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The Hawaii hotspot is a
volcanic hotspot In geology, hotspots (or hot spots) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii, Iceland, and Yellowstone hotspots. A hotspot's position ...
located near the namesake
Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost ...
, in the northern
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
. One of the best known and intensively studied hotspots in the world, the Hawaii plume is responsible for the creation of the Hawaiian–Emperor seamount chain, a mostly undersea volcanic mountain range. Four of these volcanoes are active, two are dormant; more than 123 are
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
, most now preserved as
atoll An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gro ...
s or seamounts. The chain extends from south of the island of
Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
to the edge of the Aleutian Trench, near the eastern coast of
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...
. While most volcanoes are created by geological activity at tectonic plate boundaries, the Hawaii hotspot is located far from plate boundaries. The classic hotspot theory, first proposed in 1963 by
John Tuzo Wilson John Tuzo Wilson (October 24, 1908 – April 15, 1993) was a Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics. ''Plate tectonics'' is the scientific theory that the rigi ...
, proposes that a single, fixed mantle plume builds volcanoes that then, cut off from their source by the movement of the
Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and I ...
, become increasingly inactive and eventually erode below
sea level Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardis ...
over millions of years. According to this theory, the nearly 60° bend where the Emperor and Hawaiian segments of the chain meet was caused by a sudden shift in the movement of the Pacific Plate. In 2003, fresh investigations of this irregularity led to the proposal of a mobile hotspot theory, suggesting that hotspots are mobile, not fixed, and that the 47-million-year-old bend was caused by a shift in the hotspot's motion rather than the plate's.
Ancient Hawaiian Ancient Hawaii is the period of Hawaiian history preceding the unification in 1810 of the Kingdom of Hawaii by Kamehameha the Great. Traditionally, researchers estimated the first settlement of the Hawaiian islands as having occurred sporadical ...
s were the first to recognize the increasing age and weathered state of the volcanoes to the north as they progressed on fishing expeditions along the islands. The volatile state of the Hawaiian volcanoes and their constant battle with the sea was a major element in
Hawaiian mythology Hawaiian religion refers to the indigenous religious beliefs and practices of native Hawaiians, also known as the kapu system. Hawaiian religion is based largely on the tapu religion common in Polynesia and likely originated among the Tahitians ...
, embodied in Pele, the deity of volcanoes. After the arrival of Europeans on the island, in 1880–1881 James Dwight Dana directed the first formal geological study of the hotspot's volcanics, confirming the relationship long observed by the natives. The Hawaiian Volcano Observatory was founded in 1912 by
volcanologist A volcanologist, or volcano scientist, is a geologist who focuses on understanding the formation and eruptive activity of volcanoes. Volcanologists frequently visit volcanoes, sometimes active ones, to observe and monitor volcanic eruptions, col ...
Thomas Jaggar Thomas Augustus Jaggar Jr. (January 24, 1871 – January 17, 1953) was an American volcanologist. He founded the Hawaiian Volcano Observatory and directed it from 1912 to 1940. The son of Thomas Augustus Jaggar, Jaggar Jr. graduated with a Ph ...
, initiating continuous scientific observation of the islands. In the 1970s, a mapping project was initiated to gain more information about the complex geology of Hawaii's seafloor. The hotspot has since been tomographically imaged, showing it to be wide and up to deep, and
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...
and
garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...
-based studies have shown its magma chamber is approximately . In its at least 85 million years of activity the hotspot has produced an estimated of rock. The chain's rate of drift has slowly increased over time, causing the amount of time each individual volcano is active to decrease, from 18 million years for the 76-million-year-old
Detroit Seamount Detroit Seamount, which was formed around 76 million years ago, is one of the oldest seamounts of the Hawaiian-Emperor seamount chain (Meiji Seamount is the oldest, at 82 million years). It lies near the northernmost end of the chain and is sout ...
, to just under 900,000 for the one-million-year-old Kohala; on the other hand, eruptive volume has increased from per year to about . Overall, this has caused a trend towards more active but quickly-silenced, closely spaced volcanoes — whereas volcanoes on the near side of the hotspot overlap each other (forming such superstructures as
Hawaii island Hawaii ( ; haw, Hawaii ) is the largest island in the United States, located in the state of Hawaii. It is the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of , it has 63% of t ...
and the ancient
Maui Nui Maui Nui or Greater Maui, is a modern geologists' name given to a prehistoric Hawaiian Island built from seven shield volcanoes. ''Nui'' means "great/large" in the Hawaiian language. 1.2 million years ago, Maui Nui was , 40% larger than the ...
), the oldest of the Emperor seamounts are spaced as far as apart.


Theories

Tectonic plates Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...
generally focus deformation and volcanism at
plate boundaries Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
. However, the Hawaii hotspot is more than from the nearest plate boundary; while studying it in 1963, Canadian geophysicist J. Tuzo Wilson proposed the hotspot
theory A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may ...
to explain these zones of volcanism so far from regular conditions, a theory that has since come into wide acceptance.


