Point Pelee Description Development Sediment Budget Lake Levels Other System Controls Long Point Description Development Sediment Supply Lake Levels Other System Controls

While Long Island in Lake Superior formed from the common oceanic process of longshore drift, Lake Erie's largest barrier systems have a uniquely different origin. As the glaciers receded from east to west across Lake Erie, they left behind piles of debris, called moraines. The moraines mark where the edges of the glaciers paused as they retreated, and there are three major north-southward-trending moraines in Lake Erie: the Pelee Moraine, the Erieau Moraine, and the Norfold Moraine. Sediment accumulated at each of these moraines as lake levels rose, and after the Nipissing "flood", platforms were cut into these sediments. These platforms served as the foundation for barrier system development, which developed where each of the three moraines meets the north and south shorelines of the present-day Lake Erie.


Map of Lake Erie, showing generalized locations of the Pelee, Erieau and Norfolk moraines.
(Modified from Coakley, Haras and Freeman, 1973)
(click to enlarge)

Post-glacial evolution of Lake Erie. (Crowe, Coakley and Ptacek, 1998)
(click to enlarge)
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Point Pelee

Point Pelee and its central marshes. (Photo by Tom Hince)
Description

Of the three large barrier spits in Lake Erie, Point Pelee is the furthest west (Theberge, 1989). A cuspate foreland built by two conjoined barrier spits, it has a large central marsh surrounded by wooded sand ridges and dunes (Crowe, Haras and Freeman, 1973). It covers an area of 50 km2, extends southward 15 km (Coakley, Crowe and Huddart, 1998). Settlement of the spit began in the 1800's, as the land was cleared and the northern marshes were drained for agriculture. The lower 9 km of shoreline is the Point Pelee National Park established in 1918, which is an important resting site for migrating Monarch butterflies (Theberge, 1989). Creation of the park brought lots of recreational traffic (including cabins and hotels), which necessitated conservation measures in 1960, which included eliminating overnight camping, restricting parking, and buying back private land (Crowe, Coakley and Ptacek, 1998).


Map of Point Pelee, Ontario, Canada. (Coakley, Crowe and Huddart, 1998)
(click to enlarge)
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Development

Point Pelee's origins began with the Pelee Moraine, which lies north-south from Point Pelee, Ontario to Lorain, Ohio. As lake levels rose with glacial meltwater, an extensive foreland developed to the south and east of Point Pelee's present location. Lake levels rose abruptly during the time of the Nipissing "flood", and a broad, flat, wave-eroded platform of clay-rich till was formed. This platform was then covered with fine glaciolacustrine sand, forming the base for the spit development. Point Pelee's current central marsh and coalesced barriers appeared around 3,500 years ago (Crowe, Coakley and Ptacek, 1998).


Development of Point Pelee. (Coakley, Crowe and Huddart, 1998)
(click to enlarge)
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Sediment Budget

Point Pelee is fed predominantly by eroding glacial bluffs to the east and west. The western side, however, also receives additional sediment from erosion of the nearshore glacial sediments by storm waves, which transport them to shore. While Point Pelee is outbuilding on the west, the eastern side is plagued by a destructive eastern wind and is eroding (Crowe, Haras and Freeman, 1973).

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Lake Levels

As all locations in the Great Lakes, Point Pelee is subject to changes in sea level due to large-scale and local influences.

  1. Seasonal variations. Like most locations in the Great Lakes, lake levels can fluctuate locally due to spring ice and snowmelt, and the amount of precipitation and evaporation during a given season.
  2. Isostatic rebound. Like Lake Superior, Lake Erie is experiencing faster isostatic rebound on one end of the base than the other. The east side is uplifting more quickly than the west, and since the water's exit to Lake Ontario is also on the east side of the lake, the water is piling up on the west side since it can't exit as quickly. Each location in Lake Erie will experience a different rate of isostatic rebound, and Point Pelee itself sees an uplift of 0.1 mm per year (Crowe, Coakley and Ptacek, 1998).
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Other System Controls
  1. Winds. West and northwest winds are common at Point Pelee, however the most significant waves are produced by east and northeasterly winds. From this direction, a 241.4 km fetch creates an average breaking-wave height of about 3 meters, while significant wave heights in deep-water can reach 8 meters (Crowe, Haras and Freeman, 1973). Winds also contribute to the aeolian transport of sand from the beach to foreshore dunes.
  2. Ice. As is typical of the Great Lakes, Point Pelee has extensive ice over during late winter, which protects the shoreline from winter storms (Crowe, Haras and Freeman, 1973).
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Long Point

