A lava lake is a large volume of exposed molten rock (magma) confined in a crater, vent, or a large depression. This term can, however, refer to partially or fully solidified magma in a vent, depression, or crater.
These lakes of lava are usually confined by levees or walls of pits, craters, and depressions. Most have a nearly circular plan from above, but some have irregular shapes, taking the shapes of pits, craters, or depressions that hold the lava.
Their sizes range from small, i.e., 10s of meters wide and deep, to large ones measuring several hundreds of meters in depth and width.
How do lava lakes form?
Lava lakes form when rising magma partially fills a crater or vent or when flowing lava ponds a depression.
Repeated and continuous eruptions can also build levees or craters higher than the surrounding ground, which will confine the lava forming this lake. .
Composition
Lava lakes have mostly basaltic magma at temperatures of 1800-2200 °F (1000-1200 °C). Common examples are Kīlauea in Hawaii USA and Erta Ale in Ethiopia. However, these lakes can contain other highly fluid (low viscosity) magma types like carbonatite, basaltic andesite, melilite nephelinite, and phonolite.
Ol Doinyo Lenga in Tanzania has carbonatite, and Mt. Michael at the South Sandwich Islands has basaltic andesite. Phonolite occurs at Mt. Erebus in Antarctica, and melilite nephelinite at Mt. Nyiragongo in the Democratic Republic of the Congo.
Active vs. inactive active
Most lava lakes are inactive and short-lived, lasting for a few weeks to months. Active ones, on the other hand, are long-lived, with some lasting for decades and rarely for centuries.
1. Active lava lakes
Active lava lakes occur in craters, vents, or fissures that have pipes connecting them to underground magma chambers or reservoirs. Therefore, they will remain active or persist for a long time.
Also, these active lakes will often convect or recirculate, churn, bubble, and slosh magma. Some, like Mauna Ulu (1969–1971) in Hawaii, achieved a near-steady magma recirculation.
How long they persist depends on whether the pipe or conduit remains open or not. The other factor that affects their longevity is the balance of forces operating in the magma chamber, conduit, and lake.
Examples of active lava lakes are Kīlauea and Kupaianaha volcanoes in Hawaii, USA; Erta Ale in Ethiopia; and Mt. Erebus in Antarctica. Erta Ale has been active for over a century now.
a). Why don’t active lava lakes solidify fast?
Active lava lakes don’t solidify quickly and remain hot for a long time because they are connected to underground magma chambers.
Therefore, they can recirculate magma via convection currents. Convection currents form when dense, degassed, and colder magma sinks while hot, molten magma rises. These currents help break the solidifying crust and keep the lava hot.
Besides convection currents, hot, escaping gases help heat magmas. These rising gas bubbles will also stir the magma as they burst near the surface, breaking the solidifying crust.
Last but not least, hot, bubbly magma can rise into the lava lake without convection currents, keeping the lake active.
b). More characteristics
- Lava fountaining spectacularly visible at night may occur in some lava lakes. It happens when escaping gas blasts jets of reddish, glowing lava into the air.
- The bursting of trapped gas bubbles, convection, and sloshing lava will continuously break the solidified crust, exposing bright-red magma between cracks that look magical at night.
- Some lava lakes can have mild, moderate-to-explosive eruption episodes caused by trapped gas bubbles. Mild or low explosivity, strombolian-type eruptions are common in Mount Erebus, while Nyiragongo and Mt. Masaya have explosive eruption episodes.
- Change in pressure and buildup of gas bubbles can cause lava levels to rise, fall, or overflow downslope from the crater.
2. Inactive lava lakes
Inactive lava lakes, on the other hand, don’t have conduits that connect them to a magma chamber or reservoir. These lakes form when lava fills depressions or if craters or vents get blocked.
They also don’t churn or convect for long and will solidify slowly and freeze with time. A notable example is the 1959 Kīlauea Iki Pond in Hawaii, USA, which took about 20 years to freeze.
Examples of Lava lakes
| Name and location | Description and years active |
|---|---|
| Halema’uma’u on Kīlauea Shield volcano in Hawaii, USA. | Halema’uma’u has been persistent for a long time until 2022. It churns, glows, fountains, and sometimes refills or erupts. Active years are 1823-1899, 2008-2018, and 2021-2022. |
| Mt. Nyiragongo stratovolcano, DRC | Mt. Nyiragongo has one of the largest lava lakes in the world that measured about 700 meters wide in 1984,first discovered in 1894. |
| Mount Erebus strato/shield volcano in Ross Island, Antarctica | This long-lived, persistent lake of lava at the inner cone’s summit has been active since the 1970s.. |
| Erta Ale shield volcano in Ethiopia | Erta Ale has long-lived one or sometimes two lava lakes that have persisted with glowing lava since 1906 or earlier. |
| Mt. Michael Stratovolcano in Saunders Island. | This persistent lake of lava was discovered in 2019 using satellite images but has been active since 2003 or earlier. |
| Masaya Volcano | It once hosted the largest lava lake in 1670 and has been active since 2016. |
| Mount Yasur stratovolcano in Vanuatu | This stratovolcano has a semi-persistent lava lake that, sometimes erupting on the central vent. It has been active over the past two decades. |
| Ambrym Volcano in Vanuatu | It had five active churning lakes up to 2018, when it drained. |
What are the hazards of lava lakes?
Lava lakes are generally safe when watched from a safe distance. However, they can erupt or breach their flanks, and some emit poisonous gases. Mount Nyiragongo breached its flanks in 1977, killing dozens of people.
Interesting facts
- Lava lakes were first observed in Kīlauea volcano in Hawaii in 1823 by missionaries.
- Erta Ale in Ethiopia has the most persistent or longest-lived one or sometimes two lava lakes, which have been persistent for over a century. Erta Ale is also one of the largest, measuring 613 meters in height.
- A volcanic eruption, fissures, and the caldera formation can destroy or drain these lakes. Some may also solidify or freeze.
- These lakes also occur in other celestial bodies, like Io’s Magma Sea of Loki Patera. Like on Earth, they occur in craters, fissures, and calderas in these celestial bodies.