Difference Between Joints and Faults

Joints vs Faults

Geology is a very fascinating subject to study, but the thing is, it has many terms that are really confusing and oftentimes difficult to understand. This is because most of the time what we see in our surroundings are described in two ways: how ordinary people perceive them and the view of scientists. A prime example of that in geology is how we define the cracks in the Earth’s surface. We average folks tend to look at all of them as the same, but scientists can distinguish two types: joints and faults.

In geology, cracks like faults and joints are collectively known as fractures or discontinuities. Explained simply, these are spaces or gaps that occur in rock formations that form in the Earth’s surface due to different factors. But the similarity between joints and faults ends here as each one of them has distinct characteristics that set them apart from one another.

The first thing that is noticeably different between a joint and a fault is its size. Joints are smaller compared to faults, and they can occur in almost all kinds of rock formations. They are often hairline cracks that are unnoticeable especially when viewed from a distance. Faults, on the other hand, are much bigger and can extend up to miles on end. But because of constant dirt formation over the Earth’s crust, it is not always possible to see fault lines, but scientists are fairly certain of their presence.

But more than the size discrepancy of joints and faults is one aspect of interest that geologists often look at when determining the kind of crack, and that is the displacement that results from movement of rocks. Joints have very little or no movement at all because they do not completely separate rock formations.

Faults are different because they are prone to lateral movement caused by tectonic forces beneath the surface of the Earth. This is because they occur as thorough cuts between large rock formations.
Depending on the direction of tectonic movement, either or both sides of a fault can move upwards, downwards, and sideways which is often the cause of earthquakes.

Another item to consider when setting apart a joint from a fault is how they are formed. Faults are created by the constant movement beneath the Earth’s crust. When rock formations are divided by faults, they become vulnerable to earthquakes. One prime example of this is the San Andreas Fault in California which extends up to 810 miles. It divides the Pacific Plate and the North American Plate.

Joints are formed when a rock is stretched to its breaking point. This happens because continued accumulation of dirt over rock formations also adds to its mass thus forcing it to break apart. But beyond all these traits, many people are wary of the potential danger that these cracks pose to human civilization.

Faults are considered as one of nature’s powerful movers, literally. This was recently displayed when plates in the Pacific Ring of Fire moved on top of one another causing a massive earthquake that hit Japan and caused the subsequent tsunami that affected many countries. Joints do not pose this kind of threat and are oftentimes marveled at because they form in uniform sets in various parts of the world.

Summary:

1.There are two types of cracks that occur in the Earth’s crust; joint and fault.
2.Both joints and faults are classified as fractures or discontinuities which is the only similarity they have.
3.Joints are smaller compared to faults.
4.Joints have no movement therefore cause none or very little displacement while faults have lateral movement that cause displacement.
5.Faults are formed because of constant tectonic movement while joints are formed when rocks are stretched to their breaking point.
6.Faults can cause deadly earthquakes and tsunamis while joints rarely pose any threat to civilization.

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