Upper mantle

A thick layer of rock is inside Earth.

It sits just under the ground. This layer is very deep. It is made of many rocks. Most of it is made of green rocks.

Heat makes the rock move. Hot rock goes up. Cool rock sinks down. This movement moves the big plates on top.

This layer is mostly solid. The heavy weight of the Earth keeps it that way. It does not melt easily.

Scientists use big ships to study it. They drill deep into the sea floor. This helps us learn about our world.

The upper mantle is a thick layer of rock. It sits just below the Earth's crust.

This layer is about 660 kilometers thick. It makes up about 20% of the whole mantle. The rock here is mostly solid. Even though it is very hot, the heavy weight of the Earth keeps it from melting. This weight is called lithostatic pressure.

The rock is made of many minerals. Most of it is olivine and pyroxene. As you go deeper, the pressure changes the rocks. This creates a transition zone. In this zone, minerals like ringwoodite form. These minerals can even hold a lot of water.

Heat makes the mantle move in a slow way. Hot material rises up. Cooler material sinks down. This movement helps move the tectonic plates on the surface.

Scientists study the mantle by drilling into the ocean floor. They use big ships like the Chikyū. These ships can reach deep below the seabed to find rock samples.

The upper mantle is a huge layer of rock inside our planet. It starts just beneath the Earth's crust. This layer sits under both the oceans and the continents.

The upper mantle is very important because it helps move the tectonic plates. These plates are the large pieces of Earth's surface. Without the movement in the mantle, our surface would look very different. The upper mantle is about 660 kilometers thick. This means it is only about 20% of the total mantle thickness.

Inside the mantle, the rock behaves in a very interesting way. It is mostly solid rock, even though it is very hot. The heat can reach 1,300 degrees Celsius. The rock does not melt because of lithostatic pressure. This is the heavy weight of all the material above it. This pressure keeps the rocks solid. Over millions of years, the mantle can flow very slowly like a thick liquid.

This slow movement is called convection. Hot material rises up while cooler material sinks down.

Scientists have learned a lot about this layer by studying waves. These are seismic waves from earthquakes. When waves travel through the Earth, they change speed. This happens because the density of the rock changes. Andrija Mohorovičić first noted a sudden change in wave speed in 1909. This boundary is called the Mohorovičić discontinuity, or the "Moho."

It marks the base of the crust. Scientists use these wave changes to map the inside of our world.

We can also learn about the mantle by looking at its minerals. The rock is mostly made of olivine and pyroxene.

About 55% of the material is olivine. About 35% is pyroxene. The rest is made of minerals like calcium oxide and aluminum oxide. As you go deeper, the pressure changes the minerals. For example, olivine changes into wadsleyite and then ringwoodite. This creates a special area called the transition zone. This zone is between 410 and 660 kilometers deep.

Exploring the mantle is a very hard job for scientists. It is easier to drill in the ocean than on land. This is because the oceanic crust is much thinner. Many ships have tried to reach the mantle. The Japanese vessel Chikyū set a world record in 2012. It drilled more than 7,000 meters below sea level.

Scientists use these deep holes to find rock samples. These samples help us understand the deep parts of our home.

The upper mantle is a massive layer of rock located inside the Earth. It begins just beneath the crust, sitting under both the oceans and the continents. This layer is approximately 660 kilometers thick. This means the upper mantle represents about 20% of the total mantle thickness. It is a vital part of our planet's system. The upper mantle is responsible for causing tectonic plates to move.

Inside this layer, the rock behaves in a very unique way. Temperatures range from the crustal boundary up to about 1,300 degrees Celsius. Even though it is very hot, the mantle is almost exclusively solid. This happens because of lithostatic pressure. This is the enormous weight from all the material above it. This pressure raises the solidus, which is the temperature at which melting begins. Because of this, the rock stays solid but can flow very slowly over millions of years. This slow, viscous-like movement is called plastic deformation.

Temperature differences drive a process called convection. Hot material upwells toward the surface, while cooler, heavier material sinks downward. This movement creates a convective material circulation throughout the mantle. At convergent plate boundaries, known as subduction zones, material moves downward into the Earth.

When hot material rises in plumes, the surface above may have high elevations. These plumes can also cause hot spot volcanism. This constant circulation is a major driver of geological activity.

Scientists study the mantle using seismic waves from earthquakes. These waves change speed as they travel through different layers. Density increases with depth because of the compression of the rock. Abrupt changes in density occur when the material composition changes. In 1909, Andrija Mohorovičić noted a sudden increase in seismic wave speed. This boundary marks the base of the crust and is called the Mohorovičić discontinuity, or "Moho."

The Moho varies in depth from 5 to 70 kilometers.

The composition of the upper mantle is mostly mafic minerals. It is dominantly peridotite, which is a rock made of several minerals. About 55% of the material is olivine. Another 35% is pyroxene. The remaining 5% to 10% consists of calcium oxide and aluminum oxide minerals. These include plagioclase, spinel, or garnet, depending on the depth.

The most abundant elements are oxygen, magnesium, silicon, and iron.

As depth increases, pressure causes minerals to change their structure. This creates a region called the transition zone between 410 and 660 kilometers deep. At 410 kilometers, a discontinuity occurs as olivine transforms into wadsleyite. Below this, olivine changes into ringwoodite. At the base of the transition zone, ringwoodite decomposes into bridgmanite and periclase. This 670 km discontinuity marks the boundary between the upper and lower mantle. These phase changes are dependent on both temperature and density.

Exploring the mantle is an immense scientific challenge. It is easier to explore the seabed than land because oceanic crust is thinner. In 1966, Project Mohole was an early attempt at mantle exploration. More recently, the Japanese vessel Chikyū set a record in 2012. It drilled more than 7,000 meters below the seafloor.

Scientists use these deep samples to understand the Earth's interior. Understanding the upper mantle helps us grasp how our entire planet functions.