Lake Erie

Lake Erie is the fourth-largest lake of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also has the shortest average water residence time. At its deepest point, Lake Erie is 210 feet deep.

Geographic features
Lake Erie (42.2° N, 81.2W) has a mean elevation of 571 feet (174 m) above sea level. It has a surface area of 9,990 square miles (25,874 km2) with a length of 241 statute miles (388 km; 209 nmi) and breadth of 57 statute miles (92 km; 50 nmi) at its widest points. It is the shallowest of the Great Lakes with an average depth of 10 fathoms 3 feet or 63 ft (19 m) and a maximum depth of 35 fathoms (210 ft; 64 m) Because Erie is the shallowest, it is also the warmest of the Great Lakes, and in 1999 this almost became a problem for two nuclear power plants which require cool lake water to keep their reactors cool. The warm summer of 1999 caused lake temperatures to come close to the 85 °F (29 °C) limit necessary to keep the plants cool. Also because of its shallowness, it is the first to freeze in the winter. The shallowest section of Lake Erie is the western basin where depths average only 25 to 30 feet (7.6 to 9.1 m); as a result, "the slightest breeze can kick up lively waves," also known as seiches. The "waves build very quickly", according to other accounts. The region around the lake is known as the "thunderstorm capital of Canada" with "breathtaking" lightning displays. Sometimes fierce waves springing up unexpectedly have led to dramatic rescues; in one instance, a Cleveland resident trying to measure the dock near his house became trapped but was rescued by a fire department diver from Avon Lake, Ohio:

Lake Erie is primarily fed by the Detroit River (from Lake Huron and Lake St. Clair) and drains via the Niagara River and Niagara Falls into Lake Ontario. Navigation downstream is provided by the Welland Canal, part of the Saint Lawrence Seaway. Other major contributors to Lake Erie include Grand River, Huron River, Maumee River, Sandusky River, Buffalo River, and Cuyahoga River. The drainage basin covers 30,140 square miles (78,100 km2).

Point Pelee National Park, the southernmost point of the Canadian mainland, is located on a peninsula extending into the lake. Lake Erie has 31 islands (13 in Canada, 18 in the U.S.), located generally in the western side of the lake. The largest of these is Pelee Island. Partial map of the Lake Erie Islands.

Water levels
Lake Erie has a lake retention time of 2.6 years, the shortest of all the Great Lakes. The lake's surface area is 9,910 square miles (25,667 km2). Lake Erie's water level fluctuates with the seasons, as in the other Great Lakes. Typically, the lowest levels are in January and February and the highest in June or July, although there have been exceptions. The average yearly level varies depending on long-term precipitation. Short-term level changes are often caused by seiches that are particularly high when southwesterly winds blow across the length of the lake during storms. These cause water to pile up at the eastern end of the lake. Storm-driven seiches can cause damage onshore. During one storm in November 2003, the water level at Buffalo rose by 7 feet (2.1 m) with waves of 10–15 feet (3.0–4.6 metres) for a rise of 22 feet (6.7 m). Meanwhile, at the western end of the lake, Toledo experienced a similar drop in water level.


 * Historic High Water. In the summer of 1986, Lake Erie reached its highest level at 5.08 feet (1.55 m) above datum. The high water records were set from April 1986 through January 1987. Levels ranged from 4.33 to 5.08 feet (1.32–1.55 m) above datum.
 * Historic Low Water. In the winter of 1934, Lake Erie reached its lowest level at 1.5 feet (0.46 m) below datum. Monthly low water records were set from July 1934 through June 1935. During this twelve-month period, water levels ranged from 1.5 feet (0.46 m) below the datum to even with the datum.

Geology
Lake Erie was carved out by glacier ice and in its current form is less than 4,000 years old, which is a short span in geological terms. Before this, the land on which the lake now sits went through several complex stages. A large lowland basin formed over two million years ago as a result of an eastern flowing river that existed well before the Pleistocene ice ages. This ancient drainage system was destroyed by the first major glacier in the area, while it deepened and enlarged the lowland areas, allowing water to settle and form a lake. The glaciers were able to carve away more land on the eastern side of the lowland because the bedrock is made of shale which is softer than the carbonate rocks of dolomite and limestone on the western side. Thus, the eastern and central basins of the modern lake are much deeper than the western basin, which averages only 25 feet (7.6 m) deep and is rich in nutrients and fish. Lake Erie is the shallowest of the Great Lakes because the ice was relatively thin and lacked erosion power when it reached that far south, according to one view.

As many as three glaciers advanced and retreated over the land, causing temporary lakes to form in the time periods in between each of them. Because each lake had a different volume of water, their shorelines rested at differing elevations. The last of these lakes to form, Lake Warren, existed between about 13,000 and 12,000 years ago. It was deeper than the current Lake Erie, and its shoreline existed about eight miles (13 km) inland from the modern one. The shorelines of these lakes left behind high ground sand ridges that cut through swamps and were used as trails for Indians and later, pioneers. These trails became primitive roads which were eventually paved. U.S. Route 30 west of Delphos, Ohio, and U.S. Route 20 west of Norwalk and east of Cleveland were formed in this manner. The ancient sand dunes are visible in the Oak Openings Region in Northwest Ohio. There, the sandy dry lake bed soil was not sufficient to support large trees with the exception of a few species of oaks, forming a rare oak savanna.