The Slate Islands are a small archipelago in

Lake Superior Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...

, Ontario, Canada, about south of the town of

Terrace Bay Terrace Bay is a township in Thunder Bay District in northern Ontario, Canada, located on the north shore of Lake Superior east of Thunder Bay along Highway 17. The name originates from a series of lake terraces formed as the water level in L ...

. The island group, consisting of 15 islands in total, was created by a

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or Natural satellite, moon. When the ...

impact which formed a crater about wide. In 1985, the

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

government established the Slate Islands as a natural environment provincial park. The islands are notable for having Ontario's largest herd of

boreal woodland caribou The boreal woodland caribou (''Rangifer tarandus caribou''; but subject to a recent taxonomic revision. See Reindeer: taxonomy), also known as woodland caribou, boreal forest caribou and forest-dwelling caribou, is a North American subspecies of ...

Geography

The island group consists of two main islands (Patterson and Mortimer), five minor islands (McColl, Edmonds, Bowes, Delaute and Dupuis islands) and numerous islets. The total surface area is about . The nearby Leadman Group of islands, about east, is often considered part of the Slate Islands. This group includes Leadman, Cape, Spar and Fish Islands.

Human history

Human sites have been found on the islands dating to about 1000CE. A

lighthouse A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a beacon for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mar ...

was built on Patterson Island, the largest island, in 1903 to help ships locate the harbour at the nearby town of

Jackfish, Ontario Jackfish is a ghost town in northern Ontario, Canada, located on the north shore of Lake Superior east of Terrace Bay. The last spike on the Canadian Pacific Railway (CPR) track between Montreal and Winnipeg was driven in west of Jackfish on May ...

. The island is named after William Patterson, a former lieutenant-governor of

Saskatchewan Saskatchewan ( ; ) is a Provinces and territories of Canada, province in Western Canada, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...

. Later, a fishing station was built on McColl Island. The original forests on the islands were modified by logging and

forest fire A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire ...

s. Up until the 1940s, the islands were used to stockpile boomed logs from the mainland Lake Superior north shore for export on

lake freighter Lake freighters, or lakers, are bulk carrier vessels that operate on the Great Lakes of North America. These vessels are traditionally called boats, although classified as ships. Since the late 19th century, lakers have carried bulk cargoes of m ...

s to

pulp Pulp may refer to: * Pulp (fruit), the inner flesh of fruit Engineering * Dissolving pulp, highly purified cellulose used in fibre and film manufacture * Pulp (paper), the fibrous material used to make paper * Molded pulp, a packaging material ...

mills in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. In 1985, the Slate Islands were protected as an Ontario Natural Environment Provincial Park. The islands remoteness is enforced by almost of open, wild, Lake Superior water and its distance from any large communities. It is frequented by naturalists, fishing parties, sailors exploring this Great Lake, and recently by an increasing number of sea kayaking parties.

Fauna

The islands are home to woodland

caribou Reindeer (in North American English, known as caribou if wild and ''reindeer'' if domesticated) are deer in the genus ''Rangifer''. For the last few decades, reindeer were assigned to one species, ''Rangifer tarandus'', with about 10 subspe ...

which migrated by

ice bridge An ice bridge is a frozen natural structure formed over seas, bays, rivers or lake surfaces. They facilitate migration of animals or people over a water body that was previously uncrossable by terrestrial animals, including humans. The most sig ...

from the mainland most recently in 1907. They have been studied extensively from 1974 to 2007 by Dr. A.T. (Tom) Bergerud. The caribou are a classic example of

island biogeography Insular biogeography or island biogeography is a field within biogeography that examines the factors that affect the species richness and diversification of isolated natural communities. The theory was originally developed to explain the pattern of ...

in action; the islands are notable for species that are absent but present on the adjacent mainland (red squirrel, moose, white-tailed deer, and grouse). No ungulates were present on the islands until the caribou arrived in the early 1900s while predators have been present only sporadically. Caribou reached the highest population density in the world on the islands before the 1990s, with the herd estimated at 650 animals.Godwin (1996), p. 3 After a food shortage and die-off in 1990, the numbers were reduced to about 100. In 2012 there were about 200 caribou on the Slate Islands.