Wilson's stationary hotspot theory

Wilson proposed that
mantle convection Mantle convection is the very slow creeping motion of Earth's solid silicate mantle as convection currents carrying heat from the interior to the planet's surface. The Earth's surface lithosphere rides atop the asthenosphere and the two form ...
produces small, hot, buoyant upwellings under the Earth's surface; these thermally active mantle plumes supply magma which in turn sustains long-lasting volcanic activity. This "mid-plate" volcanism builds peaks that rise from relatively featureless sea floor, initially as seamounts and later as fully-fledged
volcanic islands Geologically, a high island or volcanic island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed ...
. The local
tectonic plate Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...
(in the case of the Hawaii hotspot, the
Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and I ...
) gradually passes over the hotspot, carrying its volcanoes with it without affecting the plume. Over hundreds of thousands of years, the magma supply for an individual volcano is slowly cut off, eventually causing its extinction. No longer active enough to overpower erosion, the volcano slowly recedes beneath the waves, becoming a seamount once again. As the cycle continues, a new volcanic center pierces the crust, and a volcanic island arises anew. The process continues until the mantle plume itself collapses. This cycle of growth and dormancy strings together volcanoes over millions of years, leaving a trail of volcanic islands and seamounts across the ocean floor. According to Wilson's theory, the Hawaiian volcanoes should be progressively older and increasingly eroded the further they are from the hotspot, and this is easily observable; the oldest rock in the main Hawaiian islands, that of
Kauai Kauai, () anglicized as Kauai ( ), is geologically the second-oldest of the main Hawaiian Islands (after Niʻihau). With an area of 562.3 square miles (1,456.4 km2), it is the fourth-largest of these islands and the 21st largest islan ...
, is about 5.5 million years old and deeply eroded, while the rock on
Hawaii island Hawaii ( ; haw, Hawaii ) is the largest island in the United States, located in the state of Hawaii. It is the southeasternmost of the Hawaiian Islands, a chain of volcanic islands in the North Pacific Ocean. With an area of , it has 63% of t ...
is a comparatively young 0.7 million years of age or less, with new lava constantly erupting at
Kīlauea Kīlauea ( , ) is an active shield volcano in the Hawaiian Islands. Located along the southeastern shore of the Big Island of Hawaii, the volcano is between 210,000 and 280,000 years old and emerged above sea level about 100,000 years ago. His ...
, the hotspot's present center. Another consequence of his theory is that the chain's length and orientation serves to record the direction and speed of the
Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and I ...
's movement. A major feature of the Hawaiian trail is a "sudden" 60-degree bend at a 40- to 50-million-year-old section of its length, and according to Wilson's theory, this is evidence of a major change in plate direction, one that would have initiated
subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...
along much of the Pacific Plate's western boundary. This part of the theory has recently been challenged, and the bend might be attributed to the movement of the hotspot itself. Geophysicists believe that hotspots originate at one of two major boundaries deep in the Earth, either a shallow interface in the lower
mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...
between an upper mantle convecting layer and a lower non-convecting layer, or a deeper D'' ("D double-prime") layer, approximately thick and immediately above the core-mantle boundary. A mantle plume would initiate at the interface when the warmer lower layer heats a portion of the cooler upper layer. This heated, buoyant, and less-viscous portion of the upper layer would become less dense due to
thermal expansion Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kin ...
, and rise towards the surface as a Rayleigh-Taylor instability. When the mantle plume reaches the base of the
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years ...
, the plume heats it and produces melt. This
magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...
then makes its way to the surface, where it is erupted as
lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...
. Arguments for the validity of the hotspot theory generally center on the steady age progression of the Hawaiian islands and nearby features: a similar bend in the trail of the
Macdonald hotspot The Macdonald hotspot (also known as "Tubuai" or "Old Rurutu") is a volcanic hotspot in the southern Pacific Ocean. The hotspot was responsible for the formation of the Macdonald Seamount, and possibly the Austral-Cook Islands chain. It probabl ...
, the Austral–Marshall Islands seamount chain, located just south; other
Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
hotspots following the same age-progressed trend from southeast to northwest in fixed relative positions; and seismologic studies of Hawaii which show increased temperatures at the core–mantle boundary, evidencing a mantle plume.


Shallow hotspot hypothesis

Another hypothesis is that melting anomalies form as a result of lithospheric extension, which allows pre-existing melt to rise to the surface. These melting anomalies are normally called "hotspots", but under the shallow-source hypothesis the mantle underlying them is not anomalously hot. In the case of the Hawaiian–Emperor seamount chain, the Pacific plate boundary system was very different around 80 Mya, when the Emperor seamount chain began to form. There is evidence that the chain started on a
spreading ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a dive ...
(the Pacific-Kula Ridge) that has now been subducted at the Aleutian trench. The locus of melt extraction may have migrated off the ridge and into the plate interior, leaving a trail of volcanism behind it. This migration may have occurred because this part of the plate was extending in order to accommodate intraplate stress. Thus, a long-lived region of melt escape could have been sustained. Supporters of this hypothesis argue that the wavespeed anomalies seen in seismic tomographic studies cannot be reliably interpreted as hot upwellings originating in the lower mantle.


