When Quiet Undersea Volcanoes Turn Disruptive | Quanta Magazine
2 min read
Fundamentally, hidden undersea volcanoes were long thought to erupt only quietly. However, a new study near Iceland shows some can suddenly turn explosive. Specifically, scientists used special tools to see strange, flat-topped mountains deep under the sea.
For example, they learned that when volcanoes are in shallower water (around 300 meters deep), the pressure is lower. Consequently, water meeting hot lava can turn into powerful steam, making eruptions blow up. Thus, these explosive events can build temporary islands.
Moreover, this helps explain past sudden islands off Iceland. Importantly, it reveals how the Mid-Atlantic Ridge works. Similarly, other shallow ocean ridges might also see such surprises.
| Volcanic Setting | Eruption Behavior | Key Characteristics |
|---|---|---|
| Deep Ocean (below ~2,500 m) | Quiet, effusive oozing of lava | Crushing water pressure suppresses explosive gas expansion; lava hardens into rough, jagged terrain along fissures |
| Shallow Submarine (~300 m threshold) | Explosive eruptions begin | Reduced pressure lets seawater flash to steam, powering blasts; creates steep-sided, flat-topped mounds with scattered debris deposits |
| Subaerial (breaching sea surface) | Highly explosive, sustained activity | Ash and rock scattered far from vent (e.g., Surtsey, 1963); islands can rise >170 m above sea, then erode back down to ~40 m by storm waves |
| Glacially Covered (Tuyas) | Explosive but ice-capped | Magma melts through thick glacier ice, triggering steam explosions; ice sheet acts as a lid, capping volcano height; produces flat-topped “table mountains” |
| Post-Glacial Reykjanes Ridge (present day) | Intermittent, unpredictable | Retreating ice released crustal pressure, spiking volcanic activity; swelled magma chamber under Reykjanes Peninsula since ~2020; another Surtsey-type event remains possible |
Disruptive Undersea Volcanoes
Notably, researchers discovered that explosive volcanism can occur along usually calm mid-ocean ridges. Specifically, this happens at a shallow pressure threshold. Consequently, this may explain historical phantom islands like Surtsey. Moreover, the finding suggests that volcanic activity can disrupt ocean systems. Furthermore, everyone should consider how these events impact marine environments. Therefore, scientists will continue to study this depth-dependent behavior.
Hidden Volcanic Risks Surface
This indicates that mid-ocean ridges erupt explosively at shallow depths, not just quietly. Moreover, the critical depth threshold appears to be around 300 meters, where reduced pressure allows steam-driven eruptions. Similarly, wave erosion flattens volcanic tops to roughly 40 meters below sea level. Consequently, these findings explain historical phantom islands like Surtsey. Therefore, shallow ridges worldwide—from the Azores to the Galápagos—may share this volatile potential, suggesting future island-forming eruptions are possible.
“The chances are not low” for another Surtsey to rise again.
Ultimately, these findings change how we see undersea volcanoes. Therefore, shallow mid-ocean ridges deserve greater attention from scientists worldwide. Thus, explosive eruptions near the surface could affect coastal communities. Hence, ongoing research is vital to help everyone prepare for future volcanic events.
Ultimately, research reveals undersea volcanoes can shift from calm to explosive at depths around 300 meters. Consequently, this explains historical events like Surtsey’s sudden emergence. Thus, mid-ocean ridges are not always quietly stable.
As a result, current magma buildup in Iceland indicates future disruptive potential. Accordingly, we should prioritize monitoring these dynamic areas. In summary, this understanding helps everyone prepare for possible volcanic activity.
