2023 Iceland earthquakes facts for kids
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| UTC time | 2023-11-10 18:00:56 |
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| USGS-ANSS | ComCat |
| Local date | 24 October 2023 (23 days) |
| Magnitude | 5.3 Mw (largest tremor) |
| Depth | 2–10 km (1.2–6.2 mi) |
| Epicenter | 63°51′00″N 22°34′44″W / 63.850°N 22.579°W |
| Areas affected | Reykjanes Peninsula, Iceland |
| Max. intensity | VIII (Severe) |
| Casualties | None |
| 2023 Sundhnúkur eruption | |
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The 2023 eruption taken by the Icelandic Meteorological Office on 18 December 2023
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| Volcano | Svartsengi |
| Type | Fissure eruption |
| Location | Reykjanes Peninsula, Iceland 63°52′44″N 22°23′13″W / 63.879°N 22.387°W |
| Impact | Earthquakes, ground subsidence, lava fountains, lava flows; town of Grindavik heavily damaged and evacuated |
An intense earthquake swarm in Iceland's Reykjanes Peninsula began on 24 October 2023, due to a magmatic intrusion underneath the area. The frequency and intensity of the earthquakes dramatically increased on 10 November, with 20,000 tremors recorded by that time, the largest of which exceeded magnitude 5.3. An evacuation was ordered in the town of Grindavík, which is located near the area of the seismic activity. Large-scale subsidence in and around the town is reported to have caused significant damage.
On 18 December 2023, a volcanic eruption began at Sundhnúkur north of Grindavík.
Contents
Background
Although earthquakes are a frequent occurrence in Iceland due to the island straddling the Mid-Atlantic Ridge between the Eurasian and North American tectonic plates, the recent swarm was noted for being more extensive than usual. Three volcanic eruptions have occurred in the Reykjanes Peninsula since 2021, around the Fagradalsfjall volcano.
The 2023 earthquake swarm is associated with a magmatic intrusion estimated to be up to 15 kilometres (9.3 mi) long that runs in a south-westerly direction, starting at Kálfellsheiði and following the line of the Sundhnúkur crater chain at a depth of around 800 metres (2,600 ft). The largest of the earthquakes originated under the Sundhnúkur craters but subsequently propagated south-west under Grindavík and into the sea. The town stands on lava erupted from Sundhnúkur around 2,350 years ago. It is one of six communities on the peninsula that are situated on or near an eruptive fissure.
Earthquakes
The 2023 earthquakes came nearly four years after volcanic activity began near the hyaloclastite mountain Þorbjörn, which indicated that the Reykjanes Peninsula was beginning a new volcanic cycle after 800 years of inactivity. This is the fifth time a magmatic intrusion has formed in the Eldvörp-Svartsengi volcanic system since December 2019. The previous intrusions have not resulted in an eruption. Previous volcanic unrest on the peninsula has mostly been associated with the Fagradalsfjall system, where three out of four confirmed magmatic intrusions have culminated in volcanic eruptions.
October
An earthquake swarm began on the evening of 24 October due to the magmatic intrusion, with the intensity of the earthquakes decreasing by 30 October. Approximately 8,000 earthquakes were detected; most of these tremors occurred at a depth of 2–4 km (1.2–2.5 mi). The Icelandic Meteorological Office (IMO) reported that the swarm was focused around Svartsengi, north of Grindavík. Earlier in the month, the Reykjanes Peninsula experienced over 700 earthquakes, with the strongest one reaching a magnitude of 3.3.
November
The largest of the earthquakes to date reached magnitude 5.3 on 10 November. By this time, over 22,000 earthquakes had been recorded since the beginning of the swarm in October. The IMO predicted that an eruption was likely, stating that "it will take several days (rather than hours) for magma to reach the surface." The greatest extent of the magma intrusion was inferred to be around the Sundhnúkur crater chain, approximately 3.5 km (2.2 mi) north of Grindavík. Instruments detected the presence of sulphur dioxide in the atmosphere on 14 November, indicating that magma was only a few hundred metres under the surface. Although the number of earthquakes decreased somewhat since 10 November, the IMO was still recording between 700–1,000 earthquakes daily by 14 November.
Ground deformation sensors at Festarfjall and Svartsengi recorded that the ground had moved apart by 120 cm (47 in). Satellite measurements recorded the subsidence by about one metre (3 ft) of a swathe of land measuring approximately five kilometres long and two kilometres wide (3.1 by 1.2 mi), running from the Sundhnúkur craters to the western side of Grindavík. The creation of this graben-like formation has enabled scientists to estimate the volume of the magmatic intrusion as approximately 70 million cubic metres (2.5 billion cubic feet). It is estimated that the subsidence has been continuing at a rate of about four centimeters (1.6 inches) a day. A large crack opened up through the town, which old maps indicate is a reactivation of an existing fault. Scientists at the University of Iceland believe that the fault was created by the last Sundhnúkur eruption over 2,000 years ago.
