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.
cards, (usually used with a singular verb) 1  a game or games played with such a set. 2  the playing of such a game: to win at cards. 3  Casino. the winning of 27 cards or more. 4  Whist. tricks won in excess of six.