#AghamUnite: Deformation of the Crust

Summary

This educational video by the USD College of Science Glee Club delves into the phenomenon of crustal deformation caused by tectonic plate movements. It explains the forces behind deformations, including tensional, compressional, and shear forces, and the stress types they generate. The script outlines the stages of deformation: elastic, ductile, and fracture. It also covers the geological outcomes of deformation, such as faults and folds, providing a clear understanding of how the Earth's crust changes.

Takeaways

• 🌏 Deformation of the Earth's crust is caused by the shifting of tectonic plates.
• 🚗 An earthquake is an example of a sudden deformation where the ground shakes and shifts.
• 🔧 Deformations result in various geological structures such as folds, faults, foliations, and joints.
• 🤔 Stress is a force applied over an area and can be uniform or differential, with the latter having three types: tensional, compressional, and shear.
• 🔄 Tensional force pulls objects apart, increasing surface area, while compressional force pushes them together, decreasing surface area or volume.
• 🔄 Shear force causes lateral movement within an object due to internal fabric or weakness.
• 🛠 Strain refers to the changes in material size, shape, or volume due to stress.
• 🔄 Deformation stages include elastic (reversible), ductile (permanent), and fracture (irreversible).
• ⚒ Factors affecting deformation include temperature, confining pressure, strain rate, and ground composition.
• 🏞 Faults are fractures in bedrock caused by shear force where rocks on one side move relative to the other.
• 🏞 Folds are permanent wave-like deformations in layered rock or sediment caused by compressional force.

Q & A

What is meant by the term 'deformation' in the context of the Earth's crust?

Deformation in the context of the Earth's crust refers to the sudden change in the ground, such as when it shakes and shifts upwards during an earthquake, caused by the shifting of tectonic plates.

What are tectonic plates and where are they located?

Tectonic plates are large slabs of solid rock that make up the Earth's lithosphere, and they are located in the Earth's crust.

What are the different types of geologic structures produced by tectonic plate movements?

The geologic structures produced by tectonic plate movements include folds, faults, foliations, and joints.

How is stress defined in the context of deformation?

Stress is defined as a force applied over an area. It can be uniform, where equal forces are applied from all directions, or differential, where unequal forces are applied.

What are the three types of differential stress mentioned in the script?

The three types of differential stress are tensional force (or stretching force), compressional force (or contracting force), and shear force.

What is the difference between tensional and compressional forces?

Tensional force pulls objects apart, increasing their surface area, while compressional force pushes objects together, decreasing their surface area or volume.

What is shear force and how does it affect the Earth's crust?

Shear force is a stress within an object that causes a side-to-side movement along an internal fabric or weakness, and it can lead to the formation of faults in the Earth's crust.

What is strain and how does it relate to stress?

Strain refers to the changes in material size, shape, or volume due to stress. It is the result of the application of stress on rocks and tectonic plates.

Describe the three stages of deformation as rocks and tectonic plates are subjected to stress.

The three stages of deformation are elastic deformation (reversible), ductile deformation (permanent shape change), and fracture or brittle point (irreversible strain via a break in the material).

What factors can affect the degree of deformation an object undergoes?

Factors affecting the degree of deformation include temperature, confining pressure, strain rate, and the composition of the ground.

What is a fault and how is it formed?

A fault is a fracture in bedrock along which rocks on one side have moved relative to the other side, typically caused by shear force.

How are folds different from faults, and what causes them?

Folds are permanent wave-like deformations in layered rock or sediment, formed from compressional forces, whereas faults are fractures caused by shear forces.