After an earthquake swarm in Iceland and a subglacial flood, Grimsvotn is now on an increased alert. The volcano is in the final stages of its eruption and is now at critical pressure.
Grimsvotn currently is the main candidate to the next larger. explosive eruptionIceland. The latest activity has made it very close to an eruption, as you can see from all of the data. It could be days away. The volcano is under increased surveillance as it often erupts violently and explosively, sometimes with devastating effects that can extend across the Northern Hemisphere.
Below is an image of Grimsvotn’s last eruption in 2011, taken by IMO Iceland.
FIRE MEETS IICE
Iceland is a volcanic Island in the North Atlantic and one of the most active. Volcanic regionsAll over the world. History has shown that volcanic eruptions can have devastating effects on Europe, North America, the entire Northern Hemisphere, and everything in between.
The island is prone to earthquake activity due to its location on the boundary between North American and Eurasian plates. This boundary is also known to be the Mid-Atlantic Ridge. The plates are separating from one another, effectively tearing apart the island. It is the only area in the world that the Mid-Atlantic Ridge rises over the ocean floor.
The spreading can be seen in the image below. Tectonic platesIt is located in the middle of Iceland, where the Mid-Atlantic Ridge crosses. It begins in the southwest at the Reykjanes Peninsula and then heads towards the east before turning north. The main central volcanoes are marked with red triangles.
The tectonic plates were spread across the Atlantic Ocean. This is why this place is so special. It has produced a large volcanic island for millions of years.
Answer: A vertical plume of hot, molten rock from mantle. Also known as a “a” HotspotAlternatively, it could be called a Mantle Plumme. Extensive studies have shown that it lies below Iceland (similar to the hotspot beneath Hawaii). It is commonly known as the Icelandic Plume. The image below is a graphic representation of the rising plume of mantle beneath Iceland.
This plume is composed of high-pressure magma that has been ejected from the Earth’s depths. It took the path of least resistance and broke through the cracks between the tectonic plates that were spreading, creating an island.
In the image below we can see the Earth’s terrain without the oceans. The Mid-Atlantic mountain ridge can be clearly seen from the southwest. And also you can see the large “lava pillow” of sorts, on which Iceland sits. It was formed by the mantle plume pushing through the spreading plates tectonic.
We created a high-resolution video that shows the daily earthquake locations of Iceland since January 2019. It is easy to see that the main earthquake activity is located exactly on Iceland’s Mid-Atlantic Ridge, which has constant daily activity. The north and southwest are the most active. This is where the mid-Atlantic Ridge enters and exits Iceland.
The plume has its pulses, or cycles, which cause periods of higher or lower volcanic activity in Iceland. We are now in a new period with increased activity over the past few years. This plume is found under Iceland’s entire territory, but its core lies beneath the largest Icelandic glacier. Vatnajokull.
Below is an image showing the approximate center of the plume connecting with Iceland under Vatnajokull glacier. (black circle). You can also view the mid-Atlantic Ridge in orange and volcano locations.
Vatnajokull is both the largest glacier in Iceland, and the largest European ice cap. It covers approximately 7.900 km2, but it shrinks over time. Many different volcanoes can be hidden under this glacier. They are covered by hundreds upon hundreds of meters of solid snow and ice. Below is an image showing the main central volcanoes below Vatnajokull. Grimsvotn (the largest) and Bardarbunga (the smallest).
Bardarbunga’s volcano last erupted in 2014. However, the eruption took place outside the glacier. Magma traveled more than 40 km below the ground towards the northeast before finally erupting.
The eruption was of the more peaceful “Hawaiian style“, and lasted for about 6 months (August 2014 to February 2015). Below is an image showing the lava field that surrounded Vatnajokull at its end. It covers 85 km (33 miles) of land.
The other major volcano beneath the glacier is also our focal point for today. Grimsvotn. It last erupted in 2011 and, unlike the peaceful lava flow at Bardarbunga in 2014., it was explosive. Grimsvotn could be one of the main candidates for the next. explosive eruptionWe will be looking at Iceland’s recent activity as it could be days away from an eruption.
Below is an image showing the explosive eruption that occurred in Grimsvotn, May 21, 2011.
FAGRADALSFJALL VOLCANO OERUPTION 2021
Iceland usually experiences a volcanic eruption every 4-6 years. The last eruption occurred in mid-September 2021. It began on March 19, 2021. As in 2014, it was also a peaceful lava flow eruption that occurred in the Fagradalsfjall volcanic region. This area can be found on the Reykjanes Ridge, southwest Iceland. The image was taken by Icelandic Meteorological Office (IMO), the official volcano monitoring agency of Iceland.
