Guyot

Some mountains live deep under the sea.

They have very flat tops. These mountains look like big tables. Long ago, they were islands above the water. Waves hit the tops of the islands. This made them flat. The islands also grew heavy and sank. Now they sit deep in the ocean. They are found in most oceans. You will not find them in the Arctic Ocean. These flat mountains are very special.

Some mountains live deep under the sea. We call these guyots. They are also called tablemounts. These mountains have very flat tops. They look like big tables.

Most guyots are in the Pacific Ocean. You can find them in almost all oceans. However, none live in the Arctic Ocean. Harry Hammond Hess found them in 1945. He used tools on a ship to study the seafloor. He saw that some mountains had flat tops.

How do they form? First, lava comes up from the Earth. This makes a volcano. The volcano grows tall. It may even break the ocean surface. Then, waves hit the top. This makes the top flat. Waves and coral reefs help shape them.

After a long time, the mountain sinks. The rock cools and becomes dense. This means it is heavy. The heavy rock sinks into the Earth's mantle. This part of the Earth is called the asthenosphere. The mountain sinks lower and lower over millions of years. Some islands even become coral atolls before they sink. Eventually, they become guyots deep under the sea.

A guyot is a special kind of underwater mountain. Scientists also call them tablemounts because they have flat tops. These mountains are far below the surface of the sea.

They are much larger than regular undersea mountains. A typical guyot has a mean area of 10,000 square kilometers. Most regular seamounts are much smaller than that. You can think of them like giant tables sitting on the ocean floor. They are very important for studying our planet.

How does a guyot form? It starts with lava rising from the Earth's mantle. This lava comes out of vents on the seafloor. The volcano grows until it is near or above the water. Once it is at the surface, waves hit the top. These waves or growing coral reefs help flatten the mountain. After a while, the volcano stops erupting. The rock cools and becomes denser, which means it gets heavier. This causes the mountain to sink slowly into the mantle through isostasy.

We know about these mountains thanks to Harry Hammond Hess. He was a man who commanded a ship during World War II. In 1945, he used echo-sounding equipment to look at the seafloor. He noticed that some undersea mountains had flat tops. Hess named them guyots after a building at Princeton. This was named for the Department of Geosciences. His discovery helped support the theory of plate tectonics.

There are many different facts about where guyots live. There are 283 known guyots in the world's oceans. The North Pacific has the most with 119. The South Pacific has 77, and the South Atlantic has 43. The Indian Ocean has 28 and the North Atlantic has eight. There are six in the Southern Ocean and two in the Mediterranean Sea. No guyots have been found in the Arctic Ocean. However, one is found along the Fram Strait near Greenland.

Guyots tell us a lot about how the Earth moves. They ride on tectonic plates that move over the asthenosphere. The asthenosphere is the part of the mantle beneath the plates. By looking at a chain of seamounts, we can see which way a plate moves. A great example is the Hawaiian–Emperor seamount chain. These mountains also change life in the ocean. They can cause more chlorophyll and different types of tiny plants to grow nearby.

A guyot is a unique type of underwater volcanic mountain. Scientists also call these features tablemounts because of their flat summits. These mountains sit deep below the surface of the ocean. They are much larger than typical undersea mountains, known as seamounts. You can imagine them as massive, submerged tables resting on the seafloor.

They are vital for geologists studying the Earth. These structures help us understand how the ocean floor changes over millions of years.

The formation of a guyot is a long, complex process. It begins with the extrusion of lava from the Earth's mantle. This lava travels upward through vents on the seafloor. As the volcano grows, it eventually reaches or breaches the ocean surface. Once at the surface, wave action begins to erode the peak. Coral reef growth can also help create a flat-topped edifice. Eventually, the volcanic activity ceases, and other geological processes take over.

As the volcano becomes inactive, the mountain begins to sink. This happens through a process called isostasy. The rock of the guyot and the surrounding lithosphere cools over time. As it cools, it becomes denser and heavier. This increased density causes the mountain to sink lower into the mantle. A guyot may pass through several distinct stages during this subsidence. It may start as a fringed reefed mountain. It can then become a coral atoll. Finally, it settles as a flat-topped submerged mountain.

We know about these mountains because of Harry Hammond Hess. During World War II, Hess commanded a ship. In 1945, he used echo-sounding equipment to map the seafloor. His data revealed that many undersea mountains had flat tops. Hess named these mountains "guyots" after the Department of Geosciences building at Princeton. His discovery was very important for science. It helped provide evidence to bolster the theory of plate tectonics.

Guyots are widespread, though they are not found everywhere. There are 283 known guyots in the world's oceans. The North Pacific holds the most with 119. The South Pacific has 77, and the South Atlantic has 43. The Indian Ocean contains 28, while the North Atlantic has eight. There are six in the Southern Ocean and two in the Mediterranean Sea. Interestingly, no guyots are known in the Arctic Ocean. However, one has been found along the Fram Strait near Greenland.

These mountains have very specific physical characteristics. Most guyots have a steepness gradient of about 20 degrees. To be a true guyot, a mountain must stand at least 1,000 meters tall. Some are massive, like the Great Meteor Tablemount. It stands over 4,000 meters high with a diameter of 350 kilometers. The mean area of a guyot is 10,000 square kilometers. This is much larger than the mean area of a typical seamount, which is 1,000 square kilometers.

Guyots are more than just rocks on the seafloor. They provide critical data on the movement of tectonic plates. The trend of a seamount chain traces how a plate moves. This movement occurs over a fixed heat source in the asthenosphere. The asthenosphere is the part of the mantle beneath the lithosphere. The Hawaiian–Emperor seamount chain is a perfect example of this. It shows a chain of volcanoes moving from active stages to submerged guyots.

Finally, guyots influence the biology of the ocean. Their presence is associated with specific lifeforms and organic matter. Scientists observe local increases in chlorophyll a near these mountains. There are also changes in phytoplankton species composition around them. These underwater mountains create unique environments that affect how carbon is incorporated into the ocean ecosystem. By studying guyots, we learn how geology and biology interact in the deep sea.