Consider the following statements. 1. Limestones are well jointed and...
Explanation:
The correct answer is option 'C' which means that both statements are correct.
Statement 1:
Limestones are well jointed and it is through these joints and cracks that rainwater finds its way into the underlying rock.
Explanation of Statement 1:
Limestone is a sedimentary rock that is composed primarily of calcium carbonate. It is formed from the remains of marine organisms such as coral and shells that accumulate over time. Limestones are known to have a high degree of jointing, which means they have natural cracks and fissures.
Rainwater is slightly acidic due to the presence of dissolved carbon dioxide from the atmosphere. When rainwater comes into contact with limestone, it reacts with the calcium carbonate present in the rock. This reaction is known as carbonation, and it leads to the dissolution of the limestone.
The joints and cracks in limestone provide pathways for the rainwater to enter the underlying rock. Over time, as more and more rainwater seeps into these joints, it further dissolves the limestone and widens the cracks. This process is known as solution weathering. As a result, the joints become larger and interconnected, allowing even more rainwater to penetrate the rock.
Statement 2:
Progressive widening by solution enlarges these cracks into trenches and a most intriguing feature called limestone pavement is developed.
Explanation of Statement 2:
As mentioned earlier, the rainwater that enters the joints and cracks of limestone gradually dissolves the rock, resulting in the widening of these cracks. Over a long period of time, this continuous dissolution and widening process can lead to the formation of trenches.
Limestone pavement is a unique and intriguing landform that is developed as a result of the solution weathering of limestone. It is characterized by a flat and exposed surface with distinctive patterns of interconnected cracks and fissures. These cracks are known as grikes, and the flat blocks of limestone between the cracks are called clints.
The development of limestone pavement is a gradual process that involves the dissolution of limestone through rainwater infiltration, the widening of cracks into trenches, and the formation of grikes and clints. The resulting landform is visually striking and often supports unique ecosystems due to its distinctive hydrological and ecological conditions.
In conclusion, both statements are correct. Limestones are indeed well jointed, and rainwater does find its way into the underlying rock through these joints and cracks. The progressive widening of these cracks by solution weathering leads to the formation of trenches and the development of limestone pavement.
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