Semeru Volcano Erupts and the Big Impacts

Semeru volcano erupts with various eruption types and many impacts. Since the beginning of 2025, increasing activity has occurred. It is marked by volcanic earthquakes. Until the end of year, its activity consistently occurred. It peaked at the end of the year, similar to the previous year. Various risks arise from the continuous eruptions, varying in strength.

Semeru Volcano Erupts Based on Its Chronology

The series of Semeru's eruptions this year is very long. The consistently increasing activity created greater risks. Below is a record of Semeru's eruptions, from the initial increasing activity at the beginning of the year, the first eruption, the most powerful eruption, until the increasing and decreasing activity status at the end of the year.

1. Volcanic Activity Starts to Increase

Since the beginning of the year, Semeru has started to increase in activity. It was signed with regular eruptions from minor to moderate eruptions. All of these include phreatic eruptions.

Phreatic eruptions occur due to the heating of crater water or groundwater by the heat of magma. Magma at its very high temperature boils water before it explodes. After the water boiled and exploded, some materials, like hot steam, water, sand, small rocks, and dust, were released.

These explosions are triggered by extreme heat, not magma pressure. The pattern of activity has consistently increased, marked by successive eruptions and a growing ash column. The frequency of volcanic earthquakes has also increased.

2. First Explosive Eruption

In the middle of the year, on July 9^th, the first explosive eruption occurred. According to the prediction, it has become a mark of a more active and larger eruption era. The ash plume flowed farther and more frequently. The activity status was raised to Advisory (Level II).

3. Increase to Level III

As volcanic activity increased, a subsequent eruption on September 23^rd raised the activity status to Alert (Level III). Based on monitoring, there were incandescent lava flows and thick white to gray ash columns. A total of 65 volcanic earthquakes occurred, with 11 to 22 mm in range of amplitudes.

4. Increase to Level IV

The status activity was changed from Level III to Warning (Level IV) after a massive explosive eruption. The thick gray smoke, hot lava, and a 13-kilometer of hot clouds are the impacts of an eruption on November 19^th. It is the peak of Semeru's activity that always occurs at the end of the year. It aligns with its track record.

5. Decrease to Level III

Activity was actually high from November 19-28, but without being accompanied by strong new magma. A minor to moderate eruption was recorded on November 29^th. There was no magma pressure from within. The status was decreased to Level III. At the end of the year, several eruptions occurred on December 3-28. Subsequently, 38 eruptions and two tectonic earthquakes occurred on December 29^th.

The Impacts of Eruption

Semeru has a regular eruption cycle. Semeru volcano erupts with explosive and effusive, a mixed eruption type. These eruption types cause many impacts as follows.

1. Ash Rain

The impact of ashfall depends on many factors related to the eruption conditions. The factors are the strength of eruption, the eruption type, the size of ash particles, and the explosive power of water vapor. Thick ashfall generally occurs during explosive eruptions. The distribution of ash is more even in all directions if the particles are fine and the wind is blowing in all directions.

2. Hot Cloud Fall

The next extremely threatening is the pyroclastic avalanches that have hot temperatures and rapid movement. The massive eruption on November 19^th sent pyroclastic materials up to 13 km to the southeast. The impact extended to residential areas and land.

3. Lava Floods

Massive eruptions that release incandescent lava and pyroclastic material occur at the peak activity at the end of the year. The peak of the rainy season is also at the end of year, and potential for extreme rainfall. When extreme rainfall meets a massive eruption, it has the potential to trigger lava floods. This already occurred after the major eruption on November 19^th.

4. Injured Victims

Although it didn’t cause fatalities, three people suffered burns because of a major eruption on November 19^th. After several days in intensive care, their condition has been getting better. Hundreds of residents were displaced to several safe locations, but some of them have returned home.

5. Material Loss

The massive eruption on November 19^th also damaged the residential area, land, and public facilities. All of these were caused by avalanches of hot clouds, ejections of solid material, heavy ashfall, and lava floods. The material losses were enormous.

6. Infrastructure Damage

Not only residential areas, but the eruption also damaged many infrastructures. It was due to the accumulation of solid material that slid down with the pyroclastic flow. Lava flooding also worsened the severity. Road access was cut off due to the series of eruptions and their impacts.

Semeru volcano erupts with various impacts that could have been reduced through increased risk mitigation. Pre-disaster mitigation measures are crucial. The basis is an early warning system with an alarm or siren as a warning signal. The emergency messages complete the warning signals, so it can improves the public awareness and expedite evacuation.

Emergency messages can be sent in real time through mobile phones. An emergency message-sending machine based on SMS (Short Message Service) is a solution. It has a wide range of 500 m up to 2 km for real-time message delivery. All operators will receive the same delivery speed. The government can procure the machine at smsbroadcaster.com.