gravel wiki:
is rock that is of a certain size range. In geology, gravel is any loose rock that is at least two millimeters in its largest dimension (about 1/12 of an inch), and no more than 75 millimeters (about 3 inches). Sometimes gravel is restricted to rock in the 2-4 millimeter range, with pebble being reserved for rock 4-75 millimeters (some say 64 millimeters). The next smaller size class in geology is sand, which is 0.02 mm to 2 mm in size. The next larger size is cobble, which is 75 (64) millimeters to 256 millimeters (about ten inches).
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penguin wiki:
>For other uses, see Penguin (disambiguation). Aptenodytes Eudyptes Eudyptula Megadyptes PygoscelisSpheniscus Penguins (order Sphenisciformes, family Spheniscidae) are an order of flightless birds living in the southern hemisphere. '''
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