{{Short description|Underwater pillar-like rock or coral formation}} {{Use dmy dates|date=May 2026}}[[File:Southwest Pinnacle, Ko Tao, Thailand (4571143972).jpg|right|thumb|300px|alt=Southwest Pinnacle, Ko Tao, Thailand|Southwest Pinnacle, Ko Tao, Thailand]]
An '''underwater pinnacle''' is a steep, pillar-like geological or coral structure that rises abruptly from the seafloor but does not break the ocean surface.
Because they often crest near the sea surface, underwater pinnacles are popular scuba-diving destinations, but they also present significant navigational hazards to marine vessels.
==Comparisons with seamounts and guyots==
A guyot features a distinct flat summit, while a typical seamount has more gentle slopes and a summit at least {{convert|2000|ft|m}} below the sea surface.<ref>{{Cite news |title=Guyot {{!}} Oceanic Plateau, Seamount & Submarine Volcano {{!}} Britannica |url=https://www.britannica.com/science/guyot |archive-url=http://web.archive.org/web/20250719160421/https://www.britannica.com/science/guyot |archive-date=19 July 2025 |access-date=23 May 2026 |work=Encyclopedia Britannica |language=en}}</ref>
By definition, a seamount rises at least {{convert|3000|ft|m}} above the surrounding deep-sea floor and is a volcanic mountain.<ref>{{Cite news |title=Seamount {{!}} Volcanic, Marine Ecosystems & Biodiversity {{!}} Britannica |url=https://www.britannica.com/science/seamount |archive-url=http://web.archive.org/web/20260128030614/https://www.britannica.com/science/seamount |archive-date=28 January 2026 |access-date=23 May 2026 |work=Encyclopedia Britannica |language=en}}</ref>
In contrast, underwater pinnacles are generally much smaller in total volume than seamounts or guyots, feature significantly steeper vertical walls, and can have summits that sit just below the water line. Usually they are near the shore or are parts of other underwater topography.<ref name="Galbraith">{{Cite journal |last=Galbraith |first=Gemma F. |last2=Cresswell |first2=Benjamin J. |last3=McCormick |first3=Mark I. |last4=Bridge |first4=Thomas C. |last5=Jones |first5=Geoffrey P. |date=2022 |title=Contrasting hydrodynamic regimes of submerged pinnacle and emergent coral reefs |url=https://pmc.ncbi.nlm.nih.gov/articles/PMC9380949/ |journal=PLOS ONE |volume=17 |issue=8 |pages=e0273092 |pmc=9380949}}</ref><ref name="McLaughlin2019">{{Cite journal |last=McLaughlin |first=Patrick I. |last2=Emsbo |first2=Poul |last3=Brett |first3=Carlton E. |last4=Bancroft |first4=Alyssa M. |last5=Desrochers |first5=André |last6=Vandenbroucke |first6=Thijs R. A. |date=1 June 2019 |title=The rise of pinnacle reefs: A step change in marine evolution triggered by perturbation of the global carbon cycle |url=https://www.sciencedirect.com/science/article/pii/S0012821X19301451 |journal=Earth and Planetary Science Letters |volume=515 |pages=13–25 |doi=10.1016/j.epsl.2019.02.039 }}</ref>
==Scientific significance==
The steep vertical profiles of underwater pinnacles force localized shifting of deep ocean currents, generating strong upwelling zones, bringing nutrients which drive immense biological productivity. Marine biologists target underwater pinnacles because their relative geographic isolation makes them excellent laboratories for studying biological evolution and species distribution.<ref name="Galbraith" />
Geologically, their structural layers offer researchers core data regarding prehistoric ocean circulation, plate tectonics, and localized volcanic history.<ref name="McLaughlin2019" />
==Coral Pinnacles==
A coral reef can form pinnacles. Coral pinnacles support rich, dense marine ecosystems, including sea anemones, sponges, specialized reef corals, and schooling fish.<ref name="Galbraith" />
They rise from the surrounding lagoon bottom or flat seafloor. Their heights can reach several meters, and they may rise near the surface. They may support high biodiversity,<ref name="The Science of Coral Pinnacles">{{Cite web |date=January 14, 2026 |title=What Is a Bommie? The Science of Coral Pinnacles |url=https://biologyinsights.com/what-is-a-bommie-the-science-of-coral-pinnacles/ |access-date=2026-05-27 |website=Biology Insights |language=en-US}}</ref> and currents are often strong.<ref name="Galbraith"/>
==Formation==
Like seamounts, some underwater pinnacles begin as volcanic features,<ref name=oceanography-geo>{{cite journal|author1=Hubert Straudigal |author2=David A Clauge |name-list-style=amp |title=The Geological History of Deep-Sea Volcanoes: Biosphere, Hydrosphere, and Lithosphere Interactions |journal=Oceanography |volume=32 |series=Seamounts Special Issue |issue=1 |url=http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/23_1/23-1_staudigel2.pdf |access-date=25 July 2010 |archive-url=https://web.archive.org/web/20100613141518/http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/23_1/23-1_staudigel2.pdf |archive-date=13 June 2010}}</ref> manifesting as heavily eroded volcanic cones or the jagged remains of collapsed caldera complexes. Others are formed via tectonic uplift or faulting, where blocks of seafloor bedrock are forced upward.<ref>{{Cite web |title=How Do Seamounts Form |url=https://oceanexplorer.noaa.gov/wp-content/uploads/2025/04/how-seamounts-form-fact-sheet.pdf |website=Ocean Explorer}}</ref>
