3 Ways That Abrasion Will Wear Down Rocks

The wearing down of rocks through abrasion is the process of those rocks receiving friction, scraping, rubbing, or contact with other rocks.  Abrasion will affect rocks by breaking them up into smaller rocks.  The more abrasion the rocks receive, the smaller and more numerous those rocks will become.

Small particles of sand are a great example of rocks receiving abrasion to a great degree.  When you walk on the beach all that sand you see is very tiny small rocks.  Those almost hard to see rocks were once part of larger rocks before they were broken down through abrasion.

There are three ways abrasion will wear down rocks:

1. Abrasion by water.

Abrasion of rocks through water happens when rocks continuously bump into each other while in water.  Rivers, lakes, and the sea will move rocks around together and cause abrasion.  This abrasion will wear down rocks quite quickly depending on water flow and how many rocks are together. 

The Sea – The turbulence of the sea can grind and spit up rocks onto its beaches.  Each wave as it laps on the beach and then pulls back to the sea, will cause all those rocks to rub against each other constantly.

The commotion is so violent not only on the beach, but can be just as turbulent further out in deeper waters.    

Lakes – Lakes can have similar effects as the sea but typically to a lesser degree.  There are often currents and water flow about larger bodies of water.  That flow of water will cause abrasion of rocks that will wear them down. 

Rivers and streams – The flow of water by rivers and streams is plenty enough to wear down rocks through abrasion.  Rocks will continuously roll down river bumping, grinding, and pushing into other rocks.

You will often find larger rocks in and around rivers and streams.  Along with those larger rocks will commonly be smaller rocks, even to the size of sand and smaller.  Often smaller rocks, like sand, will get kicked up by water flow and rub against larger rocks as they move down river.

Rocks tumbling down rivers and streams will often round them out.

2. Abrasion by wind.

Abrasion of rocks by wind involves small particles of rock, like sand, being blown over larger rocks.  The smaller particles will collide and rub against the larger rocks wearing them down in the process.

Some places in the world can be quite windy, or continuously and routinely windy.  Often, deserts can express the abrasion by wind quite nicely as you might see the effects of it on nearby rocks.

Some of you might be familiar with what is called sandblasting.  Sandblasting is forcing high moving air onto a surface with the addition of small particles of sand.  This “blasting” of small particles of sand onto a dirty surface will cause a great amount of abrasion.  This abrasion will clean or clear off any debris on the affected surface.   

3. Abrasion by gravity.

The abrasion of rocks by gravity is when the nature of gravity sends rocks that are higher, down onto other rocks below.  The collision of rocks on the way down will wear those rocks down.

What loosens these rocks so that they might fall down onto other rocks below can be a number of causes.  Some common causes could be by animals, humans, plants, rain water, earthquakes, and alternating temperature to name a few.

Gravity is a constant vector.  “What goes up must come down” is not just a saying, but a fact when it comes to gravity.  The earth will push rocks up from below by volcanoes, while gravity will do all it can to send those rocks back down.

We have all likely sent rocks off from a higher place.  When you watch that rock you tossed, or kicked, hit other rocks on the way down, you are seeing abrasion by gravity.  Each collision on the way down will contribute to the breaking down of that rock. 

Conclusion

Abrasion will wear away rocks, and the land for that matter, through the flow of water, wind, and gravity.  Keep in mind that abrasion is the involvement of friction and the collision of rocks with each other. 

The next time you are out in nature, I encourage you to see if you can’t point out at least one of the 3 ways that abrasion has worn down the rocks you see around you.

Did you know that abrasion is a type of mechanical weathering?  Weathering is the process of rocks breaking down through not only abrasion, but through other ways as well. 

For more in depth detail on weathering, I highly suggest reading my article on weathering “The Breaking Down of Rocks by Different Types of Weathering”.  This article will get into the details of all the different types of weathering along with abrasion.