Wolves The wolf (''Canis lupus''; plural, : wolves), also known as the gray wolf or grey wolf, is a large Canis, canine native to Eurasia and North America. More than thirty subspecies of Canis lupus, subspecies of ''Canis lupus'' have been reco ...

reached the archipelago in the early 1990s, preying heavily on the caribou, but for reasons not entirely understood, they disappeared a few years later. Wolves are again present on the island since winter 2015/16 (or earlier) as evidenced by aerial observation and scat. The waters surrounding the Slate Islands have been protected from commercial fishing to preserve one of the last native stocks of

lake trout The lake trout (''Salvelinus namaycush'') is a freshwater char living mainly in lakes in northern North America. Other names for it include mackinaw, namaycush, lake char (or charr), touladi, togue, and grey trout. In Lake Superior, it can also ...

in Lake Superior. The Islands have been a source of lake trout brood stock used at the Dorion Fish Hatchery, and fingerlings are planted back to Lake Superior to restore the fishery.

Species

Mammals found on the islands include woodland caribou, grey wolf,

beaver Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers ar ...

muskrat The muskrat (''Ondatra zibethicus'') is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitat ...

snowshoe hare The snowshoe hare (''Lepus americanus''), also called the varying hare or snowshoe rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet. The animal's feet prevent it from sink ...

red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the Order (biology), order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe ...

meadow jumping mouse The meadow jumping mouse (''Zapus hudsonius'') is the most widely distributed mouse in the family Zapodidae. Its range extends from the Atlantic coast in the east to the Great Plains west, and from the arctic tree lines in Canada and Alaska to ...

, and

little brown bat The little brown bat or little brown myotis (''Myotis lucifugus'') is an endangered species of mouse-eared microbat found in North America. It has a small body size and glossy brown fur. It is similar in appearance to several other mouse-ea ...

. Bird species include

American bittern The American bittern (''Botaurus lentiginosus'') is a species of wading bird in the heron family. It has a Nearctic distribution, breeding in Canada and the northern and central parts of the United States, and wintering in the U.S. Gulf Coast ...

bald eagle The bald eagle (''Haliaeetus leucocephalus'') is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle (''Haliaeetus albicilla''), which occupies the same niche as ...

Canada goose The Canada goose (''Branta canadensis''), or Canadian goose, is a large wild goose with a black head and neck, white cheeks, white under its chin, and a brown body. It is native to the arctic and temperate regions of North America, and it is o ...

common loon The common loon or great northern diver (''Gavia immer'') is a large member of the loon, or diver, family of birds. Breeding adults have a plumage that includes a broad black head and neck with a greenish, purplish, or bluish sheen, blackish o ...

great blue heron The great blue heron (''Ardea herodias'') is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North America and Central America, as well as the Caribbean and the Galápagos ...

grey jay The Canada jay (''Perisoreus canadensis''), also known as the gray jay, grey jay, camp robber, or whisky jack, is a passerine bird of the family (biology), family Corvidae. It is found in taiga, boreal forests of North America north to the Tre ...

herring gull Herring gull is a common name for several birds in the genus ''Larus'', all formerly treated as a single species. Three species are still combined in some taxonomies: * American herring gull (''Larus smithsonianus'') - North America * European he ...

red-breasted merganser The red-breasted merganser (''Mergus serrator'') is a diving duck, one of the sawbills. The genus name is a Latin word used by Pliny and other Roman authors to refer to an unspecified waterbird, and ''serrator'' is a sawyer from Latin ''serra'', ...

, and

peregrine falcon The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a Cosmopolitan distribution, cosmopolitan bird of prey (Bird of prey, raptor) in the family (biology), family Falco ...

. Amphibians present include

blue-spotted salamander The blue-spotted salamander (''Ambystoma laterale'') is a mole salamander native to the Great Lakes states and northeastern United States, and parts of Ontario and Quebec in Canada. Their range is known to extend to James Bay to the north, an ...

boreal chorus frog The boreal chorus frog (''Pseudacris maculata'') is a species of chorus frog native to Canada from central Quebec to eastern British Columbia and north to the Northwest Territories and the southern portion of the Yukon.Bee, M. A., Cook, J. M., L ...

Cope's gray treefrog Cope's gray treefrog (''Dryophytes chrysoscelis'') is a species of treefrog found in the United States. It is almost indistinguishable from the gray treefrog ('' Dryophytes versicolor''), and shares much of its geographic range. Both species ar ...

, western

American toad The American toad (''Anaxyrus americanus'') is a common species of toad found throughout Canada and the eastern United States. It is divided into three subspecies: the eastern American toad (''A. a. americanus''), the dwarf American toad (''A. a ...

