What is the Difference Between Active and Dormant Volcanoes?

Volcanoes are an impressive force of nature. Physically, they dominate the landscape, and have an active role in shaping our planet’s geography. When they are actively erupting, they are an extremely dangerous and destructive force. But when they are passive, the soil they enrich can become very fertile, leading to settlements and cities being built nearby.

Such is the nature of volcanoes, and is the reason why we distinguish between those that are “active” and those that are “dormant”. But what exactly is the differences between the two, and how do geologists tell? This is actually a complicated question, because there’s no way to know for sure if a volcano is all done erupting, or if it’s going to become active again.

Put simply, the most popular way for classifying volcanoes comes down to the frequency of their eruption. Those that erupt regularly are called active, while those that have erupted in historical times but are now quiet are called dormant (or inactive). But in the end, knowing the difference all comes down to timing!

Sarychev volcano, (located in Russia's Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA
Sarychev volcano, (located in Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA

Active Volcano:

Currently, there is no consensus among volcanologists about what constitutes “active”. Volcanoes – like all geological features – can have very long lifespans, varying between months to even millions of years. In the past few thousand years, many of Earth’s volcanoes have erupted many times over, but currently show no signs of impending eruption.

As such, the term “active” can mean only active in terms of human lifespans, which are entirely different from the lifespans of volcanoes. Hence why scientists often consider a volcano to be active only if it is showing signs of unrest (i.e. unusual earthquake activity or significant new gas emissions) that mean it is about to erupt.

The Smithsonian Global Volcanism Program defines a volcano as active only if it has erupted in the last 10,000 years. Another means for determining if a volcano is active comes from the International Association of Volcanology, who use historical time as a reference (i.e. recorded history).

Aleutian island #volcano letting off a little steam after the new year on Jan 2, 2016. #YearInSpace. Credit: NASA/Scott Kelly/@StationCDRKelly
Aleutian island #volcano letting off a little steam after the new year on Jan 2, 2016. #YearInSpace. Credit: NASA/Scott Kelly/@StationCDRKelly

By this definition, those volcanoes that have erupted in the course of human history (which includes more than 500 volcanoes) are defined as active. However, this too is problematic, since this varies from region to region – with some areas cataloging volcanoes for thousands of years, while others only have records for the past few centuries.

As such, an “active volcano” can be best described as one that’s currently in a state of regular eruptions. Maybe it’s going off right now, or had an event in the last few decades, or geologists expect it to erupt again very soon. In short, if its spewing fire or likely to again in the near future, then it’s active!

Dormant Volcano:

Meanwhile, a dormant volcano is used to refer to those that are capable of erupting, and will probably erupt again in the future, but hasn’t had an eruption for a very long time. Here too, definitions become complicated since it is difficult to distinguish between a volcano that is simply not active at present, and one that will remain inactive.

Volcanoes are often considered to be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant for a long period of time. For instance, the volcanoes of Yellowstone, Toba, and Vesuvius were all thought to be extinct before their historic and devastating eruptions.

The area around the Vesuvius volcano is now densely populated. Credit: Wikipedia Commons/Jeffmatt
The area around Mount Vesuvius, which erupted in 79 CE, is now densely populated. Credit: Wikipedia Commons/Jeffmatt

The same is true of the Fourpeaked Mountain eruption in Alaska in 2006. Prior to this, the volcano was thought to be extinct since it had not erupted for over 10,000 years. Compare that to Mount Grímsvötn in south-east Iceland, which erupted three times in the past 12 years (in 2011, 2008 and 2004, respectively).

And so a dormant volcano is actually part of the active volcano classification, it’s just that it’s not currently erupting.

Extinct Volcano:

Geologists also employ the category of extinct volcano to refer to volcanoes that have become cut off from their magma supply. There are many examples of extinct volcanoes around the world, many of which are found in the Hawaiian-Emperor Seamount Chain in the Pacific Ocean, or stand individually in some areas.

For example, the Shiprock volcano, which stands in Navajo Nation territory in New Mexico, is an example of a solitary extinct volcano. Edinburgh Castle, located just outside the capitol of Edinburgh, Scotland, is famously located atop an extinct volcano.

An aerial image of the Shiprock extinct volcano. Credit: Wikipedia Commons
Aerial photograph of the Shiprock extinct volcano. Credit: Wikipedia Commons

But of course, determining if a volcano is truly extinct is often difficult, since some volcanoes can have eruptive lifespans that measure into the millions of years. As such, some volcanologists refer to extinct volcanoes as inactive, and some volcanoes once thought to be extinct are now referred to as dormant.

In short, knowing if a volcano is active, dormant, or extinct is complicated and all comes down to timing. And when it comes to geological features, timing is quite difficult for us mere mortals. Individuals and generations have limited life spans, nations rise and fall, and even entire civilization sometimes bite the dust.

But volcanic formations? They can endure for millions of years! Knowing if there still life in them requires hard work, good record-keeping, and (above all) immense patience.

We have written many articles about volcanoes for Universe Today. Here’s Ten Interesting Facts About Volcanoes, What are the Different Types of Volcanoes?, How Do Volcanoes Erupt?, What is a Volcano Conduit?, and What are the Benefits of Volcanoes?

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

Sources:

Stunning Photo of Volcanic Lightning at Volcán de Colima in Mexico

The Colima volcano in Mexico is active again, and has been spewing out large plumes of ash nearly 3 kilometers into the air. Astrophotographer César Cantú captured this spectacular picture of lightning slicing through the cloud of ash.

