A jumble of boulders in an Australian creekbed

Within geology, a boulder occurs as big rock, greater than 256 mm (X around) from side to side (watch grain size for standards in have). When the boulder can be microscopic plenty to move or even roll manually, others come pleasantly massive. Occasionally illustrious rock formations require gargantuan boulders contaminated by erosion, for example a Devil's Marbles in Australia's Northern Territory.

Within virtually all common usage, the term boulder is most typically utilized to refer to big boulders, especially ones overlarge for a human to move. Outside of the field of geology, little boulders come normally upright known as rocks or stones.

Example of an extremely large boulder—note size of tree for comparison

A select few humans take to climb larger-sized boulders for even unpaid purposes or as a method of educational videos for mountaineering and free climbs. This practice is referred to as bouldering.

ja:岩石