volcanic dome. tholoid A mound of viscous lava, usually rhyolite in composition, which has grown and built up over a vent. The mound of solid lava is covered by coarse, angular blocks which form by chilling and brecciation of the growing dome's surface. The blocks accumulate around the growing dome to produce a scree slope of crumble breccia. Domes can grow by repeated injection of magma into the dome body (endogenous dome) or by repeated eruption of small volumes of magma from the surface of the dome (exogenous dome) ref: Oxford Dictionary of Earth Sciences, 1999
This definition is the one you should use not the one in the following glossary
http://volcano.und.nodak.edu/vwdocs/glossary.html
Volcanic and Geologic Terms
Compound Volcano: A volcano that consists of a complex of two or more vents, or a volcano that has an associated volcanic dome, either in its crater or on its flanks. Examples are Vesuvius and Mont Pelee.
http://www.webref.org/geology/v/volcanic_dome.htm
volcanic dome
A bulb-shaped solid that forms over a vent when lava so viscous that it cannot flow out of the volcanic crater cools and hardens. When a volcanic dome forms, it traps the volcano's gases beneath it. They either escape along a side vent of the volcano or build pressure that causes another eruption and shatters the volcanic dome.
http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/mgn_f15s214_1.html
Venus - Magellan
Slumped volcanic dome near Atla Regio,Venus
Magellan radar image of a volcanic dome near Atla Regio, Venus. This 32 km volcanic dome exhibits a large slump scar and debris flow on its south side (north is up). The lower part of the debris flow appears to have been covered by later plains deposits. (Magellan F-MIDR 15S214;1,framelet 41)
http://volcano.und.nodak.edu/vwdocs/current_volcs/montserrat/montserrat.html
Soufriere Hills, Montserrat, West Indies
Location: 16.7N, 62.2W
Elevation: 3,002 feet (915 m)
Pyroclastic flows from Montserrat dome collapses have flowed down the White River creating a new delta where they entered the sea. It is uncertain if this delta will survive or be eroded by seawaves.
http://envam1.env.uea.ac.uk/mbctahw2002_text.html
Matthews, A.J., J. Barclay, S.A. Carn, G. Thompson, J. Alexander, R. A. Herd, and C. Williams, 2002
Rainfall-induced volcanic activity on Montserrat
Geophys. Res. Lett., 29 (13), 10.1029/2002GL014863.
New Scientist article
Further details of Montserrat volcanic activity and rainfall project
Technical Abstract
Dome-forming volcanic eruptions cyclically extrude bodies of lava over several months, which then become gravitationally unstable and collapse, generating pyroclastic flows. On 29 July 2001 extreme rainfall over Montserrat coincided with a major collapse of the Soufriere Hills lava dome. We present rainfall and seismic records that demonstrate, for the first time, a relationship between intense rainfall and lava dome collapse, with associated pyroclastic flow generation. After seven months of little rain and a period of sustained dome growth, the onset of intense rain was followed within hours by dome collapse and pyroclastic flows. The large-scale weather system responsible for the rain was identifiable in satellite images and predicted by meteorological forecasts issued 60 hours prior to the volcanic activity. It is suggested that weather prediction of intense rainfall be incorporated with existing geophysical and geochemical measurements to improve warnings of these hazardous events.
http://volcano.und.nodak.edu/vwdocs/volc_images/south_america/guat/santa_maria.html
Santa Maria and Santiaguito, Guatemala
http://www.geo.mtu.edu/volcanoes/santamaria/domes.html
Of the fourteen extrusive units mapped on Santiaguito dome, 5 are volcanic domes. Santiaguito was originally formed in the center of the explosion crater created by Santa Marķa's 1902 activity. This crater was volumetrically much smaller (0.5 km³) than the amount of material erupted during the 1902 event, and local slumping near the crater has occurred and is continuing along a series of east-trending faults. The general westward growth of the dome complex and many of the structural features on Santiaguito are controlled by these near-vertical faults. The domes are studded with Pelean spines.