Below is an image of the lava fields during eruption. The eruptive conical lights are glowing red and the eruptedlava is already cooling down and turning darker. The eruption points were constantly erupting lava, and there was a lot of lava spattering. Photo by: Almannavarnir/Björn Oddsson.
The Icelandic Met Office estimates that approximately 151,000,000 cubic meters of lava erupted (5.3 billion cu ft) over an area of 4.8km2 (1.9 square miles). Below is a @geoviews map showing the spread of lava field and the eruption cones.
EXPLOSIVE GRIMSVOTN VOLCANO
Grimsvotn, a subglacial volcanic eruption, is completely covered in snow and ice. It has high thermal power. This means it melts the ice from below, creating Grimsvotn lake. This is a crucial part of the volcano, which we will discuss below.
This isn’t your typical pointy mountain volcano. calderaComplex, made from individual calderas. Its calderas were formed after large volcanic eruptions over hundreds of years.
A caldera is a depression that forms in the ground after a large volcanic eruption. The ground sinks to the bottom of the volcano’s void, which was previously occupied with magma that had erupted. Large calderas are the best volcanoes in the entire world.
Grimsvotn is active quite often, with its most recent eruptions occurring in 1998, 2004 and 2011. This gives an average interval of 6 to 7 years between eruptions. Its last eruption was May 21, 2011 and ended May 28, 2011. It was a large explosive explosion.
It has been more than 10 years since the event. However, this eruption was very explosive and the volcanic system may take longer to recover. Below is a satellite photo from NASA/MODIS of the eruption plume during the 2011 eruption.
The most explosive eruption in Iceland in over 100 years was the last Grimsvotn. The ash plume reached 20km (12 miles) in height, creating an enormous ash cloud. The image below shows a radar scan that shows the ash column’s tops at 15km above the ground at the time the scan was taken.
The ash cloud caused minor disruptions in air travel, with around 900 flights cancelled across Europe. This is a far smaller number than the 95.000 flights that were cancelled last year.
The Eyjafjallajokull volcano erupted in spring 2010. It sent an ash cloud straight towards Europe. It caused widespread cancellation of air traffic, resulting in the destruction of billions of dollars to the global economy. The image below shows how the ash fell over Europe in 2010. This caused a lockdown of airspace over Europe and the North Atlantic.
Grimsvotn’s 2011 eruption was much bigger than the 2010 eruption of Eyjafjallajokull, yet it caused only 1% of the total flight cancellations that we have seen during the 2010 eruption. The image below shows the rising ash column during the 2011 eruption, taken by Ólafur Sigurjónsson.
Because the ash cloud was mostly carried away from Europe by the high altitude winds, there were fewer flights that were cancelled in 2011. A new set of air traffic protocols and rules was introduced after the 2010 eruption. The only way to cancel a flight is if it reaches a certain level of ash or is detected at the airport traffic flight level.
However, the new rules do not apply if the winds carry the 2011 ash cloud towards Europe. It would still cause severe air traffic disruptions.
It is often said that the Grimsvotn volcanic eruption is imminent. Volcanoes can change their behavior at any moment, so they are never overdue. Although Grimsvotn has experienced calm periods of over 15 years with no eruptions, it is still a rare event in modern records.
Why is it that some Icelandic eruptions are very calm with lava flows and others can send ash clouds around Northern Hemisphere? The answer is simple: Ice.
Iceland can experience very explosive eruptions from volcanoes that erupt below ice (a subglacial volcanic eruption). This is because of the rising heat magmaThe glacier meets ice (or water/lake below it) on its way to the surface, creating an explosive reaction.
ROAD TO ERUPTION
Monday morning, December 6th, saw an M3.6 earthquake in the Grimsvotn volcano. It was located near the surface. This earthquake was unusually strong for the volcano and was the strongest in Grimsvotn since its last eruption. Grimsvotn saw 16 earthquakes in this earthquake swarm. Smaller earthquakes are now following closely.
Below is a map from the IMO that shows earthquake activity within the last 48 hours around Vatnajokull glacier. The star indicates the location of M3.6 earthquake which occurred at Grimsvotn volcano. There are several other earthquakes that can be seen in the volcano. They form a linear pattern.