Sensors emplaced in a borehole in Svartsengi detected the presence of sulphur dioxide on 16 November, a classic signature of magma close to the surface. This has led the IMO to conclude that the area around the volcanic edifice of Hagafell approximately 2 km (1.2 mi) north of Grindavík, is at the highest level of risk. A rapid 30-millimetre (1.2 in) uplift of the ground in the Svartsengi area was recorded from 18–21 November, likely indicating an upwelling of magma from a source five or more km (3.1 or more miles) below the ground. An eruption was still regarded as likely on 21 November, but as seismic activity declined from 24 November that likelihood also began to decline.
According to Professor Magnús Tumi Guðmundsson, a geophysicist at the University of Iceland, the magma channel, approximately two meters wide, has undergone rapid solidification. Around 90% of the magma solidified within 10 to 15 days due to the cold nature of the earth's crust, with some remaining magma near Sundhnúkur posing potential risks for further activity if underground pressure increases. Magnús notes that while the magma cools quickly, the surrounding rock stays hot and weak, maintaining a state of geological vulnerability in the area for several months, necessitating ongoing caution and monitoring. If an eruption occurs, it is most likely to take place in the area between Sýlingarfell and Hagafell mountains.
Significant land movements were recorded around the Svartsengi area, with a displacement of about 100 cm (39 in) to the west and 25 cm (10 in) to the north. During the evacuation of Grindavík on 10 November, the ground near Svartsengi initially descended by 35 cm (14 in) and subsequently rose by 25 cm (10 in). A GPS station at Festarfjall, situated east of Grindavík, underwent a shift of 60 cm (24 in) eastward and 40 cm (16 in) southward, along with an upward movement of 12 cm (4.5 in). Moreover, the GPS station in Grindavík, directly above the magma conduit, moved 30 cm (12 in) eastward. On 10 November, at the aforementioned location, there was a dramatic drop of 100 cm (39 in), followed by an additional sinking of 20 cm (8 in).
December
By 1 December "relatively few earthquakes" were being detected, although the IMO maintained that an eruption was still possible. It is most likely that the magma accumulating under Svartsengi is feeding the 15 km-long (9.3 mi) Sundhnúkur crater chain, where the magma intrusion occurred. Deformations are still being measured at stations near the conduit, but it is believed that this is due to the land uplift occurring at Svartsengi. At the beginning of the month, recent GPS data from the IMO showed that the land had risen above its level prior to the start of the earthquake series. Professor Þorvaldur Þórðarson, a volcanology expert from the University of Iceland, theorized that this elevation could be attributed to a combination of tectonic movements and magma build-up. Notably, the pronounced terrestrial shifts on 10 November may have facilitated the migration of magma from deeper reservoirs to more superficial ones.
The ongoing volcanic activity at Svartsengi entered a new phase with increased chances of magma propagation and potential eruptions. The observed pattern suggested a possible repetition of events, where magma accumulating beneath Svartsengi feeds a dike beneath Grindavík, similar to the one formed on 10 November.
The recent seismic trends at Svartsengi, characterized by varying intensities and a concentration of activity along a dike, closely resembled the seismic and volcanic patterns experienced during the Krafla Fires, which began in 1975. In the Krafla Fires, over a period of ten years, the region witnessed 20 distinct magma propagations, nine of which culminated in eruptions. These events were marked by varying magma volumes feeding the same dike, leading to different eruption scales. In Svartsengi, geodetic data showed a similar pattern of reduced magma volumes compared to levels observed before the 10 November dike intrusion, parallelling the smaller magma accumulations at Krafla that were sufficient to trigger new propagations and subsequent eruptions.
From the beginning of the earthquakes until 10 November, the land at Svartsengi elevated by more than 10 cm (4 in) within a span of 16 days. Following a substantial subsidence of 35 cm (14 in), a new phase of activity led to a land rise of 20 cm (7.9 in) over an equivalent 16-day period. Currently, the land has consistently ascended to about 30 cm (12 in) in approximately 30 days. As a result, the rate of uplift went to double the initial rate and surpassed its height just before the precursor of the magmatic intrusion. The subsidence previously mentioned was due to the path of magma originating from Svartsengi, moving under Grindavík, and extending towards the Sundhnúkur craters in the northeast.
