Which term is used to describe a fact that has always been observed true but could at some future time not be observed as true.

Theory

Explanation:

Theory is the set of fundamental principles of an art or a science, which provides a synthesized opinion, is a general notion, which can be refuted and reformulated.

A theory is the speculative part of a science, as opposed to practice. It is a system consisting of observations, ideas and axioms or postulates, constituting in its entirety a set that tries to explain certain phenomena. The explanation formed by a theory can be questioned in the future with the advancement of technology and the discovery of new concepts.

glacial erosion, the picking up and movement of earth beneath a glacier, is also referred to as plucking. erosion and transportation of individual pieces of bedrock, especially large "joint block occur as a result of this glacial erosion. plucking is type of erosion in which rocks become frozen into the bottom and sides of the glacier.as the glacier moves downhill it 'plucks' the rocks frozen into the glacier from the ground.