Lithology sense of displacement across the zone. In igneous rocks, small-scale structures are mostly observed in lavas such as pahoehoe versus ʻAʻā basaltic flows, and pillows showing eruption within a body of water or beneath ice. Unconsolidated surficial materials may also be given a lithology. This is defined by grain size and composition, and is often attached to an interpretation of how the unit formed. Surficial lithologies can be given to lacustrine, coastal, fluvial, aeolian, glacial, and recent volcanic deposits, among others. Examples of surficial lithology classifications used by the US Geological Survey are, "Glacial Till, Loamy", "Saline Lake Sediment", and
Mental substance Mental substance Mental substance is the idea held by dualists and idealists, that minds are made-up of non-physical substance. This substance is often referred to as consciousness. This is opposed to the materialists, who hold that what we normally think of as mental substance is ultimately physical matter (i.e., brains). Descartes, who was most famous for the assertion "I think therefore I am", has had a lot of influence on the mind–body problem. He describes his theory of mental substance (which he calls res cogitans distinguishing it from the "res extensa") in the "Second Meditation" (II.8) and in "Principia Philosophiae"