[BRIEF NOTE] "The bright red mud"

[rfmcdonald]

Red soil
Originally uploaded by rfmcdpei

More red soil
Originally uploaded by rfmcdpei

Red mud
Originally uploaded by rfmcdpei

The chemical reactions responsible for the characteristic and very nearly unique (I've seen southeastern New Brunswick) iron oxide-red soils of Prince Edward Island are described here.

Iron oxides are responsible for the red soil on Prince Edward Island. It is possible to trace the reactions of iron from the time it is released from rock. Iron olivine is a good example of a rock which contains iron. This iron can be released due to environmental conditions.

Weathering of iron olivine leads to hydrolysis yielding iron oxide and silicic acid:

Fe₂SiO₄ + 2HOH --> 2FeO + H₄SiO₄

Both of these products are somewhat soluble and can be lost be leaching. However, in the presence of free oxygen, and when moisture and temperature conditions are favorable for chemical activity, the iron in the soil minerals is oxidized and hydrated into red and yellow compounds. The iron oxide (FeO) is oxidized to only slightly soluble iron oxides such as Fe₂O₃ or its hydrated counterpart Fe₂O₃ * xH₂O (the x indicates that the quantity of 2 3 2 3 2 associated water can vary). This is oxidation reaction:

4FeO + O₂ = 2Fe₂O₅

Because of the extremely low solubility of these iron oxides, very little of the iron is lost.

This results in a characteristic red color of the soil where the reaction occurs.

When I first saw gray soil on the mainland, in Nova Scotia at the age of 4, I broke into tears at the site of the unnaturally grayed earth. What, exactly, had happened to do so much damage to the Earth?

* * *

In other news, I have two more sets of photos on Flickr, one comprising 21 photos of rural southeastern Prince Edward Island that I took on the 2nd of June, the other 46 photos of Charlottetown that I took on the 3rd.

(I think that I like digital cameras. Who knew?)