7 Properties of Igneous Rocks in Geography For UPSC
(1) Property of Igneous Rocks in Geography
Overall, the igneous rocks are quite hard, and water percolates with difficulty along the joints. Due to prolonged exposure to external conditions, the boulders can sometimes become so soft that they can be readily pulled out with a shovel (e.g., basalt).
(2) Property of Igneous Rocks in Geography
Igneous rocks are granular or crystalline rocks, but the size, shape, and texture of grains vary greatly because these qualities are heavily influenced by the rate and location of cooling and solidification of magmas or lavas. For example, when lavas are rapidly cooled and consolidated near the earth’s surface, there is insufficient time for the formation of grains/crystals.
As a result, either no crystals exist in the resulting basaltic rocks, or the crystals that do exist are so minute that they cannot be seen without the use of a microscope. In contrast, if magmas are cooled and solidified at a relatively slow rate inside the earth, there is enough time for the entire development of grains, and the resulting igneous rocks have coarse grains.
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(3) Property of Igneous Rocks in Geography
Unlike sedimentary rocks, igneous rocks lack stratification. When lava flows occur in a location in numerous stages, layers following layers of lavas are deposited and hardened one upon another, creating some misunderstanding regarding the layers or strata, although they are not strata, but rather layers of lavas.
Such instances may be seen throughout the Western Ghats, where many lava flows throughout the Cretaceous period resulted in the construction of a thick basaltic cover with numerous layers of lavas of varied compositions. Such lava layers can be seen in Khandala or along the deeply entrenched valleys of the Koyna River, Krishna River, Saraswati River, and other rivers in and around the Mahabaleshwar plateau.
(4) Property of Igneous Rocks in Geography
Because water does not easily enter the rocks, igneous rocks are less impacted by chemical weathering, whereas basalts are quickly weathered and worn away when in continual contact with water. Coarse-grained igneous rocks are quickly fragmented and decomposed as a result of mechanical or physical weathering.
(5) Property of Igneous Rocks in Geography
Igneous rocks do not contain fossils because: I there was no life on the newly formed earth when the ancient igneous rocks were formed due to cooling and solidification of molten rock materials at the time of the earth’s origin; and (ii) there was no life on the newly formed earth when the ancient igneous rocks were formed due to cooling and solidification of molten rock materials at the time of the earth’s origin.
(ii) Because igneous rocks occur as a result of the cooling and solidification of very hot and molten elements, any vestiges of plants or animals (fossils) are obliterated by the extremely high temperatures.
(6) Property of Igneous Rocks in Geography
In every igneous rock, the number of joints rises higher. The joints arise as a result of: I cooling and contraction, (ii) mechanical weathering expansion and contraction, (iii) a decrease in superincumbent load owing to material loss through denudational processes, and (iv) earth movement produced by isostatic disturbances.
(7) Property of Igneous Rocks in Geography
Because igneous rocks are commonly connected with volcanic activity, they are sometimes known as volcanic rocks. Igneous rocks are more commonly encountered in volcanic zones.