In response to the earthquake swarm, the aviation code for Grimsvotn volcano has been changed from yellow to orange. The color code was changed from orange to yellow due to the significant decrease in activity. Below is the Iceland volcano alert map, which shows 3 volcanoes that are under yellow alert.
The earthquake swarm on its own is not such a big deal if it weren’t for two important factors. First, there was a glacial flooding ongoing from the Grimsvotn volcanic. And second, the volcano is already close to the “breaking point” with an eruption starting from just one more strong earthquake.
GPS measurements showed that the ice sheets over the volcano have begun to subside, which indicated that Grimsvotn was probably causing flooding.
In the first few days, the ice sheet subsided by 60 cm. The speed of subsidence increased quickly. These measurements suggest that water has probably started to leave the subglacial lakes beneath the ice sheets.
Below is an image that shows GPS measurements of Grimsvotn’s glacier. We can see that the ice layer over the volcano has decreased by an incredible 78m (256ft). This is because the water from the subglacial lake was flowing, and the ice sheet then collapses into the void.
There have been instances in the past of Grimsvotn eruptions that started after a flood. An eruption can be initiated when the pressure on the volcano is reduced by the loss of water from the Grimsvotn lakes. This was also true in 2004 and 1934, respectively. The eruption began in 2004 three days after the first observations of flood onset. In the days before the eruption, there were several earthquakes.
The sinkhole can be seen in the ice sheet to the southeast of the volcano. It is most likely that the water is being drained away from the subglacial lakes. Photo by IMO – Njál Fannar Reynisson.
Below is the image of the tremor levels recorded at two monitoring stations in Grimsvotn. As the water from the subglacial lake was released, we can see the tremors increasing in frequency over time. The vibrations from a large mass under the ice create the tremor. The ice sheet subsidence has declined significantly and tremor has now slowed down. It is believed that most of the water has left Grimsvotn.
The current tremor can be seen on the image below. It is visible from a monitoring station located directly on top. The tremor is clearly visible and the return of previous levels can be seen. We do not see that the signal is calm as there is constant microseismicity in the volcano.
The display below shows microseismicity in greater detail. It also shows many earthquakes taking place in Grimsvotn. They are too weak to register and properly locate. Some of the activity can also be found on the ice sheet.
According to current data, Grimsvotn is now in its final phase before the eruption. It is currently among the top three candidates for the next major explosive eruption in Iceland, alongside Hekla and Katla volcanoes to the southwest.
Grimsvotn was the only volcano among the three that was at the orange alert level. It is active with regular earthquakes, and all data confirms that it is at the eruption threshold levels. It can be triggered by a single larger earthquake at the right spot.
Since late 2019, we have been seeing a steady but slow increase in the number Grimsvotn earthquakes. We saw the highest monthly earthquake rate in March 2020 since the eruption of 2011.
An ongoing and steady increase in Seismic activityThis is often a sign that a volcano is on the verge of erupting. The graphic below is by IMO. It shows the daily, weekly and monthly earthquake rates over time. The monthly rate nicely illustrates the steady increase.
But earthquake numbers are only one part. Sometimes, it is more important that we look at the earthquake power as well as their energy release. One or more powerful earthquakes can have a greater impact than 1,000 smaller ones.
The earthquake was captured by IMO in the image below Energy release(seismic moment), at Grimsvotn. It is quite easy to read. It is evident that Grimsvotn needs to release some energy in order for it to trigger an eruption. This was the case in 2004 and 2011.
This is directly related to the volcanic pressure increase. Thanks to the latest magnitude 3.6 earthquake, we have now crossed the threshold for an eruption. It was very energetic and caused a strong spike. This pushed the total seismic energy released at Grimsvotn up to the highest levels ever recorded between eruptions.
To give you an idea of where these earthquakes are occurring, we created a map showing the Grimsvotn earthquakes between 2019 and 2021. The area around the Grimsvotn calderas is shown in the top outline. The bottom outline is another volcano that is part of the Grimsvotn volcano system. The colors show the depth of the earthquakes measured in meters.
It is easy to see that most earthquakes occur on the east and south sides of Grimsvotn. They occur when the magma chamber beneath the volcano is rebuilding pressure and recovering. This creates strain on the crust around the volcano, cracking the ground, and causing earthquakes.
Ground movement around the volcano is also important to confirm an eruption. We must look for signs that earthquakes may be being caused by fresh hot magma, which is entering the volcanic systems underground, accumulating and increasing the pressure inside the volcano. It’s like a balloon being inflated until it explodes. Ground deformation and accumulating magma are called Inflation.
