Natural Weathering By Nina Bergold

What is Natural Weathering? Natural weathering, or physical weathering, is the term used to describe the process of the shaping of specific elements by the means of natural forces. Natural weathering, like many other forces, comes in many different forms, such as erosion, oxidation, the freeze-thaw process, and many more. Some famous examples of the results of natural weathering are the Grand Canyon, Bryce Canyon, and Monument Valley. Natural weathering, like all forces in nature, doesn’t happen overnight. It takes millennia of constant exposure to the elements for a landscape to change.

Wind Erosion Wind erosion happens when a rock is exposed to constant wind for long periods of time. Over many years, particles that are exposed to the wind are blown away, gradually sculpting the beautiful rock formations that make places like Monument Valley so famous. The results of wind erosion are commonly seen in places with little or no vegetation. Another example of this kind of erosion are sand dunes, both on the beach and the desert.

Water Erosion Water erosion happens when a landscape is exposed to water, from melting snow to rivers, for long periods of time. As time passes, the water acts like a natural knife; it cuts through the landscape, making itself a little path. The Grand Canyon, the world’s deepest canyon, would never be the same without centuries of being exposed to the Colorado River cutting through it. Of course, water erosion doesn’t always result in iconic canyons. It’s a farmer’s worst enemy, as it can destroy soil and crops, as the picture below illustrates.

Oxidation Oxidation is the reaction between the molecules in metal and oxygen, hence the name. Tarnishing and rusting, which are two forms of oxidation, are a huge problem not only for people who work with silver and iron, but also for car owners. Since the paint is always exposed to the elements, the paint, without proper care, will eventually peel and fall off, which exposes the other layers of the car, which will rust and cause major problems. Another good example of oxidation is the exposure of a bitten apple to the air. After a few minutes, the inside of the apple turns brown, which is why they should be eaten right away.

The Decaying Process Since objects like the tombstones shown here, are constantly exposed to the elements, they eventually become weathered and they start to decay. In fact, the building we’re in is decaying as I speak, but it may not seem like it because it’s constantly maintained. The tombstones, however, are replaced very infrequently. They are only replaced after they decay so much that the words are illegible and when they’re very crumbly and fragile. The decaying process varies from place to place. If someone were buried in a very wet place with lots of humidity, they and their gravestone would decay faster than if one were to be buried in a drier environment.

Discussion Questions Based on what you now know, what conclusions can you draw from what I just taught you? When you look at something that has rust or tarnish on it, what process did it go through? What do you think our world would be like with no natural weathering? Explain what would happen in detail. You don’t have to go to a national park or even a graveyard to see natural weathering in action. What examples of natural weathering can one find in his/her everyday life? What would decay faster, a gravestone that’s constantly exposed to rain or one that is in the middle of the desert?

Links and Resources http://www.stonecaretechniques.com/8_m.htm http://www.weathering.org/weathering/natural.htm http://en.wikipedia.org/wiki/Weathering http://library.thinkquest.org/20035/physical.htm http://www.tulane.edu/~sanelson/geol111/weathering.htm Pictures are from Google.