A new model explaining this mysterious process suggests the core was created as dribs and drabs of iron percolated inward from Earth's lower mantle, according to a study published Oct. 6 in the journal Nature Geoscience. The mantle is the viscous, rocky layer between the crust and Earth's iron core.
Definition of flash card. : a card bearing words, numbers, or pictures that is briefly displayed (as by a teacher to a class) usually as a learning aid.
Recent Examples of flash card from the Web Old-school is an all too literal way to describe classroom work: white boards, markers, flash cards, board games, and the occasional textbook have reappeared. â lizette alvarez, New York Times, Some Schools Reopen in Puerto Rico, Making Do Without Power, 24 Oct. 2017