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The Mauna Loa Volcano – Still Very Much Alive

Mauna Loa is the world’s largest active volcano, measuring 13,697 feet above sea level and around 3,100 feet below sea level, making it the biggest volcano on earth. It is a shield volcano covering more than 50 per cent of the Hawaii Island. It erupted 33 times between 1843 and 1984, just once in World War I and not at all in World War II. It has a total volume estimated to be over 75,000 cubic kilometres (18,000 cubic miles) and is located on the Pacific plate that sags because of its weight. More than 98 per cent of the surface is covered with lava flow less than 10,000 years old. The first ever eruption of the Mauna Loa volcano is estimated to have happened about 700,000 to 1 million years ago.[2]

The name “Mauna Loa” means “long mountain” in Hawaiian, and it is an appropriate name because the volcano covers an area of about 2,035 square miles (5,271 square kilometres). It is so large that it can be seen from space, and it dominates the landscape of the Big Island.

Mauna Loa has erupted 33 times since its first well-documented eruption in 1843. It last erupted for about 12 days in late 2022, the first eruption since 1984. These eruptions have been characterised by relatively gentle, effusive flows of lava.

Picture Credit: Screenshot from Video of Mauna Loa’s 2022 Eruption. US Park Service. © Copyright acknowledged.
Video URL:

Mauna Loa in Antiquity
Unfortunately, there is no written record of what Mauna Loa was like in antiquity, as no written languages were present on the Hawaiian Islands until the arrival of European explorers in the late 18th century. However, some evidence suggests what Mauna Loa may have been like before human arrival.

Geological and ecological studies of the region suggest that the slopes of Mauna Loa were once covered in a diverse array of plant species, including koa and ʻōhiʻa trees, ferns, and other shrubs. These plants likely supported a variety of native bird and insect species.

It is also believed that ancient Hawaiian people used the slopes of Mauna Loa for farming and other agricultural practices. They likely grew crops such as taro and sweet potato and may have used the abundant water resources in the area for irrigation.

Although no definitive record exists of what Mauna Loa was like in antiquity, the volcano was likely a thriving ecosystem with a diverse array of plant and animal species, as well as a centre for human activity and agriculture.

Volcanic Eruptions

  • There are more than 1500 active volcanoes on Earth.
  • Around three to five per cent of volcanoes erupt every year.
  • There are 82 volcanoes in Europe, of which 32 are in Iceland.
  • Most volcanoes are not well-monitored.
  • Some volcanoes erupt almost continuously (for example, Mt. Etna and Stromboli), but some don’t erupt for tens, hundreds or even thousands of years.

Volcanic eruptions happen when pressure builds up inside a volcano, causing hot magma to explode from the top, as happens at Mauna Loa, one of the world’s most active volcanoes. Volcanic eruptions can be explosive, sending ash, gas and lava high up into the atmosphere, or the magma can form lava flows, known as effusive eruptions. Whether an eruption is explosive or effusive largely depends upon the amount of gas in the magma. Sometimes, when magma erupts through water, it causes a special kind of explosive eruption called a phreatomagmatic eruption. This happened during the Eyjafjallajökull eruption in 2010 when the magma erupted under the ice. Some underwater volcanoes can also have phreatomagmatic eruptions, like Surtsey in Iceland, which formed a new island.

Explosive eruptions can be really dangerous because they can form pyroclastic flows that destroy everything in their path and send ash high into the atmosphere. But if the magma is runny and has low viscosity, gas can escape easily, and the eruption will be less explosive. This kind of eruption creates lava flows and is not as dangerous. Mauna Loa has had both types of eruptions in the past, but most recent ones have been less explosive, with lava flows that move slowly, allowing people to evacuate the area.

Types of Volcanic Eruption
During an eruption, lava, tephra (ash, lapilli, volcanic bombs, and volcanic blocks), and various gases are expelled from a volcanic vent or fissure—these have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behaviour has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series. There are three different types of eruptions:

  • Magmatic eruptions are the most well-observed type of eruption. They involve the decompression of gas within magma that propels it forward.
  • Phreatic eruptions are driven by the superheating of steam due to the close proximity of magma. This type exhibits no magmatic release, instead causing the granulation of existing rock.
  • Phreatomagmatic Eruptions are driven by the direct interaction of magma and water, unlike phreatic eruptions, where no fresh magma reaches the surface.