, northern

spring peeper The spring peeper (''Pseudacris crucifer'') is a small chorus frog widespread throughout the eastern United States and Canada. They prefer permanent ponds due to their advantage in avoiding predation; however, they are very adaptable with respect ...

, and

wood frog ''Lithobates sylvaticus'' or ''Rana sylvatica'', commonly known as the wood frog, is a frog species that has a broad distribution over North America, extending from the boreal forest of the north to the southern Appalachians, with several nota ...

Flora

The cooling effect of

makes the Slate Islands a particularly harsh habitat for its latitude. As a result, islands harbour arctic and alpine plant species such as alpine chickweed (at its most southerly occurrence),Pye (1997), p. 83 '' Dryas drummondii'' (not found again for 1600 km (1000 mi) north), and

alpine bistort ''Bistorta vivipara'' (Synonym (taxonomy), synonym ''Persicaria vivipara'') is a perennial plant, perennial herbaceous flowering plant in the knotweed and buckwheat family Polygonaceae, commonly known as alpine bistort. Scientific synonyms includ ...

, an

Inuit Inuit (; iu, ᐃᓄᐃᑦ 'the people', singular: Inuk, , dual: Inuuk, ) are a group of culturally similar indigenous peoples inhabiting the Arctic and subarctic regions of Greenland, Labrador, Quebec, Nunavut, the Northwest Territories ...

delicacy eaten with seal oil. These arctic disjuncts are reminders of ice ages and associated tundra conditions in this area in the past. Vascular plants found on the islands are: *balsam fir (''Abies balsamea'') *black spruce (''Picea mariana'') *eastern white cedar (''Thuja occidentalis'') *mountain ash (''Sorbus decora'') *trembling aspen (''Populus tremuloides'') *white birch (''Betula papyrifera'') *alpine bistort (''Bistorta vivipara'') *alpine chickweed (''Cerastium alpinum'') *alpine cliff fern (''Woodsia alpine'') *alpine sedge (''Carex glaciali'') *American dune grass (''Leymus mollis'') *American Mountain-ash (''Sorbus Americana'') *Appalachian fir-clubmoss (''Huperzia appalachiana'') *beach pea (''Lathyrus japonicus'') *bird's-eye primrose (''Primula mistassinica'') *black crowberry (''Empetrum nigrum'') *butterwort (''Pinguicula spp.'') *Canadian yew (''Taxa Canadensis'') *common butterwort (''Pinguicula vulgaris'') *creeping snowberry (''Gaultheria hispidula'') *cut-leaved anemone (''Anemone multifada'') *devil's club (''Oplopanax horridus'') *dwarf rattlesnake plantain (''Goodyera repens'') *entire-leaved mountain-avens (''Dryas integrifolia'') *goldie's round-leaved orchid (''Platanthera macrophyll'') *goldthread (''Coptis trifolia'') *heartleaf twayblade (''Listera cordata'') *horned dandelion (''Taraxacum ceratophorum'') *knotted pearlwort (''Sagina nodosa'') *Labrador tea (''Rhododendron groenlandicum'') *lady fern (''Athryium felix-femina'') *large-leaved sandwort (''Moehringia macrophylla'') *leafy lichen (''Peltigera spp.'') *low spike-moss (''Selaginella selaginoides'') *moonwort grape-fern (''Botrychium lunnaria'') *mountain avens/yellow dryas (''Dryas drummondii'') *mountain bladder fern (''Cystopteris montana'') *mountain cranberry (''Vaccinium vitis-idaea'') *mountain clubmoss (''Huperzia selago'') *mountain fir-moss (''Huperzia appalachiana'') *northern meadow sedge (''Carex praticola'') *northern white anemone (''Anemone parviflora'') *northern woodsia (''Woodsia alpina'') *old man’s beard (''Usnea spp.'') *prairie spikemoss (''Selaginella densa'') *prickly rose (''Rosa acicularis)'' *rand's goldenrod (''Solidago simplex ssp. Randii'') *red stemmed feather moss (''Pleurozium schreberi'') *reindeer lichen (''Cladonia rangiferina'') *rock tripe (''Umbilicaria spp.'') *rose twisted stalk (''Roseus streptosus'') *roundleaf shadbush (''Amelanchier sanguinea'') *scirpus sedge (''Carex scirpus'') *smooth woodsia (''Woodsia glabella'') *sphagnum moss (''Sphagnum spp.'') *spike trisetum (''Trisetum spicatum'') *stair-step moss (''Hylocomium splendens'') *viviparous knotweed (''Polygonum viviparum'') *white mountain-saxifrage (''Saxifraga paniculata'') *wild chives (''Allium schoenoprasum var. sibiricum'') *wild sarsaparilla (''Aralia nudicaulis'')

Geology

The islands are not made of

slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. ...