Moving hotspot theory

The most heavily challenged element of Wilson's theory is whether hotspots are indeed fixed relative to the overlying tectonic plates. Drill samples, collected by scientists as far back as 1963, suggest that the hotspot may have drifted over time, at the relatively rapid pace of about per year during the late
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
and early
Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...
eras (81–47 Mya); in comparison, the
Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North A ...
spreads at a rate of per year. In 1987, a study published by Peter Molnar and Joann Stock found that the hotspot does move relative to the Pacific Ocean; however, they interpreted this as the result of the relative motions of the
North American North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the ...
and Pacific plates rather than that of the hotspot itself. In 2001 the Ocean Drilling Program (since merged into the Integrated Ocean Drilling Program), an international research effort to study the world's seafloors, funded a two-month expedition aboard the research vessel ''JOIDES Resolution'' to collect lava samples from four submerged Emperor seamounts. The project drilled
Detroit Detroit ( , ; , ) is the largest city in the U.S. state of Michigan. It is also the largest U.S. city on the United States–Canada border, and the seat of government of Wayne County. The City of Detroit had a population of 639,111 at t ...
, Nintoku, and
Koko seamount Koko Guyot (also sometimes known as ''Kinmei'' and Koko Seamount) is a 48.1-million-year-old guyot, a type of underwater volcano with a flat top, which lies near the southern end of the Emperor seamounts, about north of the "bend" in the volcani ...
s, all of which are in the far northwest end of the chain, the oldest section. These lava samples were then tested in 2003, suggesting a mobile Hawaiian hotspot and a shift in its motion as the cause of the bend. Lead scientist John Tarduno told ''
National Geographic ''National Geographic'' (formerly the ''National Geographic Magazine'', sometimes branded as NAT GEO) is a popular American monthly magazine published by National Geographic Partners. Known for its photojournalism, it is one of the most widel ...
'':
The Hawaii bend was used as a classic example of how a large plate can change motion quickly. You can find a diagram of the Hawaii–Emperor bend entered into just about every introductory geological textbook out there. It really is something that catches your eye."
Despite the large shift, the change in direction was never recorded by
magnetic declination Magnetic declination, or magnetic variation, is the angle on the horizontal plane between magnetic north (the direction the north end of a magnetized compass needle points, corresponding to the direction of the Earth's magnetic field lines) an ...
s,
fracture zone A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on e ...
orientations or plate reconstructions; nor could a
continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produ ...
have occurred fast enough to produce such a pronounced bend in the chain. To test whether the bend was a result of a change in direction of the Pacific Plate, scientists analyzed the lava samples' geochemistry to determine where and when they formed. Age was determined by the
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...
of radioactive isotopes of
potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
and
argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice a ...
. Researchers estimated that the volcanoes formed during a period 81 million to 45 million years ago. Tarduno and his team determined where the volcanoes formed by analyzing the rock for the magnetic mineral
magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With ...
. While hot lava from a volcanic eruption cools, tiny grains within the magnetite align with the
Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magneti ...
, and lock in place once the rock solidifies. Researchers were able to verify the latitudes at which the volcanoes formed by measuring the grains' orientation within the magnetite. Paleomagnetists concluded that the Hawaiian hotspot had drifted southward sometime in its history, and that, 47 million years ago, the hotspot's southward motion greatly slowed, perhaps even stopping entirely.


