Boulder
Videos
In geology, a boulder is a rock fragment with size greater than 25.6 cm in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others
This balancing boulder, "Balanced Rock", stands in Garden of the Gods park in Colorado Springs, Colorado, United States.
Boulder in British Columbia, Canada
Kämmenkivi stone on the Pisa hill in Kuopio, Finland
Balanced granite boulders at Hyderabad, India
Clastic rock
Videos
Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks, and smaller grains of rock broken off other rocks by physic
A thin section of a clast (sand grain), derived from a basalt scoria. Vesicles (air bubbles) can be seen throughout the clast. Plane-polarized light above, cross-polarized light below. Scale box is 0.25 mm.
Claystone from Montana
Conglomerate
Breccia. Notice the angular nature of the large clasts