The City of Cambridge Cambridge • Ontario • Canada

Cambridge hosts a rich diversity of natural heritage features due to its location at the intersection of several major environmental systems. This Natural Heritage Tour is designed to give you an introduction to and description of those systems and features so that you can explore, learn about, enjoy and care for the environment in which we all live.


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The geology of Cambridge, like that of Southern Ontario, is composed of layers of rock and soil material deposited layer upon layer. The older layers are deeper underground and the most recent layers are at the surface. The rocks are what was left behind by major earth-forming events. These events are often separated by long periods with little change. The rock record is not a continuous documentation of all the events that happened.

Often, there are large gaps between events seen in the history of the area's rocks. If we divide the layers into similar types, then there are four important ones.

• Layer One is the oldest, lying deep underground in this area of Ontario, never being exposed. However, it is an important foundation. This layer is known as Canadian Shield rock - the kind of rock that is exposed in 'Cottage Country' north of Barrie. This is some of the oldest rock in the world (544 million to 2.5 billion years old - this time period is called the Proterozoic eon). When this rock was formed by volcanic and tectonic activity and modified by mountain building, there was no life (as we know it now) on earth, other than simple bacteria.

• Layer Two lies on top of this old foundation of Shield rock. We know the time period when it was formed as the Palaeozoic era. During this time, the climate of Cambridge was much warmer. The area was covered by a very warm, shallow sea filled with marine life. We see evidence of this in the rock as fossils left in the sands and clays that settled at the bottom of the sea. This layer of rock is called sedimentary and we see it in the dolomitic limestone cliffs (Site 27 - Riverbluffs Park) along the Grand River. The deposited sediments compressed over a long period of time and became rock. All of this happened between 350 million and 600 million years ago.

• Layer Three is next. This layer lies atop the sedimentary rocks and contains both consolidated rock and unconsolidated earth material. These materials are the glacial sediments eroded within the past 2.5 million years by thick sheets of ice from rocks elsewhere in Ontario and deposited here in Cambridge. Several times in the past million years there was a kilometre thick layer of ice on top of the present day surface of Cambridge. Commonly people think that there was an "ice age" - meaning a single span of time when ice covered the surface. This is a bit misleading because there were several times in the past when ice covered the area. These were separated by warm climate periods called "interglacials". Deposits of sediments from these periods are sandwiched between sediments that were obviously laid down by ice or water from melting ice. The last series of ice ages was known as the Pleistocene (the last million years) and these deposited sediments in thicknesses of 200 metres or more.

• Layer Four lies atop all. It is the layer with which we are most familiar, being the layer that contains the natural landscape. This landscape that was created and sculpted by the last glaciation is greatly altered by human activity. Our cities, roads, parking lots, sewers, power plants, shoreline management, agricultural activity and inhabitation of the area result in changes to the surface that rival the work of the great glaciers of the past. Remember that this upper layer was barren rock and sediment at the end of the last glaciation - approximately 10 to 15 thousand years ago. From that time to the present, plants and animals have moved northward and colonized as the climate warmed and modern temperature and precipitation patterns developed.

Many of the landscape features present in the Cambridge area are still recognizable as those laid down by the ice of the Pleistocene glaciation. The last ice sheet was the Laurentide Ice Sheet which reached its maximum size and thickness about 20,000 years ago when it covered much of northern North America. The ice sheet was irregular in shape and had many finger-like lobes that protruded from its southern boundary. These lobes covered much of the Great Lakes Basin, including Cambridge and the surrounding area. Most remarkable from our perspective are the surface features that resulted from the Huron Lobe, the Simcoe Lobe and the Ontario Lobe. These advanced and retreated over the surface and left behind the drumlins, moraines, eskers, kames, kettles, erratics and till plains that make up our surrounding area.

Drumlins (Site 7) are elongated hills that look like large upturned boats. They tell us the direction of flow of the ice that deposited them.

Moraines (Site 4) are large ridges formed by the dumping or pushing of sediment along the front of ice sheets. Many contain large volumes of sand and gravel and for that reason are often extensively excavated (Site 2 - Churchill Park).

