Discover How Erosion Affects Different Substances with
Your Weather Erosion Deposition Kit

This kit enables you to conduct some of the most intriguing and fun geology experiments. It contains materials for studying various erosion types and the effects of erosion of substances like shale, limestone, and sandstone. The materials in this kit make it possible for you to learn about sediment erosion in an exciting, hands-on way. Order today.

After you've explored various kinds of weathering and physical and chemical erosion, this kit also enables you to perform a deposition geology experiment. Instructions are included for making your very own stalactites and stalagmites - enabling you to observe the workings of the deposition process first-hand.

Materials in this geology kit include meter tapes, hydrochloric acid (HCl), limestone, sandstone, shale, small and large plastic containers and lids, masking tape, yarn, anchoring spikes, zinc coated washers, yarn, floating balls, Epson salts, thermometers, mesh bacgs, pH paper, stopwatches, beans, and instructions for teachers and students.

This free report on chemical erosion was made possible by the weather erosion deposition kit. See the wealth of discovery and knowledge that you can gain!

The Effects of Chemical Solutions with Varying pH on the
Dissolution of Micaceous Sandstone
By Christopher A

Introduction

It is an accepted fact that erosion plays an important role in shaping the geologic features of our planet. Erosion is defined as the wearing away and transport of rock material and soil. The erosional forces are responsible for the gaps or unconformities found in the geologic and fossil record.

Erosion occurs at different rates depending on the type of rock, and, most importantly, the environment the rock is located in. If a rock outcrop is located in a region of intense precipitation, then it will weather and erode at a faster rate than if the rock was located in a more arid region.

A prime example of this involves Cleopatra's Needle. Cleopatra's Needle was a gift granted to the United States by Egypt. This rock monument was moved from the arid climate of Egypt to New York City's Central Park, an area that receives considerably more rain. The monument, which contained hieroglyphics, resisted years of erosion while in Egypt, but within years of its relocation, the hieroglyphics began to weather away until they were no longer legible.

Likewise, the rock's composition plays a large part on the rate at which erosion will occur. For example, if one compared the rate of erosion of limestone to granite, one would find that limestone erodes much quicker than granite.

If a layer of rock, A, is receding backwards while rock layer, B, above or below layer A remains relatively unaffected, this is evidence that rock layer B is more resistant to erosion than rock layer A, or at least to the form of erosion the layers were presented with.

There are various types of erosion. There is wind erosion, gravitational erosion, and, as this research project set out to study, environmental erosion caused by an aqueous substance, usually in motion. This project focuses on how variations in the pH level of a substance affect the rate at which a rock erodes.

The project pays special attention to sedimentary rocks, in this case, micaceous sandstone, due to its ability to contain fossils. It is because of erosion that there are gaps in the fossil record, which makes the piecing together of evolutionary trends and other paleontological studies more difficult.

It is expected that if the solution is more acidic, then the rate of erosion of micaceous sandstone, of which the origin and composition are the same, will be greater than if the solution is less acidic.

Materials and Methods

As previously mentioned, the fossiliferous rock being used in this project is micaceous sandstone that has a very fine grain size of approximately 0.2 to 0.006 cm.

This type of sandstone is unique because it contains large quantities of mica. The mica contained within the rock can be one of two types: biotite, muscovite, or a combination of the two. The type of mica included in the micaceous sandstone being tested is undetermined, but a possible theory is mentioned in Discussion Two.

All the sandstone in the project has been collected from the Chicapee Falls site in mid-western Massachusetts. The rock dates back to the Triassic Period that occurred from approximately 248 million to 206 million years ago. These rocks represent an aqueous environment, probably a lake, that can be determined by the mica present in the rocks. The glitter' of the mica can be seen in the rock sample in figure 1. Trace fossils left by worms can also be seen.

To test how variations of pH affect the rate of erosion of micaceous sandstone, samples of the rock were massed on electronic balances and placed in Petri dishes containing 0.1 molar hydrochloric acid, 0.001 molar hydrochloric acid, 0.00001 molar hydrochloric acid or distilled water.

