which volcano erupted today?

PETROPAVLOVSK-KAMCHATSKY, Russia, April 11 (Reuters) - One of Russia's most active volcanoes erupted on the far eastern Kamchatka peninsula on Tuesday, shooting a vast cloud of ash far into the sky that smothered villages in drifts of grey volcanic dust and triggered an aviation warning.

The Shiveluch volcano erupted just after midnight and reached a crescendo about six hours later, spewing out an ash cloud over an area of 108,000 square kilometres (41,700 square miles), according to the Kamchatka Branch of the Russian Academy of Sciences' Geophysical Survey.

Lava flows tumbled from the volcano, melting snow and prompting a warning of mud flows along a nearby highway while villages were carpeted in drifts of grey ash as deep as 8.5 centimetres (3.5 inches), the deepest in 60 years.

Pictures showed the cloud billowing over the forests and rivers of the far east and of villages covered in ash.

"The ash reached 20 kilometres high, the ash cloud moved westwards and there was a very strong fall of ash on nearby villages," said Danila Chebrov, director of the Kamchatka branch of the Geophysical Survey.

"The volcano was preparing for this for at least a year... and the process is continuing though it has calmed a little now," Chebrov said.

Around 24 hours after the volcano began erupting, a 5.8 magnitude earthquake struck off the coast of Kamchatka, the geological survey said. Russian scientists said the quake was an aftershock from an April 3 earthquake.

About 300,000 people live on Russia's vast Kamchatka peninsula, which juts into the Pacific Ocean northeast of Japan.

The volcano, one of Kamchatka's largest and most active, would probably calm now, Chebrov said, though he cautioned that further major ash clouds could not be excluded. Chebrov said the lava flows should not reach local villages.

There were no immediate reports of casualties, though scientists said the volcano was still erupting 15 hours after the start of the eruption.

The Kamchatka Volcanic Eruption Response Team (KVERT) issued a red notice for aviation, saying "ongoing activity could affect international and low-flying aircraft".

Some schools on the peninsula, about 6,800 km east of Moscow, were closed and residents ordered to stay indoors, head of the Ust-Kamchatsky municipal region Oleg Bondarenko said in a Telegram post.

"Because what I have just seen here with my own eyes, it will be impossible for children to go to school, and in general, the presence of children here is questionable," Bondarenko said.

He said residents' power had been restored and drinking water was being supplied.

Shiveluch has had an estimated 60 substantial eruptions in the past 10,000 years, the last major one being in 2007.

It has two main parts, the smaller of which - Young Shiveluch - scientists have reported as being extremely active in recent months, with a peak of 2,800 metres (9,186 feet) that protrudes out of the 3,283 metre-high Old Shiveluch.

Sulfur dioxide (SO2) emission rates of approximately 180,000 tonnes per day (t/d) were measured on December 1, 2022 and remain elevated at this time. Volcanic gas is rising high and vertically into the atmosphere before being blown to the west at high altitude, generating vog (volcanic air pollution) in areas downwind. The International Volcanic Health Hazard Network has detailed information about vog: https://vog.ivhhn.org/. Forecasts for the dispersion of vog can be found on the Vog Forecasting Dashboard: http://weather.hawaii.edu/vmap/new/

Fissure 3 is generating a lava flow traveling to the north toward the Daniel K. Inouye Highway (Saddle Road) that has reached flatter ground and slowed down significantly over the past several days, as expected. As of 7 a.m. today, December 4, the flow front was about 2.3 mi (3.6 km) from the Daniel K. Inouye Highway (Saddle Road). During the past 24 hours, the lava flow advanced at an average rate of about 40 feet per hour (12 meters per hour). Though the advance rate has slowed over the past several days, the lava flow remains active with a continuous supply from the fissure 3 vent.

Advance rates may be highly variable over the coming days and weeks. On the flat ground between Mauna Loa and Mauna Kea, lava flows advance more slowly, spread out, and inflate. Individual lobes may advance quickly, and then stall. Additional breakouts may occur if lava channels get blocked upslope. There are many variables at play and both the direction and timing of flow advances are expected to change over periods of hours to days, making it difficult to estimate when or if the flow will impact Daniel K. Inouye Highway.

Tremor (a signal associated with subsurface fluid movement) continues beneath the currently active fissures. This indicates that magma is still being supplied to the fissure, and activity is likely to continue as long as we see this signal.

There is no active lava within Moku'āweoweo caldera nor the Southwest Rift Zone. We do not expect any eruptive activity outside the Northeast Rift Zone.

Most recent eruption map:  https://www.usgs.gov/maps/december-3-2022-mauna-loa-eruption-map

Information on lava viewing: https://www.khon2.com/local-news/mauna-loa-eruption/new-4-5-mile-route-opened-to-view-mauna-loa-eruption/

Volcanic Hazards:

Air quality/volcanic gas plume (fissure eruption): High levels of volcanic gas, including sulfur dioxide (SO2), are emitted from the fissure vents. As SO2 is released from the eruption, it will react in the atmosphere with oxygen, sunlight, moisture, and other gases and particles and within hours to days, convert to fine particles downwind. The particles scatter sunlight and cause the visible haze, known as vog (volcanic air pollution, from “volcanic smog”). Vog creates the potential for airborne health hazards to residents and visitors, damages agricultural crops and other plants, and affects livestock operations.

Lava flows: Hawaiian lava flows generally advance slowly enough that people can avoid them. They can destroy everything in their paths, including vegetation and infrastructure—which can cut off road access and utilities. Hazards associated with active or recent lava flows include hot and glassy (sharp) surfaces that can cause severe burns, abrasions, and lacerations upon contact with unprotected or exposed skin; uneven and rough terrain can lead to falls and other injuries; hot temperatures that can cause heat exhaustion or dehydration, or in heavy rain can produce steamy ground-fog that can be acidic, severely limiting visibility and sometimes causing difficulty breathing.

Tephra fall:  Pele's hair and other lightweight volcanic glass fragments from lava fountains and spattering will fall downwind, dusting the ground within a few hundred meters (yards) of the vent. High winds may waft lighter particles and transport them greater distances downwind. Residents are urged to minimize exposure to these volcanic particles, which can cause skin and eye irritation similar to volcanic ash.

Secondary hazards: Lava flow advance into vegetated areas may generate secondary hazards by igniting small fires in vegetation adjacent to lava flow margins. Lava flows that cover and burn vegetation and soil also introduce the hazard of subsurface natural gas pockets igniting, which can cause methane explosions. These explosions can blast lava fragments up to several meters (yards) away and can be hazardous to observers.