Crust

The Earth's crust is the outermost solid layer of the Earth. It is composed of a variety of igneous, metamorphic, and sedimentary rocks, and is the thinnest layer of the Earth, averaging about 5-70 kilometers in thickness.

Composition

The crust is primarily composed of oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium. These elements combine to form various minerals, such as quartz, feldspar, and mica, which are the building blocks of the crust. The crust also contains trace amounts of other elements and compounds.

Types of Crust

There are two main types of crust: continental crust and oceanic crust. Continental crust is thicker and less dense than oceanic crust, and is primarily composed of granitic rocks. Oceanic crust is thinner and more dense, and is primarily composed of basaltic rocks.

Structure

Beneath the Earth's crust lies the mantle, which is a semi-solid layer of rock. The boundary between the crust and mantle is known as the Mohorovičić discontinuity (or Moho), where there is a significant change in seismic wave velocities. This boundary separates the rigid crust from the more ductile mantle.

Study Guide

• Describe the composition of the Earth's crust and the most abundant elements.
• Explain the differences between continental and oceanic crust in terms of thickness, density, and composition.
• Discuss the significance of the Mohorovičić discontinuity in understanding the Earth's structure.
• Compare and contrast the crust with the other layers of the Earth (mantle and core) in terms of composition, thickness, and behavior.

[Crust] Related Worksheets and Study Guides:

• Earth's CrustEarth Science • High School
• Plate tectonicsScience • Eighth Grade
• Our EarthScience • Kindergarten