What is Deformation? - Definition, Types & Process

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: What is Topsoil? - Definition, Composition & Uses

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 Definition of Deformation
  • 0:30 How Deformation Works
  • 2:03 Types of Deformation
  • 2:52 Factors Affecting Deformation
  • 4:22 Bending or Breaking…
  • 5:47 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Erika Steele

Erika has taught college Biology, Microbiology, and Environmental Science. She has a PhD in Science Education.

This lesson will discuss the various types of deformation that shape the Earth's crust. After the lesson, there will be a brief quiz to test what you have learned.

Definition of Deformation

The rocks that make up mountains have a great variety of lines and swirls that make them unique and beautiful. Have you ever wondered how hard rocks get their patterns? Deformation is any process that affects the shape, size, or volume of an area of the Earth's crust. The type of deformation that occurs depends on the type of stress and the type of rock present in the area of the Earth's crust that you are observing.

How Deformation Works

Rocks aren't stressed out in the same way a college student is stressed out, but they are constantly under pressure that causes them to change their shape over time. Stress is defined as a force applied over an area. If stress is applied uniformly, it is called confining stress and the rock or Earth's crust does not change shape. When the force is not applied equally in all directions differential stress occurs. As you can see in Figure 2 on screen, there are three types of differential stress to which rocks can be subjected:

  1. Tensional
  2. Compressional
  3. Sheer

Let's learn more about each of these types.

Figure 3: Tensional stress is caused by the crust being pulled in opposite directions.
tensional stress

Tensional Stress

As Figure 3 shows, tensional stress stretches rocks. Over time, this results in the formation of valleys. Tensional stress is caused by the crust being pulled in opposite directions.

Figure 4: When two large pieces of rock collide, compression occurs.
compressional stress

Compressional Stress

This type of stress forms tall mountain ranges like the Himalayas and Smokey mountains. Compressional stress, as Figure 4 shows, is the result of two large pieces of the Earth's crusts, such as two continental plates, colliding with each other.

Figure 5: Shear stress is caused by two plates moving past each other and results in a fault line such as the San Andreas fault.
Shear stress

Shear Stress

Fault lines are the results of shear stress. As Figure 5 shows, shear stress happens when two plates rub against each other in opposite directions. Shear stress is caused by two plates moving past each other and results in a fault line, such as the San Andreas Fault.

Types of Deformation

The response to stress is also called strain. Rocks will show strain by changing shape, volume, or size. If the area is able to return to its original shape after the strain, it is said to have experienced elastic deformation. If the area does not recover from the change in shape, it has experienced plastic deformation.

Let's talk about two types of deformation:

Figure 6: The curves seen in the rock are the result of ductile deformation.
ductile deformation

When the Earth's crust is folded or bent without breaking, as you can see in Figure 6, it is called ductile deformation. The curves seen in the rock are the result of ductile deformation.

Figure 7: The arrows in the figure show a fracture in the rock that is the result of brittle deformation.
brittle deformation

When a rock breaks under stress it is called brittle deformation. As you can see in Figure 7, the arrows in the figure show a fracture in the rock that is the result of brittle deformation.

Factors Affecting Deformation

Let's first look at temperature. Temperature affects the deformation of rocks in two ways. At higher temperatures, rock is able to stretch more when stress is applied. Since rock is more malleable at high temperatures, it forms more ductile structures. At lower temperatures closer to the surface of the Earth, rock is more likely to fracture or break when stressed. This is similar to what happens when glass is heated. At room temperature, glass is easily shattered. When you heat glass it becomes more flexible and can be shaped without breaking, as Figure 8 shows. The Earth's crust becomes more ductile toward the core because of heat, and more brittle towards the surface because of cooling. Temperature changes can also cause rock to expand and contract, which leads to fracturing or brittle deformation. If you have ever accidentally heated a Pyrex glass dish on the stove, you have seen how temperature can cause brittle deformation of rock.

Figure 8: At higher temperatures rock becomes more flexible or ductile and can be shaped.
the effect of temperature

Now, let's look at pressure. At high pressure, rocks are more likely to form ductile structures than brittle structures. This is effected by something called strain rate. Strain rate is the amount of strain over time. Lower strain rates result in the formation of ductile structures, while faster strain rates result in fracturing or brittle structures. Imagine a piece of taffy. If you pull it apart quickly, it will break. If you pull it apart slowly, it will stretch.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account