A volcano is an opening in a planet or earth’s crust through which molten rock and gases trapped under the surface erupt, often forming a hill or mountain. According to the United States Geologic Survey, there are approximately 1,500 potentially active volcanoes worldwide.
Submarine volcanoes, or ‘underwater volcanoes’ as they are sometimes called, are vents or fissures located underwater, on the surface of the earth. These underwater volcanoes act just like those on land. They can erupt and produce magma.
Amazingly, some of the biggest individual volcanoes and the biggest volcanic chain – the Ring of Fire, are located in the oceans. They are the most common at divergent plate boundaries or areas where tectonic plates are separating. The plate movement is incredibly important in determining what type of volcano is formed. This holds true for volcanoes on land, also known as subaerial volcanoes.
One of the most famous submarine volcanoes is Krakatoa, located between Java and Sumatra. Krakatoa erupted in 1883 to devastating consequences. The eruption and the resulting tsunami killed more than 36,000 people. Over 70% of the Krakatoa island and the archipelago were destroyed. It is now noted as one of the deadliest volcanic eruptions in recorded history. It was so loud that the explosion was heard up to 1,930 miles (3,110 km) away in Australia. Ships as far away as South Africa were impacted by tsunamis. The eruption is thought to have been caused by the entry of pyroclastic flow into the sea. Following the eruption, seismic activity flourished for the next year.
Where are Submarine Volcanoes Located?
The majority of submarine volcanoes are located near mid-ocean ridges. These are areas of tectonic plate formation and hydrothermal vents. The vents are created and maintained through volcanic heat and can be found all around the world. Although it seems like it might be an easy process, to locate these immense volcanoes, it’s not quite so easy. Scientists use a CTD package that measures various ocean temperature changes, conductivity, and depth. These readings help them identify specific changes that might signify a hot spring under volcanoes in the process of erupting. Some of the signs include the temperature and the cloudiness of the water.
Scientists also use hydrophones to seek out erupting volcanoes. These are microphones designed to be used underwater, and, if the volcano is close enough and not too deep, it can pick up the sound of boiling water.
How are Submarine Volcanoes Different?
The presence of water in and around a volcano changes the way that it acts. At volcanic sites, seawater runs into the seafloor, entering through cracks. There, it is heated by the molten rock. This results in a chemical reaction in which the seawater is changed into a hydrothermal fluid. The fluid is propelled back into the ocean, creating a hydrothermal vent.
When a volcano erupts, the presence of water means that the magma will cool much faster than it would on land. It is, in fact, sometimes transformed into volcanic glass. Volcanic glass is a product of the rapidly cooling magma. There are a variety of different types of volcanic glass. These include pumice, tachylite, palagonite, Pele’s hair, Limu o Pele, and Sideromelane. In general, lava takes different shapes and forms when it cools underwater.
As soon as the lava touches the water, a crust forms around it, creating what is known as pillow lava. It takes its name from the pillow-shaped forms that are created as a result of the crust forming. They are usually around one meter in diameter and made out of basalt. They might also be formed of komatiite, boninite, rhyolite, and more. Most submarine eruptions do not disturb ocean surface.
Pillow lavas are used to confirm volcanic activity throughout the ages of the Earth. Eruptions and lava flow from submarine volcanoes allow volcanic islands to grow and develop thriving ecosystems.
Volcanic eruptions vary depending on the depth of the water as well. For example, if the eruption occurs in excess of the critical pressure of water, then it becomes a supercritical fluid. This refers to a substance created at a temperature/pressure beyond its critical point, where phases of liquid and gas do not exist. But below the pressure required to create a solid. This is only one of several reasons why it’s difficult for scientists to find and study these eruptions. Without the sound of boiling water, hydrophones are useless at great distances.
Formation of Volcanic Islands
There are two primary factors essential for the formation of volcanic islands from submarine volcanoes: the supply of magma and tectonic activity.
Magma is supplied from the melting of the Earth’s mantle, a crucial process for creating most oceanic island and submarine volcanoes.
