Iceland earthquakes, 18000 in a week Fagradalsfjall Volcano

  • Thread starter Astronuc
  • Start date
  • Tags
In summary, according to the USGS, there have been 18,000 earthquakes in Iceland since the last week. Volcanologists are concerned about an impending eruption in the southwestern corner of the island after 800 years of dormancy. SE corner of Iceland. The strongest earthquake so far in the last two weeks occurred yesterday, at a magnitude of 5.7.
  • #71
My family has added daily videos of that volcano to our routine; just like weather reports. Someday, it would be wonderful to go there to see it with our own eyes.

Below is a satellite picture, showing the extent of the lava. One branch is clearly heading toward the sea, but at the moment, most of the lava is heading NE. Unlike water heading downhill, lava cools and hardens, thus forming barriers. As it fills up a valley and hardens, it eventually forms a dam causing fresh lava to find another direction to flow. Another volcano in Iceland from the distant past is estimated to have produced 42 km3 of lava.

Earth sciences news on
  • #72
anorlunda said:
My family has added daily videos of that volcano to our routine; just like weather reports. Someday, it would be wonderful to go there to see it with our own eyes.
Apparently, flights to Reykjavik are relatively inexpensive at the moment. I don't know about hotels though, or rental cars. I suppose one could hire a local.

Iceland Volcano Update - New Lava Barrier and Lava Flow Forecast (June 14) - one comment indicates the lava volume estimated at 63 M m3, 0.063 km3. The lava flow seems to be increasing and enroaching on a main road to the south of Natthagi Valley. Essentially, three valleys are getting filled.

From an older map in May.


  • iceland-eruption-map23may21.jpg
    48.1 KB · Views: 156
  • #73
Sat, 24 Jul 2021, 05:25 - Fagradalsfjall volcano (Reykjanes Peninsula, Iceland): monthly eruption summary, activity seems to have slowed down
Lava flow area
The lava flow area covered 3.96 square km.

Lava flow volume
Scientists estimate that approximately 96,1 million cubic meters of the lava have so far erupted from all vents. The lava flow has mostly accumulated in the Meradalir valley. No lava flows occurred in Geldingadalur, Nátthaga, and Syðri Meradalir valleys over the past two weeks.

Rock geochemistry
The graph shows the weight percent (wt.%) of magnesium oxide (MgO) (9,7%) and titanium oxide (TiO2) (9,9%) in the erupted magma.
So what is the balance? Silica?

How a volcano saved Iceland's travel industry
  • #74
As evenings are getting longer, I found some time to make some thin section slides of the lava which I collected at Fagradalsfjall. It contains long needles of plagioclase (sodium-calcium feldspar), augitic pyroxenes, some olivine and small black cubic magnetite crystals. This is quite what one would expect from a MORB (middle oceanic ridge basalt). The second picture is taken in linearly polarized light, the third one with crossed polarisator and analysator to bring out the birefringence induced colours. The fourth one is at higher magnification.


  • IMG_0005.JPG
    57.3 KB · Views: 133
  • IMG_0003.JPG
    124.4 KB · Views: 121
  • IMG_0004.JPG
    117.1 KB · Views: 112
  • IMG_0005.JPG
    87.5 KB · Views: 119
Last edited:
  • Like
  • Love
  • Informative
Likes davenn, Tom.G, anorlunda and 4 others
  • #75
Astronuc said:
So what is the balance? Silica?
Strangely enough I did not succeed in finding some real analyses of the lava or basalt from Fagradalsfjall, So I'll try to present my own layman conclusions.
To begin with, the lava contains certainly little silica, because this would lead to a very high viscosity. If you watch the videos, you'll notice that it flows like water, so viscosity is really low.
This is also confirmed by inspection. The lava contains some olivine which is largely incompatible with free SiO2.
The microscopic analysis shows mainly plagioclase, clino- (~ MgCaSi2O6) and orthopyroxenes (~Mg2Si2O6) where Mg may be substituted by iron, and magnetite (Fe3O4), but no quartz or sanidine (K-feldspar). This is a typical composition for a Olivine-Tholeiite from mid-oceanic ridges, or oceanic islands.
From some texts on the internet I infer that the magma is very primitive and stems directly from the asthenosphere, which is in line with the composition found.
  • Like
Likes Astronuc, jedishrfu and BillTre
  • #76
DrDu said:
The microscopic analysis shows mainly plagioclase, clino- (~ MgCaSi2O6) and orthopyroxenes (~Mg2Si2O6) where Mg may be substituted by iron, and magnetite (Fe3O4), but no quartz or sanidine (K-feldspar).
So, bascially, a dark, fine-grained basalt composed largely of plagioclase with pyroxene and olivine?
  • #77
  • #78
In the debris of the basalt, I found one small splinter of olivine, whose optical properties I measured yesterday on a spindle stage attached to the microscope. Check
for a description of the technique.
The olivine has an angle 2V_x between the two optical axes of 89.15 degrees and is optically negative. The axis angle is a monotonous function of the forsterite content of the olivine (W. E. Tröger, Optische Bestimmung der Gesteinsbildenden Minerale, Part 1 Bestimmungstabellen) from which an forsterite content of about 85 % is inferred.
This is quite in line with the values reported for various icelandic basalts in
which range from 78.1 to 90.2 % Forsterite.
Of course my measurement was made on one crystal, only, so that the statistics is rather poor :-)
Last edited:
  • Like
Likes dlgoff and Astronuc
  • #79
Here a picture of the olivine between crossed polarizers. Note the interference colours due to the strong birefringence.


