When Quiet Undersea Volcanoes Turn Disruptive | Quanta Magazine
3 min read
For example, scientists made an important discovery about undersea volcanoes. Specifically, they found that some mid-ocean ridges can have explosive eruptions at shallow depths. Crucially, this happens when water pressure is low enough for steam to form.
Furthermore, this explains how islands like Surtsey suddenly appear. Similarly, other shallow ridges around the world might act this way too. Therefore, these quiet volcanic zones can sometimes become very disruptive.
| Feature | Deep-Ocean (Quiet) Eruptions | Shallow/Explosive Eruptions |
|---|---|---|
| Depth Threshold | Below ~2,500 meters; extreme pressure suppresses explosive gas expansion | Above ~300 meters; reduced pressure allows seawater to flash to steam, driving explosions |
| Eruption Mechanism | Lava oozes along fissures, hardens into rough, jagged terrain; gases remain dissolved under pressure | Steam-driven explosions blast debris far from the vent; can breach the sea surface and build islands |
| Resulting Landform | Rugged ridge segments and pillow-lava fields typical of mid-ocean ridges | Steep-sided, flat-topped seamounts (tuyas) capped at ~40 m depth by North Atlantic storm-wave erosion |
| Historical Example | The vast majority of the Mid-Atlantic Ridge, which has erupted quietly for 200 million years | Surtsey (1963): island rose 171 m above sea level before wave erosion reduced it; at least 14 eruptions on the northern Reykjanes Ridge in the past 1,000 years |
| Role of Glacial Retreat | Ice-sheet pressure stabilises crust; volcanic activity remains suppressed | Retreating glaciers relieve crustal pressure, spiking volcanic activity; may have indirectly fuelled explosive shallow eruptions along the Reykjanes Ridge |
Disruptive Undersea Volcanoes
Similarly, scientists discovered that mid-ocean ridges are not always quiet. Moreover, a specific depth threshold (around 300 meters) allows for explosive eruptions. Furthermore, this explains the formation of Surtsey, a volcanic island. Additionally, falling glacial pressure may have fueled past activity. Consequently, similar shallow ridges worldwide could pose a future risk for everyone.
Shifting from Calm to Explosive
This indicates a critical pressure threshold around 300 meters depth where explosive volcanism becomes possible. Therefore, lower pressure allows seawater contact with magma to generate steam and explosive eruptions. Similarly, historical events like Surtsey’s formation illustrate this disruptive shift. Moreover, once a volcano breaches the surface, wave erosion shapes its flat top at about 40 meters depth. In contrast, deeper mid-ocean ridges typically see only effusive lava flows. Consequently, the chart suggests shallow segments of global ridges pose disruptive risks. Thus, understanding these depth parameters is crucial for coastal communities. Hence, ongoing magma movement under Iceland raises concerns for future surface events. Accordingly, monitoring these underwater pressure zones helps us prepare. As a result, this research highlights overlooked volcanic hazards beneath the waves.
“The key parameter here is depth
Ultimately, the discovery that shallow undersea volcanoes can erupt explosively challenges old assumptions about quiet mid-ocean ridges. In conclusion, these eruptions, like the one that formed Surtsey, occur where water pressure is low enough for steam-driven explosions.
Therefore, this new understanding helps explain mysterious “phantom islands” from history. Thus, with ongoing volcanic activity near Iceland, another similar island could emerge in the future. Accordingly, scientists must monitor these dynamic systems to better understand the risks.
