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Volcanoes found on the ocean floor can erupt as violently as those on land. Known as submarine volcanoes or seamounts, they are underwater cracks or vents in the Earth’s surface that can erupt magma. Some oceanographers believe there could be as many as a million in the Pacific Ocean, around 750 times as many volcanoes on land as on the ocean floor.
See the fact file below for more information on Submarine Volcanoes, or you can download our 29-page Submarine Volcanoes worksheet pack to utilize within the classroom or home environment.
Key Facts & Information
IN NATURE
- The presence of subsea volcanoes and volcanic vents is widespread in specific regions. Some are active and make their existence known by venting steam and rock debris above the ocean’s surface. Numerous others are located so far below the feeling that the immense pressure created by the water’s weight above them precludes the creation and explosive release of steam and gases. Significant eruptions at depth could not even reach the ocean’s surface.
- Submarine volcanoes, surrounded by an infinite water supply, may exhibit unusual behavior compared to their terrestrial counterparts. When ocean water rushes into hot, shallow subsurface vents, violent steam-blast eruptions result.
- For this reason, lava that flows into the sea from land or erupts into a shallow sea floor may swiftly cool and shatter into sand and rubble. “Black sand” beaches of Hawaii were formed almost instantly when molten lava met the ocean.
- Yet, new deep-diving submersible observations have demonstrated that certain undersea eruptions produce flows and other volcanic structures comparable to those formed on land.
- In recent years, hydrothermal plumes and vents emitting boiling water have been discovered in some mid-ocean volcanic rift systems. To this day, however, no one has caught an active deep undersea eruption on camera. Submarine volcanoes, surrounded by an infinite water supply, may exhibit unusual behavior compared to their terrestrial counterparts. When ocean water rushes into hot, shallow subsurface vents, violent steam-blast eruptions result. For this reason, lava that flows into the sea from land or erupts into a shallow sea floor may swiftly cool and shatter into sand and rubble. As a result, a great deal of volcanic debris is broken into tiny pieces.
- Large debris heaps form around the volcanic vent during an underwater eruption, seen from the water’s surface.
- The debris in shallow water is reshaped by ocean currents, while debris that has fallen from the cone’s upper half travels into deep water along the seafloor. Flying clouds disperse the acceptable debris and ash from the eruptive plume across a large area. The same eruptive plume’s coarse debris falls into the ocean and accumulates on the cone’s sides. The pumice from the eruption is carried by the ocean currents and spreads out over a broad region.
EFFECTS
- Underwater volcanoes can have very different explosions and eruptions from those on land because of the presence of water.
- In the case of a volcanic eruption, for example, water speeds up magma’s cooling and solidification, resulting in volcanic glass formation. Lava emitted from undersea volcanoes has different textures and shapes than lava released from land-based volcanoes.
- A complex shell forms over the lava when it touches water. Pillow lava is formed when molten rock flows into an existing crust.
- When the pressure exceeds the critical pressure of water, the water ceases to boil and becomes a supercritical fluid, existing at a temperature of absolute zero. This occurs at ocean depths of around 2,200 m. Hydrophones have difficulty picking up deep-sea volcanoes from far away if they don’t hear sputtering or bubbling sounds.
- The usual presence of salts in saltwater causes a rise in both the critical temperature and pressure. In the presence of hot basalt and while moving through the cracks of hot rocks, the aqueous solution will likely have a different chemical composition than the bulk water.
ERUPTION
- More than 70% of all volcanic eruptions occur underwater, yet scientists still need to learn more about them since thousands of feet of water hide the explosions.
- The superheated lava of West Mata volcano causes an explosive eruption, sending a flash of heat into the water before it sinks back to the ocean floor. The explosion throws ashes and rocks into the lake while lava bubbles brightly below. This volcano is located in the Pacific Ocean, not far from Fiji. Its highest point is almost two miles below sea level, while its lowest is nearly a mile below the surface.
- Magma is pushed up from the Earth’s interior and erupts onto the land or ocean surface. When the magma rises, its pressure decreases, causing the dissolved gases inside it to escape into bubbles. When these dissolved gases are released unexpectedly, an explosive eruption occurs on land. Imagine the bubbles in a coke bottle bursting all at once when the bottle is opened after being shaken.
- Nevertheless, after the magma sinks to the seafloor, it must contend with the enormous weight of the ocean. Scientists believe that the Havre volcano’s pressure, which is between 92 and 122 times that of sea level and extends for around 3,000 to 4,000 feet below sea level, muted its explosiveness and molded the diverse types of lava flows.
- Lava also forms under pressure, with water reacting very differently to cooling magma than it does to the air. In an instant, water evaporates when it comes into contact with molten lava at 800 degrees Celsius. Its quick transformation into steam can be destructive enough to shatter the lava. When magma comes into contact with water, however, the temperature drop is so significant that the magma rapidly hardens in a process called quenching.
