A stack or sea stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by wave erosion.<span>[</span>
Acid Rain is the natural cause which causes volcanic eruptions and emissions from vegetation.
<u>Explanation:
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The volcanic eruption is a natural phenomenon that is caused due to the liberation of the lava from the heap of the earth along with the gases. The volcanic eruption results in causing major damages to the vegetation lying above the erupted crater of the volcano.
This results in the immense release of gases such as “carbon dioxide, carbon monoxide, sulphur dioxide, hydrogen chloride, hydrogen fluoride, methane and ammonia” and these gases are major pollutants of the air. When these gases react with water vapour that are present in the atmosphere, they condense in the form of acid rain.
<span>The earliest civilizations that arose in the world developed in the late fourth and the third millennia BC in parts of Asia and north Africa. The three large alluvial systems of the Tigris-Euphrates, the Nile and the Indus supported three great ancient civilizations. Other urban communities also arose during this time. For example, settlement mounds known as tells or tepes, occur in almost all major valleys between Iraq and Pakistan in one direction and between the Caspian Sea and the Indian Ocean in the other and many that have been explored are known to have been occupied in the same period. However, unlike the great civilizations of Egypt, Mesopotamia and Indus, these communities did not form part of a unified economic system, and these small units, though clearly able for a time to support large, wealthy and organized societies, were much weaker than the vast civilizations of the alluvial lowlands. </span>
