HEADLINE: Manitoulin Island holds history lessons
BY BACKROADS BILL
For Wild Northerner
A destination can be unusual because it is interesting or different. Manitoulin Island is blessed with incredible natural beauty mainly because of the rocks. Its rocks are oddities. We can learn much from these anomalies. Take the time this fall to experience its uniqueness. Most often you need a guide.
Spirit Island
Follow this through. It is the 172nd largest island in the world and is the 31st largest in Canada. Known as the “Spirit Island”, this island itself has 108 freshwater lakes, some of which have their own islands; in turn several of these ’islands within islands‘ have their own ponds. Lake Manitou is the largest lake in a freshwater island in the world, and Treasure Island in Lake Mindemoya is the largest island in a lake on an island in a lake in the world. These facts alone give the island an atypical introduction.
It is about 130 km long and 50 km wide and its intriguing landscape resulted from the action of ancient rivers and glaciers that altered the soft bedrock. These actions are what make the island distinctive. It is an extension of the Bruce Peninsula and the Niagara Escarpment.
When compared to the granite of the Canadian Shield found in most of Northern Ontario, it is the white quartz and limestone rock and the alvars that make the island the exception. Five hundred million years ago, Paleozoic limestone was deposited in shallow, tropical seas; at the time, over top of the bumpy landscape of the Canadian Shield. Slowly the island was buried by these limestone sediments made from millions of sea shell pieces.
The accumulation of the invertebrates’ hard parts after their deaths generated the sediment; all of this hardened into the limestone features. Limestone is a hard sedimentary rock consisting of calcium carbonate, formed by the deposition of plant and animal remains on the sea floor and is thus known as a calcareous rock. You are standing at the bottom of a sea. Limestones often contain the visible remains (fossils) of shells and corals, and this is another feature of the island. The rocks here are different.
Clints and Grikes
Alvars, (a Swedish word), are globally rare, naturally open habitats with either a thin covering of soil or no soil over a base of carbonate rock, such as limestone and dolostone; another reason why Manitoulin is unique. The rock is easily dissolved by water in its many forms through a process of karstification or karst landforms. Most of the features on the island likely formed it the last 15,000 years following the last glaciation period.
The alvar vegetation community developed on many of the island’s bedrock barrens. It is a rare and sensitive ecosystem that is not found outside the Great Lakes basin. Juniper bushes and herbaceous plants such as grasses and sedges are typical of the alvar plant community. This delicate ecosystem manages to eke out a living under extreme and fluctuating conditions of temperature, moisture and poor soils.
When you visit you will see a great deal of almost flat-lying, smooth pavement, linked to the movements of the glaciers. Soils are thin or almost non-existent. Because of the softness, the pavements cracks form and become increasingly dissected. These collect soil and plants take root. The sparsely vegetated bedrock barrens that develop are in fact the alvars.
I contacted one of the three authors of ‘Manitoulin Rocks!’.
Peter Russell is the Curator for the Earth Sciences Museum at the University of Waterloo. Their aim was to present a ’simplified account‘ of the geological history and to present interesting and unusual facts. It is a guide book you will want to have before visiting.
And Peter knows his rocks. The ‘Peter Russell Rock Garden,’ named in his honour is the best outdoor space on campus. While originally created to commemorate the 25th anniversary of the University of Waterloo in 1982, this educational and beautiful university landmark located in the heart of campus has grown steadily over the years to contain over 70 large specimens of rocks and minerals.
Of particular interest on the island are the clints and grikes. Due to the solubility of limestone, found everywhere on Manitoulin, limestone pavements are associated with some very curious and unusual landforms. The most characteristic surface feature of limestone pavements is their division into blocks, called clints, bounded by deep vertical fissures known as grikes.
Water dissolves the stone, enlarging joints and bedding planes. On the surface, the chemical weathering widens and deepens cracks to form grikes. This leaves exposed blocks of limestone. called clints, and the resulting pattern of blocky rock is called a limestone pavement. A limestone pavement is a natural karst landform consisting of a flat, incised surface of exposed limestone that resembles an artificial pavement. The term is mainly used in the United Kingdom where many of these landforms have developed distinctive surface patterning resembling paving blocks.
Walkerton Tragedy
“The main action of the most recent glaciers was that it scoured the rock clean off any superficial cover that formerly may have lain on the surface, thus exposing and smoothly polishing the underlying bedrock which we know today as the largest classic karst limestone pavements on the island. The grikes average about 13 cm or so across. As the fractures widen through dissolution, the ground water flows to the water table. The importance of recognizing such passageways in bedrock cannot be overstated, because they bear on locating landfills, sewage treatment and management of livestock manure,” Russell said.
Russell explained the tragic events at Walkerton, situated on the limestone laden Bruce Peninsula.
“In May, 2000 water movied quickly through the fractured bedrock of clints and grikes, and, combined with subsequent lack of chlorination caused an outbreak of E.coli (Escherichia coli) bacteria in the town’s water supply,” he said.
The result was more than 2300 cases of gastrointestinal disease and eventually seven deaths. It was attributed to farm runoff into an adjacent well that had been known for years to be vulnerable to contamination and to two employees of the Walkerton Public Utilities Commission who could have admitted (falsifying reports) to the contaminated water sooner.
Go for a Visit
The question to Russell was, is there a location that represents both the alvar community and the karst process?