History of study


Ancient Hawaiians

The possibility that the Hawaiian islands became older as one moved to the northwest was suspected by
ancient Hawaii Ancient Hawaii is the period of Hawaiian history preceding the unification in 1810 of the Kingdom of Hawaii by Kamehameha the Great. Traditionally, researchers estimated the first settlement of the Hawaiian islands as having occurred sporadicall ...
ans long before Europeans arrived. During their voyages, seafaring Hawaiians noticed differences in erosion, soil formation, and vegetation, allowing them to deduce that the islands to the northwest (
Niihau Niihau ( Hawaiian: ), anglicized as Niihau ( ), is the westernmost main and seventh largest inhabited island in Hawaii. It is southwest of Kauaʻi across the Kaulakahi Channel. Its area is . Several intermittent playa lakes provide wetland ha ...
and
Kauai Kauai, () anglicized as Kauai ( ), is geologically the second-oldest of the main Hawaiian Islands (after Niʻihau). With an area of 562.3 square miles (1,456.4 km2), it is the fourth-largest of these islands and the 21st largest islan ...
) were older than those to the southeast (Maui and Hawaii). The idea was handed down the generations through the legend of Pele, the Hawaiian goddess of volcanoes. Pele was born to the female spirit Haumea, or Hina, who, like all Hawaiian gods and goddesses, descended from the supreme beings, Papa, or
Earth Mother A mother goddess is a goddess who represents a personified deification of motherhood, fertility goddess, fertility, creation, destruction, or the earth goddess who embodies the bounty of the earth or nature. When equated with the earth or t ...
, and Wakea, or Sky Father. According to the myth, Pele originally lived on Kauai, when her older sister
Nāmaka In Hawaiian mythology, Nāmaka (or Nā-maka-o-Kahai, the eyes of Kahai) appears as a sea goddess in the Pele family. She is an older sister of Pele-honua-mea. She is the daughter of Ku-waha-ilo and Haumea, whose other children are Pele, the H ...
, the Goddess of the Sea, attacked her for seducing her husband. Pele fled southeast to the island of Oahu. When forced by
Nāmaka In Hawaiian mythology, Nāmaka (or Nā-maka-o-Kahai, the eyes of Kahai) appears as a sea goddess in the Pele family. She is an older sister of Pele-honua-mea. She is the daughter of Ku-waha-ilo and Haumea, whose other children are Pele, the H ...
to flee again, Pele moved southeast to Maui and finally to Hawaii, where she still lives in
Halemaʻumaʻu Halemaumau (''six syllables: HAH-lay-MAH-oo-MAH-oo'') is a pit crater within the much larger Kīlauea Caldera at the summit of Kīlauea volcano on island of Hawaiʻi. The roughly circular crater was x before collapses that roughly doubled ...
at the summit of
Kīlauea Kīlauea ( , ) is an active shield volcano in the Hawaiian Islands. Located along the southeastern shore of the Big Island of Hawaii, the volcano is between 210,000 and 280,000 years old and emerged above sea level about 100,000 years ago. His ...
. There she was safe, because the slopes of the volcano are so high that even Nāmaka's mighty waves could not reach her. Pele's mythical flight, which alludes to an eternal struggle between volcanic islands and ocean waves, is consistent with geologic evidence about the ages of the islands decreasing to the southeast.


