Pumice, volcanic glass formed by the solidification of lava that is permeated with gas bubbles. Usually found at the surface of a lava flow, it is colorless or light gray and has the general a...

Hawran or Hauran [Heb.,=hollow or cavernous land], district, SW Syria. It is a largely treeless region marked by conical volcanic peaks, barren lava fields, and rich lava soil. In the northeas...

Volcano, vents or fissures in the earth's crust through which gases, molten rock, or lava, and solid fragments are discharged. Their study is called volcanology. The term volcano is commonly a...

Rhyolite, fine-grained light-colored acidic volcanic rock. Rhyolite is chemically the equivalent of granite, and is thus composed primarily of quartz and orthoclase feldspar with subordinate a...

Sakurajima, peninsula, Kagoshima prefecture, S Kyushu, Japan, in Kagoshima Bay opposite Kagoshima. Formerly an island, Sakurajima became a peninsula in 1914 when lava from three volcanic cones...

Thingvellir, Icelandic Þingvellir, a wide lava plain, since 1928 a national park, the ancient place of assembly of the Icelandic Althing, which met there from 930 to 1798. It is located c.30 m...

Black Rock Desert, arid region of lava beds and alkali flats, NW Nev., in Toiyabe National Forest, stretching c.70 mi (110 km) NE from Gerlach. The Jackson Mts. rise to the east; the Black Roc...

Damavand or Demavend, volcanic cone, 18,606 ft (5,671 m) high, in the Elburz range, N Iran. A permanently snow-covered volcano of recent geologic origin, it emits gases and small quantities of...

Blue Mountains, uplifted, eroded part of the Columbia Plateau, c.6,500 ft (1,980 m) high, NE Oreg. and SE Wash. Lava flows cover much of the surface. The upper, wooded slopes are used for lumb...

Paektu or Baekdu, Mount, inactive volcanic peak, 9,003 ft (2,744 m) high, on the border between North Korea and China. The highest mountain in Korea, it rises from a basalt lava plateau that i...