The North Shore Highlands are a physiographic and ecological region of the U.S. state of Minnesota in central North America. They were formed by a variety of geologic processes, but are principally composed of rock created by magma and lava from a rift about 1.1 billion years ago, which rock formations are interspersed with and overlain by glacial deposits. Their ecology derives from these origins, with thin, rocky soils supporting flora and fauna typical of their northern, inland location.
The North Shore Highlands are part of what once was called the Cabotian Mountains, a name applied to the highlands north of Lake Superior. [1] They are bounded on the south by the North Shore of Lake Superior, from which they rise in rock formations ranging from gentle slopes to sheer cliffs. They extend from the Dalles of the Saint Louis River in Jay Cooke State Park on the west near Thomson, Minnesota, to the Grand Portage Highlands in the Grand Portage Indian Reservation at the easternmost extremity of the state. [2] Between these anchors are cliffs along the shore such as Silver Creek Cliff, Split Rock, Palisade Head, and Shovel Point; the Sawtooth Range, also lakeside in the central part of the uplands; and the inland Misquah Hills to the east, containing Eagle Mountain, the highest point in Minnesota.
Geologically, the region is part of the southern reaches of the rugged Canadian Shield, the core of the North American craton. The bedrock was created during the Midcontinent Rift, a failed rift which occurred some 1.1 billion years ago. As the continent sundered, magma and lava flowed upward, which cooled into the present-day rock of the Duluth Complex and North Shore Volcanic Group. Much of these rocks remain exposed, often in prominences which were more resistant to erosion. Mafic intrusions of gabbro of the Duluth Complex anchor both ends of the highlands, to the west of Duluth and above Grand Portage Bay to the east. Between them is an area of basaltic rocks of the North Shore Volcanics, interspersed with occasional mafic rocks. These basaltic layers, formed from lava emitted from rift fissures in the center of what is now Lake Superior, subsided in the middle (forming the present lake basin); the edges angle upward from the lake in a serrated series of ridges known as the Sawtooth Mountains along the lakeshore.
Both the mafic and volcanic rocks have been partially eroded, leaving the more resistant rock standing above the surrounded country. Much of that erosion took place in repeated glaciations. The most recent of these glaciations, the Wisconsin, included the Superior lobe, which passed over the area along the lake basin from the northeast to southwest. This left a terminal moraine where the glacier halted, and a ground moraine in other areas once covered by the continental glacier. The terminal moraine, known as the "Highlands Moraine", parallels the lakeshore, and forms the inland hills of the North Shore Highlands. The "Highland Flutes" lie between the moraine and the lake; [3] [4] the "Toimi Drumlin Field" is on the far side of the moraine, just west of the highlands. [4]
The North Shore Highlands therefore are composed of mafic outcroppings and volcanic ridges along the lakeshore overlain in places by a ground moraine, and an inland glacial moraine paralleling that shoreline.
Ecologically, the area is the North Shore Highlands Subsection of the Northern Superior Uplands Section of the Laurentian Mixed Forest Province of Minnesota. Soils are thin and rocky. The region remains heavily forested. Flora are those of the Temperate broadleaf and mixed forests Biome, containing both deciduous and coniferous trees. [3]
The rugged nature of the terrain limited exploration in pre-industrial times, except in two places where the highlands were pierced by rivers. The St. Louis River on the western edge gave fur traders and other explorers a route from the Saint Lawrence River and Great Lakes to the watersheds of the Mississippi and Rainy Rivers via the Savanna Portage; the latter basin could also be reached from the east by the Pigeon River, the main route of the fur brigades to the interior of Upper Canada. [5]
Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
The richly textured landscape of the United States is a product of the dueling forces of plate tectonics, weathering and erosion. Over the 4.5 billion-year history of the Earth, tectonic upheavals and colliding plates have raised great mountain ranges while the forces of erosion and weathering worked to tear them down. Even after many millions of years, records of Earth's great upheavals remain imprinted as textural variations and surface patterns that define distinctive landscapes or provinces.
Split Rock Lighthouse State Park is a state park of Minnesota on the North Shore of Lake Superior. It is best known for the picturesque Split Rock Lighthouse, one of the most photographed lighthouses in the United States. Built by the United States Lighthouse Service in 1910, the lighthouse and some adjacent buildings have been restored and the Minnesota Historical Society operates them as a museum. The 2,200-acre (890 ha) state park offers a unique cart-in campground and scenic trails for hiking, cross-country skiing, and bicycling.
The North Shore of Lake Superior runs from Duluth, Minnesota, United States, at the western end of the lake, to Thunder Bay and Nipigon, Ontario, Canada, in the north, to Sault Ste. Marie, Ontario in the east. The shore is characterized by alternating rocky cliffs and cobblestone beaches, with forested hills and ridges through which scenic rivers and waterfalls descend as they flow to Lake Superior.
Interstate Park comprises two adjacent state parks on the Minnesota–Wisconsin border, both named Interstate State Park. They straddle the Dalles of the St. Croix River, a deep basalt gorge with glacial potholes and other rock formations. The Wisconsin park is 1,330 acres (538 ha) and the Minnesota park is 298 acres (121 ha). The towns of Taylors Falls, Minnesota and St. Croix Falls, Wisconsin are adjacent to the park. Interstate Park is within the Saint Croix National Scenic Riverway and the Ice Age National Scientific Reserve. The western terminus of the Ice Age National Scenic Trail is on the Wisconsin side. On the Minnesota side, two areas contain National Park Service rustic style buildings and structures that are listed on the National Register of Historic Places.
