Hummocks are rounded or conical mounds within a volcanic landslide or debris avalanche deposit. Hummocks contain a wide range of rock debris, reflecting the variation of deposits that previously formed the flanks of the volcano. Some hummocks contain huge intact blocks tens to hundreds of meters in diameter. Some of the original layering of lava flows and other deposits can be seen in these large hummocks, but most of the large rock fragments are thoroughly shattered. In other hummocks the rock debris is thoroughly mixed as if the material had been in a blender and thoroughly mixed together.
Photograph by E. Klimasauskas on 30 April 1998
A large hummock on the 1980 landslide deposit from Mount St. Helens stands above a wetland area (foreground) that lies between other hummocks. These hummocks once formed part of the volcano's summit, which was removed by an enormous landslide on 18 May 1980. The landslide scattered the summit rocks widely in the North Fork Toutle River valley.
Did you know?
Studies of the hummocky debris avalanche deposit at Mount St. Helens have led to the identification of hundreds of volcanic debris avalanche deposits around the world.
The 1980 Mount St. Helens debris-avalanche deposit contains as many as 625 individual hummocks.
The debris-avalanche deposit at Mount St. Helens blocked tributary river valleys, which filled with water to form two new lakes within a few months of the 1980 eruption.

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


Look at other dictionaries:

  • hummock — s.n. Blocuri de gheaţă provenind din spargerea banchizelor. [< engl., fr. hummock]. Trimis de LauraGellner, 21.04.2005. Sursa: DN  HUMMÓCK s. n. monticul format din blocuri de gheaţă provenind din spargerea banchizelor. (< engl., fr.… …   Dicționar Român

  • Hummock — Hum mock, n. [Prob. a dim. of hump. See {Hump}.] 1. A rounded knoll or hillock; a rise of ground of no great extent, above a level surface. [1913 Webster] 2. A ridge or pile of ice on an ice field. [1913 Webster] 3. Timbered land. See {Hammock}.… …   The Collaborative International Dictionary of English

  • hummock — [ymɔk] n. m. ÉTYM. 1851; mot angl., d orig. obscure; probablt dimin; cf. hillock, de hill. ❖ ♦ Géogr. Monticule formé par des plaques de glace qui se rencontrent sur la banquise et chevauchent les unes sur les autres. 1 (…) cet icefield océanique …   Encyclopédie Universelle

  • hummock — knoll, hillock, 1550s, originally nautical, conical small hill on a seacoast, of obscure origin, though second element is dim. suffix ock. In Florida, where the local form is hammock, it means a clump of hardwood trees on a knoll in a swamp or on …   Etymology dictionary

  • hummock — ► NOUN ▪ a hillock or mound. DERIVATIVES hummocky adjective. ORIGIN of unknown origin …   English terms dictionary

  • hummock — [hum′ək] n. [orig. naut. < ?] 1. a low, rounded hill; knoll; hillock 2. a ridge or rise in an ice field ☆ 3. a tract of fertile, heavily wooded land, higher than a surrounding marshy area ☆ hummocky adj …   English World dictionary

  • Hummock — A hummock (of uncertain derivation; cf. hump or hillock) is a boss or rounded knoll of ice rising above the general level of an ice field, making sledge travelling in the Arctic and Antarctic region extremely difficult and unpleasant.Hummocky ice …   Wikipedia

  • Hummock — Vue de hummocks de pergélisol sur le mont Kenya …   Wikipédia en Français

  • hummock —    1) [ geomorphology ]     a) (not preferred see hillock). An imprecise, general term for a rounded or conical mound or other small elevation.     b) (not preferred) A slight rise of ground above a level surface. GG    2) [ patterned ground ]… …   Glossary of landform and geologic terms

  • hummock — UK [ˈhʌmək] / US noun [countable] Word forms hummock : singular hummock plural hummocks mainly literary a small area of ground that is slightly higher than the ground around it …   English dictionary

  • hummock — noun Etymology: alteration of 2hammock Date: 1555 1. a rounded knoll or hillock 2. a ridge of ice 3. hammock II,2 • hummock verb • hummocky adjective …   New Collegiate Dictionary

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