Question

Contraction or shrinkage is the cause of which joints?

(a) Radial joints

(b) Vertical joints

(c) Sheet joints

(d) Mural joints

I got this question in quiz.

This intriguing question comes from Origin of Joints and Engineering Considerations topic in chapter Joints and Jointing of Engineering Geology

Answer 1

Right option is (b) Vertical joints

The explanation is: During the formation of igneous rocks, tensile forces are developed in them due to cooling and the force is strong enough to cause joints. Such contraction or shrinkage is generally, accepted to be the cause of the vertical type of joints in granites and the so well -known columnar joints of basalts and other effusive rocks.