  • IMG_0019.JPG
    18.6 KB · Views: 122
  • Like
Likes dlgoff and Astronuc
  • #80
Fagradalsfjall in Geldingadalur is still producing.

Live camera has been discontinued
Last edited:
  • #81
Wow! How far is the camera from the volcano and hot might it be at that spot?

The camera conveys the feeling of being close but being safe which means its likely not safe at all if the volcano erupted.
  • #82
jedishrfu said:
Wow! How far is the camera from the volcano and hot might it be at that spot?

The camera conveys the feeling of being close but being safe which means its likely not safe at all if the volcano erupted.
I believe the cameras are some km from the fissures and up-hill. The close up views are done with zoom lens. The cameras have been moved back from the original site as new fissures opened closer to the cameras.
  • #83
During vacations I found some time to look at the plagioclase in the basalt under the microscope using a so-called "universal stage" which allows to rotate the thin section around 4 axes, see the picture. This makes it possible to determine the orientations of the principal optical axes relative to some characteristic crystal faces.

As these orientations are known as a function of the composition of the plagioclase, namely the albite (NaAlSi3O8)-anorthite (CaAl2Si2O8) ratio, it is possible to estimate this ratio quite accurately without the necessity to do a chemical analysis or a X-ray microprobe analysis. It turned out that the plagioclase is about 95% anorthite, which is what one would expect for a MORB.

In comparison to albite, anorthite contains less SiO2 and is therefore said to be more basic. The low SiO2 content means that the temperature, where crystals begin to form in the lava is quite high, and the viscosity of the lava is low. This is in line with pictures where the lava can be seen to flow like water. The high anorthite content also points to the lava being quite primitve, meaning that it is still quite similar to the primary magma that formed when the mantle material melted.

So quite a lot can already be learned about this kind of rocks without high-tech equipment.


  • photo5400019376209508627.jpg
    53.7 KB · Views: 108
  • Informative
Likes anorlunda and Astronuc
  • #84
Lava is erupting again on the Reykjanes Peninsula in the Meradalir Valley less than a year after is stopped in the initial eruption at Fagradalsfjall. According to National Geographic, "The latest eruption, which started at 1:18 p.m. local time on August 3, opened up at a fissure only a few hundred feet away from the cone crafted by last year’s volcanic outburst."

The eruption in Meradalir could be 5-10 times stronger than last year
  • #85

Recent findings from Iceland's Fagradalsfjall eruptions change what we know about how volcanoes work (well some volcanoes)​

. . . We can think of the Earth's mantle—from the top of the core to under the tectonic plates—operating much like a lava lamp." As the heat causes regions of the mantle to rise and plumes form and move buoyantly upward toward the surface, he explained, molten rock from these plumes accumulates in chambers and crystallizes, gases escape through the crust and the pressure builds until the magma finds a way to escape.

For the first few weeks, as described in the paper, what erupted was the expected "depleted" magma type that had been accumulating in the reservoir, located about 10 miles (16 km) below the surface. But by April, evidence showed that the chamber was being recharged by deeper, "enriched" type melts with a different composition that were sourced from a different region of the upwelling mantle plume beneath Iceland. This new magma had a less modified chemical composition, with a higher magnesium content and a higher proportion of carbon dioxide gas, indicating that fewer gases from this deeper magma had escaped. By May, the magma that dominated the flow was the deeper, enriched type. These rapid, extreme changes in magma composition at a plume-fed hotspot, they say, "have never before been observed in near real-time."

These changes in composition may not be so rare, Jackson said; it's just that opportunities to sample eruptions at such an early stage are not common. For example, prior to the 2021 Fagradalsfjall eruption, the most recent eruptions on Iceland's Reykjanes peninsula occurred eight centuries ago. He suspects that this new activity signal the start of a new, possibly centuries-long volcanic cycle in southwest Iceland.

