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  • Geography Notes On – Volcanic Landforms – For W.B.C.S. Examination.

    Volcanic eruptions result in the formation of landforms and here we are going to discuss volcanic landforms.Continue Reading Geography Notes On – Volcanic Landforms – For W.B.C.S. Examination.

    Intrusive Forms

    • The lava that is discharged during volcanic eruptions on cooling develops into igneous rocks.
    • The cooling may take place either on arriving on the surface or also while the lava is still in the crustal portion.
    • According to the location of the cooling of the lava, igneous rocks are categorized as plutonic rocks and volcanic rocks.
    • The lava that cools inside the crustal portions takes diverse forms. These forms are called intrusive forms.
    Batholiths
    • Batholiths are the cooled portion of magma chambers.
    • It is a large body of magmatic material that cools in the deeper depth of the crust moulds in the form of large domes.
    • They appear on the surface only after the denudation processes eliminate the overlying materials.
    • These are granitic bodies.
    Laccoliths
    • These are large dome-shaped intrusive bodies with a level base and linked by a pipe-like channel from below.
    • It bears a similarity to the surface volcanic domes of the composite volcano, only these are located at deeper depths.
    • It can be considered as the localized source of lava
    • The Karnataka plateau is patterned with dome hills of granite rocks.
    Lopolith
    • When the lava moves upwards, a part of the same tends to move in a horizontal direction wherever it finds a weak plane.
    • It can get rested in various forms. If it develops into a saucer shape, concave to the sky body, it is called lopolith.
    Phacolith
    • It is a wavy mass of intrusive rocks found at the base of synclines or at the top of the anticline in the folded igneous country.
    • These wavy materials have a definite outlet to source beneath in the form of magma cavities.
    Sills
    • The near horizontal bodies of the intrusive igneous rocks are called sill
    • The thick horizontal deposits are called sills whereas the thinner ones are called sheets.
    Dykes
    • Dykes are the most commonly found intrusive forms in the western Maharashtra area.
    • When the lava makes its channel through cracks and the fissures, it solidifies almost perpendicular to the ground.
    • This gets cooled in the same position to grow a wall-like structure. Such structures are known as dykes.
    • These are regarded as the feeders for the eruptions that led to the development of the Deccan traps.

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