Seamount

Big hills live under the sea.

They are made by old volcanoes. These hills rise from the bottom. But they do not reach the top.

The hills change over time. Some grow tall and become islands. Then, the waves wear them down. They become flat on top.

Many sea animals live there. Fish and corals like the hills. The moving water brings them food. These hills are busy homes in the deep.

A seamount is a large hill under the sea.

It rises from the ocean floor. But it does not reach the surface. Most seamounts are old volcanoes. They are often shaped like a cone.

Scientists say a seamount must rise at least 1,000 meters.

Seamounts change over a long time. Some grow tall enough to become islands. Then, ocean waves wear down the top. This makes the peak flat. We call these flat-top seamounts guyots.

These hills are busy homes for sea life. They rise up into moving water. This water brings food to many animals. Fish, corals, and whales gather there.

There are more than 14,500 seamounts in the world. Many are in the North Pacific Ocean. Some seamounts are still active volcanoes. For example, Kamaʻehuakanaloa is an active volcano.

As seamounts get old, their sides can break. This can cause large landslides. These landslides can even make big waves called tsunamis.

A seamount is a huge underwater mountain that rises from the ocean floor.

These landforms are special because they do not reach the water's surface. This means they are not islands or cliffs. Most seamounts are actually extinct volcanoes. They usually have a conical shape, which means they look like a cone.

Scientists define a seamount as a rise that is at least 1,000 meters high. They often grow from 100 to 4,000 meters in height. If a hill is smaller than 1,000 meters, it is called a knoll.

Seamounts grow through a step-by-step volcanic process. First, magma rises from deep inside the Earth to build the core and sides. During the most active stage, the volcano erupts almost all of its material. Some volcanoes even grow tall enough to break the surface and become islands.

After the eruptions stop, the volcano becomes extinct. Over a long time, ocean waves erode the top of the mountain. If the peak becomes flat, it is called a guyot or a tablemount.

These flat-topped mountains stay hundreds of meters below the sea level.

Researchers have identified more than 14,500 seamounts across the world's oceans. Many of these are found in the North Pacific Ocean. This area has the most seamounts and guyots.

The largest seamount is located in the North Pacific and covers 15,500 square kilometers. In the Indian Ocean, seamounts have a larger average size than in other places. The Arctic Ocean has very few, with only 16 seamounts. Some seamounts are even still active today. For example, Kamaʻehuakanaloa in the Hawaiian Islands is an active undersea volcano.

These underwater mountains are very important for marine life. Because they rise high into the water, they change how currents move. This movement creates eddies, which are swirling patterns in the water.

These currents bring food like plankton up to the mountain. Because of this, many animals like fish, corals, and whales gather there.

The commercial fishing industry also uses seamounts to find fish. However, fishing can sometimes hurt these homes. For example, bottom trawling can scrape ecosystems away. This has caused populations of the orange roughy to decline.

Exploring the deep sea is a big job for scientists. Many seamounts have not even been mapped yet. Experts use technology like satellite altimetry to find them.

Finding these mountains is important for safety. In 1973, a ship called the Muirfield struck an uncharted seamount.

There are also dangers from landslides. As seamounts get older, their sides can collapse. These massive landslides can even create tsunamis.

A seamount is a large, isolated submarine landform that rises from the ocean floor.

To be classified as a seamount, the feature must rise at least 1,000 meters above the surrounding seafloor. These structures are typically conical in shape and do not reach the ocean surface. Because they remain submerged, they are distinct from islands or islets. Seamounts are vital components of the marine environment. They serve as major hubs for biological activity in the deep sea.

Most seamounts are volcanic in origin. They form through specific geological processes involving magma. Near mid-ocean ridges, volcanoes are built by decompression melting of rock in the upper mantle. In these areas, lower density magma rises through the crust to the surface. Other seamounts form near subducting zones. In these regions, a tectonic plate slides under another plate. This process adds volatiles to the overriding plate. These volatiles lower the melting point of the rock, creating magma. This magma leads to more explosive and viscous eruptions.

The life cycle of a seamount follows a predictable evolutionary pattern. First, early activity builds the core and the flanks of the volcano. This is followed by a period of intense volcanism. During this stage, the volcano erupts nearly 98% of its total magmatic volume. Some volcanoes grow large enough to break the sea surface and become islands. Eventually, the eruptions die away and the volcano becomes extinct. Over geologic time, waves erode the summit. If the volcano subsides and the peak is worn flat, it becomes a guyot.

Seamounts and guyots are found in every ocean basin. They are most abundant in the North Pacific Ocean. In this region, they cover 4.39% of the seafloor area. The North Pacific also contains the largest guyots in the world. These include the Kuko Guyot, which is about 24,600 square kilometers. Other massive examples are the Suiko and Pallada guyots. In contrast, the Arctic Ocean has only 16 seamounts and no guyots. The Indian Ocean features the largest mean seamount size at 890 square kilometers.

These underwater mountains create unique and productive marine ecosystems. Because they rise high into the water column, they disturb standard ocean currents. This interaction creates eddies, which are swirling patterns of water movement. These currents can reach speeds of 0.9 knots. This movement helps bring plankton and nutrients upward. As a result, seamounts attract corals, fish, and marine mammals. Many support extensive fisheries that the commercial industry relies upon.

Human activity can impact these sensitive deep-sea habitats. The commercial fishing industry often targets species near seamounts. This has led to documented stock declines in species like the orange roughy.

A major concern is bottom trawling. This fishing method involves dragging nets across the seafloor. It is estimated that 95% of ecological damage on seamounts is caused by bottom trawling. This process can scrape entire ecosystems off the sides of the mountains.

Mapping and studying seamounts remains a significant scientific challenge. Many of the more than 14,500 identified seamounts have not been studied in detail. Scientists use technologies like bathymetry and satellite altimetry to map the seafloor. Mapping is essential for maritime safety. In 1973, the ship Muirfield collided with an uncharted seamount.

Beyond navigation, there is a geological risk. As seamounts age, internal pressure can cause flank collapses. These massive underwater landslides have the potential to generate tsunamis.