WAEC Geography 2022 Theory — Question 24

Model answer

(a) Volcanic intrusion is a body of intrusive igneous rock formed by the crystallisation of magma as it slowly cools below the earth's surface (forming features such as batholiths and dykes as it penetrates and solidifies within existing rock). (b)(i) Block mountains form suddenly (relative to fold mountains); they are lower in altitude than fold mountains; their summits are flat; they have steep slopes on all sides; they are often associated with an adjacent rift valley/graben; they are less widespread than fold mountains and are made up of sedimentary and metamorphic rocks. (ii) Block mountains form when two tectonic plates move apart, creating cracks/faults in the earth's crust; where parallel faults occur, the block of land between them may be uplifted, forming the block mountain (the raised block is called a horst). (c) Laccoliths, sills, dikes.