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.
A flashcard or flash card is a set of cards bearing information, as words or numbers, on either or both sides, used in classroom drills or in private study. One writes a question on a card and an answer overleaf. Flashcards can bear vocabulary, historical dates, formulas or any subject matter that can be learned via a question-and-answer format. Flashcards are widely used as a learning drill to aid memorization by way of spaced repetition.