Editing Hawaiian Islands (section)

==Geology==
{{Main|Hawaii hotspot}}
{{Further|List of rivers of Hawaii}}

[[File:Hawaii hotspot.jpg|thumb|upright=1.2|Eruptions from the [[Hawaii hotspot]] left a trail of underwater mountains across the Pacific over millions of years, called the [[Hawaiian–Emperor seamount chain|Emperor Seamounts]].]]

This chain of islands, or [[archipelago]], developed as the [[Pacific Plate]] slowly moved northwestward over a [[hotspot (geology)|hotspot]] in the [[Earth's mantle]] at a rate of approximately {{convert|32|mi|km|}} per million years. Thus, the southeast island is volcanically active, whereas the islands on the northwest end of the archipelago are older and typically smaller, due to longer exposure to [[erosion]]. The age of the archipelago has been estimated using potassium-argon dating methods.<ref>{{Cite web|title=Tectonics, geochronology, and origin of the Hawaiian-Emperor Volcanic Chain|url=http://www.botany.hawaii.edu/Faculty/Morden/BotZool450/Clague1989.pdf|work=The Geology of North America, Volume N: The Eastern Pacific Ocean and Hawaii|year=1989|access-date=January 17, 2011|publisher=The Geology Society of America|url-status=dead|archive-url=https://web.archive.org/web/20110611080721/http://www.botany.hawaii.edu/Faculty/Morden/BotZool450/Clague1989.pdf|archive-date=June 11, 2011}}</ref> From this study and others,<ref>{{Cite journal|title=Potassium-Argon Ages of Lavas from the Hawi and Pololu Volcanic Series, Kohala Volcano, Hawaii|url=http://gsabulletin.gsapubs.org/content/83/12/3731.abstract|publisher=Geology Society of American Bulletin|year=1972|volume=83|pages=3731–3738|access-date=January 17, 2011|doi=10.1130/0016-7606(1972)83[3731:PAOLFT]2.0.CO;2|last1=McDougall|first1=IAN|last2=Swanson|first2=D. A.|journal=Geological Society of America Bulletin|issue=12|bibcode=1972GSAB...83.3731M|archive-date=May 24, 2022|archive-url=https://web.archive.org/web/20220524010430/https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/83/12/3731/7435/Potassium-Argon-Ages-of-Lavas-from-the-Hawi-and?redirectedFrom=fulltext|url-status=live}}</ref><ref>{{Cite journal|title=Petrography and K-Ar Ages of Dredged Volcanic Rocks from the Western Hawaiian Ridge and the Southern Emperor Seamount Chain|url=http://bulletin.geoscienceworld.org/cgi/content/abstract/86/7/991|publisher=Geology Society of America Bulletin|year=1975|volume=86|pages=991–998|access-date=January 17, 2011|doi=10.1130/0016-7606(1975)86<991:PAKAOD>2.0.CO;2|issue=7|issn=0016-7606|last1=Clague|first1=David A.|last2=Dalrymple|first2=G. Brent|last3=Moberly|first3=Ralph|journal=Geological Society of America Bulletin|bibcode=1975GSAB...86..991C|archive-date=November 11, 2011|archive-url=https://web.archive.org/web/20111111123116/http://bulletin.geoscienceworld.org/cgi/content/abstract/86/7/991|url-status=live}}</ref> it is estimated that the northwesternmost island, [[Kure Atoll]], is the oldest at approximately 28 million years (Ma); while the southeasternmost island, [[Hawaii (island)|Hawaiʻi]], is approximately 0.4 Ma (400,000 years). The only active volcanism in the last 200 years has been on the southeastern island, Hawaiʻi, and on the submerged but growing volcano to the extreme southeast, [[Kamaʻehuakanaloa Seamount|Kamaʻehuakanaloa]] (formerly Loʻihi). The [[Hawaiian Volcano Observatory]] of the [[United States Geological Survey|USGS]] documents recent volcanic activity and provides images and interpretations of the volcanism. [[Kīlauea]] had been erupting nearly continuously since 1983 when it stopped August 2018.

Almost all of the [[magma]] of the hotspot has the composition of [[basalt]], and so the Hawaiian volcanoes are composed almost entirely of this igneous rock. There is very little coarser-grained [[gabbro]] and [[diabase]]. [[Nephelinite]] is exposed on the islands but is extremely rare. The majority of eruptions in Hawaiʻi are [[Hawaiian eruption|Hawaiian-type eruptions]] because basaltic magma is relatively fluid compared with magmas typically involved in more explosive eruptions, such as the andesitic magmas that produce some of the spectacular and dangerous eruptions around the margins of the Pacific basin.

