pillow lava

Interconnected, sack-like bodies of lava formed underwater.
A type of submarine lava flow consisting of interconnected, elongated lava tubes. Cross-sections of individual lava tubes resemble pillows with convex upper surfaces and flat or concave lower surfaces (Schmidt and Schminke, 2000, p. 383). Both radial and concentric cooling fractures may be present along the margins of individual pillows, and these fractures are brought on by thermal contraction during cooling. Growth of the pillow tubes takes place as the outer, commonly striated outer glassy surface of the pillow tube fractures, and a new tube "buds" from the fracture in a manner similar to the way that toothpaste is squeezed out of a tube.
When basalts erupt underwater, they commonly form pillow lavas, which are mounds of elongate lava "pillows" formed by repeated oozing and quenching of the hot basalt. First, a flexible glassy crust forms around the newly extruded lava, forming an expanded pillow. Next, pressure builds until the crust breaks and new basalt extrudes like toothpaste, forming another pillow. This sequence continues until a thick sequence may be deposited. When geologists find pillow basalts in ancient rock sequences, they may conclude that the area was once under water.
Photograph by Richard D. Grigg
Diver examines elongate pillowed flow lobe off the coast of Kilauea volcano, Hawai`i.

Glossary of volcanic terms. - University of Wisconsin Oshkosh. . 2001.

Look at other dictionaries:

  • Pillow lava — à Hawaii (NOAA) Pillow lava au Chenaillet ( …   Wikipédia en Français

  • pillow-lava — ● pillow lava, pillow lavas nom féminin (anglais pillow, coussin, et lava, lave) Ellipsoïde de lave généralement basaltique, de grand axe environ 1 m, à surface vitreuse, résultant de l émission de lave en fusion sous la mer. ● pillow lava,… …   Encyclopédie Universelle

  • Pillow Lava — lava solidified underwater assuming pillowlike shapes …   Eponyms, nicknames, and geographical games

  • pillow lava —    A general term for lava displaying pillow structure (discontinuous, close fitting, bun shaped or ellipsoidal masses, generally < 1 m in diameter); considered to have formed in a subaqueous environment; such lava is usually basaltic or… …   Glossary of landform and geologic terms

  • Pillow-Lava — Kissenlava (NOAA) Kissenlava, OIB ocean island basalt, Caldera de Taburiente …   Deutsch Wikipedia

  • pillow lava — Geol. lava in the form of an agglomeration of rounded, pillow shaped masses, the result of subaqueous or subglacial volcanic eruption. [1900 05] * * * …   Universalium

  • pillow lava — /ˈpɪloʊ lavə/ (say piloh lahvuh) noun lava which has cooled into a mass of rounded pillow like shapes with a fine grained surface, thought to result from sudden cooling under water …   Australian English dictionary

  • pillow lava — noun The rock type typically formed when lava emerges from an underwater volcanic vent or a lava flow enters the ocean …   Wiktionary

  • pillow lava — noun lava that hardened in rounded shapes suggestive of pillows; believed to result from underwater eruptions • Hypernyms: ↑lava …   Useful english dictionary

  • pillow lava — noun lava which has solidified as rounded masses, characteristic of eruption under water …   English new terms dictionary

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