Modern studies

Three of the earliest recorded observers of the volcanoes were the Scottish scientists Archibald Menzies in 1794, James Macrae in 1825, and David Douglas in 1834. Just reaching the summits proved daunting: Menzies took three attempts to ascend
Mauna Loa Mauna Loa ( or ; Hawaiian: ; en, Long Mountain) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. The largest subaerial volcano (as opposed to subaqueous volcanoes) in both mass and ...
, and Douglas died on the slopes of
Mauna Kea Mauna Kea ( or ; ; abbreviation for ''Mauna a Wākea''); is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii and second-highest peak of an island on Earth. The peak ...
. The
United States Exploring Expedition The United States Exploring Expedition of 1838–1842 was an exploring and surveying expedition of the Pacific Ocean and surrounding lands conducted by the United States. The original appointed commanding officer was Commodore Thomas ap Catesby ...
spent several months studying the islands in 1840–1841. American geologist James Dwight Dana was on that expedition, as was Lieutenant
Charles Wilkes Charles Wilkes (April 3, 1798 – February 8, 1877) was an American naval officer, ship's captain, and explorer. He led the United States Exploring Expedition (1838–1842). During the American Civil War (1861–1865), he commanded ' during the ...
, who spent most of the time leading a team of hundreds that hauled a pendulum to the summit of Mauna Loa to measure gravity. Dana stayed with missionary
Titus Coan Titus Coan (February 1, 1801 – December 1, 1882) was an American minister from New England who spent most of his life as a Christian missionary to the Hawaiian Islands. Early life and family Titus Coan was born on February 1, 1801 in Killingwor ...
, who would provide decades of first-hand observations. Dana published a short paper in 1852. Dana remained interested in the origin of the Hawaiian Islands, and directed a more in-depth study in 1880 and 1881. He confirmed that the islands' age increased with their distance from the southeasternmost island by observing differences in their degree of erosion. He also suggested that many other island chains in the Pacific showed a similar general increase in age from southeast to northwest. Dana concluded that the Hawaiian chain consisted of two volcanic strands, located along distinct but parallel curving pathways. He coined the terms "Loa" and "Kea" for the two prominent trends. The Kea trend includes the volcanoes of
Kīlauea Kīlauea ( , ) is an active shield volcano in the Hawaiian Islands. Located along the southeastern shore of the Big Island of Hawaii, the volcano is between 210,000 and 280,000 years old and emerged above sea level about 100,000 years ago. His ...
,
Mauna Kea Mauna Kea ( or ; ; abbreviation for ''Mauna a Wākea''); is a dormant volcano on the island of Hawaii. Its peak is above sea level, making it the highest point in the state of Hawaii and second-highest peak of an island on Earth. The peak ...
, Kohala, Haleakalā, and West Maui. The Loa trend includes Lōihi,
Mauna Loa Mauna Loa ( or ; Hawaiian: ; en, Long Mountain) is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean. The largest subaerial volcano (as opposed to subaqueous volcanoes) in both mass and ...
, Hualālai,
Kahoolawe Kahoolawe (Hawaiian: ), anglicized as Kahoolawe (), is the smallest of the eight main volcanic islands in the Hawaiian Islands. Kahoolawe is located about southwest of Maui and also southeast of Lānaʻi, and it is long by wide, with a total l ...
, Lānai, and West Molokai. Dana proposed that the alignment of the Hawaiian Islands reflected localized volcanic activity along a major fissure zone. Dana's "great fissure" theory served as the working hypothesis for subsequent studies until the mid-20th century. Dana's work was followed up by the 1884 expedition of geologist C. E. Dutton, who refined and expanded Dana's ideas. Most notably, Dutton established that the island of Hawaii actually harbored five volcanoes, whereas Dana counted three. This is because Dana had originally regarded Kīlauea as a flank vent of Mauna Loa, and Kohala as part of Mauna Kea. Dutton also refined others of Dana's observations, and is credited with the naming of
'a'ā Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...
and
pāhoehoe Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
-type lavas, although Dana had also noted a distinction. Stimulated by Dutton's expedition, Dana returned in 1887, and published many accounts of his expedition in the ''
American Journal of Science The ''American Journal of Science'' (''AJS'') is the United States of America's longest-running scientific journal, having been published continuously since its conception in 1818 by Professor Benjamin Silliman, who edited and financed it himsel ...
''. In 1890 he published the most detailed manuscript of its day, which remained the definitive guide to Hawaiian volcanism for decades. In 1909 two major books about Hawaii's volcanoes were published (''"The volcanoes of Kilauea and Mauna Loa"'' by W.T. Brigham and ''"Hawaii and its volcanoes"'' by C.H. Hitchcock). In 1912 geologist
Thomas Jaggar Thomas Augustus Jaggar Jr. (January 24, 1871 – January 17, 1953) was an American volcanologist. He founded the Hawaiian Volcano Observatory and directed it from 1912 to 1940. The son of Thomas Augustus Jaggar, Jaggar Jr. graduated with a Ph ...
founded the Hawaiian Volcano Observatory. The facility was taken over in 1919 by the
National Oceanic and Atmospheric Administration The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditi ...
and in 1924 by the
United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
(USGS), which marked the start of continuous volcano observation on Hawaii island. The next century was a period of thorough investigation, marked by contributions from many top scientists. The first complete evolutionary model was first formulated in 1946, by USGS geologist and
hydrologist Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
Harold T. Stearns. Since that time, advances (e.g. improved rock dating methods and submarine volcanic stages) have enabled the study of previously limited areas of observation. In the 1970s, the Hawaiian seafloor was mapped using ship-based
sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on o ...
. Computed SYNBAPS (Synthetic Bathymetric Profiling System) data filled gaps between the ship-based sonar bathymetric measurements. From 1994 to 1998 the
Japan Agency for Marine-Earth Science and Technology Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
(JAMSTEC) mapped Hawaii in detail and studied its ocean floor, making it one of the world's best-studied marine features. The JAMSTEC project, a collaboration with USGS and other agencies, employed manned
submersibles A submersible is a small watercraft designed to operate underwater. The term "submersible" is often used to differentiate from other underwater vessels known as submarines, in that a submarine is a fully self-sufficient craft, capable of ind ...
,
remotely operated underwater vehicle A remotely operated underwater vehicle (technically ROUV or just ROV) is a tethered underwater mobile device, commonly called ''underwater robot''. Definition This meaning is different from remote control vehicles operating on land or in the a ...
s, dredge samples, and
core sample A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The ...
s. The Simrad EM300 multibeam
side-scanning sonar Side-scan sonar (also sometimes called side scan sonar, sidescan sonar, side imaging sonar, side-imaging sonar and bottom classification sonar) is a category of sonar system that is used to efficiently create an image of large areas of the se ...
system collected bathymetry and backscatter data.


Characteristics


Position

The Hawaii hotspot has been imaged through
seismic tomography Seismic tomography or seismotomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on ...
, and is estimated to be wide. Tomographic images show a thin
low-velocity zone The low-velocity zone (LVZ) occurs close to the boundary between the lithosphere and the asthenosphere in the upper mantle. It is characterized by unusually low seismic shear wave velocity compared to the surrounding depth intervals. This range ...
extending to a depth of , connecting with a large low-velocity zone extending from a depth of to the core-mantle boundary. These low seismic velocity zones often indicate hotter and more buoyant mantle material, consistent with a plume originating in the lower mantle and a pond of plume material in the upper mantle. The low-velocity zone associated with the source of the plume is north of Hawaii, showing that the plume is tilted to a certain degree, deflected toward the south by mantle flow.
Uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
decay-series disequilibria data has shown that the actively flowing region of the melt zone is  km wide at its base and at the upper mantle upwelling, consistent with tomographic measurements.