Long Point, Ontario, Canada. (Photo by Dave Mickelson)
Description

At 41 km long, Long Point is the largest barrier system in the Great Lakes, extending eastward into the deepest part of Lake Erie. For simplicity of discussion, it can be split up into three different regions: the proximal (close to mainland, 20.5 km of shoreline), central (6.3 km of coast), and distal (lakeward end, 14.2 km of shoreline). The proximal end includes the Long Point Provincial Park and Nature Reserve, Big Creek Marsh, and substantial area of recreational cottages which occupy 6 km of shoreline. At the distal end is a Canadian Wildlife Service reserve, and the remaining area is mostly owned by duck-hunting clubs and left undisturbed (Davidson-Arnott and Fisher, 1992).


Map of Long Point, Ontario, Canada. (Davidson-Arnott and Fisher, 1992)
(click to enlarge)
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Development

Like Point Pelee, Long Point is the result of another north-south-trending moraine, the Norfolk moraine, which joins the southern shore of the lake just west of Presque Isle, Ohio. The Norfolk moraine was covered with glaciolacustrine sediment, and when rising lake-levels broke through the southern part of the moraine near Presque Isle, an elongated cuspate foreland was created. Massive amounts of sand accumulated from littoral drift from the west, and the foreland migrated eastward and northward as lake-levels rose. At the time of the Nissipsing "flood", the foreland submerged, creating a broad sandy shoal, which became the formation platform for Long Point. The platform continued to be reworked by shallow-water wave action, and the present eastward-trending flying spit was formed (Crowe, Coakley and Ptacek, 1998).

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Sediment Supply

The main source of sediment for Long Point also comes from the glacial sediment eroded from bluffs to the west, which experience recession rates of 0.6 to 2.0 meters per year, and contribute 1 million m3 per year of sand. While this may sound like a substantial amount, not all sections of Long Point benefit from the sediment input. Most of the sediment ends up in the distal region, which is prograding south and eastward at a rate of 4 to 7 meters per year. It has a wide beach and many dune ridges which protect the spit and limit overwash (Davidson-Arnott and Fisher, 1992).

However, the proximal and central regions are narrow and are eroding northward due to overwash, inlet formation and aeolian processes. As the wind blows onshore, a significant amount of sediment is transferred landward (3 to 5 m3 per year), much of that during the winter and early spring. Additionally, as the spit progrades, the wide distal end shelters the proximal region from waves that counter the direction of longshore drift, which would allow more sediment to remain in the proximal region's budget (Davidson-Arnott and Fisher, 1992). This leaves the proximal and central regions vunerable to overwash during storms and high lake levels, opening up inlets periodically (Crowe, Coakley and Ptacek, 1998).

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Lake Levels
  1. Storm variations. Because of Lake Erie's shallow depth and the shape of its basin, storms can raise levels more than 2 meters.
  2. Seasonal variations. Spring snowmelt can cause lake levels to fluctuate 0.3 to 0.5 meters seasonally.
Other System Controls
  1. Winds.The prevailing winds at Long Point are from the west and southwest, across the longest fetch of 270 km. This can produce significant wave heights of 1 to 2 meters, and a peak period of 4 to 6 sec., with maximums of 3 meters in height and 8 sec. periods. There is limited wave action from the southeast because of the limited fetch (60 km), but large waves can come from the east-northeast (fetch of 100 km), although their effects are tempered by the deep water at end of spit which limits limits refraction (Davidson-Arnott and Fisher, 1992).
  2. Human intervention. There has been some protection installed on the shoreline near the cottages in the proximal region to prevent the overwash that commonly effects the proximal and distal regions (Davidson-Arnott and Fisher, 1992).
  3. Ice. Long Point is usually protected by ice from December to March (Crowe, Coakley and Ptacek, 1998).
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A COMPARISON OF OCEANIC BARRIER SYSTEMS AND GREAT LAKES BARRIER SYSTEMS
Copyright 2004, Jennifer Bruce