Tag Archives: meromictic lake

Brampton’s Kettle Lakes

Saturday May 28, 2016

Heart Lake Conservation Area contains two kettle lakes which formed when the last ice age retreated.  Around 20,000 years ago the Wisconsin Ice Age reached it’s maximum with an ice sheet that stretched from Newfoundland to British Columbia and south to Ohio and Illinois.  In the Toronto area the ice was over 1 kilometer thick or about twice the height of the CN Tower.  The advancing ice acted like a giant ice scoop clearing everything in it’s path.  Melting glaciers it deposited this debris in many ways.  Rivers of meltwater carried nearly straight lines known as eskers and the 7 kilometer long Brampton Esker runs south from Heart Lake.  The debris the glacier contained was left behind in the form of outwash.  Sometimes larger chunks of the iceberg would calve away and get buried by the glacial till in the outwash.  Later, when the ice melted it left behind a hole that would fill with water and be known as a kettle lake.  Both Heart Lake and Teapot Lake were formed in this manner and they both take their names from their shapes.  Island Lake near Orangeville is also a kettle lake but it takes it’s name from a former land owner.  On the 1877 county atlas map below Teapot Lake is missing and Heart Lake isn’t drawn in it’s inverted heart shape.

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There are a few free parking places in Donnelley East Park near Sandalwood and Heart Lake Road.  This is the northern trailhead for The Esker Lake Trail which runs south for 8 kilometers.  Walking under Sandalwood Parkway the trail can be shared with more than just pedestrians and cyclists.  This little painted turtle was using the underpass to avoid the traffic above.  The Heart Lake Conservation Area is home to over 250 flora species and 86 fauna, some of them on the protected or endangered lists.

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The trail leads into the conservation area through sections of planted pine forests growing in straight rows.  There are still large tracts of natural cover in the park making it the largest park in Brampton.  Over 8 kilometers of trails are marked out in the park, some for mixed use and some just for hiking.

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Heart Lake was opened as a conservation area in 1957 with it’s kettle lake as a centre piece.  Swimming and fishing are allowed on the lake and a splash pad has been added.  Several thousand rainbow trout are stocked each year and the lake is also home to Largemouth Bass.  Worms are the only live bait allowed in an effort to protect against invading species.

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More recently they have added tree top trekking and zip lining to the list of activities.  The picture below shows the moment of truth for the zip line across the lake.

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The scent of lilacs fills the air for a few weeks each spring.  They are a member of the olive family and are symbols of love in the language of flowers.

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Teapot Lake is another example of a kettle lake but this one was formed by a long thin chunk of ice.  The lake is very deep compared to the surface area and so this is a meromictic lake.  Most lakes have the water stirred up once or twice per year when the water temperature at the surface cools down and the water becomes denser than the water at the bottom of the lake.  This keeps the water at the bottom oxygenated and allows for plant and marine life in the lower reaches of the lake.  These ordinary lakes are known as holomictic.  Teapot lake, at 12 meters, is deep enough that only the top layer mixes annually and the bottom layer remains undisturbed.  The lake drops off in a series of steep terraces that may indicate previous water levels within the lake.  While measuring water temperature and oxygen levels over an extended time period algae began to grow on the chain that held the sensor.  No algae grew below 3.75 meters deep and the lake is dead below this level.  The official plan for the lake is to not allow public usage so that it remains undisturbed.  Wetlands and environmentally sensitive areas surround the lake and all formal trails have been routed well away from it.
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The lake is surrounded by a ring of trees that helps to shelter it and keep it’s record of the past intact.
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Meromictic lakes slowly fill up with sediment and eventually disappear.  Teapot Lake has been collecting silt for a few thousand years and there are several meters in the bottom.  Core samples were taken to look for clues that might reveal the local history around the lake.  The lowest layers of silt, those deeper than about 4 meters, contain a lot of eastern hemlock and spruce pollen.  At a point roughly 5,400 years ago there is a sudden loss of all of this pollen from the sediment.  It is then replaced with beech pollen which is interesting because beech trees are a species that is early in the succession of reforestation.  This time period coincides with the hypsithermal period of global warming and may suggest that an insect outbreak destroyed the forest cover.  Emerald Ash Borer insects are currently visiting a similar destruction by killing 99.9 % of all the ash trees in the GTA.  For the period 500 to 1500 AD there is an increase in fine carbon in the sediment.  This can sometimes mean the presence of a community but there were no other indicators such as the presence of corn pollen.  Corn pollen had led to the discovery of a village of longhouses at Crawford Lake.  Several swamps provide wetland habitat but for some reason were empty of herons.
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 Canada Anemone grows in moist meadows and spreads quickly through underground rhizomes.  A rhizome is a stock or stem of a plant that can send out new roots and shoots from little nodes along it.  Canada Anemone was used by the native peoples as an astringent and to sterilize wounds.
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There is a lot to be explored at Heart Lake Conservation Area but Hiking the GTA is in no way suggesting that you should attempt to go to Teapot Lake.  The picture in the story above and the cover photo are left to preserve the visual record of this little lake.
 A recent review of some popular hikes can be found here.

