Boulder

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title: "Boulder" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["rocks", "rock-formations", "garden-features", "natural-materials"] description: "Natural rock fragment larger than 10 inches" topic_path: "general/rocks" source: "https://en.wikipedia.org/wiki/Boulder" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Natural rock fragment larger than 10 inches ::

::callout[type=note] large rocks ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/2/2f/Balanced_Rock.jpg" caption="Colorado Springs]], Colorado, United States."] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/b/b7/Boulder_along_the_chief_hike_in_Stawamus_Chief_Provincial_Park,BC(DSCF7553).jpg" caption="Boulder in [[British Columbia]], Canada"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/3/33/Kämmenkivi_stone_in_Pisa,_Kuopio,_Finland.jpg" caption="''Kämmenkivi'' stone on the Pisa hill in [[Kuopio]], Finland"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/8/8a/Bolders_on_Mahendra_Hills,_India.jpg" caption="Balanced granite boulders at [[Hyderabad]], India"] ::

In geology, a boulder (less commonly spelled bowlder) 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 are extremely massive. In common usage, a boulder is too large for a person to move. Smaller boulders are usually just called rocks or stones.

Etymology

The word boulder derives from boulder stone, from Middle English bulderston or Swedish bullersten.

About

In places covered by ice sheets during ice ages, such as Scandinavia, northern North America, and Siberia, glacial erratics are common. Erratics are boulders picked up by ice sheets during their advance, and deposited when they melt. These boulders are called "erratic" because they typically are of a different rock type than the bedrock on which they are deposited. One such boulder is used as the pedestal of the Bronze Horseman in Saint Petersburg, Russia.

Some noted rock formations involve giant boulders exposed by erosion, such as the Devil's Marbles in Australia's Northern Territory, the Horeke basalts in New Zealand, where an entire valley contains only boulders, and The Baths on the island of Virgin Gorda in the British Virgin Islands.

Boulder-sized clasts are found in some sedimentary rocks, such as coarse conglomerate and boulder clay.

References

References

1. {{cite Merriam-Webster. bowlder
2. "Bowlder". Collins English Dictionary.
3. (2005). "Glossary of Geology". American Geological Institute.
4. "Boulder".
5. [http://dictionary.reference.com/browse/boulder boulder. (n.d.)] Online Etymology Dictionary. Retrieved December 9, 2011, from Dictionary.com website.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::