As seen on the monitoring equipment, Grimsvotn is one the fastest inflating volcanoes both in Iceland and around the globe. It is located very close to the center Icelandic plume and receives a constant supply of new material into its deep magmatic systems.
Below is an image from IMO showing data from a Grimsvotn GPS station, which monitors ground movement. The graph at the bottom shows ground movement up and down. This is what is most important.
The ground at Grimsvotn has risen by more than 60 cm (2ft) since the 2011 eruption. The magma that has accumulated under the volcano is causing enough pressure for the ground to rise. This is a common occurrence at volcanoes about to erupt. However, there is no rule to determine how much a volcano needs to inflate before it erupts.
ASH CLOUD FORECAST
Grimsvotn is very likely to experience an explosive eruption in the near-future. It is powerful enough that it could have an impact on Europe, and other parts of the Northern Hemisphere.
A large explosive eruption, like the one in 2011, could severely limit air traffic if it blows towards Europe. It could have a huge economic impact. This is why Iceland’s large explosive volcanoes are closely monitored. However, it is important to consider the direct impacts of ash on Icelandic daily life.
Below are images from the NOAA Hysplit modeling. It shows the movement and size of the ash cloud in the event that Grimsvotn had a medium-sized eruption on December 9. This simulation was forced by the weather forecast. Each 12 hour, one line is simulated so that we can see how the trajectory changes over time.
The first image shows the ash dispersal at 10km (33.000ft) elevation, which is below the aviation level. The ash cloud would initially move to the north and then rapidly descend over Scandinavia into central Europe. This would likely close most of Europe’s airspace.
We can see the same story at 8km (26.000ft), which is slightly lower. The ash cloud is likely to have dispersed over Scandinavia, and into central Europe.
Below, you can see how the air motion at 10km (33.000ft), would move the ash particles around the Northern Hemisphere. This simulation is only a simulation and much depends on when the eruption occurred. This scenario could look very different if an eruption occurred on Dec 14th. This is only to demonstrate the potential for the ash cloud to be dispersed.
Grimsvotn’s past is far more violent than closing airspace. A series of Grimsvotn eruptions, around 10.000 years ago deposited large amounts of ash across the region. The ash layer resulting from these eruptions was found in numerous locations, including Iceland, the North-Atlantic Ocean, northern Europe, parts central Europe, and the Greenland Ice Sheet.
This layer is called the Saksunarvatn Tephra and is so widespread it is being used to mark a common point in time when studying the sediment layers and analysing history. This ash deposit wasn’t formed from one single eruption. It was created from a series large Grimsvotn eruptions that occurred over a 500 year span.
But much more “recently”, in 1783, an eruption occurred in Iceland, on the Lakifissure line is actually part of Grimsvotn’s volcanic system. The eruption of the Laki volcanic fissure in the south of the island is considered by some experts to be the most devastating in Iceland’s history.
It caused the greatest environmental, economic, and social catastrophe in Iceland. 50 to 80 percent of Iceland’s livestock was killed, leading to a famine that left a quarter of Iceland’s population dead.
The volume of lava that erupted is large. Nearly 15 cubic kilometers (3.66 miles) of lava were released, making it the second-largest lava eruption on Earth in the last millennium. Below is a map showing the location of Laki fissure lines within the two red lines.
The Laki eruption had a huge impact and lasted well beyond Iceland. Global temperatures fell, with crop failures in Europe and famine in Europe. Millions of tonnes of sulfur dioxide (and hydrofluoric acid) clouds were released into Europe’s Northern Hemisphere. Although some experts believe that the eruption could have contributed to the French revolution, this remains a topic of debate.
Laki is part of the large Grimsvotn volcano system, which extends well past the main Grimsvotn caldera. It also includes several other volcanoes along the same line towards southwest Grimsvotn. It is unlikely that another Laki-style or larger eruption will occur in our lifetime, but it is possible.
Globally, the main effects of Grimsvotn’s near future are large ash cloud formations that could disrupt air traffic and impact the already fragile global economy following the Covid-19 crisis. Ash deposits in Europe are also possible after an explosive eruption.
We will be keeping an eye on Grimsvotn, and all Icelandic volcanoes, and we will notify you of any developments. The Icelandic Meteorological Office is the official agency in Iceland to monitor volcanoes. Here you can find live data and additional information as well as all official warnings.
ENSO Update: La Nina has reached its peak cooling for Winter Season. An El Nino event is now more likely for next year.
Source: Severe Weather