Hazards in the water

Volcanic activity

An erupting or restless volcano near or under the sea, with a keep-clear radius around it.

Volcano warnings keep ships away from vents that may erupt without notice — at sea level, eruptions can throw out rock, produce steam explosions or build new islands. The keep-clear radius is set by the authority watching the volcano and can change as activity changes.

Submarine volcanoes are hard to watch; ship reports of discoloured water, pumice or steam are often the first sign of activity.

What the archive shows

192 messages in this archive use “Volcanic activity”, the earliest issued 1987-12-21 and the latest 2026-09-08. 6 of them are in force in the latest lists we collected. A hazard reported again and again counts once per message.

The largest yearly count is 2006, with 17 messages. Collection is incomplete between 2024-05 and 2026-08-17, so 2024, 2025 and 2026 are not comparable with fully collected years.

Volcanic accounts for 144 of 192 recorded messages (75%), the largest warning type group in this selection.

Located messages that use it fall in 14 sea areas; the most frequent are Philippine Sea (87), North Pacific Ocean (35) and South Pacific Ocean (30).

Messages that use it are issued most often in January (25 across all years) and least often in June (6).

By warning series: HYDROPAC 118, USGS 40, HYDROLANT 12 and NAVAREA IV 11, and 3 more.

Messages using it, by year of issue

'87

'88

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'90

'91

'92

'93

'94

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'99

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'01

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'17

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'22

'23

'24

'25

'26

By month of issue, all years

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Where it appears · 14 sea areas

In force now · 6

NAVAREA XI 401/26 · Volcanic · Philippine Sea2026-09-08 · in force
080200UTC ISSUED AT 080200UTC SEP 2026 VOLCANIC WARNING VOLCANO NAME:NISHINO SHIMA LOCATION:27-14.6N 140-52.7E INFLUENCE OF ERUPTION IS…
080200UTC issued at 080200UTC sep 2026 volcanic warning volcano name:nishino shima LOCATION:27-14.6N… →
HYDROPAC 2039/26 · Volcanic · North Pacific Ocean2026-07-16 · in force
…NORTHERN MARIANA ISLANDS. 1. DISCOLORED WATER WITH INCREASED LIKELIHOOD OF SUBMARINE VOLCANIC ACTIVITY REPORTED IN VICINITY 20-26.00N 145-01.00E AT 160013Z JUL. 2. CANCEL HYDROPAC…
Discolored water with increased likelihood of submarine volcanic activity reported in vicinity 20-26.00N… →
HYDROPAC 2242/25 · Volcanic · Philippine Sea2025-09-02 · in force
NORTH PACIFIC. PHILIPPINE SEA. JAPAN. DNC 12. VOLCANIC ACTIVITY REPORTED AT IO-TO IN VICINTY OF 24-45.00N 141-17.3E.
Volcanic activity reported at io-to in vicinty of 24-45.00N 141-17.3E →
NAVAREA XI 412/25 · Volcanic2025-09-02 · in force
NORTH PACIFIC, NANPO SHOTO. IO TO. VOLCANIC ERUPTION CONTINUE. VESSELS REQUESTED TO BE CAUTION ADVISED. CANCEL 0539/24.
Volcanic eruption continue →
NAVAREA XI 492/24 · Volcanic · Philippine Sea2024-09-19 · in force
NORTH PACIFIC, NANPO SHOTO. 180500Z ISSUED AT 190200Z SEP. VOLCANIC WARNING. VOLCANO NAME : SUMISU SHIMA. LOCATION : 31-26.3N 140-03.0E INFLUENCE OF…
180500Z issued at 190200Z sep →
NAVAREA XI 207/23 · Volcanic · Philippine Sea2023-06-14 · in force
…DISCOLOURED WATER OBSERVED IN VICINITY OF 24-17.2N 141-28.8E AT 140350Z JUN. SUBMARINE VOLCANIC ERUPTION CONTINUE. VESSELS REQUESTED TO BE CAUTION ADVISED. CANCEL 0110/22.
Discoloured water observed in vicinity of 24-17.2N 141-28.8E at 140350Z jun →

How it reads in recent messages

HYDROPAC 2580/26 · Volcanic · Philippine Sea2026-09-08
NORTH PACIFIC. PHILIPPINE SEA. JAPAN. VOLCANIC ACTIVITY REPORTED IN AREA WITHIN ONE MILE OF 27-14.60N 140-52.70E AT 080200Z SEP.
Volcanic activity reported in area within one mile of 27-14.60N 140-52.70E at 080200Z sep →
USGS-US6000TL36 · Quakes · North Pacific Ocean2026-08-15
VOLCANO ISLANDS, JAPAN REGION. 1. EARTHQUAKE MAGNITUDE 5.6 (MWW) IN 23.461N 142.835E, DEPTH 55…
Earthquake magnitude 5.6 (mww) in 23.461N 142.835E, depth 55 km at 151932Z aug 26 →
USGS-US7000S1CQ · Quakes · North Pacific Ocean2026-03-02
VOLCANO ISLANDS, JAPAN REGION. 1. EARTHQUAKE MAGNITUDE 6.0 (MWW) IN 22.973N 144.210E, DEPTH 20…
Earthquake magnitude 6.0 (mww) in 22.973N 144.210E, depth 20 km at 020355Z mar 26 →
USGS-US7000RR5G · Quakes · Philippine Sea2026-01-21
VOLCANO ISLANDS, JAPAN REGION. 1. EARTHQUAKE MAGNITUDE 6.1 (MWW) IN 23.200N 142.604E, DEPTH 8 KM…
Earthquake magnitude 6.1 (mww) in 23.200N 142.604E, depth 8 km at 211637Z jan 26 →

Earliest in the archive

NOAAORR-6537 · Spills · Gulf of Alaska1987-12-21
…gas field in Upper Cook Inlet. At about 2320, the plume of gas caught fire, with flames erupting over 300 feet. The fire burned throughout the next several days. Those personnel not…
Upper cook inlet, alaska →

Often in the same message

Related terms

Discoloured water: Patches of unusually coloured sea — often a sign of a submarine volcano or of a shoal.
Pumice: Light volcanic rock floating in rafts after a submarine eruption; it can clog engine cooling intakes.
Safety zone / exclusion zone: An area ships must stay out of, or may only enter with permission, for safety or security.

Warning types that use it

Volcanic — Submarine eruptions, discoloured water, pumice rafts.

Counts cover the messages in this archive that use the term, recounted 2026-09-24; see coverage for what is collected and since when. Not for navigation — follow official NAVAREA and coastal broadcasts.