Lava is awesome. Molten rock that erupts onto the surface at thousands of degrees! Our mainly strong earth (save for the liquid outer main, but that metallic, not lava) can melt but all that molten product is not the exact same. People discrepancies in composition are what drives the unique actions of lava on the surface.
There is a (mainly) uncomplicated marriage involving lava composition and actions. The a lot more silica (SiO2) in the lava, the “stickier” it is. This raise in viscosity usually means that lava goes from totally free-flowing to scarcely-flowing. Various volcanoes will erupt unique compositions of lava based on how the rock melts at the volcano and how it variations as it would make its way to the surface.
The composition is not the only component that variations the lava’s stickiness. The hotter the lava, the runnier it is. Additional crystals in the lava? Stickier. Additional drinking water dissolved in the lava? Runnier. Additional bubbles forming? Stickier. The closing viscosity of the lava is a difficult mix of all these variables, but composition seriously drives the bus.
Suitable now, we have a few remarkable eruptions taking place throughout the world that seriously demonstrate 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 extended, snaking lava flows. At the exact same time, La Soufrière on St. Vincent has a squat lava dome forming.
Kīlauea’s Lava Lake
The surface of the Kilauea Lava Lake found on January 10, 2021. The cooler, hardened surface can be found on the suitable. Credit rating: Rob Simmon, World.
Considering that late 2020, Kīlauea has burst back again to existence immediately after in excess of two decades of silent. The summit eruption has started off to fill the deep crater that formed through the 2018 Decrease East Rift Zone activities. In the system, a new lava lake (above) as established by itself at the summit and it is becoming fed by a vent on the side of the lake. After about a thirty day period of eruption, the lake is now in excess of 650 ft (two hundred meters) deep!
In this animated GIF (below) of the filling of the lava, you can see how fluid it is as a floating island of cooled lava moved close to its surface. You can also see how the surface behinds like a layer of “plates” of lava that are established and wrecked — a bit like a mini version of plate tectonics. The vent feeding the lava lake is close to the base of the impression.
Animated GIF of thermal photographs from the new Kilauea lava lake. Credit rating: USGS/HVO.
Lava lakes demand reduced silica lava termed basalt. Now, by “reduced silica”, we’re nonetheless chatting forty seven% of the lava is made of silica along with factors like iron, magnesium, calcium and lots of other individuals. This basalt has shut to the lowest viscosity and highest temperature of any lava erupting on Earth currently and that will allow for a lava lake to sort as along as new lava is continually fed.
Etna’s Lava Flows
The lava flows (suitable side of summit) from Etna found by Sentinel-2 on January 19, 2021. Credit rating: ESA.
On the other side of the world, Etna on Sicily has been erupting vigorously so far this yr. The eruptions have produced explosions at the summit as effectively as lava flows that have headed down the jap slopes. The eruption has also spread ash on the slopes of the volcano.
Thermal impression of the lava flows from Etna in Italy on January 21, 2021. The lava flows demonstrate up as vivid in this impression. Credit rating: INGV Osservatorio Etneo.
The basaltic andesite lava erupting at Etna is somewhat a lot more silica loaded than Kīlauea’s. This usually means it is stickier and tends to create Strombolian eruptions. These eruptions have explosions triggered by massive bubbles of gas climbing via the pipe that sales opportunities from the source of the lava beneath the volcano to the surface. The lava is nonetheless runny sufficient to sort lava flows from the vent as effectively and that’s what is taking place at Etna suitable now. The infrared impression from Sentinel-2 reveals the lively flows coming down from the Southeast Crater.
La Soufrière’s Lava Dome
Finally, we get to lava domes. These are formed by even stickier lava that erupts like squeezing toothpaste out of a tube. The lava does get far and as an alternative just “piles up” making a thick dome. Volcanoes like La Soufrière on St. Vincent erupt andesite (not to be confused with the previously outlined basaltic andesite) that may have up to sixty five% silica. This would make it much 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: University of West Indies Seismic Analysis Heart.
The new lava dome forming at La Soufrière is in excess of one,one hundred ft (380 meters) throughout and three hundred ft (90 meters) thick. It started off forming at the incredibly conclude of 2020 and it was the initial eruption at La Soufrière given that 1979. Test out this video clip of a helicopter flight in excess of the escalating lava dome.
The domes steep sides and serious thickness looks extraordinary for andesite lava erupting when compared to the basalt lava of Kīlauea. On the other hand, the viscosity of lava goes up speedy when a lot more silica is added. The lava in the Soufriére dome may be up thousands of situations stickier than the Hawaiian basalt. If you evaluate the far ends of the lava compositional spectrum — basalt and rhyolite — you find that rhyolite is a billion situations a lot more viscous! Some rhyolite lava domes and coulees (sort of like a hybrid of a dome and circulation) can be hundreds of ft thick.
Most eruptions of lava to sort these attributes are reasonably passive. When you’re thinking about volcanic hazards, lava flows are undesirable for properties and infrastructure but not people today. All of this difference in stickiness is what drives the unique types of lava lakes, flows and domes.