North Shore Highlands
Encyclopedia
Ecoregion
An ecoregion , sometimes called a bioregion, is an ecologically and geographically defined area that is smaller than an ecozone and larger than an ecosystem. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural...
of the U.S. state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...
of Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
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
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
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.
Geography
The North Shore Highlands are part of what once was called the Cabotian Mountains, a name once applied to the highlands north of Lake Superior. They are bounded on the south by the North Shore of Lake SuperiorLake Superior
Lake Superior is the largest of the five traditionally-demarcated Great Lakes of North America. It is bounded to the north by the Canadian province of Ontario and the U.S. state of Minnesota, and to the south by the U.S. states of Wisconsin and Michigan. It is the largest freshwater lake in the...
, from which they rise in rock formations ranging from gentle slopes to sheer cliffs. They extend from the Dalles of the Saint Louis River
Saint Louis River
The St. Louis River is a river in the U.S. states of Minnesota and Wisconsin that flows into Lake Superior. The largest U.S. river to flow into the lake, it is 179 miles in length and starts near Hoyt Lakes, Minnesota. The river's watershed is in area...
in Jay Cooke State Park
Jay Cooke State Park
Jay Cooke State Park is a Minnesota state park located about ten miles southwest of Duluth, just outside the small town of Thomson. Jay Cooke is situated on the St...
on the west near Thomson, Minnesota
Thomson, Minnesota
Thomson is a city in Carlton County, Minnesota, USA, along the St. Louis River. The population was 159 at the 2010 census.Thomson is adjacent to Jay Cooke State Park and is located on the Willard Munger State Trail....
, to the Grand Portage Highlands in the Grand Portage Indian Reservation
Grand Portage Indian Reservation
The Grand Portage Indian Reservation is located in Cook County near the tip of Minnesota's Arrowhead Region in the extreme northeast part of the state. The community was considered part of the Lake Superior Band of Chippewa, but is not a party to the treaties that group signed...
at the easternmost extremity of the state. Between these anchors are
cliffs along the shore such as Silver Creek Cliff, Split Rock
Split Rock Lighthouse State Park
Split Rock Lighthouse State Park is a state park of Minnesota, USA, 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...
, Palisade Head
Palisade Head
Palisade Head is a large rock formation 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...
, and Shovel Point; the Sawtooth Range
Sawtooth Mountains (Minnesota)
The Sawtooth Mountains are a range of low, serrated ridges situated on the North Shore of Lake Superior in the U.S. state of Minnesota, extending about 30 miles from Carlton Peak near Tofte on the west, to Grand Marais on the east.-Description:...
, also lakeside in the central part of the uplands; and the inland Misquah Hills
Misquah Hills
The Misquah Hills are a range of large hills or small mountains in northeastern Minnesota, in the United States. They are located in or near the Boundary Waters Canoe Area Wilderness within Superior National Forest...
to the east, containing Eagle Mountain, the highest point in Minnesota.
Geology
Geologically, the region is part of the southern reaches of the rugged Canadian ShieldCanadian Shield
The Canadian Shield, also called the Laurentian Plateau, or Bouclier Canadien , is a vast geological shield covered by a thin layer of soil that forms the nucleus of the North American or Laurentia craton. It is an area mostly composed of igneous rock which relates to its long volcanic history...
, the core of the North American craton
Craton
A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by...
. The bedrock was created during the Midcontinent Rift, a failed rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
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
Duluth Complex
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...
and North Shore Volcanic Group. Much of these rocks remain exposed, often in prominences which were more resistant to erosion. Mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
intrusion
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
s of gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....
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 basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
ic rocks of the North Shore Volcanics, interpersed 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
Sawtooth Mountains (Minnesota)
The Sawtooth Mountains are a range of low, serrated ridges situated on the North Shore of Lake Superior in the U.S. state of Minnesota, extending about 30 miles from Carlton Peak near Tofte on the west, to Grand Marais on the east.-Description:...
along the lakeshore.
Both the mafic and volcanic rocks have been eroded, leaving the more resistant rock types standing above the surrounded country. Much of that erosion took place in repeated glaciations. The most recent of these glaciations, the Wisconsin
Wisconsin glaciation
The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....
, included the Superior lobe, which passed over the area along the lake basin from the northeast to southwest. This left a terminal moraine
Terminal moraine
A terminal moraine, also called end moraine, is a moraine that forms at the end of the glacier called the snout.Terminal moraines mark the maximum advance of the glacier. An end moraine is at the present boundary of the glacier....
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
Flute (glacial)
A glacial flute is a landform created by the movement of a glacier around a boulder. They are long ridges on the ground parallel to the movement. Examples can be found in many places including Iceland, Alaska and Canada....
" lie between the moraine and the lake; the "Toimi Drumlin
Drumlin
A drumlin, from the Irish word droimnín , first recorded in 1833, is an elongated whale-shaped hill formed by glacial ice acting on underlying unconsolidated till or ground moraine.-Drumlin formation:...
Field" is on the far side of the moraine, just west of the highlands.
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.
Ecology
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, and the region remains heavily forested. Flora are those of a mixed forest, containing both deciduous and coniferous trees.History
Historically, the rugged nature of the terrain limited exploration in pre-industrial times, except where the highlands were pierced by two rivers. The St. Louis River on the western edge gave fur traders and other explorers a route from the Saint Lawrence RiverSaint Lawrence River
The Saint Lawrence is a large river flowing approximately from southwest to northeast in the middle latitudes of North America, connecting the Great Lakes with the Atlantic Ocean. It is the primary drainage conveyor of the Great Lakes Basin...
and Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...
to the watersheds of the Mississippi
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
and Rainy Rivers; 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.
Sources
- "North Shore Highlands Subsection", Ecological Classification System, Minnesota Department of Natural ResourcesMinnesota Department of Natural ResourcesThe Minnesota Department of Natural Resources is the agency of the U.S. state of Minnesota charged with conserving and managing the state's natural resources. The agency maintains areas such as state parks, state forests, recreational trails, and recreation areas as well as managing minerals,...
2010.