SUBMARINE VOLCANOES AROUND THE WORLD
- Located in the volcanic arc between Bougainville and the Solomon Islands, Kavachi is one of the most active undersea volcanoes in the southwest Pacific Ocean. At least eight times, the volcano has emerged from the sea before being eroded back into the water.
- The volcano has a basal diameter of 8 km, rises from a depth of around 1.1 km, and is approximately conical in shape. In 2003, the volcano erupted, creating a 15-meter-high island that quickly vanished. Kavachi has been the subject of some impressive film footage of underwater and underwater explosions.
- They aid in demonstrating the ongoing dynamic interplay between volcanic (endogenetic) and surface (exogenetic) processes that contribute to the evolution of volcanic landforms.
- On the steep inner western slope of the Lesser Antilles ridge around 8 kilometers north of Grenada and about 8 kilometers west of Ronde Island in the Grenadines lies Kick-em-Jenny, an active undersea volcano or seamount in the Caribbean Sea. Kick-em-Jenny towers 1,300 meters above the seafloor.
- Although Kick ’em Jenny appears on early maps, it was either the name of a small island now known as Diamond Rock or the strait between Grenada and Ronde Island. The volcano itself was not discovered until 1939. The term comes from the fact that the waters can sometimes get quite choppy.
- Around 35 kilometers off the southeastern coast of Hawaii lies the active undersea volcano known as the Kamaβehuakanaloa seamount. The top of the seamount is about 975 m (3,200 ft) below sea level. Mauna Loa, the largest shield volcano on Earth, has this seamount as a flank. The Hawaiian name Kamaβehuakanaloa means “glowing child of Kanaloa,” the ocean god.
- Based on studies at the Bishop Museum, the name was assigned by the Hawaiian Board on Geographical Names in 2021 and adopted by the U.S. Geological Survey. It appears in two Hawaiian meles (songs or poems) from the 19th and early 20th centuries.
- Axial seamount on the Juan de Fuca Ridge in the Pacific Ocean, about 480 kilometers west of Cannon Beach, Oregon. At 1,100 meters high, it is the youngest and currently active volcano in the Cobb-Eickelberg Seamount chain.
- The seamount is located at the intersection of a mid-ocean ridge and a geological hotspot, making it a geologically complicated feature, the origins of which are still poorly understood. The summit of Axial seamount is on a long, low plateau, with two massive rift zones trending 50 km to the northeast and southwest, respectively.
- The volcano’s geology is complex by its intersection with numerous smaller seamounts and because it has a peculiar rectangular caldera and flanks that are pockmarked with cracks, vents, sheet flows, and pit craters to 100 m deep.
Submarine Volcanoes Worksheets
This fantastic bundle includes everything you need to know about Submarine Volcanoes across 29 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Submarine Volcanoes. Volcanoes found on the ocean floor can erupt as violently as those on land. Known as submarine volcanoes or seamounts, they are underwater cracks or vents in the Earth’s surface that can erupt magma.
Complete List of Included Worksheets
Below is a list of all the worksheets included in this document.
- Submarine Volcanoes Facts
- Underwater Volcano
- Seamounts
- Tamu Massif
- Scheme
- Compare and Contrast
- How Bad?
- Volcanic Facts
- Eruption
- The Process
- Breaking News!
Frequently Asked Questions
What are submarine volcanoes?
Submarine volcanoes are volcanoes that are located underwater, typically on the ocean floor. They can be found in various places around the world, including along the mid-ocean ridges, at oceanic hotspots, and in volcanic arcs.
How are submarine volcanoes formed?
Submarine volcanoes are formed in much the same way as terrestrial volcanoes, through the movement of magma from the Earth’s mantle up to the surface. However, the unique conditions of the ocean floor, including the high pressure and cold temperatures, can affect the way that magma behaves and the types of rocks that are formed.
What are the hazards associated with submarine volcanoes?
Submarine volcanoes can pose a number of hazards, including the release of toxic gases, the generation of tsunamis, and the formation of new islands that can disrupt shipping lanes. In addition, submarine eruptions can create underwater lava flows that can damage underwater infrastructure such as cables and pipelines.
What are some examples of famous submarine volcanoes?
One famous example of a submarine volcano is the Axial Seamount, which is located off the coast of Oregon and is the most active submarine volcano in the Pacific Northwest. Another well-known submarine volcano is the Loihi Seamount, which is located off the coast of Hawaii and is expected to eventually emerge as a new island.
Why are submarine volcanoes important?
Submarine volcanoes play an important role in the geology and oceanography of the Earth. They are thought to be one of the main mechanisms by which new oceanic crust is created, and they also provide a habitat for a variety of deep-sea creatures that are adapted to the extreme conditions of the deep ocean. In addition, the minerals and metals that are associated with submarine volcanoes have the potential to be valuable resources for human use.
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