What is the Earth's mantle made of ultramafic rock?

Earth's mantle is composed of ultramafic rocks, which are igneous and meta-igneous rocks characterized by very low silica content and high concentrations of iron and magnesium. A prominent example of this rock type is peridotite, a dense, coarse-grained rock dominated by olivine and pyroxene that forms the dominant rock of the upper mantle. These rocks provide direct samples and clues about the composition and early history of the Earth.

What we know

• Earth's mantle is composed of ultramafic rocks. [2]
• Ultramafic rocks contain less than 45% silica, generally more than 18% MgO, high FeO, and low potassium. [2]
• Peridotite is a dense, coarse-grained igneous rock that constitutes the dominant rock of the upper part of Earth's mantle. [5]
• Peridotite nodules brought up by kimberlite pipes and basalts provide physical samples of Earth's mantle from depths of 30 km to over 200 km. [5]

Still open

• The terms ultramafic and ultrabasic are often used interchangeably, but they are not wholly equivalent, as ultrabasic is a more inclusive term for low-silica rocks that may not be extremely enriched in iron and magnesium.

Where to go next

• how it workedHow do igneous rocks form from magma?
• a case in pointWhat are the characteristics of peridotite?
• the bigger pictureWhat are the three major types of rock?
• how we knowHow do mantle nodules reveal Earth's history?
• compared withHow does ultrabasic differ from ultramafic?
• an unexpected connectionHow does gemstone peridot relate to the Earth's mantle?The gemstone peridot consists of pale green olivine, which is the primary silicate mineral making up peridotite, the dominant rock of Earth's upper mantle.

Sources

• [1]ultramafic rock (Wikidata Q1143398) · CC0 1.0
• [2]Ultramafic rock · CC BY-SA 4.0
• [3]List of rock types · CC BY-SA 4.0
• [4]Igneous rock · CC BY-SA 4.0
• [5]Peridotite · CC BY-SA 4.0

Your path

1. What is a pyroclastic flow?
2. /What is sedimentary rock?
3. /What is the massive Haleakala volcano on Maui?
4. /How was the Yellowstone Caldera formed?
5. /How was Maui Nui formed?
6. /What is the Earth's mantle made of ultramafic rock?