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Lakes and Ponds -- Geology 101
This page describes the formations of most common types of man-made and naturally occuring lakes and ponds.
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Anthropogenic (Man-Made) Lakes
- Farm Pond -- impoundment dug or dammed, or both, for agricultural purposes, or perhaps recreational purposes on a family farm.
- Levee Lake -- formed by levee deposits along a channel or river.
- Ornamental Lake -- a type of reservoir lake, dam-created, exclusively for decorative purposes. Also known as a garden pond.
- Quarry Lake -- formed when water floods the remains of quarrying activities, whether above or below ground. May be a simple as a gravel pit, which is more commonly referred to as a pit lake or simply a pit.
- Recreational Lake -- a type of reservoir lake, dam-created, exclusively for recreational purposes.
- Reservoir Lake -- dam-created lake, either for hydroelectric power, water supply, or other purpose for water impoundment.
- Abandoned Fluvial Channel Lake -- Fluviatile lake in which the outwash channel from a glacier creates a lake.
- Alluvial Fan Dam Lake -- When an alluvial fan completely crosses a valley, blocks a stream or river, and creates an impoundment. Often called simply fan dam lakes.
- Barrier Lake -- Also known as a Shoreline Lake. Lake next to a larger body of water formed when a spit of land, peninsula, etc. connects to land and impounds a lagoon or inlet. Could be a small lake cut off from a large lake, a small lake next to an ocean, sea, or whatever.
- Billabong -- Australian term. When a bend in a river is cut off from the main river at both ends (the river finds a new channel) and an impound remains. Called an Oxbow Lake in North America.
- Cirque Lake -- Lake that forms in a mountain cirque. A cirque is a half-open hollow in a mountain region that appears to have been scooped out with an ice cream scooper. Glacially formed.
- Dead Ice Complex Lake -- Like a kettle lake, but bigger, and usually form as multiple impoundments with narrow strips of earth between. Picture a big chunk of shattered ice, with earth bunched up into the cracks. The ice then melts, leaving a series of nearly connected and connected lakes that are formed in the shape of the ice chunklets.
- Fjord Lakes -- long, narrow, deep lakes seemingly like giant grooves in the bedrock. Walls are bedrock on both sides of the lake.
- Fluviatile Lake -- any lake created as a by-product of an alluvial fan. Alluvial Fan Dam Lakes are a specific type of Fluviatile Lake.
- Glacial Lake -- any lake created by glaciation.
- Glacial Kettle Lake -- also called pothole lakes. Fill surrounded a remnant chunk of glacier, and the ground level built up higher than the bottom of the ice chunk. The ice chunk then melted, leaving a pothole filled with water. In cases where these potholes are not water filled year-round, the formation is simply called a kettle or a pothole.
- Ground Moraine Lake -- permanent water-filled basin, in which the basin was created by ice-age glaciers.
- Ice Lake -- any glacial lake in which permanent ice forms part of the impoundment.
- Landslide Lake -- just like it sounds, a landslide slides down, dams a valley, forms a lake.
- Moraine Lake -- a glacier deposits moraine, which dams up a valley, which results in a lake.
- Oxbow Lake -- when a bend in a river is cut off from the main river at both ends (the river finds a new channel) and an impound remains. Called a billabong in Australia.
- Piedmont Lake -- glacially formed lake among mountain foothills.
- Pothole Lake -- see Glacial Kettle Lake, above.
- Sand Bar Lake -- generally pools or small ponds formed along a river course by a deposited sand bar. Different from an oxbow lake in that the river does not change course as the result of a sand bar lake.
- Scour Lake -- glacially formed lake in which the complete body is "scoured" out of solid rock.
- Shoreline Lake -- Also known as a Barrier Lake. Lake next to a larger body of water formed when a spit of land, peninsula, etc. connects to land and impounds a lagoon or inlet. Could be a small lake cut off from a large lake, a small lake next to an ocean, sea, or whatever.
- Solution Lake -- Impoundment created when water dissolves surface or subsurface salt, limestone, or gypsum. The resulting hole then fills with water. In some subsurface situations, the lake may be in the collapsed "roof."
- Volcanic Lake -- lake formed when waterway is dammed by a lava flow.
- Beaver Dam Lake -- impoundment created by a beaver dam.
- Coral Lake -- lake formed near ocean, on island, shorline, etc. where coral growth, decay, and further growth create a fresh water impoundment.
- Phytogenetic Lake -- usually begins as a swamp or wetland, then sticks, trees, plant debris or other organic material forms a natural dam.
Exceptions to the Rule
Like anything else on this planet, there are always a few examples that don't quite fit in with the rules. Take a "logjam" lake or pond, for instance. A natural logjam would create an organic lake -- phytogenic to be specific. A man-made logjam would result in an anthropogenic lake. But what would you call it? An Anthropophytogenetic Lake? Now let's assume the logjam occurred near Mt. Saint Helens as the cataclysmic result of a volcanic explosion. Would that be organic or volcanic? The debris is organic, but it is the result of volcanic processes.
When a spit of land in the bay connects to the opposite shore and impounds water, the result is a shoreline lake. But what if the connection is the result of a landslide? Is this a landslide shoreling lake? Geologists don't always agree on specific terms for these circumstances. Fact is, many lakes and ponds are the result of multiple factors -- the key is to make sure that the description you use gives clear explanation to the listener or reader.
Roadside Geology -- If you travel at all, you absolutely have to start building your library of Roadside Geology Books. These are the fascinating geological wonders that professional geologists know about, but us amateurs drive right past without a clue. At the very least you ought to get the guide for your home state. If you are a rock collector, or just an armchair geologist, these books are more important than your GPS. The link goes to Amazon, so you can click safely. Your purchase earns a few cents toward operating this website, at no added cost to you.
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