Question

The magma, when forced upwards, fills vertical cracks or fissures in existing rocks, and it then hardens there to form ______.

Options

• Necks

• Sills

• Dykes

• Laccoliths

Answer 1

The magma, when forced upwards, fills vertical cracks or fissures in existing rocks, and it then hardens there to form dykes.

Explanation:

Dykes are formed when magma from beneath the earth’s surface is forced upwards and fills vertical cracks or fissures in the existing rock layers. As the magma rises and cools in these vertical fractures, it solidifies to form a hard, wall-like structure known as a dyke. Dykes are a type of intrusive igneous feature, meaning they originate from magma that cools and crystallises below the earth’s surface. Unlike sills, which spread horizontally between layers of rock, dykes cut across existing strata in a vertical or steeply inclined orientation.