ice age any cold period in Earth's history marked by extensive glaciation and alternated with a period of warmth. The most recent ice age, extending from approximately 2 million to 10,000 years ago and consisting of at least four large-scale glacial advances, was the Pleistocene epoch.
iceblink a yellowish glare in the sky over an ice field.
icefall an avalanche of ice.
ice field any floating sheet of ice greater than 6 miles (10 km) across.
ice floe any floating sheet of ice less than 6 miles (10 km) across.
indicator a glacially transported rock that can be traced back to its original bedding ground.
kame mounds of stratified sand and gravel deposited along the edge of a glacier by glacial streams.
kettles depressions in moraines, often filling with water and creating lakes anywhere from 10 meters to 10 kilometers in diameter.
loess wind-transported silt and clay, ground fine and deposited by glaciers, and responsible for creating the rich, loamy soils and billowing topography of the Midwest.
moraine a large accumulation of glacially deposited rocks and boulders (till).
moulin a whirlpool of melted water and rocks that falls through a crevasse and carves out a shaft through a glacier to the ground. Also known as a glacier mill.
neve glacial or mountain snow that becomes ice. Also known as firn.
nunatak a hill or mountain peak surrounded by a glacier.
pack ice a large slab of sea ice consisting of chunks and floes held closely together.
pancake ice evolving from frazil or slush, rounds of ice of various sizes, resembling pancakes.
permafrost permanently frozen ground.
Pleistocene epoch a period from approximately 2 million to 10,000 years ago, marked by alternating cold and warm climates and increased glacial activity. Four major glacial advances—when ice covered as much as two-thirds of North America in depths reaching 3,000 meters—are recognized during the Pleistocene epoch. From oldest to youngest, these are known as the Nebraskan, the Kansan, the Illi- noian, and the Wisconsin, collectively referred to as the Ice Age.
pressure ridge a ridge of sea ice uplifted by horizontal pressure.
regional snow line the altitude in which more snow accumulates than melts in the summer season, thus eventually forming a glacier.
rock flour rock pulverized by a glacier and carried off by running water.
sastrugi large, sharp ridges or irregularities carved into a bed of snow by wind.
serac a pinnacle of ice upraised on the surface of a glacier by the intersection of two or more crevasses.
snow bridge an arch of snow formed over a crevasse.
striations scratches and grooves left on rocks and bedrock by passing glaciers.
surge a sudden or rapid advancement of a glacier, sometimes having catastrophic consequences.
till a mixture of powdered rock, gravel, and rocks carried and deposited by a glacier.
trimline the boundary between old, larger trees untouched by glacial movement and younger, smaller trees that sprouted after ice receded.
warm glacier one that reaches melting temperature during summer.
LAKES, PONDS, AND swamps
alkali lake a lake with a high content of sodium carbonate.
battery a large island of decayed vegetation and bottom material floated to the surface of a swamp by swamp gas; the island then floats, grows new vegetation, and gradually roots itself to the bottom.
bayou a marshy inlet or outlet of a lake or river.
benthos the plants and animals that inhabit the bottom of a pond, lake, or other body of water.
bitter lake a lake with a high content of sodium sulfate.
blowup the act of swamp gas blowing bottom material to the surface of a swamp.
boatman an aquatic insect that skims the surface of water.
bog a spongy wetland characterized by peat deposits, floating sedge or sphagnum mats, heath shrubs, and coniferous trees.
brackish describing a mixture of salt water and freshwater, such as found in coastal marshes.
caldera a crater lake formed by volcanic activity.
cirque a small circular basin lake found on the side of a mountain.
detritus particles of decaying plants and animals used as a source of food by many aquatic animals.
dimictic a lake whose waters overturn twice a year, due to temperature mixing, most commonly found in temperate regions.
eutrophic of a body of water, having its oxygen depleted by lush vegetation.
eutrophication the gradual filling-in of a lake by the growth of vegetation and rising sediment so that it gradually becomes a pond, then a marsh, then a swamp, and then finally dries up, the natural aging process of all lakes.
eyes small areas of open water in mat-covered bogs.
fen a marsh or bog.
floaters floating plants, such as water lilies and duckweed.
foxfire luminescence caused by the decaying of wood by certain fungi, seen in swampy areas at night.
hammocks tree islands found in swampy areas.
ice scour a relatively shallow lake formed by glaciers making a shallow depression over a level area.
kettle a natural lake formed in a depression in a glacial moraine.
lacustrine like a lake or pertaining to a lake.
lagoon the pond or body of water within a coral atoll, or any small body of water connecting with a river, lake, or sea.
limnologist one who studies lakes. limnology the study of lakes.
littoral the shore area from the waterline to the plant line.
loch Scottish word for a lake.
marsh the shallow body of water partially filled in with vegetation, evolving from a pond.
methane marsh or swamp gas formed by decaying plants.
mire swampy ground or deep mud.
monomictic a lake whose water overturns once a year, due to temperature mixing.
moraine lake a lake formed when rocks and debris dumped by a glacier dam a river.
morass soft, wet ground, as in a marsh or bog.
muskeg a mossy bog found in northern, coniferous forest regions.
oligotrophic a body of water with a high oxygen content and largely devoid of plants and animals.
oxbow lake a lake formed when a bend or meander in a river is cut off from the main flow and isolated.
paternoster lakes a series of glacier-carved basins filled with water and resembling a string of beads.
peat decayed and partially carbonized vegetable matter found in bogs and used for fuel.
plankton tiny plants and animals that float or swim near the surface of water.
playa lake a shallow, temporary lake that forms in a desert playa or basin.
Pleistocene the epoch of glacial activity beginning 2.5 million years ago, when many of Earth's lakes were formed.
pluvial lake a lake that formed during a period of increased rainfall and decreased evaporation, most notably in nonglaciated southern regions of North America during the time of the last ice age.