Hawaiʻi island (the Big Island) is the biggest and youngest island in the chain, built from five volcanoes. [[Mauna Loa]], taking up over half of the Big Island, is the largest [[shield volcano]] on the Earth. The measurement from sea level to summit is more than {{convert|2.5|mi|km|0}}, from sea level to sea floor about {{convert|3.1|mi|km|0}}.<ref>{{Cite web|title=Mauna Loa Earth's Largest Volcano|url=http://wwwhvo.wr.usgs.gov/maunaloa/|work=Hawaiian Volcano Observatory web site|publisher=United States Geological Survey|date=February 2006|access-date=December 9, 2009|archive-date=November 17, 2014|archive-url=https://web.archive.org/web/20141117061824/http://wwwhvo.wr.usgs.gov/maunaloa/|url-status=dead}}</ref>

===Earthquakes===
{{Main|List of earthquakes in Hawaii}}

The Hawaiian Islands have many [[earthquake]]s, generally triggered by and related to volcanic activity. Seismic activity, as a result, is currently highest in the southern part of the chain. Both historical and modern earthquake databases have correlated higher magnitude earthquakes with flanks of active volcanoes, such as Mauna Loa and Kilauea. The combination of erosional forces, which cause slumping and landslides, with the pressure exerted by rising magma put a great amount of stress on the volcanic flanks. The stress is released when the slope fails, or slips, causing an earthquake. This type of seismicity is unique because the forces driving the system are not always consistent over time, since rates of volcanic activity fluctuate. Seismic hazard near active, seaward volcanic flanks is high, partially because of the especially unpredictable nature of the forces that trigger earthquakes, and partially because these events occur at relatively shallow depths. Flank earthquakes typically occur at depths ranging from 5 to 20&nbsp;km, increasing the hazard to local infrastructure and communities.<ref>{{Cite journal|last=crossref|title=Chooser|url=https://chooser.crossref.org/|access-date=January 17, 2024|website=chooser.crossref.org|doi=10.1785/0120000060|archive-date=August 26, 2023|archive-url=https://web.archive.org/web/20230826192842/https://chooser.crossref.org/|url-status=dead}}</ref> Earthquakes and landslides on the island chain have also been known to cause [[tsunami]]s.

Most of the early earthquake monitoring took place in [[Hilo, Hawaii|Hilo]], by missionaries [[Titus Coan]] and Sarah J. Lyman and her family. Between 1833 and 1896, approximately 4 or 5 earthquakes were reported per year.<ref>{{Cite web|url=https://earthquake.usgs.gov/regional/states/hawaii/history.php|title=Hawaii Earthquake History|access-date=December 9, 2009|publisher=United States Geological Survey|year=1972|url-status=dead|archive-url=https://web.archive.org/web/20090419112209/http://earthquake.usgs.gov/regional/states/hawaii/history.php|archive-date=April 19, 2009}}</ref> Today, earthquakes are monitored by the [[Hawaiian Volcano Observatory]] run by the [[United States Geological Survey|USGS]].

Hawaii accounted for 7.3% of the United States' reported earthquakes with a [[Richter magnitude scale|magnitude]] 3.5 or greater from 1974 to 2003, with a total 1533 earthquakes. Hawaii ranked as the state with the third most earthquakes over this time period, after [[Alaska]] and [[California]].<ref>{{Cite web|url=https://earthquake.usgs.gov/regional/states/top_states.php|title=Top Earthquake States|access-date=December 9, 2009|publisher=United States Geological Survey|year=2003|archive-url=https://web.archive.org/web/20090831032740/http://earthquake.usgs.gov/regional/states/top_states.php|archive-date=August 31, 2009|url-status=dead}}</ref>

[[2006 Kiholo Bay earthquake|On October 15, 2006, there was an earthquake]] with a magnitude of 6.7 off the northwest coast of the island of Hawaii, near the [[Kona District, Hawaii|Kona]] area. The initial earthquake was followed approximately five minutes later by a magnitude 5.7 [[aftershock]]. Minor to moderate damage was reported on most of the Big Island. Several major roadways became impassable from rock slides, and effects were felt as far away as [[Honolulu]], Oahu, nearly {{convert|150|mi|km}} from the [[epicenter]]. Power outages lasted for several hours to days. Several water mains ruptured. No deaths or life-threatening injuries were reported.

On May 4, 2018, there was a [[2018 Hawaii earthquake|6.9 earthquake]] in the zone of volcanic activity from [[Kīlauea]].

Earthquakes are monitored by the [[Hawaiian Volcano Observatory]] run by the [[United States Geological Survey|USGS]].

