Question

Q. A wavy mass of intrusive rocks found at the base of synclines or at the top of the anticline in folded igneous strata is called:

• A. Batholiths
• B. Laccoliths
• C. Phacolith
• D. Lopolith

Answer 1

The correct option is C Phacolith

Explanation:

The lava that cools inside the crustal portions takes diverse forms. These solidified rock structures in the interior of the earth are called intrusive landforms. They are:

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.

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 a localized source of lava

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.

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:

• 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. Dykes are the most commonly found intrusive forms in the western Maharashtra area.