Conscious that some of the terms above may not be familiar, here is a brief description of them:

  • Ash: Small particles of volcanic glass, minerals, and rock less than 2 mm in diameter. Ash can be carried long distances by the wind and can cause various hazards, including respiratory problems, structural damage, and aviation hazards. For more information, visit the USGS website on volcanic ash[3].
  • Effusive Eruption: A type of volcanic eruption that is relatively gentle and characterised by the outpouring of lava flows.
  • Explosive Eruption: A type of volcanic eruption that is more violent and can produce ash, pyroclastic flows, and other hazards.
  • Granulation: A term used to describe the process of fragmenting magma into small pieces or clumps during a volcanic eruption. Granulation can occur when gas bubbles expand and burst within the magma, causing it to break apart.
  • Hot Magma: Hot molten rock stored beneath the Earth’s surface, which is expelled during a volcanic eruption.
  • Lapilli: Small volcanic rock fragments larger than 2 mm but smaller than 64 mm in diameter. Lapilli are produced during explosive eruptions and can be carried several kilometres from the volcano. For more information, visit the USGS website on lapilli[4].
  • Lava Flows: Streams of molten rock that flow from a volcano during an eruption.
  • Low Viscosity: A term that describes more fluid and less sticky magma, allowing gases to escape more easily and reducing the likelihood of an explosive eruption.
  • Magmatic Eruptions: An eruption involving magma release from within the Earth’s crust. Magmatic eruptions can be explosive or effusive, depending on the viscosity of the magma and the amount of gas it contains.
  • Phreatic Eruptions:  An explosive volcanic eruption caused by the interaction between magma and water, but in this case, the water is not mixed with the magma before the eruption. Instead, groundwater or other water sources are heated by magma and flash to steam, causing the eruption. Phreatic eruptions typically produce ash and other small particles, but do not produce lava flows.
  • Phreatomagmatic Eruption: A type of explosive volcanic eruption that occurs when magma interacts with water, typically resulting in the formation of ash, tephra, and other volcanic debris.
  • Pyroclastic Flows: Avalanches of hot volcanic debris, gas, and ash that can travel down the slopes of a volcano at high speeds, often causing widespread destruction.
  • Volcanic blocks: Large fragments of solid rock ejected from a volcano during explosive eruptions. Volcanic blocks can be several meters in diameter and can be carried several kilometres from the volcano. For more information, visit the USGS website on volcanic blocks[5].
  • Volcanic bombs: Large, rounded or elongated pieces of lava ejected from a volcano during explosive eruptions. Volcanic bombs can be several meters in diameter and travel several kilometres from the volcano. For more information, visit the USGS website on volcanic bombs[6].

The activity of Mauna Loa is closely monitored by the Hawaiian Volcano Observatory, which is part of the United States Geological Survey. The observatory tracks changes in the volcano’s seismic activity, gas emissions, and deformation, which can indicate an impending eruption. The data collected by the observatory is used to issue warnings and inform the public about the potential hazards posed by Mauna Loa.

In addition to being an active volcano, Mauna Loa is also an important scientific site. The Mauna Loa Observatory, located near the volcano’s summit, is one of the world’s most important atmospheric monitoring stations. Since 1958, it has been used to measure atmospheric carbon dioxide concentrations, which have increased steadily over the past century and are a major contributor to global climate change. The observatory’s data has been used to support climate research around the world, and the “Keeling Curve,” a graph of atmospheric carbon dioxide concentrations, is named after the scientist who established the observatory.

The Keeling Curve
The Keeling Curve is a graph that shows the steady increase of carbon dioxide (CO2) in Earth’s atmosphere over time and is named after the scientist who first started measuring atmospheric CO2, Charles David Keeling. The curve was first established in 1958 at the Mauna Loa Observatory in Hawaii and has been continuously measured and recorded since then.

The Keeling Curve is considered a vital tool in understanding climate change and its impacts, as carbon dioxide is a potent greenhouse gas that traps heat in the atmosphere, leading to a warming planet. The graph shows a clear, upward trend in atmospheric CO2 levels and has become an iconic symbol of the ongoing and increasing threat of climate change.

