Submarine eruption

Mid ocean ridges for example are the most active volcanic systems on Earth but roughly only 5% of their length has been studied in detail.

[2] Initial knowledge of these eruptions came from volcanic rocks being recovered from the ocean floor when repairs were made to the Transatlantic telegraph cable in the 1800s.

[4] Other tools have included seismic signals, acoustic waves and high resolution UAV multibeam mapping.

For example, an explosive eruption at West Mata in Lau Basin at a depth of 1200 m was studied using submersibles.

[3] This changes with a number of variables including magma viscosity, water depth, effusion rate and volatile content.

It is believed that increased pressure restricts the release of volatile gases, resulting in effusive eruptions.

[1] At shallow depths it is common for submarine eruptions to be explosive due to the reaction between volatiles in the magma and water which generates a significant quantity of steam.

Magma being transported into the ocean through tunnels may see gases being exsolved before reaching the water and so the eruption is effusive.