; the rock is mainly of metamorphosed volcanic rocks greater than 2.7 billion years old. Also present are sedimentary rocks of the

Rove Rove may refer to: Places * Le Rove, a commune in the Bouches-du-Rhône department in southern France * Rove, Honiara, a suburb of Honiara, Solomon Islands * Rove, Vojnik, a settlement in the hills east of Frankolovo in the Municipality of Vojnik ...

and

Gunflint Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start fires ...

formations, approximately 1.85-2.10 billion years old. There is evidence that about 1.1 billion years ago, there was volcanic centre on Paterson Island, however almost all volcanic rocks have been removed by erosion.Pye (1997), p. 84 The youngest rocks are

diatreme A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe formed by a gaseous explosion. When magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the ...

s, referring to

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

-filled

volcanic pipe Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are considered to be a type of ''diatreme''. Volcanic pipes are composed of a deep, narrow cone o ...

s that were formed by gaseous explosions. They occur as

dikes Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes ...

or sills which criss-cross the all older rocks types. Also located in the islands are good examples of

shatter cones Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions. They are evidence that the rock has been subjected to a shock with pressures in the ra ...

, rare geological features formed in bedrock by the high velocity shock waves created by meteorite impacts. They have a distinctively conical shape with thin grooves (striae) that radiate from the top (apex) of the cone. The Slate Islands are home to a shatter cone measuring , one of the largest examples in the world (pictured here). Allogenic

is present, notably on the east and north sides of the islands.

Impact crater

The Slate Islands mark the centre of a large

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

. The original crater rim is estimated at about in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...

, but this and most of the crater has subsequently eroded away, leaving the islands which are interpreted as a central uplift. The age of the

impact event An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...

is estimated to be about 450 million years (

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

). Another source estimates the age at 800-500 million years (late

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...

to early

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

).Sharpton, Dressler, (1996), p. 1178 It may be one of several Middle Ordovician meteors that fell roughly simultaneously 469 million years ago, part of a proposed

Ordovician meteor event The Ordovician meteor event was a dramatic increase in the rate at which L chondrite meteorites fell to Earth during the Middle Ordovician period, about 467.5±0.28 million years ago. This is indicated by abundant fossil L chondrite meteorites in ...

, including the

Decorah crater The Decorah crater, also called the Decorah impact structure, is a possible impact crater located on the east side of the city of Decorah in Iowa, United States. It is thought to have been caused by a meteor about wide which struck during the Mi ...

in Iowa, the Ames crater in Oklahoma, and the

Rock Elm crater The Rock Elm Disturbance is an impact crater in Pierce County, Wisconsin, United States, roughly southwest of Menomonie. The disturbance is named for Rock Elm, Wisconsin, a nearby town. Description The meteorite that caused the impact cra ...

in Wisconsin.

Provincial park

The Slate Islands Provincial Park was established in 1985 to protect the biodiversity and provincially significant elements of the natural and cultural landscape, and to maintain the islands' ecology by controlling development and focusing recreational use. While it is a non-operating park, some facilities are available, such as a dock, warm-up shelter, and five backcountry campsites. Permitted activities include boating, camping, canoeing, fishing, and hiking. It is only accessible via boat or floatplane.

References

Bibliography

* * Pye, E.G. (1997). ''Roadside Geology of Ontario: North Shore of Lake Superior'', Ontario GEOservices Centre, ROCK ON Series 2. * Sharpton, V.L. and Dressler, B.O. 'The Slate Islands Impact Structure: Structural Interpretation and Age Constraints', ''Lunar and Planetary Science''. March 1996: vol. 27 * Godwin, L. (February 1996
"Woodland Caribou in Northwestern Ontario - Why they are different..."
''Northwestern Ontario Boreal Forest Management Technical Note TN-07''

External links

*
Aerial exploration of the Slate Islands Impact Crater
{{Ontario parks Impact craters of Ontario Ordovician impact craters Landforms of Thunder Bay District Islands of Lake Superior in Ontario Archipelagoes of Canada