Twenty-five new chemical analyses show Santiaguito's eruptive products to be soda-rich dacite of the calc-alkaline suite. The dome lava has differentiated quite significantly from the overwhelmingly abundant pyroxene andesite magma which makes up Santa Marķa and the older volcanic rocks in the area. The rocks of the dome complex are uniform, gray-brown phorphyritic dacite and andesite, usually with oxyhornblende phenocrysts as well as plagioclase. Dome units are generally more grayish in color than the flows, are less vesicular, have more inclusions, and show little or no evidence of flow in response to gravity after extrusion. They comprise a much larger volume than the flow units. Spines and slabs stud the summits. The largest spine now preserved is on the La Mitad Dome; it is 200 m long and 70 m high. The shape of the dome units is sometimes circular, as in the case of the La Mitad and the El Brujo units, suggesting a simple extrusive vent. The Caliente unit was extruded from two or more vents and the El Monje dome can be subdivided into two elongate units on the basis of aerial photography control at various dates. Extrusive vents for the El Monje domes were apparently along fissures striking eastward.
http://www.theoceanadventure.com/CS2000/CS10.html
Thousands of years ago the center of the volcano collapsed and formed this gigantic crater. At one time the caldera was filled with water, like Crater Lake in Oregon. Then, in 1971, a hiker noticed that a rock was sticking out of the center of the lake. The rock was the top of a volcanic dome that was forming under the crater lake. The dome started getting bigger and bigger and the lake got smaller and smaller. In the last four or five years the water has almost completely disappeared in the crater. A small lake is all that is left of the billions of gallons of water that once filled the crater. Now a large volcanic dome grows inside the caldera. (Remember the huge volcanic dome or plug that was in the middle of Mont Pele's caldera?)
La Soufriere erupted in 1979, and ash and sulfurous gases spewed out. The ash covered not only St. Vincent, but also Barbados, over 100 miles away! Fortunately, scientists gave plenty of warning and the people had left the areas below the volcano where lava flowed through. Today there are special scientific instruments in the caldera to monitor constantly any volcanic activity. Scientists are checking the growth of the volcanic dome, measuring any earthquakes, listening for any sounds deep underground, and taking samples of gases that are coming out of the dome. If there is a future eruption, especially a big one, scientists hope their research will allow them to give people plenty of warning to leave the dangerous areas.
Principal Types of Volcanoes
Geologists generally group volcanoes into four main kinds--cinder cones, composite volcanoes, shield volcanoes, and lava domes.http://pubs.usgs.gov/gip/volc/types.html
Volcanic or lava domes are formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and around its vent. A dome grows largely by expansion from within. As it grows its outer surface cools and hardens, then shatters, spilling loose fragments down its sides. Some domes form craggy knobs or spines over the volcanic vent, whereas others form short, steep-sided lava flows known as "coulees." Volcanic domes commonly occur within the craters or on the flanks of large composite volcanoes. The nearly circular Novarupta Dome that formed during the 1912 eruption of Katmai Volcano, Alaska, measures 800 feet across and 200 feet high. The internal structure of this dome--defined by layering of lava fanning upward and outward from the center--indicates that it grew largely by expansion from within
This page is <http://pubs.usgs.gov/gip/volc/types.html>
Maintained by Kathie Watson
Last modified 2/6/97
A Dictionary of Earth Sciences, SECOND EDITION, Edited by AILSA ALLABY and MICHAEL ALLABY
Oxford New York, OXFORD UNIVERSITY PRESS
VOLCANIC DOME. THOLOID - A mound of viscous lava, usually rhyolite in composition, which has grown and built up over a vent. The mound of solid lava is covered by coarse, angular blocks which form by chilling and brecciation of the growing dome's surface, The blocks accumulate around the growing dome to produce a scree slope of crumble breccia. Domes can grow by repeated injection of magma into the dome body (endogenous dome) or by repeated eruption of small volumes of magma from the surface of the dome (exogenous dome).(lava dome is not listed)