Boulder

In geology, a boulder is a rock fragment with size greater than 25.6 cm (10.1 in) in diameter.[1] Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive.[2] In common usage, a boulder is too large for a person to move. Smaller boulders are usually just called rocks or stones.

## Contents

* 1 Etymology
* 2 About
* 3 See also
* 4 References
* 5 External links

## Etymology

The word boulder derives from boulder stone, from Middle English bulderston or Swedish bullersten.[3] It was previously sometimes spelled bowlder, which survives as a less common variant spelling.[4][5]

## 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.[2] 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.

## See also

* Bouldering, free climbing performed on small rock formations or artificial climbing walls
* Moeraki Boulders, unusually large spherical boulders found in New Zealand
* Monolith, a geological feature consisting of a single massive rock
* List of individual rocks
* Floaters

## References

1. ↑ Glossary of Geology (5th ed.). Alexandria, Virginia: American Geological Institute. 2005. p. 79. ISBN 978-0922152896.
2. ↑ 2.0 2.1 "Boulder". Boulder. http://dictionary.reference.com/browse/boulder. Retrieved 30 November 2025.
3. ↑ boulder. (n.d.) Online Etymology Dictionary. Retrieved December 9, 2011, from Dictionary.com website.
4. ↑ "Bowlder". Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/bowlder.
5. ↑ "Bowlder". Collins English Dictionary. https://www.collinsdictionary.com/dictionary/english/bowlder.

## External links

* v
* t
* e

Coastal geography

Landforms|

* Anchialine pool
* Archipelago
* Atoll
* Avulsion
* Ayre
* Barrier island
* Bay
* Baymouth bar
* Bight
* Bodden
* Brackish marsh
* Cape
* Channel
* Cliff
* Coast
* Coastal plain
* Coastal waterfall
* Continental margin
* Continental shelf
* Coral reef
* Cove
* Dune
* cliff-top
* Estuary
* Firth
* Fjard
* Fjord
* Förde
* Freshwater marsh
* Fundus
* Gat
* Geo
* Gulf
* Gut
* Headland
* Inlet
* Intertidal wetland
* Island
* Islet
* Isthmus
* Lagoon
* Machair
* Marine terrace
* Mega delta
* Mouth bar
* Mudflat
* Natural arch
* Peninsula
* Reef
* Regressive delta
* Ria
* River delta
* Salt marsh
* Shoal
* Shore
* Skerry
* Sound
* Spit
* Stack
* Strait
* Strand plain
* Submarine canyon
* Tidal island
* Tidal marsh
* Tide pool
* Tied island
* Tombolo
* Windwatt

Beaches|

* Beach cusps
* Beach evolution
* Coastal morphodynamics
* Beach ridge
* Beachrock
* Pocket beach
* Raised beach
* Recession
* Shell beach
* Shingle beach
* Storm beach
* Wash margin

Processes|

* Blowhole
* Cliffed coast
* Coastal biogeomorphology
* Coastal erosion
* Concordant coastline
* Current
* Cuspate foreland
* Discordant coastline
* Emergent coastline
* Feeder bluff
* Fetch
* Flat coast
* Graded shoreline
* Headlands and bays
* Ingression coast
* Large-scale coastal behaviour
* Longshore drift
* Marine regression
* Marine transgression
* Raised shoreline
* Rip current
* Rocky shore
* Sea cave
* Sea foam
* Shoal
* Steep coast
* Submergent coastline
* Surf break
* Surf zone
* Surge channel
* Swash
* Undertow
* Volcanic arc
* Wave-cut platform
* Wave shoaling
* Wind wave
* Wrack zone

Management|

* Accretion
* Coastal management
* Integrated coastal zone management
* Submersion

Related|

* Bulkhead line
* Grain size
* boulder
* clay
* cobble
* granule
* pebble
* sand
* shingle
* silt
* Intertidal zone
* Littoral zone
* Physical oceanography
* Region of freshwater influence

* Category
* Commons

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