“There is some beautifully exposed pavement on both sides of the road with excellent development of clint and grike karst,” said Russell. “It is one of my favorite places to visit, especially in October when the maple trees turn red and yellow. The trees are short bonsai-like due to the lack of soil.”
This location is found at N45° 43’ 38.8” W82° 14’ 43.4” or WGS 84 17 T E403094 N5064519.
It is found north of Providence Bay, off Highway 551 (SW corner of Mindemoya Lake). Highways 551 and 542 merge in Mindemoya, the village. Turn north on to Monument Rd. (west of Mindemoya) and drive north, 1.5 km; this is quiet country back road, good for parking. It is a wonderful site to see the fractures and a multitude of sensitive ferns, stunted Junipers and exposed dolostone pavement with no topsoil.
And watch out for the erratic rocks, ranging in size from pebbles to huge boulders. These erratics, often rocks of a different type to the limestone, are one of the most visible indicators of glaciation, contrasting the limestone pavement.
There is so much to see on Manitoulin Island including finding trace fossils at Gore Bay and the Cup and Saucer Trail, close to Little Current. And don’t miss Bridal Veil Falls at Kagawong. ‘Manitoulin Rocks!’ is an ideal reference guide for tourists, teachers, students, nature lovers, or anyone else who wants to understand the natural history of this beautiful Island. It contains 131 pages, full colour production including more than 150 original line drawings and photographs. The first half of the book treats a broad range of topics and concepts required to appreciate the geology of Manitoulin Island, using local examples wherever possible. The second half of the book is a detailed field guide to 50 field stops on and north of Manitoulin Island to examine rocks and landforms. Location maps and clear driving directions are provided for each stop. (Pers. Comm. a tip of the hat to the authors, I would give it a “camp badge,” this is how information for visitors should be presented, with GPS coordinates.) You can order it through the Earth Sciences Museum, University of Waterloo ([email protected]) or 519-888-4567 ext.32469 on online.
Most people know a crack when they see one, but that doesn't mean they understand or have thought much about cracks like the clints and grikes of Manitoulin Island. Understanding the Walkerton tragedy through visiting the Manitoulin alvars may prove to be more than just interesting.
Backroads Bill is the founder of the Canadian Ecology Centre and teaches part time at Nipissing University and Canadore College. Contact the author at [email protected] or www.steerto.com ; LIKE on Fbook, Back Roads Bill Steer.
hundred million years ago, Paleozoic limestone was deposited in shallow, tropical seas; at the time, over top of the bumpy landscape of the Canadian Shield. Slowly the island was buried by these limestone sediments made from millions of sea shell pieces.
The accumulation of the invertebrates’ hard parts after their deaths generated the sediment; all of this hardened into the limestone features. Limestone is a hard sedimentary rock consisting of calcium carbonate, formed by the deposition of plant and animal remains on the sea floor and is thus known as a calcareous rock. You are standing at the bottom of a sea. Limestones often contain the visible remains (fossils) of shells and corals, and this is another feature of the island. The rocks here are different.
Look for the Paleozoic invertebrates in the dolostone, some are very well preserved.
Alvars, (a Swedish word), are globally rare, naturally open habitats with either a thin covering of soil or no soil over a base of carbonate rock, such as limestone and dolostone; another reason why Manitoulin is unique. The rock is easily dissolved by water in its many forms through a process of karstification or karst landforms. Most of the features on the island likely formed it the last 15,000 years following the last glaciation period.
The alvar vegetation community developed on many of the island’s bedrock barrens. It is a rare and sensitive ecosystem that is not found outside the Great Lakes basin. Juniper bushes and herbaceous plants such as grasses and sedges are typical of the alvar plant community. This delicate ecosystem manages to eke out a living under extreme and fluctuating conditions of temperature, moisture and poor soils.
When you visit you will see a great deal of almost flat-lying, smooth pavement, linked to the movements of the glaciers. Soils are thin or almost non-existent. Because of the softness, the pavements cracks form and become increasingly dissected. These collect soil and plants take root. The sparsely vegetated bedrock barrens that develop are in fact the alvars.
I contacted one of the three authors of ‘Manitoulin Rocks!’.
Peter Russell is the Curator for the Earth Sciences Museum at the University of Waterloo. Their aim was to present a ’simplified account‘ of the geological history and to present interesting and unusual facts. It is a guide book you will want to have before visiting.
And Peter knows his rocks. The ‘Peter Russell Rock Garden,’ named in his honour is the best outdoor space on campus. While originally created to commemorate the 25th anniversary of the University of Waterloo in 1982, this educational and beautiful university landmark located in the heart of campus has grown steadily over the years to contain over 70 large specimens of rocks and minerals.
Of particular interest on the island are the clints and grikes. Due to the solubility of limestone, found everywhere on Manitoulin, limestone pavements are associated with some very curious and unusual landforms. The most characteristic surface feature of limestone pavements is their division into blocks, called clints, bounded by deep vertical fissures known as grikes.
Water dissolves the stone, enlarging joints and bedding planes. On the surface, the chemical weathering widens and deepens cracks to form grikes. This leaves exposed blocks of limestone. called clints, and the resulting pattern of blocky rock is called a limestone pavement. A limestone pavement is a natural karst landform consisting of a flat, incised surface of exposed limestone that resembles an artificial pavement. The term is mainly used in the United Kingdom where many of these landforms have developed distinctive surface patterning resembling paving blocks.
Clints and Grikes