LaSalle Park Lake Iroquois Earthcache
{Please stay on the boardwalk and trails while completing the earthcache.}
The posted coordinates bring you to a plaque on the boardwalk that mentions Ancient Lake Iroquois. Here you will see the remaining shoreline of the ancient lake.
Lake Iroquois was a prehistoric lake that existed approximately 13,000 years ago. The lake was essentially an enlargement of the present Lake Ontario. It drained to the southeast, through a channel passing near present day Rome, New York. The Rome Sand Plains has several sand ridges that geologists think were formed at this time. The channel then followed the valley of the Mohawk River to the Hudson River. The lake was fed by Early Lake Erie, as well as Lake Algonquin, an early partial manifestation of Lake Huron, that drained directly to Lake Iroquois across southern Ontario, bypassing Early Lake Erie.
The Lake Iroquois plain is a nearly level terrace, about 2 miles wide, bordering the north shore of Lake Ontario. It slopes up from about 250 feet elevation near Lake Ontario to about 350 feet near the old Lake Iroquois shoreline. Most of the city of Hamilton is built on part of this plain. The level plateau west of the Iroquois gravel bar, which crosses the west part of the city of Hamilton, is here named the Westdale plain. It is the westward extension of the Iroquois plain, which was cut off from Lake Iroquois by the growth of the gravel bar. The Westdale plain slopes from about 320 feet near the middle of the plain to about 330 feet near the margins. Later dissection has removed a large area in the middle of the plain now known as Cootes Paradise. Dundas was built on an alluvial fan of gravel, which has its apex at the base of the Niagara escarpment at an elevation of about 400 feet. The fan slopes gently eastward to about 300 feet elevation. Southwest of Dundas is an area of sharp ridges and valleys cut in till. It is believed that the present surface is primarily a result of stream erosion. So little of the original surface appears to have been preserved that its nature is mostly unknown.
Crustal rebound during and following glacial retreat tilted the Lake Ontario basin towards the southwest. Rising waters built large gravel bars on top of the offshore sand deposits in the Hamilton and Aldershot areas. A protected bay or lagoon, similar to present day Hamilton Harbour, developed west of the gravel bars. Plant and animal remains, which have recently been recovered from deposits of Lake Iroquois in the Hamilton area, include a mammoth tusk, wood, and molluscs. When the St. Lawrence valley became free of ice, Lake Iroquois drained, and the water level dropped much below the present level of Lake Ontario. During this low-water stage, the lagoon deposits near Westdale were deeply eroded by a stream whose mouth was probably several miles east of Hamilton. Possibly the Dundas gravel fan was deposited during this time by Spencer Creek. Gradually the land at the east end of Lake Ontario recovered from its depressed position brought about by the weight of glacial ice that had covered the area, and the outlet down the St. Lawrence valley was raised. This tilting of the basin has continued to the present, reflooding part of the Dundas valley. Another bar has been built across the valley forming Hamilton Harbour. In recent times streams have dissected the till plains and lake deposits distributing sand, silt, and clay on flood plains along their courses. Peat bogs and swamps have developed in the poorly drained depressions in outwash channels. Peat and muck are seldom more than 5 feet thick.
Other Remnant Shorelines
Two ancient shorelines in the Toronto area mark the existence of former lakes. About 2 km inland from the shore a ridge known as the Iroquois Shoreline can be discerned. The old shoreline runs west-east running roughly parallel to Davenport Road just south of St. Clair Avenue West. Further east, the Scarborough Bluffs also formed part of the shoreline of the ancient lake. Another ancient shoreline exists between 2–4 km offshore of Toronto. It is known as the Toronto Scarp and formed the shore of Lake Warren or Admiralty Lake. From Bluffer's Park in Scarborough to just west of Hanlan's Point is an underwater bluff. In New York, Ridge Road and New York State Route 104 run from west to east along a ridge of the old shoreline of Lake Iroquois.
To log a find for this earthcache you must email me the correct answers to the following questions. Please do not post the answers in your log.
(Q-1) What geological period created Lake Iroquois?
(Q-2) What are some current features at the base of the bluff?
(Q-3) Take an elevation reading at the posted coordinates and stage 2 to determine the depth in metres from the shoreline to the base.
(Q-4) Measure the distance of the shoreline in metres from stage 3 to stage 4.