Eskers are winding ridges of sand and gravel that formed in caverns within and beneath the ice. Streams of water flowed in the caverns carrying and depositing sand and gravel. When the ice melted, the esker was left behind as a deposit of well-sorted sand and gravel.

Kames are isolated hills composed of sand and gravel deposited by streams of water that melt from the ice (Site 14 - Schiedel Woodlot).

Kettle lakes (Site 6 - Franklin Pond) formed when blocks of ice buried deep within the glacial materials melted at the end of the last ice age. Overlying materials collapsed to leave craters (kettle holes), which became filled with water. The bottom sediments of many kettle lakes in Southern Ontario preserve pollen and other organisms that are used to determine how climate has changed in the local area.

Erratics are rocks removed by glaciers or ice sheets from the parent source and deposited in another location (Site 13 - Hilborn Knoll).

Till is the mixture of rock and unconsolidated material deposited by the ice sheets. It commonly underlies good farmland because it often has deep rich soil on top. Its great drawback is that if the till is stony the action of freezing and thawing of the soil in winter works large stones and boulders to the surface making it difficult for farmers to till.

Additional earth-shaping processes such as erosion and sedimentation have occurred in the time since the last glaciers retreated. Cambridge is at the junction of two large rivers (the Grand and the Speed) that occupy former channels for glacial meltwaters and have been altered by the action of these rivers.

The two rivers can best be appreciated at:

Site 15 - Hespeler Mill Pond at Ellacott Lookout*
Site 21 - Riverside Park - Speed River Footbridge*
Site 22 - Settler's Fork
Site 23 - Moyer's Landing

These rivers were the lifeblood and reason for the original settlement (pre- and post-European) of the area.

There are also several small streams that flow through Cambridge to join the major rivers. We are very fortunate that these are very high quality streams because of their sources in

sands and gravels and their extensive natural vegetative cover. These streams are best seen at Site 26 Devil's Creek and Site 24 Mill and Blair Creek at Sheave Tower where the sources are cold water all year, supporting the highest quality aquatic systems. Site 8 - Soper Park - Mill Creek Naturalization provides an interesting example of recent work to restore the natural character of a more urban stream.

The varying geology, soils and climate combined to create distinct vegetation types and wildlife habitats that we call ecoregions. Cambridge lies at the southern extremity of the Great Lakes - St Lawrence Forest Region, the Huron Ontario lobe. The natural upland cover of this region is generally dominated by sugar maple, American beech, basswood, white ash, oaks, eastern hemlock and white pine. These communities can be seen at various locations on the tour:

Site 1 - Dumfries Conservation Area
Site 10 - Avenue Road and Shade's Mills Conservation Area
Site 28 - Victoria Park
Site 14 - Schiedel Woodlot

The lowland areas usually contain silver maple, white elm, black ash and white cedar. These can be found at:

Site 12 - Portuguese Swamp
Site 19 - Boxwood Woodlot

Different types of wetland communities (marshes, wet meadows, etc.) can be found at:

Site 16 - Forbes Creek Headwaters
Site 17 - East Creek Headwaters
Site 20 - Riverside Park - Whitney Boardwalk

Because we are close to the next region to the south the Deciduous Forest Region - there are occurrences of a number of species that are common in more southern climates. These are often referred to as "Carolinian". Visit Site 11 - A. Wayne Taylor Park and Site 23 - Moyer's Landing.

There is also a number of unusual habitat types in Cambridge such as the alvar communities developed on shallow soils over limestone at Site 25 - rare and rare prairie plants at Site 2 - Churchill Park and Site 9 - Remnant Prairie Along Railway/Clyde Road.

The Cambridge Natural Heritage Tour will take you to many of the special natural places in the city. You will see evidence of the last glaciation as well as the plants and animals that moved in when the ice sheet retreated for the last time.

The members of the Cambridge Environmental Advisory Committee who developed the tour invite you to visit and appreciate the City's natural heritage.

School, Natural Heritage Tour Route, Sites and Greenspaces in Cambridge
A Natural History of Cambridge