The magma flow into the Sundhnúkur crater chain ceased and is now accumulating under Svartsengi at a rate comparable to the flow of the Elliðaár river. The magma lies at a depth of about five to six kilometres (3 to 3.5 mi).
Eruption
On the evening of 18 December 2023, a volcanic eruption occurred at Sundhnúkur north of Grindavík, with images showing lava spewing from fissures in the ground. The intensity of the eruption and accompanying seismic activity decreased early on 19 December, with lava seen spreading laterally from both sides of the newly opened fissures.
The IMO said the eruption occurred at around 22:17 GMT following a series of small earthquakes at around 21:00. It pinpointed the origin of the eruption near Hagafell, about 4km (2.5 miles) north-east of Grindavik, and noted that the eruption stemmed from a fissure with a length of about 3.5 km, with lava flowing at a rate of around 100 to 200 cubic metres per second, adding that seismic activity appeared to be moving towards the direction of Grindavik. An Icelandic Civil Defence official told the Icelandic national broadcaster RÚV that the eruption had happened quickly and appeared to be "quite a large event". The eruption was described as the largest in the area since the beginning of activity in 2021, and was visible as far away as the capital Reykjavik, 42 kilometers away. By 19 December, the scent of smoke and ash was being detected as far as 30km from the eruption site, raising fears that volcanic gases could reach Reykjavik by the next day.
Impact
Grindavík
Following the 5.2 tremor on 10 November, a state of emergency was declared, and evacuation plans were put into effect for Grindavík. This culminated in the relocation of nearly 4,000 residents, equivalent to nearly 1 percent of Iceland's entire population. The Icelandic civil protection authority deployed the patrol boat ICGV Þór to the area "for safety purposes". It also closed all roads to Grindavík except for emergency and evacuation purposes. On 13 November, authorities allowed residents to return briefly to the town to retrieve their belongings. Boat owners were also allowed to remove their vessels from the harbour. The Icelandic government is seeking to accommodate displaced residents in holiday homes and little-used properties while the emergency continues. The subsidence, faulting and earthquakes have caused widespread damage to properties and infrastructure in the town. The seismic activity has received significant coverage by the international media. The evacuation of Grindavík has been described as the first community-level evacuation in Iceland since the eruption of Heimaey in 1973.
Prior to the evacuation, reports emerged of individuals relocating due to the incessant tremors disrupting sleep and fears of potential consequences. During the evacuation, the Icelandic Red Cross provided accommodations for about 1,700 displaced residents at three emergency centers in Keflavík, Kópavogur, and Selfoss. Of these individuals, approximately 140 actually spent the night in these centers. The majority of the other displaced residents independently found alternative accommodations elsewhere. Furthermore, every individual in the Grindavík area received an SMS message from 112, Iceland's emergency service, with the headline 'EVACUATION'.
The Icelandic government plans to assist around 700 residents, who are part of about 200 families, from the original 3,700 population of Grindavík. The plan includes purchasing up to 210 new apartments through the Bríet and Bjarg housing associations, primarily in the Reykjanes area and the Capital Region. This is to be supplemented by temporary financial support for increased housing costs, with the entire support system estimated to cost about 220–240 million ISK per month, subject to a three-month reassessment. This initiative represents a comprehensive effort to provide both immediate and sustainable housing solutions for Grindavík's displaced residents. On 1 December, the government, in partnership with the Government Property Agency, began seeking additional temporary rental properties from private and corporate owners to assist displaced Grindavík residents as part of a larger pre-established housing support program that includes wage and rental subsidies. A week later, a platform for Grindavík residents was launched online, targeting temporary housing in the Reykjanes peninsula, the Capital Region, and neighboring municipalities. It enables direct leasing between residents and property owners, supported by government rental subsidies.
In a collaborative response to the disaster and ongoing uncertainty in Grindavík, Iceland's major banks – Arion banki, Íslandsbanki, and Landsbankinn, in partnership with Finance Iceland (SFF) – agreed to waive interest and indexation on housing loans for Grindavík residents for three months. This relief applies to loans up to 50 million ISK. The measure aims to provide equitable support, including options like deferred loan repayments. Each bank will further outline the specifics of these relief measures, ensuring they are tailored to the evolving needs of their customers in Grindavík.
The State Commissioner of Police, in consultation with the Police Commissioner in the Reykjanes peninsula, downgraded the earthquake risk level in Grindavík from emergency to critical level, effective from 23 November. This decision, based on a new assessment by the Icelandic Meteorological Office, indicated a reduced likelihood of a sudden eruption in Grindavík. Residents and businesses in Grindavík are now permitted to enter the area between 7 a.m. and 9 p.m. to retrieve valuables, attend to their properties, and conduct business activities. However, the town remains closed to the general public and unauthorized traffic. Safety measures, including limited vehicle access, and a prepared evacuation plan, were established and are still in effect. The area, under continuous surveillance, is still considered dangerous, with restrictions on utilities and certain types of vehicles. Residents were advised to keep records of valuables taken and to contact their insurance companies, and to be cautious as houses might be unsafe. However, a resident of Grindavik was later caught staying at his home with his wife for several nights and was threatened with arrest.
