The above coordinate will take you to a parking lot that accesses
the Walter Bean Grand River Trail that follows the Grand River from
Cambridge, through Kitchener and ending in Waterloo.
Between 23,000 and 14,000 years ago, the area now known as the
Regional Municipality of Waterloo was covered by glacial ice
hundreds of metres thick.
The glaciers flowed to this area from what is now central Quebec
and northern Ontario, gathering blocks of bedrock along the way. As
the glaciers retreated, they left an assortment of rocks in their
paths. Some of these rocks have distinctive characteristics that
indicate where the glaciers picked them up. Rocks carried here from
areas outside of the Kitchener-Waterloo area are called glacial
erratics. You can see some erratics at the Economical Insurance
Trailway access point. These erratics are composed of the following
material:
MARBLE
Formed by the alteration of limestone under extreme heat and
pressure, a process called metamorphism. It is composed of sugary,
coarse-grained crystals of calcite.
GOWGANDA CONGLOMERATE
Composed of pebbles and boulders cemented by fine-grained, gray
mud.
GNEISS
Metamorphic rock formed about 25 kilometres below the Earth's
surface consisting of dark coloured bands (mica and hornblende) and
light coloured bands (quartz and feldspar) that were originally
straight but have been bent or faulted into a zigzag line.
PILLOW LAVA
Volcanic rock created when molten lava, submerged in water, cooled
rapidly, forming pillow-shaped rocks.
DOLOSTONE
Sedimentary rock created when magnesium in sea water displaces some
of the calcium in limestone to form magnesium carbonate.The holes
in the rock are a characteristic of dolostone.
RUSTY SCHIST
Layered metamorphic rock. It contains shiny flakes of mica and
rusty colour formed from the weathering of iron-rich minerals.
As well, the bedrock that lies beneath the landscape of the
Regional Municipality of Waterloo is layered with the oldest rock
in the bottom layer. First encountered over 600 metres down, this
bottom layer is crystalline rock that includes granite. Above the
crystalline layer lies a succession of shale and limestone layers.
In the Region of Waterloo, you can see shale and limestone rocks
exposed along the banks of the Speed and Grand Rivers in Cambridge.
These rocks contain fossils, indicating that they were deposited in
a warm shallow sea.
After the deposited sediments from this sea hardened, tectonic
forces moulded the Earth's surface above sea level, eventually to
be eroded by the effects of rivers, glaciers and weather. One of
the rivers, an ancestor of the Grand River, flowed southeast
through the southwestern part of the Region of Waterloo towards the
present-day Dundas area where it formed a waterfall as it flowed
over the Niagara Escarpment.
Alternating layers of glacial debris or "till" and layers of stream
and lake sediment were deposited on the bedrock layers during the
Pleistocene epoch. This layering pattern indicates that a milder
climate alternated with the colder glacial climate. A stream
deposit found about 30 metres below the University of Waterloo
campus contained pieces of wood suggesting that a pine and spruce
forest covered this area about 40,000 years ago.
The most recent glacial deposits in this area indicate that about
20,000 years ago, meltwater which was trapped between two ice lobes
deposited sand, gravel and till to form the Waterloo moraine. About
14,000 years ago, as the ice began a final retreat, it left behind
sand and gravel ridges called eskers, sand and gravel hills called
kames (such as the Baden hills and the Chicopee ski hill), and
half-egg-shaped hills of bouldery till called drumlins. Pauses in
the movement of the ice sheets created long, linear mounds and
hills of bouldery till called "end" moraines. Giant chunks of ice
buried in the glacial debris melted to leave water-filled
depressions called kettles, such as Sunfish and Puslinch Lakes.
Over the next 12,000 years, the exposed glacial deposits weathered,
and depressions in the landscape partially filled in with sediments
and vegetative debris, forming the rich soils that attracted the
pioneer settlers to Waterloo County.
As you can see, there is a lot of geologic history in the area,
much of it caused by advancing and retreating glaciers.
To log this EarthCache: Your task is to locate a glacial erratic
along the Walter Bean Grand River Trail and have a picture taken
with the erratic and all of the members in your group. There is a
clue in this posting approximately where on the trail this can be
accomplished. Given the 6 types of erratics that could have ended
up in this area, take an informed guess as to which type of
material your erratic is made from and record this in your log. As
usual, you must also state how many people are in your group.