According to Naomi Oreskes, Professor of History of Science at Harvard University, the Keeling curve is one of the most important scientific works of the 20th century.[8] Many scientists credit the Keeling curve with first bringing the world’s attention to the current increase of CO2 in the atmosphere.[9]

What do the results mean?
The results of the Keeling Curve indicate that the concentration of carbon dioxide (CO2) in Earth’s atmosphere has been steadily increasing over time. This increase in CO2 is primarily due to human activity such as burning fossil fuels, deforestation, and other land use changes, which release carbon into the atmosphere and contribute to the greenhouse effect.

The Keeling Curve shows that the atmospheric CO2 concentration has risen from around 315 parts per million (ppm) in 1958 to over 400 ppm in recent years, with annual fluctuations due to natural processes such as seasonal changes in plant growth and decay. The curve demonstrates that CO2 concentrations continue to rise, indicating that human activities continue to increase the amount of CO2 in the atmosphere.

The implications of this trend are significant, as increased atmospheric CO2 leads to a warming planet and changes in global climate patterns. The Keeling Curve serves as a visual reminder of the ongoing and increasing threat of climate change and highlights the urgent need to reduce greenhouse gas emissions and transition to more sustainable energy systems.

Sources for more information on the Keeling Curve:

  • The Scripps Institution of Oceanography, where Keeling conducted his research, has a webpage dedicated to the Keeling Curve that provides background information and context on the history of the curve[10].
  • The National Oceanic and Atmospheric Administration (NOAA) provides a data visualisation of the Keeling Curve on its website, as well as background information on the significance of the curve[11].
  • The United Nations Framework Convention on Climate Change (UNFCCC) references the Keeling Curve in its work on climate change and provides information on the impacts of increasing atmospheric CO2 levels[12].

Citation: 28th November 2022 – Mauna Loa eruption as viewed from Waikoloa at about 1:25am local time (HST). The eruption is occurring from the summit of the volcano, though lava has overflowed the caldera.
Attribution: United States Geological Survey, Public domain, via Wikimedia Commons
Page URL:

What causes Mauna Loa to Erupt
Mauna Loa, located on the Big Island of Hawaii, is one of the world’s most active and massive shield volcanoes. The volcano is known for its frequent eruptions, which are caused by a combination of factors, including magma supply, Tectonic Activity, and volcanic gases.

The primary cause of Mauna Loa’s eruptions is the movement of magma from the Earth’s mantle into the volcano’s magma chamber, which is located beneath the volcano’s summit. As the magma rises, it creates pressure that can lead to fissures and cracks in the volcano’s surface, allowing magma to escape and form lava flows.

Tectonic activity also plays a role in Mauna Loa’s eruptions. The volcano sits on the Pacific Plate, which is slowly moving northwest over a stationary hotspot beneath the Earth’s crust. As the plate moves, it carries the volcano away from the hotspot, causing a decrease in magma supply and a period of dormancy. However, as the volcano approaches the hotspot again, the magma supply increases, leading to a renewed period of volcanic activity.

Finally, volcanic gases, such as sulphur dioxide, water vapour, and carbon dioxide, can contribute to Mauna Loa’s eruptions. As magma rises to the surface, it releases gases trapped in the molten rock. These gases can build up pressure, causing explosive eruptions, or they can escape from the volcano’s vents, creating lava fountains and flows.

The complex interplay of these factors, including magma supply, tectonic activity, and volcanic gases, contribute to the frequent eruptions of Mauna Loa.

Diagram of the common structural features of a Shield Volcano.

Tectonic Activity: Plate tectonics means ’pertaining to building’ and is the generally accepted scientific theory that considers the Earth‘s lithosphere (see below) to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The Earth’s 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 or more. The crust and upper mantle are distinguished based on chemistry and mineralogy.

Types of Volcanoes[13]
Mauna Loa is a shield volcano – characterised by gentle, sloping sides and a large, broad shape resembling a shield. These volcanoes are formed by the accumulation of many layers of thin, fluid lava flows, which travel long distances before solidifying. The lava is typically low in viscosity and has a low gas content, which allows it to flow more easily than the thick, sticky lava of other types of volcanoes. Usually, shield volcanoes are not very explosive, and their eruptions are distinguished by the effusion of lava flows. For more information about shield volcanoes, visit the United States Geological Survey website[14].