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The Longhouse People of Crawford Lake

Saturday Nov. 21, 2015

Crawford Lake is one of a handful of meromictic lakes in Ontario and this fact led to the discovery of a pre-contact native village.  It was snowing off and on as I parked in the Crawford Lake conservation area where having correct change would have saved me including a small donation in the envelope.

In the late 1960’s a University of Toronto professor became convinced that Crawford Lake had the characteristics to be a meromictic lake.  Most lakes have the water turn over at least once per year.  As the water cools it becomes denser causing it to sink.  The water at the top mixes with the water at the bottom providing a more even temperature and oxygenation.  In meromictic lakes the surface area is less than the depth and the water doesn’t mix.  In Crawford Lake there are three sections of lake and only the top 15 metres mixes annually.  The middle depth of the lake acts as a buffer while the bottom 9 metres or more never gets disturbed.  This part of the lake is always cold and has no oxygen.  Life doesn’t exist down here and the layers of sediments tell the history of things falling in the lake. Samples taken from the lake bottom revealed 1,000 years of history.  Sediment layers representing the period between 1300 and 1600  have high levels of corn pollen trapped in them in varying concentrations.  This led to the conclusion that an agricultural society had existed near the lake, closer to the shore when the concentrations were higher.  When settlers arrived, cut down the trees and created fields ragweed spread and the upper layers of sediment reflect this.  Crawford Lake is calm in the picture below.

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Local land owners confirmed that they had found artifacts on their properties and when Thomas Howard sold to the conservation authority in 1971 he donated an ungrooved ax or celt he had found here.  It is part of a 10,000 artifact collection that has been uncovered between 1973 and 1989.  The post holes for the frames of 11 longhouses have been discovered and three of these have been reconstructed. Two others have been partially formed including the frame outline seen below.  The positions of the fire pits have been exposed.

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Completed longhouses would have looked like the ones at Crawford Lake except that experts agree there were no ‘panic bars’ on the doors and no little electrical outlets on the outsides.

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It is unknown exactly which peoples lived here.  It may have been the Wendat (Huron) or Attawandaron (Neutral) but either way they were part of the Iroquoian speaking nations and are referred here as Iroquoian for simplicity.  Inside each of the longhouses an individual clan lived. Smaller longhouses may have had 30 people while larger ones up to 100 .  Individual families lived across from each other and shared a common fire.  The lower levels were used to sleep on because they were close to the fire and below the constant smoke.  Upper levels were used for storage with food being hung in the rafters where smoke kept both insect and rodent away.  It is common to find the carbonized remains of food around the fire pits or in the dump sites and these frequently include corn, beans and squash.  For some reason there was no squash found at the Crawford Lake village.

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The art of making stone tools is known as knapping.  It took a great deal of skill to master it but then a piece of chert could be turned into a razor sharp projectile in just 15 minutes.  Along with arrowheads, spear tips, knives and drills were knapped.  Among the findings at the site was a tip known as a turkey-tail arrowhead.  It is out of place by up to 3,000 years suggesting that the idea of collecting antiques may have extended to this culture as well.  The turkey-tail point is displayed along with other arrowheads and is on the tallest shaft in the middle of the picture below.

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Pottery was made by the women and the vessels could be as large as 15 litres.  Each family decorated their pottery in a unique manner that was passed on from mother to daughter. Specific markings on pottery have been used to trace the movements of families and clans over time.  The pottery fragments recovered in the village have been carefully put back together including the 47 pieces of this jug.

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This tract of land was eventually sold to the British Crown to be granted to European settlers and the natives who had lived here for centuries would never return.

Along the Crawford Lake Trail is a series of wood carvings known as the Hide and Seek Trail. Ontario has almost 200 species that are considered to be at risk, seven of which are represented with larger than life wood carvings.  The Eastern Wolf in the carving below is pictured howling, as they commonly do, to communicate within their packs and alert other packs to stay away. They are found in Ontario and Quebec but are now predominantly in Algonquin Park.  They are unable to survive in the small patches of forest left in the more urban parts of the province.

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In 1883 George Crawford bought the lake and 100 acres of land which he transferred it to his son Murray a couple years later.  They operated a saw mill on the south end of the lake to take advantage of the ample timber on the surrounding lands.  In 1898 the name of the lake was changed from Little Lake to Crawford Lake when they opened the Crawford Lake Company. When times were tough during the depression the Crawford family ran a resort on the lake. They also built themselves a cottage and boathouse.  In 1969 the lake and property was sold to the conservation authority and the cottage has since been destroyed.  All that remains is the concrete from the front porch and a set of steps leading down to where the boathouse once stood.

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This cedar tree stands along the side of the trail and is unique in that all three stems are twisted from top to bottom.

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Crawford Lake was formed at the end of the last ice age and has been collecting it’s local history lesson ever since.  Steam was rising off of Crawford Lake even as the snow was falling onto it.

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Crawford Lake Trail and the interpretive reconstruction of the Iroquoian village has been made wheelchair accessible so no one has to miss out.

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I only investigated the village and Crawford Lake Trail but the conservation area contains 7 hiking trails including part of the Bruce Trail.  It looks like you can spend a whole day here and still miss things.

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