Tonga Volcano | What is the difference between submarine volcanic eruptions and ordinary surface volcanoes?

Tonga’s submarine volcano erupted violently on January 15, triggering a tsunami that hit many nearby coasts, and tsunami warnings were issued thousands of kilometers away in Japan and Hawaii. What is the difference between submarine volcanoes and ordinary volcanoes, what is the difference between eruptions, and how big is the impact?

Changes in the crust are closely related to plates and dissolved carbon. Volcanoes are mainly caused by the pushing of crustal plates and the gas pressure in the magma reaching a certain pressure, causing eruptions. Most of the volcanoes are located at the junction of the edges of the crustal plates, but the edges of the plates are not only distributed on the ground, but also on the seafloor, so submarine volcanoes appear.

Hunga Haʻapai in Tonga is part of the seabed near Tonga, part of the Tonga-Kermad Islands volcanic arc, located in the subduction zone of the crust extending northeast of New Zealand to Fiji. The crust here is very active, and volcanoes have erupted several times in recent years.

The biggest difference between the eruption of submarine volcanoes and the volcanoes on the ground is that the scale of volcanic eruptions is often much smaller due to the huge relationship between the underwater water pressure. At the same time, because the magma will be instantly cooled when it comes into contact with water, the lava generally does not spew out of the sea. But some shallower submarine volcanoes can still cause cooling lava to erupt along with seawater due to accumulated water vapor.

When an underwater volcano erupts, it will also cause a certain degree of tsunami. The erupted volcanic gases, including methane and sulfides, also dissolve into the water, affecting nearby seafloor ecology.

Like surface volcanoes, submarine volcanic eruptions can also cause changes in the landscape, and a large amount of molten rock floating to the surface will create volcanic islands. For example, the eruption of underwater volcanoes in Tonga has created “new territory” for Tonga from time to time. One of the newly formed islands is Hongaha’apai Island, which has erupted this time. Before the outbreak the island became a new world for greenery and birds.

However, such volcanic islands may not necessarily become real islands for a long time, and some islands will gradually disappear due to the natural weathering of seawater. It takes a period of continuous volcanic activity and magma replenishment to solidify the foundations into a true island.