Temperature

Indirect studies found that the magma chamber is located about underground, which matches the estimated depth of the Cretaceous Period rock in the oceanic lithosphere; this may indicate that the lithosphere acts as a lid on melting by arresting the magma's ascent. The magma's original temperature was found in two ways, by testing
garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...
's melting point in lava and by adjusting the lava for
olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...
deterioration. Both USGS tests seem to confirm the temperature at about ; in comparison, the estimated temperature for mid-ocean ridge basalt is about . The surface heat flow anomaly around the Hawaiian Swell is only of the order of 10 mW/m2, far less than the continental United States range of 25–150 mW/m2. This is unexpected for the classic model of a hot, buoyant plume in the mantle. However, it has been shown that other plumes display highly variable surface heat fluxes and that this variability may be due to variable hydrothermal fluid flow in the Earth's crust above the hotspots. This fluid flow advectively removes heat from the crust, and the measured conductive heat flow is therefore lower than the true total surface heat flux. The low heat across the Hawaiian Swell indicates that it is not supported by a buoyant crust or upper lithosphere, but is rather propped up by the upwelling hot (and therefore less-dense) mantle plume that causes the surface to rise through a mechanism known as "
dynamic topography The term dynamic topography is used in geodynamics to refer the elevation differences caused by the flow within Earth's mantle. Definition In geodynamics, ''dynamic topography'' refers to topography generated by the motion of zones of differing ...
".


Movement

Hawaiian volcanoes drift northwest from the hotspot at a rate of about a year. The hotspot has migrated south by about relative to the Emperor chain.
Paleomagnetic Paleomagnetism (or palaeomagnetismsee ), is the study of magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.'' Certain magnetic minerals in rock ...
studies support this conclusion based on changes in
Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magneti ...
, a picture of which was engrained in the rocks at the time of their solidification, showing that these seamounts formed at higher latitudes than present-day Hawaii. Prior to the bend, the hotspot migrated an estimated per year; the rate of movement changed at the time of the bend to about per year. The Ocean Drilling Program provided most of the current knowledge about the drift. The 2001 expedition drilled six seamounts and tested the samples to determine their original latitude, and thus the characteristics and speed of the hotspot's drift pattern in total. Each successive volcano spends less time actively attached to the plume. The large difference between the youngest and oldest lavas between Emperor and Hawaiian volcanoes indicates that the hotspot's velocity is increasing. For example, Kohala, the oldest volcano on Hawaii island, is one million years old and last erupted 120,000 years ago, a period of just under 900,000 years; whereas one of the oldest, Detroit Seamount, experienced 18 million or more years of volcanic activity. The oldest volcano in the chain, Meiji Seamount, perched on the edge of the Aleutian Trench, formed 85 million years ago. At its current velocity, the seamount will be destroyed within a few million years, as the
Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and I ...
slides under the
Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent an ...
. It is unknown whether the seamount chain has been subducting under the Eurasian Plate, and whether the hotspot is older than Meiji Seamount, as any older seamounts have since been destroyed by the plate margin. It is also possible that a collision near the Aleutian Trench had changed the velocity of the Pacific Plate, explaining the hotspot chain's bend; the relationship between these features is still being investigated.


Magma

The composition of the volcanoes' magma has changed significantly according to analysis of the
strontium Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is e ...
niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has s ...
palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself ...
elemental ratios. The Emperor Seamounts were active for at least 46 million years, with the oldest lava dated to the Cretaceous Period, followed by another 39 million years of activity along the Hawaiian segment of the chain, totaling 85 million years. Data demonstrate vertical variability in the amount of strontium present in both the alkalic (early stages) and tholeiitic (later stages) lavas. The systematic increase slows drastically at the time of the bend. Almost all magma created by the hotspot is
igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...
basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...
; the volcanoes are constructed almost entirely of this or the similar in composition but coarser-grained
gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ...
and
diabase Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grain ...
. Other igneous rocks such as
nephelinite Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite). If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may res ...
are present in small quantities; these occur often on the older volcanoes, most prominently Detroit Seamount. Most eruptions are runny because basaltic magma is less
viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...
than magmas characteristic of more
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma su ...
s such as the
andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomin ...
magmas that produce spectacular and dangerous eruptions around Pacific Basin margins. Volcanoes fall into several eruptive categories. Hawaiian volcanoes are called "Hawaiian-type". Hawaiian lava spills out of craters and forms long streams of glowing molten rock, flowing down the slope, covering acres of land and replacing ocean with new land.


Eruptive frequency and scale

There is significant evidence that lava flow rates have been increasing. Over the last six million years they have been far higher than ever before, at over per year. The average for the last million years is even higher, at about . In comparison, the average production rate at a
mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a div ...
is about for every of ridge. The rate along the Emperor seamount chain averaged about per year. The rate was almost zero for the initial five million or so years in the hotspot's life. The average lava production rate along the Hawaiian chain has been greater, at per year. In total, the hotspot has produced an estimated of lava, enough to cover
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
with a layer about thick.D. A. Clauge and G. B. Dalrymple (1987). "The Hawaiian-Emperor volcanic chain: Part 1. Geologic Evolution". United States Geological Survey Professional Paper 1350. p. 23. The distance between individual volcanoes has shrunk. Although volcanoes have been drifting north faster and spending less time active, the far greater modern eruptive volume of the hotspot has generated more closely spaced volcanoes, and many of them overlap, forming such superstructures as Hawaii island and the ancient
Maui Nui Maui Nui or Greater Maui, is a modern geologists' name given to a prehistoric Hawaiian Island built from seven shield volcanoes. ''Nui'' means "great/large" in the Hawaiian language. 1.2 million years ago, Maui Nui was , 40% larger than the ...
. Meanwhile, many of the volcanoes in the Emperor seamounts are separated by or even as much as .


