Brennisteinsfjöll

Seismicity by period · derived statistics from Skjálftalísa (Icelandic Met Office)

Status (automatic)

No particular signs of unrest in the last 24 hours — 3 earthquakes recorded, within the system's normal range.

VONA (Reykjanes): Yellow (unchanged since 2025-08-05) · source

Volcano is experiencing signs of elevated unrest above known background levels.

VONA = Volcano Observatory Notice for Aviation; the official Met Office colour code for aviation. Independent of Skjálfti's automatic analysis.

🕰️ Last eruption / event — ~687 years ago

Gráfeldur (Selvogshraun lava, around 1340) (~1340). The system's last eruption was around 1340, producing the Gráfeldur (Selvogshraun) lava that flowed south to Selvogur. It was part of a 1340–1341 fissure episode on the Reykjanes Peninsula when several systems erupted.

Fissure system east of Kleifarvatn — the most productive system of the Reykjanes Peninsula in the Holocene. Last erupted in the 14th century (~1341). Can send lava toward the capital area. (overview — more at vedur.is) · circle on the map = rough outline of the system (radius).

📜 Did you know?

Brennisteinsfjöll (literally “Sulfur Mountains”) is named for the sulfur mined and exported there in the 18th–19th centuries. It is the volcanic system closest to the capital area on the Reykjanes Peninsula (about 20–25 km from Reykjavík) and last erupted around 1340, when the Gráfeldur lava flowed south to Selvogur. Its best-known flow is Kristnitökuhraun, which erupted around the year 1000 — by tradition while Christianity was being adopted at the Alþingi.

Historical eruptions in the system — points colored by size, blue circle shows where we are now in time.

☁ Air quality — SO₂

Real-time SO₂ from Environment Agency (2026-09-11T18:00 UTC). Yellow > 20 µg/m³, orange > 125 (health threshold), red > 350. Nearest stations to this system; past 24h shown for the highest.

Vogar4.9 µg/m³

Reykjavík (Grensás)3.5 µg/m³

Hafnarfjörður (Hvaleyrarholt)1.7 µg/m³

Reykjavík (Laugarnes)1.6 µg/m³

Garðabær (Garðaholt)0.6 µg/m³

Depth is automatic and uncertain; earthquakes alone do not show magma movement — deformation (GPS) and gas are needed. Grey points: automatic fixed-depth values. b-value computed for M≥1.5 (automatic magnitudes make lower completeness unreliable). Preliminary data.

Glossary & magnitude scale →

🌊 Volcanic tremor — The baseline tremor is currently elevated, but its variations are well explained by stron…

IMO tremor plot (station kas). Most of the signal is weather and surf — not eruption confirmation. All stations: vedur.is ↗.

Weather now: waves 3.3 m — notable — likely weather.

The baseline tremor is currently elevated, but its variations are well explained by strong wind and ocean waves. (AI)

Band analysis past 9 days (from digitized RSAM values). High 2-4 Hz + low 0.5-1 Hz = possible magma-movement signal; high 0.5-1 Hz without 2-4 Hz = weather/surf.