Jay Cooke State Park is a state park of Minnesota, United States, protecting the lower reaches of the Saint Louis River. The park is located about 10 miles (16 km) southwest of Duluth and is one of the ten most visited state parks in Minnesota. The western half of the park contains part of a rocky, 13-mile (21 km) gorge. This was a major barrier to Native Americans and early Europeans traveling by canoe, which they bypassed with the challenging Grand Portage of the St. Louis River. The river was a vital link connecting the Mississippi waterways to the west with the Great Lakes to the east.
Judge C. R. Magney State Park is a state park in the U.S. state of Minnesota, on the North Shore of Lake Superior. It was named for Clarence R. Magney, a former mayor of Duluth and justice of the Minnesota Supreme Court, who was instrumental in getting 11 state parks and scenic waysides established along the North Shore. The park is best known for the Devil's Kettle, an unusual waterfall and rock formation in which half of the Brule River disappears into a pothole.
The geology of Minnesota comprises the rock, minerals, and soils of the U.S. state of Minnesota, including their formation, development, distribution, and condition.
The Midcontinent Rift System (MRS) or Keweenawan Rift is a 2,000 km (1,200 mi) long geological rift in the center of the North American continent and south-central part of the North American plate. It formed when the continent's core, the North American craton, began to split apart during the Mesoproterozoic era of the Precambrian, about 1.1 billion years ago. The rift failed, leaving behind thick layers of igneous rock that are exposed in its northern reaches, but buried beneath later sedimentary formations along most of its western and eastern arms. Those arms meet at Lake Superior, which is contained within the rift valley. The lake's north shore in Ontario and Minnesota defines the northern arc of the rift. From the lake, the rift's eastern arm trends south to central lower Michigan, and possibly into Indiana, Ohio, Kentucky, Tennessee, and Alabama. The western arm runs from Lake Superior southwest through portions of Wisconsin, Minnesota, Iowa, and Nebraska to northeastern Kansas, and possibly into Oklahoma.
Palisade Head is a headland on the North Shore of Lake Superior in the U.S. state of Minnesota. It is within Tettegouche State Park but not contiguous with the rest of that park. Palisade Head is located at milepost 57 on scenic Minnesota State Highway 61 in Lake County, approximately 54 miles (87 km) northeast of Duluth and 3 miles (4.8 km) northeast of Silver Bay.
The glacial history of Minnesota is most defined since the onset of the last glacial period, which ended some 10,000 years ago. Within the last million years, most of the Midwestern United States and much of Canada were covered at one time or another with an ice sheet. This continental glacier had a profound effect on the surface features of the area over which it moved. Vast quantities of rock and soil were scraped from the glacial centers to its margins by slowly moving ice and redeposited as drift or till. Much of this drift was dumped into old preglacial river valleys, while some of it was heaped into belts of hills at the margin of the glacier. The chief result of glaciation has been the modification of the preglacial topography by the deposition of drift over the countryside. However, continental glaciers possess great power of erosion and may actually modify the preglacial land surface by scouring and abrading rather than by the deposition of the drift.
The Duluth Complex, the related Beaver Bay Complex, and the associated North Shore Volcanic Group are rock formations which comprise much of the basement bedrock of the northeastern part of the U.S. state of Minnesota in central North America. The Duluth and Beaver Bay complexes are intrusive rocks formed about 1.1 billion years ago during the Midcontinent Rift; these adjoin and are interspersed with the extrusive rocks of the North Shore Volcanic Group produced during that same geologic event. These formations are part of the Superior Upland physiographic region of the United States, which is associated with the Laurentian Upland of the Canadian Shield, the core of the North American Craton.
The Rove Formation is a sedimentary rock formation of Middle Precambrian age underlying the upper northeastern part of Cook County, Minnesota, United States, and extending into Ontario, Canada. It is the youngest of the many layers of sedimentary rocks which constitute the Animikie Group.
The Great Lakes tectonic zone (GLTZ) is bounded by South Dakota at its tip and heads northeast to south of Duluth, Minnesota, then heads east through northern Wisconsin, Marquette, Michigan, and then trends more northeasterly to skim the northernmost shores of lakes.
The Animikie Group is a geologic group composed of sedimentary and metasedimentary rock, having been originally deposited between 2,500 and 1,800 million years ago during the Paleoproterozoic era, within the Animikie Basin. This group of formations is geographically divided into the Gunflint Range, the Mesabi and Vermilion ranges, and the Cuyuna Range. On the map, the Animikie Group is the dark gray northeast-trending belt which ranges from south-central Minnesota, U.S., up to Thunder Bay, Ontario, Canada. The Gunflint Iron Range is the linear black formation labeled G, the Mesabi Iron Range is the jagged black linear formation labeled F, and Cuyuna Iron Range is the two black spots labeled E. The gabbro of the Duluth Complex, intruded during the formation of the Midcontinent Rift, separates the Mesabi and Gunflint iron ranges; it is shown by the speckled area wrapping around the western end of Lake Superior.
The geology of the Isle of Skye in Scotland is highly varied and the island's landscape reflects changes in the underlying nature of the rocks. A wide range of rock types are exposed on the island, sedimentary, metamorphic and igneous, ranging in age from the Archaean through to the Quaternary.
The geology of Missouri includes deep Precambrian basement rocks formed within the last two billion years and overlain by thick sequences of marine sedimentary rocks, interspersed with igneous rocks by periods of volcanic activity. Missouri is a leading producer of lead from minerals formed in Paleozoic dolomite.
The geology of Wisconsin includes Precambrian crystalline basement rock over three billion years old. A widespread marine environment during the Paleozoic flooded the region, depositing sedimentary rocks which cover most of the center and south of the state.
The geology of the State of New York is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.
The geology of Yukon includes sections of ancient Precambrian Proterozoic rock from the western edge of the proto-North American continent Laurentia, with several different island arc terranes added through the Paleozoic, Mesozoic and Cenozoic, driving volcanism, pluton formation and sedimentation.