Other types of volcanoes include stratovolcanoes (also known as composite volcanoes), cinder cone volcanoes, and lava dome volcanoes:

  • Stratovolcanoes are tall, steep-sided volcanoes formed by alternating layers of lava, ash, and other volcanic debris. They are typically more explosive than shield volcanoes and can produce pyroclastic flows and lahars.
  • Cinder cone volcanoes are small, steep-sided volcanoes that are formed by explosive eruptions of tephra (small, loose volcanic fragments).
  • Lava dome volcanoes are formed by viscous lava flows that solidify and form a pile around a vent, creating a dome-shaped structure.

Further Explanations [15]

  • Lahars: A type of volcanic mudflow that can be caused by various volcanic activities, including eruptions, landslides, and melting snow or ice. Lahars can be extremely dangerous and destructive, as they can travel long distances from the volcano and bury entire communities. For more information, visit the USGS website on Lahars.[16]
  • Pyroclastic flows: Avalanches of hot volcanic debris, gas, and ash that can travel down the slopes of a volcano at high speeds, often causing widespread destruction. Pyroclastic flows are one of the most dangerous hazards associated with volcanic eruptions and can cause severe burns, asphyxiation, and other injuries. For more information, visit the USGS website on pyroclastic flows.[17]
  • Tephra: A general term used to describe any form of volcanic material ejected into the air during an eruption, including ash, pumice, and volcanic bombs. Tephra can be carried long distances by the wind and can cause a variety of hazards, including respiratory problems, structural damage, and aviation hazards. For more information, visit the USGS website on tephra.[18]
  • Viscous lava: Lava that is thick and sticky, so it does not flow easily. Viscous lava is often associated with explosive eruptions and can form lava domes or flows that pile up near the vent of a volcano. For more information, you can visit the USGS website on lava viscosity.[19]

While Mauna Loa has had numerous eruptions in modern times, there have been no recorded fatalities directly caused by these eruptions. This is due to the fact that Mauna Loa’s eruptions are generally characterised by the effusion of lava flows, which move slowly enough to allow people to evacuate from the areas at risk. However, there have been cases where people have been injured or lost property due to Mauna Loa’s eruptions.

It is worth noting that while there have been no fatalities directly caused by Mauna Loa’s eruptions, there have been deaths and injuries resulting from volcanic gases and other hazards associated with the volcano. For example, in 2002, a hiker died from exposure to high levels of sulphur dioxide gas while hiking in Mauna Loa’s southwest rift zone. In addition, volcanic gas emissions from Mauna Loa and neighbouring Kilauea volcano have been known to cause health problems such as respiratory issues for people living downwind.

While Mauna Loa is an active volcano and can pose risks to people and property in its vicinity, there have been no fatalities directly caused by its eruptions in modern times. The lack of deaths directly caused by Mauna Loa’s eruptions is a testament to the effectiveness of monitoring and evacuation efforts by local authorities. While volcanic hazards cannot always be predicted accurately, early warning systems and public education campaigns can help mitigate their impact on people and property.

Chronological List of Eruptions of Mauna Loa since 1843

  • 1843: 13th to 21st May
  • 1851: 18th to 28th September
  • 1852: 2nd and 3rd February
  • 1855: 5th to 9th November
  • 1859: 21st February to 16th March
  • 1868: 23rd to 26th January
  • 1880: 26th August to 17th September
  • 1887: 9th to 31st January
  • 1903: 20th September to 10th October
  • 1916: 20th to 26th June
  • 1919: 2nd to 8th July
  • 1926: 2nd to 10th July
  • 1950: 10th November to 4th December
  • 1952: 11th March to 15th April
  • 1955: 2nd to 23rd July
  • 1959: 25th March to 8th April
  • 1960: 23rd to 28th December
  • 1962: 12th to 26th April
  • 1965: 17th to 20th August
  • 1968: 21st to 23rd December
  • 1970: 5th to 16th November
  • 1975: 5th and 6th July
  • 1984: 25th March to 15th April
  • 2022: 27th November to 13th December

As mentioned earlier, Mauna Loa erupted in 1916 during World War I, but it did not erupt at all during World War II. The reason for this difference is not well understood, but it is likely due to the complex interplay of the factors that cause volcanic eruptions.

