DESCRIPTION:
Lava Lakes

Lava lakes are large volumes of molten lava, usually basaltic, contained in a vent, crater, or broad depression. Scientists use the term to describe both lava lakes that are molten and those that are partly or completely solidified. Lava lakes can form (1) from one or more vents in a crater that erupts enough lava to partially fill the crater; (2) when lava pours into a crater or broad depression and partially fills the crater; and (3) atop a new vent that erupts lava continuously for a period of several weeks or more and slowly builds a crater higher and higher above the surrounding ground.

Active lava lakes typically consist of a partially solidified shiny gray crust because its surface is constantly cooled by the atmosphere. The crust is seldom more than 5-30 centimeters thick, or more than a few minutes or hours old, because the crust continually circulates, breaks, and sinks into the moving molten lava below. T he pattern of movement on the surface of lava lakes is often compared to the type of large-scale movement that occurs between the huge plates that make up the Earth's crust, including subduction, spreading, and strike-slip movement.

Lava lakes occur at relatively few volcanoes in the world. For example, since 1980, lava lakes have formed at Kilauea Volcano in Hawaii, Mount Erebus in Antarctica (involving rare phonolitic lava), Erta Ale in Ethiopia and Nyiragongo in the Democratic Republic of the Congo.

Another common lava product is the ponded flow or lava lake ... The surface of lava that is ponded is smooth, broken only by polygonal cooling cracks, formed in much the same way as shrinkage cracks in mud that has been dried by the sun.

Africa leads the world in lava lake production, with 9 percent of its eruptions -- all at Nyiragongo and Erta Ale - having exhibited this uncommon characteristic.

Africa Volcanoes and Volcanics Menu

Mount Erebus (3,794 meters), the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. Erebus is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit has been modified by several generations of caldera formation. A summit plateau at about 3,200 meters altitude marks the rim of the youngest caldera, within which the modern cone was constructed. An elliptical 500 x 600 meter wide, 110-meter-deep crater truncates the summit and contains an active lava lake within a 250-meter-wide, 100-meter-deep inner crater. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity has been documented since 1972, punctuated by occasional strombolian explosions that eject bombs onto the crater rim.

Antarctica Volcanoes and Volcanics Menu

Erta Ale is an isolated basaltic shield volcano that is the most active volcano in Ethiopia. The broad, 50-kilometer-wide volcano rises more than 600 meters from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The 613-meter-high volcano contains a 0.7 x 1.6 kilometers, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 kilometer-wide depression elongated parallel to the trend of the Erta Ale range is located to the southeast of the summit and is bounded by curvilinear fault scarps on the southeast side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally oveflowed its rim. The summit caldera is renowned for one, or sometimes two longterm lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the northern flank of Erta Ale.

Africa Volcanoes and Volcanics Menu

Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 kilometer caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy east and SW rift zones, which extend to the sea on both sides of the volcano. About 90 percent of the surface of Kilauea is formed of lava flows less than about 1,100 years old; 70 percent of the volcano's surface is younger than 600 years. A longterm eruption that began in 1983 has produced lava flows covering more than 100 square kilometers and has destroyed nearly 200 houses. Intensive monitoring and field research by staff of the Hawaiian Volcano Observatory, established in 1912, make Kilauea one of Earth's best studied volcanoes.

Nearly continuous lava-lake activity on the caldera floor characterized the period from before 1823 until 1924.

Africa's most active volcano, Nyamuragira is a massive basaltic shield volcano that rises north of Lake Kivu across a broad valley northwest of Nyiragongo volcano. The volcano has a volume of 500 cubic kilometers and extensive lava flows from Nyamuragira cover 1,500 square kilometers of the East African Rift. The 3,058-meter-high summit is truncated by a small 2 x 2.3 kilometer summit caldera that has walls up to about 100 meters high. Historical eruptions have occurred within the summit caldera, frequently modifying the morphology of the caldera floor, as well as from the numerous fissures and cinder cones on the volcano's flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938. Twentieth-century lava flows extend down the flanks more than 30 kilometers from the summit, reaching as far as Lake Kivu.

Africa Volcanoes and Volcanics Menu

Tongariro (New Zealand) is a large andesitic volcanic massif, located immediately northeast of Ruapehu volcano, that is composed of more than a dozen composite cones constructed over a period of 275,000 years. Vents along a northeast-trending zone extending from Saddle Cone (below Ruapehu volcano) to Te Mari crater (including vents at the present-day location of Ngauruhoe) were active during a several hundred year long period around 10,000 years ago, producing the largest known eruptions at the Tongarioro complex during the Holocene. North Crater stratovolcano, one of the largest features of the massif, is truncated by a broad, shallow crater filled by a solidified lava lake that is cut on the northwest side by a small explosion crater. The youngest cone of the complex, Ngauruhoe, has grown to become the highest peak of the massif since its birth about 2,500 years ago. The symmetrical, steep-sided Ngauruhoe, along with its neighbor Ruapehu to the south, have been New Zealand's most active volcanoes during historical time.

New Zealand Volcanoes and Volcanics Menu

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