Topography and geoid

A detailed
topographic Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scie ...
analysis of the Hawaiian–Emperor seamount chain reveals the hotspot as the center of a topographic high, and that elevation falls with distance from the hotspot. The most rapid decrease in elevation and the highest ratio between the topography and geoid height are over the southeastern part of the chain, falling with distance from the hotspot, particularly at the intersection of the Molokai and Murray fracture zones. The most likely explanation is that the region between the two zones is more susceptible to reheating than most of the chain. Another possible explanation is that the hotspot strength swells and subsides over time.Alt URL
/ref> In 1953,
Robert S. Dietz Robert Sinclair Dietz (September 14, 1914 – May 19, 1995) was a scientist with the US Coast and Geodetic Survey. Dietz, born in Westfield, New Jersey, was a marine geologist, geophysicist and oceanographer who conducted pioneering research along ...
and his colleagues first identified the swell behavior. It was suggested that the cause was mantle upwelling. Later work pointed to
tectonic uplift Tectonic uplift is the geologic uplift of Earth's surface that is attributed to plate tectonics. While isostatic response is important, an increase in the mean elevation of a region can only occur in response to tectonic processes of crustal th ...
, caused by reheating within the lower lithosphere. However, normal seismic activity beneath the swell, as well as lack of detected heat flow, caused scientists to suggest
dynamic topography The term dynamic topography is used in geodynamics to refer the elevation differences caused by the flow within Earth's mantle. Definition In geodynamics, ''dynamic topography'' refers to topography generated by the motion of zones of differing ...
as the cause, in which the motion of the hot and buoyant mantle plume supports the high surface topography around the islands. Understanding the Hawaiian swell has important implications for hotspot study, island formation, and inner Earth.


Seismicity

The Hawaii hotspot is a highly active seismic zone with thousands of
earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...
s occurring on and near Hawaii island every year. Most are too small to be felt by people but some are large enough to result in minor to moderate devastation. The most destructive recorded earthquake was the 2 April 1868 earthquake which had a magnitude of 7.9 on the
Richter scale The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 ...
. It triggered a landslide on Mauna Loa, north of
Pahala Pahala is a census-designated place (CDP) in Hawaii County, Hawaii, United States. The population was 1,403 at the 2020 census. History Pahala was created by a sugarcane plantation. The area selected to house the sugar refinery had several k ...
, killing 31 people. A
tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...
claimed 46 more lives. The villages of Punaluu, Nīnole, Kaaawa, Honuapo, and Keauhou Landing were severely damaged. The tsunami reportedly rolled over the tops of the coconut trees up to high and it reached inland a distance of a quarter of a mile (400 m) in some places.


Volcanoes

Over its 85 million year history, the Hawaii hotspot has created at least 129 volcanoes, more than 123 of which are
extinct volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
es, seamounts, and
atoll An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon partially or completely. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical oceans and seas where corals can gro ...
s, four of which are
active volcanoes An active volcano is a volcano which is either erupting or is likely to erupt in the future. An active volcano which is not currently erupting is known as a dormant volcano. Overview Tlocene Epoch. Most volcanoes are situated on the Pacific ...
, and two of which are
dormant volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...
es. They can be organized into three general categories: the
Hawaiian archipelago The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost K ...
, which comprises most of the U.S. state of Hawaii and is the location of all modern volcanic activity; the
Northwestern Hawaiian Islands The Northwestern Hawaiian Islands or Leeward Hawaiian Islands are a series of islands and atolls in the Hawaiian island chain located northwest (in some cases, far to the northwest) of the islands of Kauai and Niihau. Politically, they are all ...
, which consist of coral atolls, extinct islands, and atoll islands; and the Emperor Seamounts, all of which have since eroded and subsided to the sea and become seamounts and
guyot In marine geology, a guyot (pronounced ), also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than below the surface of the sea. The diameters of these flat summits can exceed .


Volcanic characteristics

Hawaiian volcanoes are characterized by frequent rift eruptions, their large size (thousands of cubic kilometers in volume), and their rough, decentralized shape. Rift zones are a prominent feature on these volcanoes, and account for their seemingly random volcanic structure. The tallest mountain in the Hawaii chain, Mauna Kea, rises above
mean sea level There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value ( magnitude and sign) of a given data set. For a data set, the '' ...
. Measured from its base on the seafloor, it is the world's tallest mountain, at ;
Mount Everest Mount Everest (; Tibetan: ''Chomolungma'' ; ) is Earth's highest mountain above sea level, located in the Mahalangur Himal sub-range of the Himalayas. The China–Nepal border runs across its summit point. Its elevation (snow hei ...
rises above sea level. Hawaii is surrounded by a myriad of seamounts; however, they were found to be unconnected to the hotspot and its volcanism. Kīlauea has erupted continuously since 1983 through Puʻu ʻŌʻō, a minor volcanic cone, which has become an attraction for volcanologists and tourists alike.


