Option 1: Rigid mass refers to a solid, unchanging substance. While it may seem related to the idea of an area resistant to structural transformation, it does not specifically describe the geographical concept mentioned in the question.
Option 2: Ancient landmass refers to a large land area that has existed for a long time. While some ancient landmasses may be resistant to specific types of structural transformation, this term does not specifically describe an area resistant to any massive structural transformation.
Option 3: Tectonic plate refers to a large section of the Earth`s lithosphere that moves due to plate tectonics. While tectonic plates can experience structural transformations, they are not inherently resistant to massive structural transformations.
Option 4: Shield is the correct answer. In geology, a shield is a large, stable area of ancient rocks that has not undergone significant tectonic activity or deformation. These areas are highly resistant to any massive structural transformation.