with the Ely Greenstone formation, the pattern is less regular and the depressions in the bedrock are not as deep. Thus shallower lakes are found there.
In the area underlain by the Saganaga Granite the story is a little different. Here the shapes of the lakes are dictated by cracks in the Precambrian rock. As the cracks were made wider by erosion, they became linear depressions that lakes could occupy. Many of the lakes lie in collections of linear depressions oriented in more than one direction, so that the lakes have zigzag shapes. An overhead view of the area reveals many jagged lakes interconnected by linear channels. Saganaga Lake itself is a good example.
Because of ice age glaciation and the characteristic Precambrian rock of northeastern Minnesota, the Boundary Waters Canoe Area, with all of its interconnected lakes and streams, is one of the most extraordinary recreational wilderness areas in the world.
Wind and Fire
The forests, lakes and streams of northeastern Minnesota existed long before Minnesota became a state and the wilderness took on the Boundary Waters Canoe Area Wilderness moniker. Throughout the many centuries of human habitation in the region, people have observed the natural lifecycle of the forest: seedlings sprouting, trees crashing to the earth at their live’s end, wildfires crackling until the fuel runs out or a rainstorm drenches the flames. But rarely have they observed an event like that which occurred on July 4, 1999, when a tremendous windstorm devastated vast areas of the BWCAW. Called a “derecho” by scientists and “the blow down” by concerned paddlers, the storm’s 90-mile-per-hour straight-line winds flattened an area 10 to 12 miles wide and 35 to 40 miles long. The United States Forest Service estimated that 350,000 acres were affected. The Minnesota Department of Natural Resources reported that approximately 80 percent of the trees in the wind’s path fell over or snapped as easily as a camper’s wooden match. Forest Service crews visiting the disaster area found trees jumbled like pick-up-sticks 8 feet deep. Some of the worst damage occurred along lakes described in this book as among the most scenic in the wilderness—including Knife, Kekekabic, and Little Saganaga lakes in the central BWCAW, and parts of the Tip of the Arrowhead region.
Immediately after the storm, dedicated volunteers and crews from the United States Forest Service and Minnesota Department of Natural Resources worked tirelessly to address some of the devastation before winter arrived, but in the years that followed, attention and fears turned to a second and possibly even more devastating disaster: Mile after mile of once lush and now dead trees had turned into tinder