Lava is astounding. Molten rock that erupts on to the surface at thousands of degrees! Our largely solid planet (help save for the liquid outer core, but that steel, not lava) can melt but all that molten materials isn’t the very same. Those people variances in composition are what drives the various actions of lava on the surface.
There is a (mostly) simple partnership involving lava composition and actions. The a lot more silica (SiO2) in the lava, the “stickier” it is. This enhance in viscosity implies that lava goes from totally free-flowing to hardly-flowing. Distinctive volcanoes will erupt various compositions of lava relying on how the rock melts at the volcano and how it variations as it will make its way to the surface.
The composition isn’t the only component that variations the lava’s stickiness. The hotter the lava, the runnier it is. Much more crystals in the lava? Stickier. Much more h2o dissolved in the lava? Runnier. Much more bubbles forming? Stickier. The last viscosity of the lava is a sophisticated combination of all these variables, but composition truly drives the bus.
Proper now, we have a few amazing eruptions happening across the globe that truly clearly show off the types of lava eruptions. In Hawai’i, Kīlauea has a new lava lake at its summit Halema’uma’u Crater. On Sicily, Etna has been erupting long, snaking lava flows. At the very same time, La Soufrière on St. Vincent has a squat lava dome forming.
Kīlauea’s Lava Lake
The surface of the Kilauea Lava Lake seen on January 10, 2021. The cooler, hardened surface can be seen on the proper. Credit rating: Rob Simmon, World.
Considering the fact that late 2020, Kīlauea has burst back again to lifetime following in excess of two several years of peaceful. The summit eruption has begun to fill the deep crater that shaped through the 2018 Lower East Rift Zone events. In the course of action, a new lava lake (over) as recognized alone at the summit and it is becoming fed by a vent on the facet of the lake. After about a month of eruption, the lake is now in excess of 650 toes (200 meters) deep!
In this animated GIF (beneath) of the filling of the lava, you can see how fluid it is as a floating island of cooled lava moved all around its surface. You can also see how the surface behinds like a layer of “plates” of lava that are established and ruined — a bit like a mini edition of plate tectonics. The vent feeding the lava lake is in close proximity to the bottom of the picture.
Animated GIF of thermal images from the new Kilauea lava lake. Credit rating: USGS/HVO.
Lava lakes need very low silica lava named basalt. Now, by “very low silica”, we’re still talking 47% of the lava is built of silica together with factors like iron, magnesium, calcium and a lot of other individuals. This basalt has near to the least expensive viscosity and optimum temperature of any lava erupting on Earth currently and that permits for a lava lake to form as together as new lava is continually fed.
Etna’s Lava Flows
The lava flows (proper facet of summit) from Etna seen by Sentinel-two on January 19, 2021. Credit rating: ESA.
On the other facet of the globe, Etna on Sicily has been erupting vigorously so significantly this yr. The eruptions have created explosions at the summit as very well as lava flows that have headed down the japanese slopes. The eruption has also distribute ash on the slopes of the volcano.
Thermal picture of the lava flows from Etna in Italy on January 21, 2021. The lava flows clearly show up as vivid in this picture. Credit rating: INGV Osservatorio Etneo.
The basaltic andesite lava erupting at Etna is to some degree a lot more silica rich than Kīlauea’s. This implies it is stickier and tends to generate Strombolian eruptions. These eruptions have explosions induced by large bubbles of gasoline growing as a result of the pipe that sales opportunities from the supply of the lava underneath the volcano to the surface. The lava is still runny enough to form lava flows from the vent as very well and that’s what is happening at Etna proper now. The infrared picture from Sentinel-two exhibits the energetic flows coming down from the Southeast Crater.
La Soufrière’s Lava Dome
At last, we get to lava domes. These are shaped by even stickier lava that erupts like squeezing toothpaste out of a tube. The lava does get significantly and instead just “piles up” developing a thick dome. Volcanoes like La Soufrière on St. Vincent erupt andesite (not to be puzzled with the formerly outlined basaltic andesite) that could possibly have up to sixty five% silica. This will make it a lot stickier than the lava erupting at Etna or Kīlauea.
The 2020-2021 lava dome at La Soufrière on St. Vincent in the foreground, with the 1979 dome in the track record. Credit rating: College of West Indies Seismic Analysis Center.
The new lava dome forming at La Soufrière is in excess of one,a hundred toes (380 meters) across and 300 toes (90 meters) thick. It begun forming at the extremely end of 2020 and it was the 1st eruption at La Soufrière because 1979. Check out out this online video of a helicopter flight in excess of the expanding lava dome.
The domes steep sides and intense thickness appears to be remarkable for andesite lava erupting when in comparison to the basalt lava of Kīlauea. Even so, the viscosity of lava goes up quick when a lot more silica is extra. The lava in the Soufriére dome could possibly be up thousands of occasions stickier than the Hawaiian basalt. If you review the significantly finishes of the lava compositional spectrum — basalt and rhyolite — you discover that rhyolite is a billion occasions a lot more viscous! Some rhyolite lava domes and coulees (kind of like a hybrid of a dome and move) can be hundreds of toes thick.
Most eruptions of lava to form these capabilities are rather passive. When you happen to be considering about volcanic hazards, lava flows are negative for buildings and infrastructure but not individuals. All of this big difference in stickiness is what drives the various varieties of lava lakes, flows and domes.