Most volcanic islands originate from passive lava flows on the seafloor, which solidify into rock and gradually build up the height of underwater mountains over millions of years.
Some volcanoes eventually reach a height where they break the ocean’s surface, allowing for explosive eruptions due to the lower pressure. Submarine volcanoes that do not reach sea level remain as seamounts.
Tectonic activity also plays a significant role in determining which submarine volcanoes will form islands. The movement of tectonic plates can shift a growing volcano away from its magma source in the mantle. “Tectonic activity can sometimes move the island volcano away from its magma source in the mantle because the tectonic plate on which the volcano is located is moving,” Mandeville adds.
Active Submarine Volcanoes
Here are some notable active submarine volcanoes around the world:
- Axial Seamount – Located off the coast of Oregon, USA, in the northeastern Pacific Ocean. It is one of the most active and best-studied submarine volcanoes.
- Kick ’em Jenny – Located in the Caribbean Sea, north of Grenada. It is the only active submarine volcano in the Caribbean region.
- South Sarigan Seamount – Located in the Mariana Islands region of the western Pacific Ocean, south of Sarigan Island. It has shown recent volcanic activity.
- Hunga Tonga-Hunga Ha’apai – Located in the Pacific Ocean near Tonga, this volcano gained global attention after its major eruption in January 2022.
- Loihi Seamount – Located southeast of the Big Island of Hawaii, USA. It is an active submarine volcano that is considered the youngest volcano in the Hawaiian-Emperor seamount chain.
- White Island (Whakaari) – Located in the Bay of Plenty, New Zealand. It is an active volcano with both submarine and subaerial (above-water) vents.
- Kavachi – Located in the Solomon Islands in the western Pacific Ocean. It is one of the most active submarine volcanoes, often producing visible eruptions.
- Fukutoku-Okanoba – Located in the Ogasawara Islands, Japan. It is known for frequent and sometimes violent eruptions.
These are just a few examples of active submarine volcanoes known for their ongoing or recent volcanic activity. Submarine volcanoes are challenging to study due to their underwater location, but advancements in technology have allowed scientists to better understand their behavior and the potential hazards they pose.
Submarine Volcanoes in the Ring of Fire
The most famous collection of underwater volcanoes is part of the Ring of Fire. It is an area in the basin of the Pacific Ocean in which an unusually high number of eruptions and earthquakes occur. In the ring, there are volcanic arcs and belts, as well as plate movement. There are in total of 452 volcanoes present in the ring. The ring also plays host to around 90% of the world’s earthquakes and 88% of the world’s largest volcanic eruptions.
The Havre Submarine Volcano
One of the most notable eruptions of a submarine volcano occurred in 2012 when for ninety days lava spewed from fourteen events around the opening of Havre. It is located 3,000 feet (900 meters) below the surface of the Pacific Ocean. It is one of the world’s largest, and its eruption in 2012 was the largest deepwater eruption ever recorded. As reported by the Smithsonian, scientists have compared the eruption in size and result in the eruption of Mount St. Helens in 1980 in Washington State.
But, very much unlike the Mount St. Helens eruption, Havre occurred far from the public spotlight. The eruption was discovered by a passenger on a commercial flight who noted a discolored patch of water in the ocean. After sending an email, a search got underway to discover the cause of this discolored patch of water. The Smithsonian also reported that about 75 percent of the lava created by Havre made it to the surface. A larger chunk of pumice was revealed to be the source of the discoloration. Pieces of pumice, like those created by Havre, are at first buoyant. They then become saturated with water and sink to the seafloor.
The 2022 Hunga Tonga–Hunga Haʻapai Eruption
The eruption of the Hunga-Tonga-Hunga-Ha’apai volcano on 15 January 2022 was the largest recorded since the eruption of Krakatoa in 1883. With an ash plume surpassing the stratosphere and a blast heard thousands of miles away, it marked one of the most explosive volcanic events in recent history, potentially rivaling the cataclysmic 1991 eruption of Mount Pinatubo. Unlike its terrestrial counterparts, Hunga Tonga is a submarine volcano, lying 500 feet beneath the Pacific’s surface, making such eruptions exceedingly rare. Hunga Tonga was formed from interactions between tectonic plates.