Earthquakes in the system

Time (UTC)	Mag	Depth (km)	Area
2026-09-11 12:11	M-0.1	3.6	Reykjanesskagi
2026-09-11 02:04	M-0.1	5.9	Reykjanesskagi
2026-09-10 20:13	M0.1	14.8	Reykjanesskagi
2026-09-10 04:30	M0.8	6.8	Reykjanesskagi
2026-09-09 16:56	M1.1	7.1	Reykjanesskagi capital area
2026-09-09 11:05	M-0.1	0.8	Reykjanesskagi capital area
2026-09-09 03:11	M0.3	4.6	Reykjanesskagi
2026-09-08 20:31	M-0.3	3.4	Reykjanesskagi
2026-09-08 16:54	M0.0	6.6	Reykjanesskagi capital area
2026-09-08 15:32	M0.9	7.0	Reykjanesskagi
2026-09-08 14:06	M-0.1	0.0	Reykjanesskagi
2026-09-08 10:42	M0.2	5.7	Reykjanesskagi
2026-09-08 08:06	M0.2	8.5	Reykjanesskagi capital area
2026-09-07 13:50	M0.0	4.5	Reykjanesskagi
2026-09-07 11:36	M-0.2	5.1	Reykjanesskagi
2026-09-07 05:18	M-0.2	6.0	Reykjanesskagi
2026-09-07 04:52	M0.0	7.9	Reykjanesskagi
2026-09-07 04:48	M0.4	6.4	Reykjanesskagi
2026-09-06 21:05	M-0.3	5.7	Reykjanesskagi
2026-09-06 12:23	M-0.9	5.6	Reykjanesskagi
2026-09-06 11:57	M0.6	6.6	Reykjanesskagi capital area
2026-09-06 11:43	M-0.8	5.2	Reykjanesskagi
2026-09-06 11:13	M-0.3	4.2	Reykjanesskagi
2026-09-06 02:15	M-0.4	4.1	Reykjanesskagi
2026-09-06 02:08	M-0.4	4.8	Reykjanesskagi
2026-09-06 02:08	M-0.2	4.6	Reykjanesskagi
2026-09-06 00:41	M0.2	6.1	Reykjanesskagi
2026-09-06 00:33	M-0.7	0.0	Reykjanesskagi
2026-09-05 22:23	M-0.6	0.0	Reykjanesskagi
2026-09-05 22:09	M0.2	5.5	Reykjanesskagi
2026-09-05 21:24	M-0.4	5.1	Reykjanesskagi
2026-09-05 20:50	M-0.2	5.4	Reykjanesskagi
2026-09-05 20:47	M-0.1	5.2	Reykjanesskagi
2026-09-05 20:46	M-0.2	5.5	Reykjanesskagi
2026-09-05 20:17	M0.4	5.9	Reykjanesskagi
2026-09-05 19:49	M0.4	7.0	Reykjanesskagi
2026-09-05 19:44	M-0.6	0.0	Reykjanesskagi
2026-09-05 19:10	M0.5	4.6	Reykjanesskagi
2026-09-05 18:28	M-0.6	0.0	Reykjanesskagi
2026-09-05 18:14	M-0.7	15.1	Reykjanesskagi capital area
2026-09-05 17:55	M-0.6	6.6	Reykjanesskagi
2026-09-05 17:19	M-0.1	6.8	Reykjanesskagi
2026-09-05 16:49	M0.3	5.5	Reykjanesskagi
2026-09-05 16:29	M-0.1	20.4	Reykjanesskagi
2026-09-05 16:09	M0.3	5.6	Reykjanesskagi
2026-09-05 16:03	M-0.4	0.0	Reykjanesskagi
2026-09-05 15:36	M-0.3	2.3	Reykjanesskagi
2026-09-05 15:23	M-0.0	5.5	Reykjanesskagi
2026-09-05 15:22	M1.2	5.7	Reykjanesskagi
2026-09-05 15:19	M-0.3	5.5	Reykjanesskagi
2026-09-05 13:35	M0.6	5.4	Reykjanesskagi
2026-09-05 13:27	M0.3	5.2	Reykjanesskagi
2026-09-05 13:04	M-1.5	5.3	Reykjanesskagi
2026-09-05 12:46	M-0.1	2.9	Reykjanesskagi
2026-09-05 11:27	M-0.6	3.4	Reykjanesskagi
2026-09-05 10:54	M0.1	5.9	Reykjanesskagi
2026-09-05 10:26	M-0.2	2.9	Reykjanesskagi
2026-09-05 10:06	M-0.0	0.0	Reykjanesskagi
2026-09-05 10:04	M0.2	5.0	Reykjanesskagi
2026-09-05 09:40	M0.6	5.9	Reykjanesskagi

For the advanced — expert charts — Coulomb, migration, InSAR

🔬 Coulomb stress transfer — advanced analysis

2 earthquakes M≥3.0 in this window on this system. Such events transfer stress to neighbouring faults — some become more likely to slip, others less ("Coulomb stress transfer"). The Met Office does not publish focal mechanisms for automatically located events, so Skjálfti does not compute this itself — it requires strike/dip/rake data which is only available for M≥4.5 events in the GCMT catalogue.

For Coulomb analysis, see: USGS Coulomb 3.4 (stand-alone software) and focal mechanisms for Iceland in Global CMT.

📡 InSAR — radar deformation across the area

InSAR is satellite radar from Sentinel-1: it measures deformation across the whole area, not just points like GNSS stations. Six-day interferograms reveal where the ground rose or subsided between passes. InSAR distinguishes vertical deformation (magma chamber inflation) from horizontal (dike intrusion) — GNSS alone cannot.

View latest interferograms and time-series at COMET LiCS portal (Sentinel-1, ~4-6 day lag).