===Tsunamis===
[[File:1960-Chilean-tsunami-Hilo-HI-USGS.jpg|thumb|right|Aftermath of the [[1960 Valdivia earthquake|1960 Chilean tsunami]] in [[Hilo]], Hawaiʻi, where the tsunami left 61 people dead and 282 seriously injured. The waves reached {{convert|35|ft|m|0}} high.]]
The Hawaiian Islands are subject to [[tsunami]]s, great [[wave]]s that strike the shore. Tsunamis are most often caused by [[earthquake]]s somewhere in the Pacific. The waves produced by the earthquakes travel at speeds of {{convert|400|–|500|mph|km/h|-2}} and can affect coastal regions thousands of miles (kilometers) away.

Tsunamis may also originate from the Hawaiian Islands. Explosive volcanic activity can cause tsunamis. The island of [[Molokai|Molokaʻi]] had a catastrophic collapse or [[debris avalanche]] over a million years ago; this underwater landslide likely caused tsunamis. The [[Hilina Slump]] on the [[Hawaii (island)|island of Hawaiʻi]] is another potential place for a large landslide and resulting tsunami.

The city of [[Hilo, Hawaii|Hilo]] on the Big Island has been most affected by tsunamis, where the in-rushing water is accentuated by the shape of [[Hilo Bay]]. Coastal cities have tsunami warning sirens.

A tsunami resulting from an [[2010 Chile earthquake|earthquake in Chile]] hit the islands on February 27, 2010. It was relatively minor, but local emergency management officials utilized the latest technology and ordered evacuations in preparation for a possible major event. The Governor declared it a "good drill" for the next major event.

A tsunami resulting from an [[2011 Tōhoku earthquake and tsunami|earthquake in Japan]] hit the islands on March 11, 2011. It was relatively minor, but local officials ordered evacuations in preparation for a possible major event. The tsunami caused about $30.1 million in damages.<ref name="USGS Open-File Report 2012-1229">{{Cite web|url=http://pubs.usgs.gov/of/2012/1229/of2012-1229_text.pdf|title=Tohoku-Oki Earthquake Tsunami Runup and Inundation Data for Sites Around the Island of Hawai'i|first1=Frank A.|last1=Trusdell|first2=Amy|last2=Chadderton|first3=Graham|last3=Hinchliffe|first4=Andrew|last4=Hara|first5=Brent|last5=Patenge|first6=Tom|last6=Weber|publisher=United States Geological Survey|date=November 15, 2012|access-date=October 11, 2016|pages=3–4|archive-date=February 8, 2017|archive-url=https://web.archive.org/web/20170208194543/https://pubs.usgs.gov/of/2012/1229/of2012-1229_text.pdf|url-status=live}}</ref>

=== Volcanoes ===
{{Main|List of volcanoes in the Hawaiian–Emperor seamount chain}}
[[File:Lava From Kilauea Volcano.webp|thumb|Lava erupting from Kīlauea, one of six active volcanoes in the Hawaiian islands. Kīlauea is the most active, erupting nearly continuously from 1983 to 2018.]]
Only the two Hawaiian islands furthest to the southeast have active volcanoes: [[Haleakalā]] on Maui, and [[Mauna Loa]], [[Mauna Kea]], [[Kīlauea|Kilauea]], and [[Hualālai|Hualalai]], all on the Big Island. The volcanoes on the remaining islands are extinct as they are no longer over the Hawaii hotspot. The [[Kamaʻehuakanaloa Seamount]] is an active submarine volcano that is expected to become the newest Hawaiian island when it rises above the ocean's surface in 10,000–100,000 years.<ref>{{Cite web|url=https://www.usgs.gov/observatories/hvo/active-volcanoes-hawaii|title=Active Volcanoes of Hawaii &#124; U.S. Geological Survey|publisher=United States Geological Survey|access-date=June 9, 2023|archive-date=June 8, 2023|archive-url=https://web.archive.org/web/20230608153922/https://www.usgs.gov/observatories/hvo/active-volcanoes-hawaii|url-status=live}}</ref> 
Hazards from these volcanoes include lava flows that can destroy and bury the surrounding surface, volcanic gas emissions, earthquakes and tsunamis listed above, submarine eruptions affecting the ocean, and the possibility of an explosive eruption.<ref>{{Cite web|url=https://www.usgs.gov/observatories/hvo/hazards|title=Hazards &#124; U.S. Geological Survey|publisher=United States Geological Survey|access-date=June 9, 2023|archive-date=June 9, 2023|archive-url=https://web.archive.org/web/20230609072759/https://www.usgs.gov/observatories/hvo/hazards|url-status=live}}</ref>
[[File:Death of Captain Cook by John Cleveley the Younger, Aquatint Francis Jukes HMA I259817 TePapa.jpg|thumb|Death of the first European visitor to the Hawaiian Islands, Captain [[James Cook]], at [[Kealakekua Bay]] on February 14, 1779]]