Mini test 1

Mini test 1

01 Environmental Science

Chemical Weathering

Stone statues and buildings that have stood in place for long periods of time have endured years of wind and weather, the effects of which are clearly visible in their outward appearances.

Corners lose their sharp angles and features seem to crumble away.

The natural process that breaks down rocks and stone is called chemical weathering.

In the natural course of things, this type of disintegration is to be expected.

When human use of fossil fuels is introduced into this equation, however, the process of chemical weathering is significantly affected.

In natura, water and acid act as primary agents in chemical weathering.

Water, whether in the form of rivers or precipitation, plays a major part in the erosion of rocks and stone formations as they are weathered.

“Dissolution” is the term scientists use for the process through which minerals are dissolved in water.

For example, sodium chloride, or salt, quickly dissipates in water.

However, most minerals will not dissolve in pure water alone.

They must have at least one other substance present in order to initiate decomposition.

When even a small amount of acid is added to water, its corrosive power is magnified.

Acid can be produced by natural means such as when organisms decay and release organic acids back into the soil.

Sulfide minerals such as pyrite release sulfuric acid into the atmosphere as they decay.

These acids are absorbed into water and cause corrosion in many rocks.

Additionally, when carbon dioxide from the atmosphere dissolves into raindrops, carbonic acid is created.

As rain and snow fall on stone over time, they wear down the layers of sediment that make up the rock.

Yet while many of these acidic reactions are to be expected in nature, the introduction of man-made byproducts has disrupted this natural cycle by hastening it along.

Man’s use of fossil fuels in factories, power plants, and vehicles has greatly increased the amount of carbon dioxide, sulfur, and nitrous oxides in the atmosphere.

This has led to an excessive amount of acid being produced and absorbed by different forms of water in the atmosphere.

Scientists point to acid precipitation, rain. with abnormally high levels of acid, as the culprit for the premature corrosion of stone statues and buildings.

Whereas the natural chemical weathering process caused by the carbonic acid in rain would wear away rocks slowly over time, now the rocks decay at a more rapid pace.

The acids that are not absorbed into rain or snow are often absorbed into the ground, seeping into ground water and affecting rocks and stones in river beds and lakes.

The process of decay and corrosion that rocks and stone structures undergo is a natural one that should take place over many years.

Rainfall over time causes erosion and changes in the rock.

Humans, however, have brought about changes in this process, increasing the speed at which stones are weathered by releasing more acid-producing compounds into the atmosphere.

The effect is that buildings and monuments of stone that have stood for generations are experiencing swift decay.