System journal

Automatic snapshots and media coverage, in chronological order. Subscribe: RSS · ntfy skjalftar-brennisteinsfjoll

2026-09-06 19:15:02 UTC

Over the last 24 hours, 18 earthquakes were detected in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, with this activity remaining similar to the past week and considered normal for this area. The largest earthquake in the last 48 hours was magnitude 3.0, and the cumulative moment magnitude for the same period was 3.0 Mw, characterized by scattered background activity rather than swarms as 61% of events over the last seven days were independent. This activity most closely resembles the period around August 20, 2017 as a historical analogue, though it must be noted that these are automatic preliminary results with unreliable depths. Maps and further details on the development can be found below on the page.

2026-09-06 13:20:02 UTC

Over the last 24 hours, 32 earthquakes were detected in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, with activity remaining similar to the past week, which is considered slightly higher than usual for this area. This represents scattered background activity rather than earthquake swarms, as 60% of events over the last seven days were independent, and the largest earthquake in the last 48 hours was magnitude 3.0 (cumulative moment magnitude Mw 3.0). This activity most closely resembles the period around August 20, 2017, when 223 earthquakes were detected, though it must be noted that these are automatic preliminary results where depth is unreliable. Maps and further details on the earthquake development can be found lower on the page.

2026-09-05 23:15:01 UTC

Over the last 24 hours, 93 earthquakes were detected in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, indicating increasing activity as the last 24 hours are well above the weekly average of 28 earthquakes per day. This represents somewhat more activity than usual for this area, characterized by scattered background activity rather than swarms, with 58% of events over the last seven days being independent earthquakes. The largest earthquake in the last 48 hours was magnitude 3.0 (M3.0), and the cumulative magnitude for the same period was 3.0 (Mw 3.0). This activity most closely resembles the period around August 20, 2017, though it must be noted that these are automatic preliminary results with unreliable depths.

Repeated × 2 since 2026-09-05 06:10:02 — last 2026-09-05 15:30:02

Over the last 24 hours, seismic activity in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, has been unusually high and is increasing compared to the weekly average. A total of 117 earthquakes were detected in the area during the last 24 hours, consisting mostly of scattered background activity rather than swarms, with the activity closely resembling the period around June 7, 2026. The largest earthquake in the last 48 hours was magnitude 3.0, and the cumulative moment magnitude for the same period was 3.0 Mw. It should be noted that these are automatic preliminary results with unreliable depths, and further details and maps can be found below on this page.

2026-09-04 20:25:02 UTC

Over the last 24 hours, 19 earthquakes were detected in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, with activity increasing as the last 24 hours are well above the weekly average of 10 earthquakes per day. This earthquake activity is, however, within what is considered normal for this area and consists mostly of scattered background activity (72%) rather than swarms, with the largest earthquake in the last 48 hours measuring magnitude 3.4 and the total seismic moment for the period also being 3.4 Mw. This activity most closely resembles the period around August 20, 2025, when 71 earthquakes were detected, although it must be noted that these are automatic preliminary results where depth is unreliable. Maps and further details on the development can be found lower on the page.

2026-09-04 16:20:03 UTC

Over the last 24 hours, 40 earthquakes were detected in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, indicating increasing activity as the last 24 hours are well above the weekly average of 9 earthquakes per day. This activity is somewhat higher than usual for this area and consists mostly of scattered background activity rather than swarms, with 73% of events over the last seven days being independent earthquakes. The largest earthquake in the last 48 hours was magnitude 0.9 and the cumulative magnitude in the area was 1.5, while earthquake epicenters have shown a significant horizontal drift to the southwest of 1.75 kilometers per day over the last seven days. These are automatic preliminary results where depth is unreliable, but the current activity most closely resembles the period around June 10, 2026. Maps and further data on the development can be found below on this page.

2026-09-03 18:15:04 UTC

Over the last 24 hours, 14 earthquakes were detected in Brennisteinsfjöll, a fissure swarm east of Kleifarvatn, with activity increasing and remaining somewhat higher than usual for this area. This represents scattered background activity rather than swarms, as 73% of events over the last seven days were independent, with the largest earthquake in the last 48 hours measuring magnitude 1.6 and the cumulative moment magnitude for the same period being 1.7. This activity most closely resembles the period around June 27, 2026, when 46 earthquakes were detected, though it should be noted that these are automatic preliminary results where depth is unreliable. Maps and further details on the development can be found below.