The acids were obtained through the process of dilution using Boyles' Law, M1V1=M2V2. The dilutions started by using 100 mL of 0.1 molar HCl and diluting it by adding 900mL of distilled water in a graduated cylinder.

The process continued to create the additional solutions used. Lab aprons, goggles and gloves were used to ensure the safety during the experiment. The samples were placed in the liquids for five minutes, taken out and massed. This occurred three times over fifteen minutes. When obtaining the samples from the large slabs, the pieces broke in irregular and unequal pieces. This required that the percent of change be calculated as the measurement of comparison.

After reviewing the first series of results, another longer immersion test was established for comparison purposes. A sample of the rock was massed and placed in each of the molar concentrations and the distilled water and left overnight. These samples were then taken out the next morning and re-massed.

Discussion One

The raw data procured from the fifteen-minute time trials provided results that were inconclusive as the masses were both increasing and decreasing. This can be seen in the three graphs below.

When the data from the hydrochloric acid was compared to that of the distilled water, possible trends appeared. The rock samples in the acid appeared to have all gained mass over the fifteen-minute period and this was originally attributed to experimental error. The samples in the distilled water showed a generally decreasing trend as seen in the graph below.

When the data from the hydrochloric acid was compared to that of the distilled water, possible trends appeared. The rock samples in the acid appeared to have all gained mass over the fifteen-minute period and this was originally attributed to experimental error. The samples in the distilled water showed a generally decreasing trend as seen in the graph below.

The increase in mass originally was thought to be caused by pores within the rock that would have trapped the solutions within them. However, the distilled water would, in theory, have done the same thing and therefore it was decided that this was not the case.

A second theory for the trends was proposed. What if the hydrochloric acid actually caused a chemical reaction on the surface or within the pores of the samples that caused the increase in mass? This would explain why the samples didn't gain mass in the distilled water. To check for a surface change, the rocks were compared under a tripod lens.

There was no obvious surface alteration, so unless the change was small and relatively insignificant, the reaction would have had to be contained within the pores. It is important to note that this theory also has its flaws as discussed in the next section.

Discussion Two

The raw data obtained from the overnight tests did not prove to be any more conclusive. In most cases the samples in the acids did continue to gain mass, however, the samples in the distilled water also appeared to have increased in mass as seen in the graph below.

There were several possible sources of experimental error to be noted: The extraction of the rock samples from the acid solutions did not always go smoothly. The agitation caused by these actions could have altered the results in some way.

In some cases, when the rock was replaced into the Petri dish, it was not fully covered by the acid and more solution had to be added. If there was any pH change in the solution due to the rock's prior immersions, the addition of additional acid would have altered the pH of the solution.

A third potential source of error can be attributed the samples themselves. Procuring samples of equal measure and surface area was impossible with the equipment available. This means there was a large variety of surface area between the samples that was not calculated or taken into account when performing the experiment.

In theory, if a sample had large surface area, whichever reaction occurred, whether it be chemical causing an increase, or something comparative to erosion, it would have been quicker than if the sample had a smaller surface area.

Another source of potential error is small and relatively insignificant, but should be mentioned nonetheless. A wind draft in the lab caused the electronic balance to alter its reading of the rock masses from time to time. Therefore a best guess at which reading was accurate was used as the data.

These sources of error, along with other unseen possibilities, could explain these inconsistencies within the data.

Conclusion

The research project yielded results that were inconclusive. The rock samples generally increased in mass that does not follow the expected trend when placing sedimentary rocks in acids. It is likely that the results were caused by experimental error, but more tests, which remove some of those error factors, are needed to determine if this is in fact the case.

Bibliography

1) Dixon, Dougal. The Practical Geologist: The Introductory Guide to the Basics of Geology and to Collecting and Identifying Rocks. Fireside, 1992.
2) How Sedimentary Rock Is Formed. 1/30/07.
3) Nedin, Chris. Fossilization. 1/30/07.
4) Pellant, Chris. Rocks and Minerals (Smithsonian Handbooks)
5) Sedimentary Rocks. ORGANIZATION OF THE SEDIMENTARY ROCK.
Learn more about this author, Christopher A.