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geochemistry

(Encyclopedia)geochemistry, study of the chemical changes on the earth. More specifically, it is the study of the absolute and relative abundances of chemical elements in the minerals, soils, ores, rocks, water, an...

geologic timescale

(Encyclopedia)CE5 geologic timescale, a chronological scale of earth's history used to measure the relative or absolute age of any part of geologic time. Of the numerous timescales, the most common is based on g...

Point Reyes National Seashore

(Encyclopedia)Point Reyes National Seashore rāˈĭs [key], 71,068 acres (28,772 hectares), W Calif.; est. 1962. Included in the area are steep bluffs overlooking the Pacific Ocean, lagoons, and esteros enclosed by...

opal

(Encyclopedia)opal ōˈpəl [key], a mineral consisting of poorly crystalline to amorphous silica, SiO2·nH2O; the water content is quite variable but usually ranges from 3% to 10%. Common opal is usually colorless...

isopleth

(Encyclopedia)isopleth īˈsəplĕthˌ [key], line drawn on a map through all points of equal value of some measurable quantity. In many meteorologic, oceanographic, or geologic studies some physical or chemical pr...

agate

(Encyclopedia)agate ăgˈĭt [key], translucent, cryptocrystalline variety of quartz and a subvariety of chalcedony. Agates are identical in chemical structure to jasper, flint, chert, petrified wood, and tiger's-e...

Burton, Gary

(Encyclopedia) Burton, Gary, 1943- , American jazz vibraphone player, composer, and bandleader, b. Anderson, In. Burton is self-taught on the vibraphone and studied ...

Penderecki, Krzysztof

(Encyclopedia)Penderecki, Krzysztof kshĭshˈtôf pändĕrĕtsˈkē [key], 1933–2020, Polish composer. His music is characterized by unusual sonorities, and he devised his own system of notation to convey the eff...

pika

(Encyclopedia)pika pīˈkə [key], short-haired mammal related to rabbits and hares, also called mouse hare and rock rabbit. Pikas live above the timber line in the mountains of N Asia and W North America. The pika...

pipit

(Encyclopedia)pipit, common name for a group of chiefly Eurasian and African birds that together with the wagtails constitute a subfamily of songbirds related to the Old World warblers and thrushes. Pipits are trim...