Flowerpot Island
Flowerpot Island
© Parks Canada

The Niagara Escarpment stretches from Tobermory to Niagara Falls. The Bruce Trail follows it 782 km (486 miles) from Little Tub to Queenston Heights.

The islands of Fathom Five National Marine Park are part of the same formation which straddles the Great Lakes, stretching like the rim of a great stone platter across south Manitoulin Island and around the far side of Lake Michigan, where another peninsula, the Door Peninsula, forms a mirror image of the Bruce at Green Bay.

These rocks are dolomite, formed over 400 million years ago in a warm, shallow sea much like the Gulf of Mexico today, at a time when fish with backbones were the latest thing, and the first primitive land plants were appearing.

Earlier in this century, it was discovered that the earth’s continents are slowly moving over its surface. This phenomenon is known as "plate tectonics," and through its study we have determined that since these rocks were formed our continent has drifted quite a distance over the earth’s surface. Back then, the land around here was down near the equator. It’s moved north and now we're about halfway between the equator and the North Pole.

In those days, twice as long ago as the age of dinosaurs, there were great coral reefs here. The shells of those countless marine creatures, made largely of calcium, built up for millions of years. As the sea slowly dried up, magnesium in the water infiltrated the calcareous ooze, causing it to eventually turn into dolomite, which is similar to limestone but harder.

Submerged Geology

Staff from the Geological Survey of Canada, members of the Ontario Marine Heritage Commitee and Parks Canada staff have been working on a number of submerged geological research projects. Over the past three years many exciting geological features have been studied. Some of the features being studied are indicated below. This is a long term study and further investigations are being planned for next season.


During the side-scan sonar survey of the lake bed, a significant geological feature, known as a pop-up, was located and mapped in the area northeast of Echo Island. Pop-ups are generally attributed to near-surface stress releases in the bedrock. They are also referred to as rock heaves or pressure ridges. This particular pop-up is one of the largest underwater features of its kind found to date in southern Ontario. Running in a northwest-southeast direction, it is approximately 1750 metres (5775 feet) long and rises sharply up to five metres (16.5 feet) high from the generally level lake bed. Along the top of this ridge is a crack, or fissure, which varies from a metre to over 6 metres wide (wide enough at one point that the submersible was able to set right down inside the crack). Mapping and filming is expected to continue in future seasons.

Features like this help scientists to measure the isostatic rebound (the springing back of land-forms after the glaciers melted during their retreat). This rebounding is still occurring today.

Submerged Waterfall

The term "submerged waterfall" has generated much confusion. How can you have a waterfall when no water is falling? Some 10, 000 to 5000 years ago, the melting glaciers were creating the structure of today’s Great Lakes. Water levels have had many major ups and downs, and much of what now lies underwater between the Bruce Peninsula and Manitoulin Island was dry land, except for rivers and "gigantic" waterfalls. Water from the west (Lake Huron) actually drained to the east (Georgian Bay) through at least two large rivers, through the present day North Bay area and down the Ottawa River to the Atlantic Ocean. One of these rivers was located near Middle Island. That portion of the Niagara Escarpment, while submerged today, was exposed and the river plummeted over this portion of the cliff creating at first a "waterfall" and later eroding to become an enormous set of rapids some 800 metres (2640 feet) long, 1000 metres (3300 feet) wide and with a drop of 40 metres (132 feet). It likely carried as much or more water than Niagara Falls does today. Sadly, however (for our tourism potential) the glaciers continued to melt, water levels increased, land forms rebounded and the Great Lakes (as we know them) were formed. Our "waterfall", now submerged under the waters of Georgian Bay, is lost to sight but continues to aid scientists in their reconstruction of the geological history of this area.

Confirming Evidence

Submerged ancient tree
Submerged ancient tree
© Parks Canada

Scientists have long had theories about ancient lake levels, but it’s always nice to find confirming evidence. In several areas of the park, scientists have located the remains of ancient trees still rooted solidly into the lake-bed. These ancient trees have been found at depths from 3 to 43 metres (10 to 142 feet). Carbon 14 dating can accurately determine the age period of these trees. One of the oldest found within Fathom Five National Marine Park was off of Cove Island and was dated at 7490± years B.P. (Before Present.) By comparing the level at which the tree was growing and its age, previous lake levels can be confirmed.

Submerged Prehistoric Shoreline Study

There was a time, back before Egypt’s pyramids had been built, when a land bridge existed between what is now the Bruce Peninsula and Manitoulin Island. This land bridge would have allowed migration of wildlife and the hunters that followed them. By close examination of submerged landforms, such as ancient river beds and lakes, research teams look for potential sites that ancient travellers might have used as encampments.

Members of the Ontario Heritage Committee utilized the SDL-1 submersible in their search for such sites. This study will continue as the research team searches for archaeological evidence of activity by the First Nations along this ancient, now submerged, land bridge.

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Our peninsula is unique in Canada for the wide variety of wildflowers that live here.

This is because for a relatively small bit of land, the Bruce has an unusually rich diversity of habitats, from the rugged cliffs of the Niagara Escarpment, to flat, dry rock plains called alvars, to various types of swampy wetlands.

© Parks Canada

One of our chief claims to fame is the profusion of species of orchids found here. Orchids are not just tropical plants. There are, believe it or not, more than sixty species in Ontario. Approximately 43 are found on the Bruce Peninsula, likely due to the area’s variety of habitats. They are picky plants that often grow along with specific fungi, making orchids almost impossible to transplant. The plant uses the fungus to obtain nutrients and vice versa in a symbiotic relationship.

From mid-May to early June, Flowerpot Island in Fathom Five National Marine Park is the place to go to see the wonderful calypso orchid. A small number of these small, delicate beauties bloom along the island's trails. Also known as fairy slipper, this orchid grows from coast to coast across northern Canada.

If you go out to have a look, remember that many others come to see these flowers every year. Large numbers of people leaving the paths to get a better look or take pictures have caused the destruction of about one-third of the calypsos that were visible from the trails ten years ago, so please view them from the trail!

One of the most unusual of our orchids is the Alaskan rein orchid, which, as its name suggests, is native to Alaska and northwest Canada. The only other places it's found are Anticosti Island in the Gulf of St. Lawrence, and here on the peninsula.

Orchids aren't the only unusual plants on the Bruce. We are also home to about half of the world's dwarf lake iris, and most of Canada's stock of Indian plantain. The peninsula is also home to more than twenty kinds of fern, including the rare northern holly fern. A reminder: it is illegal to remove anything from a national park

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Ancient Forest Discovered

Perhaps the most unusual plant find on the Bruce is the ancient cliff-edge ecosystem discovered by Dr. Doug Larson.

Island Biogeography

The islands of Fathom Five have become worlds apart because of their isolation from the mainland and from each other. Each has its own unique combination of plants and animals.

Cove Island is the largest island, and is close to the other islands and the mainland. Because of this, it has the greatest variety of island wildlife, including deer, bears and rattlesnakes.

On the other hand, Flowerpot Island, which is smaller and more remote, has fewer species. It has no rattlesnakes or bears, for instance. It you visit Flowerpot Island, which is the only island in the park with trails, washrooms, a picnic shelter and camping, you will see a lot of garter snakes, because most of the predators that eat them haven’t managed to get across to the island. You’ll also see red squirrels, but no chipmunks, because chipmunks are hibernators, and are never awake when the ice bridge forms between the mainland and Flowerpot. Red squirrels are active in winter and cross on the ice. They're the cute little fellows that will try to steal your lunch. Please don't feed them as this causes more harm than good (it's also illegal).