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.
As your children progress, the flash cards teach them how to spell and form words, often with the aid of images and pictures related to the words. Other flash cards teach basic math skills, beginning with number identification and moving on to simple addition and subtraction.