In warm, tropical marine environments, biogenic coral reefs can colonize these raised bedrock platforms, growing upward over millennia to construct massive carbonate pinnacle structures.<ref name="Galbraith" /><ref>{{Cite web |last=Rogers |first=AD |last2=Baco |first2=A |last3=Griffiths |first3=H |last4=Hall-Spencer |first4=JM |title=Corals on seamounts |url=https://pearl.plymouth.ac.uk/cgi/viewcontent.cgi?params=/context/bms-research/article/1840/&path_info=Rogers_20et_20al_202007.pdf}}</ref>
[[File:Extreme Detail, M&M Pinnacles.jpg|left|thumb|275px|alt=Map of the dive site of the M&M pinnacles off the West coast of the Cape Peninsula, South Africa|Map of the dive site the M&M pinnacles off the West coast of the Cape Peninsula, South Africa]]
==Hazards to navigation==
Because they rise abruptly out of profound ocean depths, underwater pinnacles can be exceptionally difficult to detect without high-resolution sonar or precise nautical charts. This steep vertical trajectory poses a severe collision risk to surface ships and submerged submarines alike. Maritime collisions with these formations can cause: <!--This is an alphabetized list, so please keep it as such. --> * coral reef destruction * hull breaches * loss of propulsion or steering control * loss of the vessel and/or lives * catastrophic oil and hazardous-material spills
===Incidents===
* Off Attu Island in 1943, the SS ''Dellwood'' sank after striking an uncharted underwater pinnacle.<ref name="Army Ship Photo Index">{{Cite web |title=Army Ship Photo Index |url=https://www.navsource.net/archives/30/04/0401.htm |access-date=13 May 2026 |website=www.navsource.net}}</ref> * On 26 May 2008, the nuclear submarine HMS ''Superb'' collided with an underwater pinnacle in the Red Sea. While the crew escaped injury, the vessel sustained unrepairable structural damage and was subsequently decommissioned.<ref name="UK nuclear sub strikes underwater pinnacle in Red Sea">{{Cite web |title=UK nuclear sub strikes underwater pinnacle in Red Sea |url=https://en.mercopress.com/2008/05/28/uk-nuclear-sub-strikes-underwater-pinnacle-in-red-sea |access-date=25 May 2026 |website=MercoPress |language=en}}</ref><ref name="Submarine officer given reprimand">{{Cite news |date=15 March 2010 |title=Submarine officer given reprimand |url=http://news.bbc.co.uk/2/hi/uk_news/scotland/glasgow_and_west/8568091.stm |access-date=25 May 2026 |language=en-GB}}</ref>
==Recreational diving==
The reliable upwelling currents surrounding pinnacles sustain highly active local food webs, making them world-class scuba-diving locations. However, because their vertical walls sit completely exposed to open ocean currents, they frequently experience fierce, unpredictable surges. Consequently, many pinnacle dive sites require advanced certifications and are restricted to highly experienced divers.<ref name="Galbraith" /><ref name="Scuba Diving">{{Cite web |title=6 Underwater Pinnacles You Have To Dive |url=https://www.scubadiving.com/6-underwater-pinnacles-you-have-dive |website=Scuba Diving |date=2 February 2018 |access-date=13 May 2026 }}</ref>
==See also== <!--This is an alphabetized list, so please keep it as such. --> * Flower Garden Banks National Marine Sanctuary * Gulf of Corryvreckan – features a notorious tidal pinnacle mentioned by George Orwell * Guyot * Knoll (oceanography) * Ko Tao – Thai island known for its deep pinnacle dive sites * Lava pillars * Maro Reef * Pinnacle (geology) * Seamount * Sisters' Rock * The Pinnacles
==References== {{reflist}}
==External links== * {{cite journal|url=https://daily.jstor.org/scientists-find-clues-to-the-mysteries-of-an-ocean-reef/|title=Scientists Find Clues to the Mysteries of an Ocean Reef|first=Sierra|last=Garcia|date=October 4, 2021|journal=JSTOR Daily|accessdate=May 27, 2026}} (on the Ngaraard Pinnacle) * {{cite web|url=https://seabedhabitats.org/2014/02/28/virtual-dive-in-emilys-pinnacles-bermuda/|title=Virtual Dive in Emily’s Pinnacles, Bermuda|website=Seabed Habitats|date=February 28, 2014|accessdate=May 27, 2026}} * {{cite web|url=https://www.padi.com/dive-site/south-africa/pinnacles/#overview|website=Professional Association of Diving Instructors|title=Scuba diving underwater pinnacles|accessdate=May 27, 2026}}
Category:Seamounts Category:Physical oceanography Category:Marine geology Category:Underwater diving sites