Last Updated on 02/16/2024

Although they can’t be seen, deep ocean volcanoes are the most prevalent in the world. In fact, well over 80% of all volcanic activity happens deep below the ocean surface, where volcanic eruptions occur only in certain locations where tectonic plates meet and where formations such as the mid-ocean ridge system is situated. These volcanoes are responsible for a host of events that are extremely significant for deep sea topography, climatic conditions throughout the globe and even the formations of entire islands and land masses.

Whether it’s sea mounts or the large mid-ocean ridge, undersea volcanoes dominate the bottom of the ocean in many areas of the world. In total, there are about 3.4 million volcanoes that have been discovered below sea level in various parts of the planet, and the number seems to be increasing, as oceanographers continue to use increasingly sophisticated methods and technologies to locate deep ocean volcanoes even in the lowest conceivable locations. Like regular volcanoes, undersea volcanoes commonly produce explosions of molten rock and lava, while also generating increased acidity in the water that surrounds them.

Underwater volcanoes are commonly observed in the areas that separate tectonic plates, and that is where the most eruptions occur as well. Due to the increased pressure between tectonic plates, caused mainly by their ability to “float” on melted rock and extend the pressure toward their edges, the plates’ movement, as they collide and spread apart, are a major catalyst for the formation of deep ocean volcanoes. Some of these volcanoes, such as the ones responsible for the formation of the Hawaiian islands, are also located on the interior of plates – in so-called hot spots – while a total of 60% of all undersea volcanoes are found at the boundaries between tectonic plates.

Some undersea eruptions occur at an ideal level of depth and have the perfect intensity to actually cause the formation of brand new volcanic islands. A recent eruption in 2013 was observed, offering scientists plenty of opportunities to study this phenomena in real time. The volcano erupted in the Pacific Ocean, just off the coast of Japan and generated a new islet just 600 feet in diameter. Similar eruptions occurring in the 1970s and 80s have led to the formation of other islands and islets in the region that have, however, sunk back into the depths of the ocean shortly thereafter.

Almost 4,000 feet below the ocean surface, close to the islands of Fiji, Samoa and Tonga, a spectacular underwater volcano was discovered in 2009. This is one of the deepest volcanoes ever discovered, and its eruptions enabled scientists to have a unique view on the formation of new islands and deep water volcanoes. West Mata, as the volcano was subsequently names, is just one of the many deep ocean volcanoes that are helping researchers create a clearer picture of the heat and matter transfer that goes on below the Earth’s crust, while gaining a deeper understanding of the effects deep water eruptions have on the oceans themselves.

90% of All Volcanic Activity Occurs in the Oceans

Did you know that most of the Earth’s volcanic activity is hidden beneath the waves? That’s right, 90% of all volcanic activity occurs in the oceans. This fascinating fact sheds light on the dynamic nature of our planet’s geology, most of which remains out of sight on the ocean floor. From the deep, dark abyssal plains to the towering, hydrothermal vents, the ocean’s depths are teeming with geological phenomena that are crucial to understanding Earth’s composition and the life forms it supports. In this article, we’ll dive into the depths of the ocean to uncover the mysteries of underwater volcanoes and explore why such a significant portion of volcanic activity happens there.

The Hidden World of Underwater Volcanoes

Formation and Types of Submarine Volcanoes

Underwater volcanoes, or submarine volcanoes, are similar to their terrestrial counterparts but exist beneath the ocean’s surface. The process of their formation, known as submarine volcanism, involves the eruption of magma from the Earth’s mantle through the oceanic crust. These eruptions create various volcanic structures, including seamounts and mid-ocean ridges. The most prolific of these, the Mid-Atlantic Ridge, stretches for thousands of kilometers, acting as a continuous volcanic chain beneath the Atlantic Ocean. This submerged volcanic activity plays a crucial role in shaping the oceanic landscape and contributes significantly to the Earth’s crustal dynamics.

Hydrothermal Vents and Ecosystems

One of the most fascinating aspects of submarine volcanism is the creation of hydrothermal vents. These vents emit superheated, mineral-rich water, providing energy for unique ecosystems in the deep ocean. The life forms found here, such as tubeworms and certain types of chemosynthetic bacteria, thrive in extreme conditions, relying on the chemicals dissolved in the vent fluids for energy. This process, known as chemosynthesis, is analogous to photosynthesis but does not require sunlight, highlighting the adaptability of life and the interconnectedness of geological and biological processes in the ocean’s depths.

