Lecture 2: Interior of Earth-II

Introduction

This tutorial aims to provide a comprehensive understanding of the internal structure of the Earth, focusing on the crust, Mohorovicic discontinuity, ophiolites, xenoliths, and seismic velocity variations. By following these steps, you will gain insights into geological concepts relevant to Earth sciences, which can be useful for students, educators, and anyone interested in geology.

Step 1: Understanding the Crust

• The Earth's crust is the outermost layer, composed mainly of solid rock.
• It is divided into two types: continental crust and oceanic crust.
• Continental crust is thicker (averages about 30-50 km) and less dense, while oceanic crust is thinner (averages about 5-10 km) and denser.
• Practical Tip: Familiarize yourself with key minerals found in each type of crust, such as granite in continental crust and basalt in oceanic crust.

Step 2: Exploring Mohorovicic Discontinuity

• The Mohorovicic discontinuity, often referred to as the Moho, is the boundary between the Earth's crust and the underlying mantle.
• It marks a significant change in seismic wave velocity, indicating a transition from the less dense rocks of the crust to the denser rocks of the mantle.
• Common Pitfall: Confusing the Moho with the lithosphere; remember that the lithosphere includes both the crust and the upper mantle.

Step 3: Learning about Ophiolites

• Ophiolites are sections of the Earth's oceanic crust and the underlying mantle that have been uplifted and exposed above sea level.
• They provide valuable insights into the composition and structure of oceanic crust.
• Real-World Application: Study ophiolite complexes for information on ancient oceanic crust and plate tectonics.

Step 4: Understanding Xenoliths

• Xenoliths are fragments of rock trapped in another type of rock, often found in volcanic eruptions.
• They can provide information about the composition of the Earth’s mantle and the processes occurring deep within the Earth.
• Practical Tip: Explore different types of xenoliths, such as peridotites, which are often derived from the upper mantle.

Step 5: Analyzing Seismic Velocity Variations

• Seismic velocity refers to the speed at which seismic waves travel through different materials.
• Variations in seismic velocity can indicate changes in material composition, temperature, and pressure within the Earth.
• Use seismic data to map the structure of the Earth’s interior and understand geological processes.

Conclusion

In this tutorial, you have learned about the Earth's crust, the Mohorovicic discontinuity, ophiolites, xenoliths, and seismic velocity variations. These concepts are fundamental for understanding the geology of our planet. For further exploration, consider studying geological maps or engaging in fieldwork to observe these concepts in action.