Do Rocks Dissolve?

Have you ever gathered rocks? For some children, collecting rocks may not appear to be very interesting. However, others understand that it can be really fascinating to come across a rock with a unique color or shape when you’re at the park, the beach, or even at home. Where did it come from? And how long has it been in existence?

When you think of things that are solid and long-lasting, rocks are probably the first to come to mind. Whether it’s a mountain, a stone courthouse, or a gravestone in a local cemetery, rocks seem to possess enduring characteristics.

Indeed, rocks may even appear indestructible. However, upon closer inspection of old rocks, you will notice signs of erosion. Although rocks are indeed durable materials, they are still susceptible to the physical and chemical forces of nature that gradually break down everything on Earth.

Scientists refer to this process as weathering. Weathering occurs in two main forms: mechanical and chemical. Mechanical weathering processes break rocks into smaller pieces without altering their chemical composition.

On the other hand, chemical weathering processes chemically break down rocks, transforming them into different types of rocks and minerals. Some of these new materials can be dissolved when exposed to water and air, resulting in erosion.

Mechanical and chemical weathering processes can happen simultaneously, but they are still very slow processes. Because it takes such a long time to break down and dissolve rocks, we perceive them as long-lasting, nearly indestructible materials.

Let’s examine a chemical weathering process that you are already somewhat familiar with…even if you don’t realize it. When it rains, some of the water mixes with carbon dioxide in the air or air pockets in the soil. This mixture forms a weak acid known as carbonic acid.

As carbonic acid seeps through the soil and comes into contact with cracks in the underground rock, it can chemically react with the rock, causing it to dissolve. Carbonic acid is especially reactive with calcite, which is the main mineral in limestone.

Over long periods of time, carbonic acid dissolves limestone, creating pits, holes, and widening cracks and openings in the rock. This leads to the formation of a unique type of landscape known as karst topography. Familiar features of karst topography include caves, caverns, sinkholes, and springs.

Another common type of chemical weathering occurs as a result of acid rain. Acid rain forms when rain combines with nitrogen and sulfur to produce nitric and sulfuric acids, which can dissolve calcium-based rocks like marble and limestone. Acid rain tends to be a problem in areas with higher levels of pollution from coal-burning power plants.

Although the weathering of rocks may seem like a negative phenomenon, it is actually a natural process that eventually creates valuable products. Weathered rock is the primary component of soil. Minerals from weathered rock provide sustenance for various plant life through the soil. Additionally, without the chemical weathering of rock, we would not be able to explore fascinating caves!

Give It a Try

Are you prepared to rock? Make sure to check out the following activities with a friend or family member:

Exploring Rocks and the Rock Cycle

Are you ready to become an amateur geologist? Start by collecting various rock samples, making sure to include limestone. To enhance your learning experience, download and print the “Disappearing Rocks” activity from the internet. Collaborate with a friend or family member to observe, describe, and test the different rocks. Can you identify the limestone rock? What characteristics help you distinguish it from the others?

While you may be familiar with the water cycle, did you know that there is also a rock cycle? Discover more about this fascinating process on the internet. Share your newfound knowledge with a friend or family member. It’s incredible how Earth continuously recycles materials, isn’t it?

In addition to chemical weathering, rocks also undergo mechanical weathering over time. Explore the “Rock Experiments” online to learn about simple experiments that demonstrate how mechanical weathering breaks rocks into smaller fragments.

Resources for Further Reading

  • http://www.americangeosciences.org/education/k5geosource/activities/investigations/rocks/do-rocks-dissolve
  • http://www.conservation.ca.gov/cgs/information/kids_geozone/Pages/do_rocks_last_forever.aspx
  • http://teach.albion.edu/jjn10/chemical-weathering/
  • https://www.reference.com/science/effect-acid-rain-rocks-8a1407940cfecca5

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