This event underscores the immense power of underwater volcanic activity, where shallow waters can amplify explosions by rapidly converting lava to steam. The resulting ash cloud, spanning 300 miles in diameter, devastated marine life and coated Tonga’s islands, disrupting daily life and tragically claiming lives in Peru from tsunami waves that crossed the vast ocean. As scientists continue to study the aftermath, Hunga Tonga serves as a stark reminder of the unpredictable force and global impact of submarine volcanic eruptions.
Sea Life Supported by Submarine Volcanoes
Despite the extreme volcanic conditions, these vents support a diverse array of life. Microorganisms such as bacteria and archaea thrive here, harnessing chemical energy from hydrothermal fluids. These microbes serve as the foundation of a unique food chain that includes tubeworms, shrimp, and even crabs, forming vibrant communities around the vents.
Exploring vents and active volcanoes in the deep ocean presents significant challenges. Scientists utilize CTD (Conductivity, Temperature, and Depth) instruments to detect these features. Changes in water temperature and clarity can indicate the presence of hydrothermal vents or erupting underwater volcanoes.
The discovery of these vents and volcanoes has unveiled previously unknown ecosystems and enhanced our understanding of Earth’s processes.
Scientists have discovered that marine life is often attracted to and thrives around the sight of volcanic eruptions. Specifically, while researching volcanos near Guam, scientists discovered a notable increase in the population of animals that live on top of the volcano. These include shrimp, crabs, and barnacles. These animals thrive in the intense, chemical-filled conditions that exist on top of the underwater volcanoes, taking nourishment from the eruptions. One specific shrimp has adapted special claws used to harvest food.
Ocean Insights: Hear From Our Experts
By Rida Nasir
Researcher and Conservationist, with an MSc in Environmental Science
Submarine volcanoes are not merely geological formations; they are vibrant ecosystems crucial for biodiversity and essential for the health of our planet's oceans. My research underscores the urgent need for targeted conservation efforts to protect these underwater treasures. These areas are threatened by activities like deep-sea mining and pollution, which can irreversibly damage their unique ecosystems. In my experience, protecting these habitats is vital not only to preserve rare species but also to maintain the balance of marine life. Effective conservation must prioritize strict regulations against disruptive human activities and promote sustainable practices that respect the delicate nature of these environments.
FAQs
Are underwater volcanoes dangerous?
Yes, underwater volcanoes can be dangerous. While often less visible than land volcanoes, they pose several significant risks. Powerful underwater eruptions can displace large volumes of water, potentially generating tsunamis that can devastate coastal areas. Additionally, these volcanic activities are often associated with seismic activity, which can impact marine and coastal environments. Volcanic gases, such as sulfur dioxide, can also be released during eruptions, affecting marine life and contributing to ocean acidification. Large eruptions can send ash plumes into the atmosphere, impacting air travel and climate.
Are underwater volcanoes rare?
No, underwater volcanoes are not rare. In fact, they are quite common and form a significant part of the Earth’s volcanic activity. The majority of the Earth’s volcanic activity occurs beneath the ocean, especially along mid-ocean ridges where tectonic plates are spreading apart. There are thousands of submarine volcanoes, with many more yet to be discovered. Some of the most active volcanic regions are underwater, making submarine volcanoes a widespread and integral feature of our planet’s geology.
Are underwater volcanoes hot?
Yes, underwater volcanoes are very hot. The magma that erupts from these volcanoes can reach temperatures of over 1,200 degrees Celsius (2,192 degrees Fahrenheit). When this hot magma comes into contact with the cold seawater, it rapidly cools and solidifies, but the immediate area around the eruption site remains extremely hot. This intense heat drives the formation of hydrothermal vents, such as Black Smokers, which spew out mineral-rich water heated by the volcanic activity. Despite being underwater, these volcanoes can create an incredibly hot environment in their vicinity.