2026-06-12 07:10:05 UTC

In the last 24 hours, 13 earthquakes were recorded in the Brennisteinsfjöll fissure system east of Kleifarvatn, with activity similar to the past week. Seismicity is within normal levels for this area and is characterized by distributed background activity rather than swarms. The largest earthquake was M1.3 and the cumulative moment over the last 48 hours is Mw 1.5; results are automatic preliminary results. Activity most closely resembles the period around July 21, 2024.

2026-06-05 23:10:08 UTC

In the last 24 hours, 17 earthquakes were recorded in the Brennisteinsfjöll fissure system east of Kleifarvatn, with activity similar to the past week but slightly higher than usual for this area. The increase is mostly due to short-lived swarms rather than distributed background activity, with a β-value of 3.3 and a cumulative magnitude of Mw 1.6 in the last 48 hours. These automatic preliminary results most closely resemble the period around August 24, 2025, in terms of event count. Further charts and maps are available below.

2026-06-05 09:25:07 UTC

In the last 24 hours, 13 earthquakes were recorded in Brennisteinsfjöll, a fissure system east of Kleifarvatn, and activity is decreasing compared to the weekly average. Seismicity remains within normal levels for this area, with recent increases consisting mostly of short-lived swarms rather than distributed background activity. The largest earthquake in the past 48 hours was magnitude M2.8, with a cumulative moment of Mw 2.9 for the period. Results are automatic preliminary data, and current activity most closely resembles the period around August 24, 2025.

2026-06-03 23:10:10 UTC

In the last 24 hours, 53 earthquakes were recorded in the Brennisteinsfjöll system, indicating an increase above normal background activity for this area driven mainly by short-lived swarms. The largest event was M2.8 with a cumulative magnitude of Mw 2.9 over the past 48 hours, based on automatic preliminary results. Current activity resembles the period around August 24, 2025, in terms of event count. Further details on trends and maps are available below.

2026-06-03 19:20:12 UTC

In the last 24 hours, 48 earthquakes were recorded in Brennisteinsfjöll, indicating unusually high activity for the area with the increase mainly due to short-lived swarms. The largest earthquake was M2.4 and cumulative magnitude over 48 hours was Mw 2.5, though these are automatic preliminary results with unreliable depth. Activity most resembles the period around June 29, 2024, and further charts and maps are available below.

2026-06-03 17:15:12 UTC

In the last 24 hours, 47 earthquakes were recorded in the Brennisteinsfjöll system, indicating increased activity above normal levels for the area consisting mostly of short-lived swarms. The largest event was M2.4 and the activity most closely resembles the period around June 29, 2024; these are automatic preliminary results. Further charts and maps are available below.

2026-06-03 01:45:13 UTC

In the last 24 hours, 71 earthquakes were recorded in the Brennisteinsfjöll system, indicating unusually high activity for the area with the increase mainly due to short-lived swarms. The largest earthquake was magnitude M2.4 and the cumulative moment over the last 48 hours is Mw 2.4, but these figures are automatic preliminary results. The activity most closely resembles the period around June 29, 2024, when 71 earthquakes were also recorded. Further details on trends and maps are available below.

2026-06-02 12:15:15 UTC

In the last 24 hours, 25 earthquakes were recorded in the Brennisteinsfjöll system, indicating an increase above the weekly average and higher activity than usual for this area. The increase consists mostly of short-lived swarms, with the largest event at M2.4 and a cumulative magnitude of Mw 2.4 over the past 48 hours. These are automatic preliminary results, and the activity most closely resembles the period around June 23, 2024. Further charts and maps are available below.

What do the numbers mean — and what should I do?

β (swarm signal): how high activity is versus the area's 2-year average. β above 2 means an ongoing swarm. It measures activity, not a forecast of a large quake.

Cumulative moment (Mw): the combined energy of the quakes in the period. Uplift (GNSS): whether the ground is rising or sinking, mm per year — the data are a few weeks old. Some systems (e.g. Svartsengi) deform in steps during eruption cycles rather than at a steady annual rate.

Swarm character is computed for a whole volcanic belt, not a single system — it describes the belt, not necessarily this one system.

What should I do? This is automatic monitoring for information — not an official warning. Follow official information from the Icelandic Met Office and Civil Protection (112).

Brennisteinsfjöll

Earthquakes over time

Cumulative count and moment

Magnitude distribution

Earthquakes over time

Cumulative count and moment

Magnitude distribution

Earthquakes over time

Cumulative count and moment

Magnitude distribution

Earthquakes over time

Cumulative count and moment

Magnitude distribution

Earthquakes in the system

System journal