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quartz

(Encyclopedia)quartz, one of the commonest of all rock-forming minerals and one of the most important constituents of the earth's crust. Chemically, it is silicon dioxide, SiO2. It occurs in crystals of the hexagon...

Devonian period

(Encyclopedia)Devonian period dĭvōˈnēən [key], fourth period of the Paleozoic era of geologic time between 408 and 360 million years ago (see Geologic Timescale, tablegeologic timescale, table). It was named (...

desert

(Encyclopedia)desert, arid region, usually partly covered by sand, having scanty vegetation or sometimes almost none, and capable of supporting only a limited and specially adapted animal population. The so-called ...

Sevier

(Encyclopedia)Sevier, river, c.280 mi (450 km) long, formed in SW Utah by the junction of Panguitch Creek and Assay Creek. It flows northward through canyons, then leaves the mountains and flows SW through the Sevi...

Shinano

(Encyclopedia)Shinano shĭnäˈnō [key], river, longest of Honshu, Japan, c.230 mi (370 km) long. It rises in the mountains of central Honshu and flows generally NE to the Sea of Japan at Niigata. It waters the fe...

Tagus

(Encyclopedia)Tagus tāˈgəs [key], Span. Tajo, Port. Tejo, river, c.585 mi (940 km) long, rising in the mountains E of Madrid, E Spain, and draining the central part of the Iberian Peninsula. The Tagus flows nort...

wagon train

(Encyclopedia)wagon train, in U.S. history, a group of covered wagons used to convey people and supplies to the West before the coming of the railroad. The wagon replaced the pack, or horse, train in land commerce ...

Ishikawa

(Encyclopedia)Ishikawa ēshēˈkäwä [key], prefecture, 1,619 sq mi (4,193 sq km), central Honshu, Japan. The ...

Mount Olympus

(Encyclopedia)Mount Olympus: see Cyprus; Olympic Mountains; Olympus. ...

Pulangi

(Encyclopedia)Pulangi po͞olängˈgē [key], river, c.200 mi (320 km) long, rising in the mountains of N Mindanao, the Philippines, and flowing SW to Liguasan Marsh. As the Mindanao River, it flows NW to Illana Bay...