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sediment

(Encyclopedia) sediment, mineral or organic particles that are deposited by the action of wind, water, or glacial ice. These sediments can eventually form sedimentary rocks (see rock ). Classif...

Painted Desert

(Encyclopedia) Painted Desert, badlands on the northeastern bank of the Little Colorado River, NE Ariz., stretching c.200 mi (320 km) SE from the Grand Canyon; includes Petrified Forest National Park. Strikin...

esker

(Encyclopedia) esker, long, narrow, winding ridge of stratified sand-and-gravel drift . Eskers, many miles long and resembling abandoned railway embankments, occur in Scandinavia, Ireland, Scotland, and...

period

(Encyclopedia) period, unit of time on the geologic timescale . Periods are shorter than an era and longer than an epoch. Periods are of variable length, generally lasting tens of millions of years, wit...

Kinorhyncha

(Encyclopedia) Kinorhyncha kĭn˝ərĭng´kə [key], phylum containing about 150 species of tiny pseudocoelomate worms, it is widely distributed in marine sediments. The kinorhynch body is divided int...

delta

(Encyclopedia) delta [from triangular shape of the Nile delta, like the Greek letter delta ], a deposit of clay, silt, and sand formed at the mouth of a river where the stream loses velocity and drops p...

Gnathustomulida

(Encyclopedia) Gnathustomulida nā˝thyəstəmyo͞o´lĭdə [key], phylum of microscopic worms described in 1956 that have elongated bodies, cilia, and are hermaphroditic. The 80 known species in this group ...

stromatolite

(Encyclopedia) stromatolite, layered structures produced by the binding together of sediments by a thin layer of cyanobacteria . The layers, which are deposited very slowly, gradually produce rounded or...

varve

(Encyclopedia) varve, in geology, pair of thin sedimentary layers formed annually by seasonal climatic changes. Usually found in glacial lake deposits, varves consist of a coarse-grained, light-colored summer...