The earthquakes in Grindavík significantly affected infrastructure and homes. Around 120 properties suffered damage, with 10–20 deemed uninhabitable. Two weeks following the earthquakes, a thorough damage assessment was initiated and is currently ongoing. The estimated total cost of the damages is up to 10 billion ISK. Property owners with irreparable homes were required to pay a disposal fee from their insurance payout, intended for on-site repairs or rebuilding, not for purchasing elsewhere, unless reconstruction was disallowed. In total loss scenarios, owners were to receive full fire insurance value, minus a disposal fee, typically about 12%. This ongoing evaluation process aims at facilitating community reconstruction.
Blue Lagoon
The management of the Blue Lagoon announced the site's closure to visitors from 9–16 November as a precaution following the earthquakes. Rocks dislodged by the earthquakes were reported to have fallen onto roads in the area while 30 guests left the resort following a 4.8 tremor in the early hours of 9 November. In addition to these safety concerns, the closure was also implemented to reduce increased stress on staff. The management has assured that all staff will receive their full salaries during the closure period. Furthermore, guests who were evacuated as a result of the tremor will be provided with a full refund.
The administrators of the Blue Lagoon subsequently extended the closure announcement five times due to continuing geological activity, with the anticipated reopening date set for 17 December. Despite this, staff members of the Blue Lagoon were seen bathing in the spa's geothermal waters on 8 December. Prior to reopening, the staff was trained in evacuation procedures to ensure preparedness for any emergencies, while the administration prepared an evacuation process, expected to take around two hours in case of emergency. Additionally, guests were to be informed about the current situation.
The Blue Lagoon managed to remain open for just two days before a necessary closure ensued following the 18 December eruption that occurred merely 2 to 3 kilometers away. The anticipated reopening of the Blue Lagoon is scheduled for 28 December. All guests and staff were evacuated from the site roughly one to two hours before the eruption.
Svartsengi Power Station
Since the state of emergency was declared, the Svartsengi Power Station has been unoccupied and is being remotely controlled from the Reykjanes Power Station. The management of the power station expects to maintain this remote operation mode until the end of the year. The Reykjanes Power Station is equipped to generate electricity in case the Svartsengi line is cut off. The capability to deliver hot water, a critical function of the Svartsengi Power Station, cannot be replicated by the Reykjanes facility.
Barrier construction
A strategic plan for the construction of protective barriers had been established well in advance of the recent seismic disturbances in the area. The commencement of this plan was placed on hold, as there was no pressing threat of a volcanic eruption, coupled with the significant environmental repercussions involved. However, on 10 November, due to escalating earthquake activity, a fleet of lorries began delivering materials to the predetermined site near the Blue Lagoon and Svartsengi Power Station. Yet, this initial operation was soon put on hold owing to concerns about a potential eruption later that same day. The construction process was officially resumed on 13 November, following the Althing's approval of a bill proposed by Prime Minister Katrín Jakobsdóttir. Subsequently, Justice Minister Guðrún Hafsteinsdóttir began enforcing the new regulations related to the project the next day. Following this, workers began assembling 'filler materials' into barriers at the planned sites. In parallel, the civil defence department, equipped with plans for more protective barriers, made preparations to extend these measures to Grindavík if necessary.
In response to these developments, the Icelandic government implemented a 0.008% additional property tax, levied on the fire insurance value of properties, to fund the construction of lava barriers on the Reykjanes peninsula and safeguard local infrastructure from potential volcanic eruptions. The temporary tax, which is intended to last for three years, will come into effect on 1 January 2024, and is projected to raise nearly ISK 1 billion annually. The tax is scheduled to expire on 31 December 2026.
Post-eruption
Following the volcanic eruption on 18 December, the Icelandic Coast Guard deployed a helicopter to the area to monitor activity. Numerous delays were reported at Keflavík International Airport, which remained open. The Blue Lagoon spa, which had reopened the day before, did not take bookings on the night of the eruption. Police raised alert levels while civil defence authorities warned the public not to approach the area while emergency personnel assessed the situation.
See also
In Spanish: Terremotos de Islandia de 2023 para niños
- Geology of Reykjanes Peninsula
- List of earthquakes in 2023
- List of earthquakes in Iceland
