Answer: A mafic lava cooling at earth's surface
Explanation: Basalt is the mafic igneous rock formed by the cooling of the magnesium rich and iron rich lava exposed area rapidly.It is mostly crushed for the purpose of using in construction projects. So,when mafic lava cools down on the surface of the Earth it forms basalt or basaltic lava . It is usually found in the form of columns on the Earth's surface.
