Object permanence is a skill that children acquire during 0-24 months of age. Object permanence occurs in the Sensorimotor Stage of Development (one of the four stages in Jean Piaget's theory of cognitive development). Object permanence refers to the knowledge that an object still exists, even once it is hidden. Object permanence requires the ability to form mental representations of objects.
When your baby sister knows that her toy is still there even though you have hidden it under a pillow, she possesses object permanence.
Suzie's explanation is correct because magma flows through cracks between faults and this can result in the creation of volcanoes. Johnny's statement causes trenches which could lead to magma flow but not volcanoes.
