Rocks in The Soil
Certain parent materials also contribute to soil acidification. Granites and their allied igneous rocks are called "acidic" because they have a lot of free quartz, which produces silicic acid on weathering. Also, they have relatively low amounts of calcium and magnesium. Some sedimentary rocks such as shale and coal are rich in sulfides, which, when hydrated and oxidized, produce sulfuric acid which is much stronger than silicic acid. Many coal spoils are too acidic to support vigorous plant growth, and coal gives off strong precursors to acid rain when it is burned. Marine clays are also sulfide-rich in many cases, and such clays become very acidic if they are drained to an oxidizing state.
Read more about this topic: Soil Acidification
Famous quotes containing the words rocks and/or soil:
“In a coign of the cliff between lowland and highland,
At the sea-down’s edge between windward and lee,
Walled round with rocks as an inland island,
The ghost of a garden fronts the sea.”
—A.C. (Algernon Charles)
“Prejudices, it is well known, are most difficult to eradicate from the heart whose soil has never been loosened or fertilized by education; they grow there, firm as weeds among stones.”
—Charlotte Brontë (1816–1855)