Landslides

The Hawaiian islands are carpeted by a large number of landslides sourced from volcanic collapse. Bathymetric mapping has revealed at least 70 large landslides on the island flanks over in length, and the longest are long and over in volume. These debris flows can be sorted into two broad categories: slumps, mass movement over slopes which slowly flatten their originators, and more catastrophic debris avalanches, which fragment volcanic slopes and scatter volcanic
debris Debris (, ) is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, as in geology, large rock fragments left by a melting glacier, etc. Depending on context, ''debris'' can refer to ...
past their slopes. These slides have caused massive
tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...
s and earthquakes, fractured volcanic massifs, and scattered debris hundreds of miles away from their source. Slumps tend to be deeply rooted in their originators, moving rock up to deep inside the volcano. Forced forward by the mass of newly ejected volcanic material, slumps may creep forward slowly, or surge forward in spasms that have caused the largest of Hawaii's historical earthquakes, in 1868 and 1975. Debris avalanches, meanwhile, are thinner and longer, and are defined by volcanic amphitheaters at their head and hummocky terrain at their base. Rapidly moving avalanches carried blocks tens of kilometers away, disturbing the local
water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...
and causing a tsunami. Evidence of these events exists in the form of marine deposits high on the slopes of many Hawaiian volcanoes, and has marred the slopes of several Emperor seamounts, such as Daikakuji Guyot and Detroit Seamount.


Evolution and construction

Hawaiian volcanoes follow a well-established life cycle of growth and erosion. After a new volcano forms, its lava output gradually increases. Height and activity both peak when the volcano is around 500,000 years old and then rapidly decline. Eventually it goes dormant, and eventually extinct. Erosion then weathers the volcano until it again becomes a seamount. This life cycle consists of several stages. The first stage is the submarine preshield stage, currently represented solely by Kama‘ehuakanaloa. During this stage, the volcano builds height through increasingly frequent eruptions. The sea's pressure prevents explosive eruptions. The cold water quickly solidifies the lava, producing the
pillow lava Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of discont ...
that is typical of underwater volcanic activity. As the seamount slowly grows, it goes through the shield stages. It forms many mature features, such as a
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
, while submerged. The summit eventually breaches the surface, and the lava and ocean water "battle" for control as the volcano enters the explosive subphase. This stage of development is exemplified by explosive steam vents. This stage produces mostly
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer ...
, a result of the waves dampening the lava. This conflict between lava and sea influences
Hawaiian mythology Hawaiian religion refers to the indigenous religious beliefs and practices of native Hawaiians, also known as the kapu system. Hawaiian religion is based largely on the tapu religion common in Polynesia and likely originated among the Tahitians ...
. The volcano enters the subaerial subphase once it is tall enough to escape the water. Now the volcano puts on 95% of its above-water height over roughly 500,000 years. Thereafter eruptions become much less explosive. The lava released in this stage often includes both pāhoehoe and ʻaʻā, and the currently active Hawaiian volcanoes, Mauna Loa and Kīlauea, are in this phase. Hawaiian lava is often runny, blocky, slow, and relatively easy to predict; the USGS tracks where it is most likely to run, and maintains a tourist site for viewing the lava. After the subaerial phase the volcano enters a series of postshield stages involving subsidence and erosion, becoming an atoll and eventually a seamount. Once the Pacific Plate moves it out of the
tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...
, the reef mostly dies away, and the extinct volcano becomes one of an estimated 10,000 barren seamounts worldwide. Every Emperor seamount is a dead volcano.


See also

* List of volcanic hotspots * List of volcanoes in the Pacific Ocean *
List of volcanoes in the United States A list of volcanoes in the United States and its territories. Alaska American Samoa Arizona California Colorado Hawaii /[./[Https://www.sci.news/geology/puhahonu-shield-volcano-08435.html Puhahonu ...
*
Maui Nui Maui Nui or Greater Maui, is a modern geologists' name given to a prehistoric Hawaiian Island built from seven shield volcanoes. ''Nui'' means "great/large" in the Hawaiian language. 1.2 million years ago, Maui Nui was , 40% larger than the ...
* Types of volcanic eruptions


References


External links


Pele — Goddess of Fire
Details Pele's full story, according to Hawaiian myths.
The long trail of the Hawaiian hotspot
USGS article on the Hawaiian island chain.

USGS article on the evolution of Hawaiian volcanoes over time. * {{DEFAULTSORT:Hawaii Hotspot Hotspots of the Pacific Ocean Geology of Hawaii Hawaiian–Emperor seamount chain Volcanism of Hawaii Volcanism of Oceania Seismic zones of the United States