Magma

What is Magma?

Magma is hot, melted rock that comes from deep inside the Earth. It forms when rocks melt far below the surface, creating a mix of liquid rock, tiny crystals, and gas bubbles. Magma is different from lava. Lava is what we call magma when it reaches the surface through a volcano.

Magma can be found in the mantle or the crust of the Earth. It forms in places where ocean plates dive under other plates, along rift valleys where continents pull apart, and at spots called hotspots. As magma moves upward, it can change by mixing with other melted rocks or losing gases. Sometimes it reaches the surface as lava. Other times, it cools deep underground and creates different kinds of rocks and structures.

Scientists have only seen magma directly a few times, during drilling projects in places like Iceland and Hawaii. Studying magma helps us learn how volcanoes work and how new land forms on Earth.

How Magma Looks and Feels

Magma is made of liquid rock that often has tiny solid pieces floating in it. As magma moves closer to the Earth's surface, the pressure drops, and gases that were dissolved in the liquid start to bubble out. This means that magma near the surface contains solid pieces, liquid, and gas.

Most magma is rich in a substance called silica. Silica helps decide many of magma's properties, like how thick or thin it is and its temperature. Magmas can be grouped into four types based on how much silica they have: felsic, intermediate, mafic, and ultramafic.

• Felsic magmas have the most silica and are very thick, like cool honey.
• Intermediate magmas have a bit less silica and are thinner than felsic magmas.
• Mafic magmas have even less silica and are thinner still, flowing more easily.
• Ultramafic magmas have the least silica and are the thinnest, flowing very easily.

Where Magma Comes From

Magma forms in several places inside the Earth. It can form where ocean plates dive under other plates, along rift valleys where continents pull apart, and at spots called hotspots. Water also plays a big role—it lowers the temperature at which rocks melt. This is why we find magma in places where water is released from sinking ocean plates.

When rock rises from deep within Earth, the pressure drops, and the rock can begin to melt. This process creates the ocean crust at mid-ocean ridges and causes volcanism in places like Europe and Africa.

How Magma Becomes New Land

When magma cools down, it turns into solid rocks. If it stays underground, it forms rocks like gabbro, diorite, and granite. If it erupts from a volcano, it becomes rocks such as basalt, andesite, and rhyolite. When magma erupts, it is called lava.

In Iceland, scientists tried to use heat from deep underground to make energy. In 2009, they found magma closer to the surface than they thought. They used this discovery to make electricity, creating power for the first time from magma.