The Role of Tectonic Plates in Oceanic Volcanism

Mid-Ocean Ridges and Plate Tectonics

The Earth’s lithosphere is divided into several large and small tectonic plates that constantly move over the asthenosphere. The majority of oceanic volcanic activity is concentrated along mid-ocean ridges, where tectonic plates diverge. As the plates pull apart, magma rises to fill the gap, creating new oceanic crust. This continuous process is a primary driver of seafloor spreading and plays a pivotal role in the dynamic nature of the Earth’s surface. Understanding the mechanics of mid-ocean ridges provides valuable insights into the processes that shape our planet’s geology and geography.

Subduction Zones and Volcanic Arcs

In contrast to mid-ocean ridges, subduction zones are areas where one tectonic plate slides beneath another, diving into the Earth’s mantle. This process can lead to the formation of volcanic arcs, chains of volcanoes that emerge along the overriding plate’s edge. The intense pressure and heat generated by subduction cause the melting of the subducted plate, resulting in magma that can rise to the surface and erupt as volcanic activity. These zones are not only hotspots for volcanic activity but also for earthquakes, further illustrating the dynamic and interconnected nature of Earth’s geological processes.

The Impact of Submarine Volcanism on the Ocean and Climate

Alteration of Seawater Chemistry

Submarine volcanic activity has a profound impact on the ocean’s chemistry. The eruption of underwater volcanoes releases various gases, including carbon dioxide (CO2) and sulfur dioxide (SO2), into the ocean. These emissions can alter seawater chemistry, affecting marine life and ecosystems. Moreover, the interaction between volcanic materials and seawater can lead to the formation of new minerals and contribute to the ocean’s carbon cycle, highlighting the intricate connections between geology and marine chemistry.

Influence on Global Climate

The vast scale of submarine volcanism also plays a role in regulating the Earth’s climate. Volcanic eruptions release aerosols and greenhouse gases into the atmosphere, which can influence climate patterns. While the immediate effect of these eruptions is often cooling due to aerosols reflecting sunlight, the long-term release of greenhouse gases like CO2 from submarine volcanoes can contribute to global warming. Understanding the balance between these effects is crucial for climate science and highlights the importance of studying submarine volcanism.

In conclusion, the fact that 90% of all volcanic activity occurs in the oceans opens up a realm of exploration and discovery that is vital for understanding our planet. From shaping the seafloor to influencing climate patterns, the impact of underwater volcanoes is profound and far-reaching.

FAQs

1. What causes most volcanic activity to occur in the oceans? The majority of volcanic activity in the oceans is due to the movement of tectonic plates, particularly at mid-ocean ridges where plates diverge, and at subduction zones where one plate moves beneath another. These processes allow magma to rise and erupt on the ocean floor, creating new crust and volcanic features.
2. How do underwater volcanoes affect marine life? Underwater volcanoes can create unique ecosystems, especially around hydrothermal vents, where the heat and minerals from the vents support life forms that rely on chemosynthesis. These ecosystems can thrive in the absence of sunlight, relying on the energy provided by the volcanic activity.
3. Can volcanic activity in the oceans influence the weather? Yes, volcanic activity can influence the weather and climate. The release of volcanic gases and particles into the atmosphere can lead to temporary cooling effects on the Earth’s surface. Over longer periods, the release of greenhouse gases like carbon dioxide from underwater volcanoes can contribute to global warming.
4. What are hydrothermal vents and why are they important? Hydrothermal vents are fissures on the seafloor from which geothermally heated water discharges. They are important because they support unique ecosystems with organisms adapted to high pressure, temperatures, and chemically rich environments. These ecosystems provide insights into the limits of life and biochemical cycles.
5. How is new oceanic crust formed through volcanic activity? New oceanic crust is formed at mid-ocean ridges, where tectonic plates diverge. As the plates pull apart, magma rises from beneath the Earth’s crust to fill the gap. When the magma cools, it solidifies to form new crust. This process is a key component of seafloor spreading and contributes to the dynamic nature of the Earth’s lithosphere.