One possibility is that the decreased human activity during World War II may have led to a decrease in the volcanic gases emitted from nearby industrial and agricultural activities. Volcanic gases, such as sulphur dioxide, can contribute to volcanic eruptions, and a decrease in their emission could have reduced the likelihood of an eruption.

Another possibility is that changes in the stress on the volcano caused by tectonic activity or changes in the magma supply may have been different during World War II than they were during World War I. These changes in stress could have affected the volcano’s ability to erupt.

It is also possible that the lack of eruptions during World War II was simply a coincidence, as Mauna Loa is a highly complex and unpredictable system, and the timing and frequency of its eruptions can be difficult to predict.

Worth noting is that there is still much that scientists do not fully understand about the complex processes that lead to volcanic eruptions, and the timing and duration of eruptions can vary widely. It should not be forgotten that Mauna Loa is an active volcano, and future eruptions are possible. The Hawaiian Volcano Observatory closely monitors the volcano’s activity and provides regular updates on any changes in the volcano’s seismicity, deformation, and gas emissions.

Mauna Loa’s 19th Century Eruptions[20]
Mauna Loa’s first well-documented eruption occurred on 13th May 1843 and lasted about three weeks. It produced a large lava flow that travelled over 32 kilometres (20 miles) from the vent, reaching the ocean in some places. The eruption also produced a large amount of gas and ash, which created a thick haze over the island of Hawaii. This eruption was significant because it was the first time Western scientists had been present to observe and record a volcanic eruption in Hawaii.

The eruption of Mauna Loa in the spring of 1868 and the deadly phenomena surrounding it were one of the greatest natural disasters in Hawaiian history. Seventy-seven Hawaiians died in the associated tsunami and landslides. As with most eruptions of Mauna Loa, the 1868 eruption began at its summit caldera, Moku’āweoweo.


  • Caldera: A large, circular depression that forms at the summit of a volcano after a large eruption. Calderas can develop when the roof of a magma chamber collapses, causing the volcano to collapse into the void below. Calderas can be several kilometres wide and can be filled with water to form crater lakes. For more information, visit the USGS website on calderas[21] or the Global Volcanism Program page on calderas[22].

Sources/Usage: Public Domain. URL:
Aerial image of fissure 3 on Mauna Loa’s Northeast Rift Zone erupting the morning of November 30, 2022.  Fissure 3 remains the dominant source of the largest lava flow being generated during the eruption. USGS image by K. Mulliken. 

Sources and Further Reading



CAUTION: This paper is compiled from the sources stated but has not been externally reviewed. Parts of this paper include information provided via artificial intelligence which, although checked by the author, is not always accurate or reliable. Neither we nor any third parties provide any warranty or guarantee as to the accuracy, timeliness, performance, completeness or suitability of the information and materials covered in this paper for any particular purpose. Such information and materials may contain inaccuracies or errors and we expressly exclude liability for any such inaccuracies or errors to the fullest extent permitted by law. Your use of any information or materials on this website is entirely at your own risk, for which we shall not be liable. It shall be your own responsibility to ensure that any products, services or information available through this paper meet your specific requirements and you should neither take action nor exercise inaction without taking appropriate professional advice. The hyperlinks were current at the date of publication.

End Notes and Explanations

  1. Sources: Compiled from research using information at the sources stated throughout the text, together with information provided by machine-generated artificial intelligence at: [chat] and
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  7. Sources: “Mauna Loa.” United States Geological Survey., “Mauna Loa.” National Park Service., “Mauna Loa Observatory.” National Oceanic and Atmospheric Administration., “Mauna Loa: Facts & Information.” Live Science. and “Mauna Loa.” Encyclopaedia Britannica. Information provided by artificial intelligence at:
  8. Source: Naomi Oreskes (23 January 2017). Climate Disruption (video). Awesome Documentaries TV. Cited at:
  9. Source:  Nisbet, Euan (2007). “Cinderella science” (PDF). Nature. 450 (7171): 789–790. doi:10.1038/450789aPMID 18063983. Cited at:
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  12. At: CO2-measurements
  13. “Types of Volcanoes.” National Geographic.
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  15. Information provided by artificial intelligence at:
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  20. See: “Mauna Loa.” United States Geological Survey., “Mauna Loa.” National Park Service., and “Mauna Loa: Facts & Information.” Live Science.
  21. See:
  22. See:


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