Sæmundur A. Halldórsson et al, Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland, Nature (2022). DOI: 10.1038/s41586-022-04981-x


Recent Icelandic rifting events have illuminated the roles of centralized crustal magma reservoirs and lateral magma transport1,2,3,4, important characteristics of mid-ocean ridge magmatism1,5. A consequence of such shallow crustal processing of magmas4,5 is the overprinting of signatures that trace the origin, evolution and transport of melts in the uppermost mantle and lowermost crust6,7. Here we present unique insights into processes occurring in this zone from integrated petrologic and geochemical studies of the 2021 Fagradalsfjall eruption on the Reykjanes Peninsula in Iceland. Geochemical analyses of basalts erupted during the first 50 days of the eruption, combined with associated gas emissions, reveal direct sourcing from a near-Moho magma storage zone. Geochemical proxies, which signify different mantle compositions and melting conditions, changed at a rate unparalleled for individual basaltic eruptions globally. Initially, the erupted lava was dominated by melts sourced from the shallowest mantle but over the following three weeks became increasingly dominated by magmas generated at a greater depth. This exceptionally rapid trend in erupted compositions provides an unprecedented temporal record of magma mixing that filters the mantle signal, consistent with processing in near-Moho melt lenses containing 107–108 m3 of basaltic magma.
  • Informative
Likes davenn, anorlunda and BillTre
  • #86
Well a year and a bit later and my wife and I finally got to Iceland. A geologists/volcanologists paradise.
The tour took us down the SE side of the Reykjanes Peninsula to Grindavik.
We got a glimps of the black lava flows from the road, that came from the Fagradalsfjall eruption, prior to arriving in Grindavik and then on to the Blue Lagoon for a wonderful swim in the thermal pools. Will add some photos once I have finished doing editing of several 1000 photos

  • Like
Likes BillTre and Astronuc
  • #87
What used to be a valley around Fagradalsfjall is now a lava field named Fagradalshraun.
Volcanic eruptions in Iceland lead scientists to startling discoveries | 60 Minutes

  • #89

Updated 5. July 2023 at 2:30pm

Earthquake activity commenced around 14:00 UTC yesterday (4 July 2023) beneath the Fagradalsfjall regionon the Reykjanes Peninsula, followed by an intense seismic swarm at 16:30 whichis still continuing. By noon today ~2200 earthquakes have occurred since the onset of this activity.
  • #90
Latest update

  • #91
davenn said:
Latest update
Interesting comment about the uplift of a wide area in the peninsula. The author suggests a great eruption than before.
  • #92
  • #93
Rive said:
... already a live webcam for the event o0)

Yes, they were real quick getting them up and running again a couple of days ago.
I still has them bookmarked/subscribed in Youtube from recent years

Other webcams views ---

Views from Perlan in Reykjavík, Iceland​

Langihryggur - Live from Iceland ( click on the Watch on YT link)​

Reykjanes - Norður​

Reykjanes Suður​

Geldingadalir, Iceland LIVE! Keilir​

Last edited:
  • Like
Likes Rive and Astronuc
  • #95
Smoke (or, maybe just steam) on the live cameras :wink:
Last edited:
  • #96
Rive said:
Smoke (or, maybe just steam) on the live cameras :wink:
Steam and sulfur dioxide, and probably CO2
  • A lava-producing fissure eruption is occurring closeto Litli-Hrútur mountain on the Reykjanes Peninsula.
  • The eruption is occurring in an uninhabited areaand it poses no immediate dangers to infrastructure.
  • The intensity of the eruption has decreasedconsiderably during the first 24 hours
  • Volcanic ash is not being produced by theeruption.
  • Close to the eruption, the main hazards are incandescent,flowing lava and volcanic gases.
  • Gas measurements at the eruption site during thefirst hours show levels similar to the 2022 eruption.
  • Flowing lava could also cause localised grassfires, which will further contribute to poor air quality close to the eruption site.
Seismicity intensified during 3-4 July. An earthquake swarm began at 1400 on 4 July and more than 1,600 earthquakes were detected beneath Fagradalsfjall, in the vicinity of the July 2022 dike intrusion, by mid-morning on 5 July. The earthquake locations became shallower within the first few hours of the swarm and by 5 July were at depths of 2-3 km. Seven of the earthquakes were above M 4, with the largest being M 4.6 recorded at 0821 on 5 July. At 1055 on 5 July IMO raised the Aviation Color Code to Orange (the third level on a four-color scale).

So looking at the video of the Litli-Hrútur eruption, one can see lava spewing from the fissure.

Edit/update: Volcanic eruption has started near Litli-Hrútur

Last edited:
  • Like
Likes Rive and davenn

Suggested for: Iceland earthquakes, 18000 in a week Fagradalsfjall Volcano