How can lightning strike in an ash cloud? Through friction, particles of the ash can charge each other by rubbing against each other during the eruption. When the energy is discharged, it can create lightning bolts.

The Colima volcano is one of the most active volcanoes in Mexico, and is also called ‘Volcán de Fuego’ or ‘Fire volcano.’ It has erupted more than 40 times since the first documented eruption in 1576.

The latest news on this current eruption is that local authorities have put the volcano on a yellow alert, meaning the volcano is showing increased activity, and residents who live nearby should prepare for a possible evacuation.

Stay safe César, and thanks for sharing your image with Universe Today! See a larger version on his website here.

Volcanic Blast Forms New Island Near Japan

A volcanic eruption is creating a tiny new island off the coast of Japan. The Japanese Coast Guard snapped images and video of the eruption taking place, showing the new island being formed. Footage showed heavy smoke, ash and rocks spewing from the volcanic crater. As of this writing, experts say the small island is about 200 meters (660 feet) in diameter. It is located just off the coast of Nishinoshima, a small, uninhabited island in the Ogasawara chain, also known as the Bonin Islands, about about 620 miles (1,000 km) south of Tokyo.

See a video and additional images below.

Only time will tell if the island will remain or if the ocean waters will reclaim it. According to Yahoo News, Japan’s chief government spokesman said they would welcome any new territory.

“This has happened before and in some cases the islands disappeared,” Yoshihide Suga said when asked if the government was planning on naming the new island. “If it becomes a full-fledged island, we would be happy to have more territory.”

An erupting undersea volcano forms a new island, shown by its nearest neighbor, Nishinoshima, a small unihabited island in the southern Ogasawara chain of islands. The image was taken on November 21, 2013 by the Japanese Coast Guard.
An erupting undersea volcano forms a new island, shown by its nearest neighbor, Nishinoshima, a small unihabited island in the southern Ogasawara chain of islands. The image was taken on November 21, 2013 by the Japanese Coast Guard.
This screenshot of Google Maps shows all the volcanoes in the The Japan, Taiwan, Marianas Region. Via Google Maps and the Smithsonian volcano website.
This screenshot of Google Maps shows all the volcanoes in the The Japan, Taiwan, Marianas Region. Via Google Maps and the Smithsonian volcano website.

According to the Smithsonian Global Volcanism Program website, the Japan, Taiwan, Marianas Region is a very active region in the Pacific Ring of Fire and most volcanoes in this region “result from subduction of westward-moving oceanic crust under the Asian Plate. In the Izu-Mariana chain, however, the crust to the west is also oceanic, forming more basaltic island arcs (but with volcanoes that are far more explosive than oceanic hotspot volcanoes).”

You can read more about this volcanic region here.

See an extensive gallery of images at Yahoo News.

Spectacular Eruptions of Mt. Etna in Sicily from Space and Earth

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Spectacular eruptions from Mt Etna are spewing massive quantities of lava, smoke and ash many hundreds of meters high into the skies above the island of Sicily. Mt Etna is the most active volcano in Europe and one of the most active on all of Earth. The volcano rumbled to life again this week on the evening of January 12, 2011 and lit up the night sky. Mt Etna is 3350 meters high and located on the northeast coast of Sicily near the boot of Italy (see above, below).

Updated: comment or send me your Etna erupting photos/accounts to post below.
This fearsome natural wonder is providing an awe inspiring show from both Earth and Space. Local residents and lucky tourists nearby took stunning videos and photos (below) showing fountains of brilliant lava eruptions streaming mightily from the volcano.

This Envisat MERIS image, acquired on 11 January 2011, shows the plume of smoke billowing into the atmosphere from Mount Etna, Sicily, Italy. Activity gradually increased the following day, peaking in the evening. Credits: ESA
Click to Enlarge all images

Amazing photos from space were captured by Earth orbiting satellites from NASA and ESA. NASA’s Terra satellite took the above image on Jan. 11 as Mt Etna was spewing forth smoke or ash just prior to the volcanic eruptions on Jan. 12. The photo of Etna is NASA’s Earth Observatory Image of the Day, today, Jan. 15, 2011.

ESA’s Envisat likewise snapped a gorgeous view of the billowing plume of smoke rising to space (photo at left) and the international crew aboard the ISS, which currently includes Italian astronaut Paolo Nespoli. Perhaps he’ll send us a shot !

Local news and eyewitness accounts say that tremors from the volcano began increasing on Jan. 11. Emissions of volcanic gases and water vapor have been ongoing since late September 2010. The sounds of explosive tremors from deep inside were also detected months ago.

This sizzling hot video – “Etna at Maximum Activity” – is set to music and records the magnificent flowing streams of lava and the thunderous sounds of the crackling, explosive eruptions. Be sure to view at full screen, then just sit back and enjoy !

Plumes of volcanic ash from the eruptions spread across Sicily and forced the closure of the local Fontanarossa airport – nearby to the city of Catania, which is 24 kilometers away.

Rumblings of Mt Etna have been recorded in historical documents dating back to about 1500 BC.

Another short, dramatic video with the raw sounds of the eruption from a group of German tourists visiting the beautiful city of Taormina, Sicily

Eyewitness Description:
“Mount Etna erupted in the evening of January 12, 2011 for around four hours, providing an amazing scenery. We shot this unique video from Taormina on January 12, 2011 at 11.45 p.m. and uploaded it on YouTube.


On the evening of 11th January 2011 an increase in volcanic tremor was recorded at the summit of the volcano. The recorded seismic activity reached a peak at 7 a.m. on 12th January when the source moved from north of NE crater to the SE crater. The eruption started with strombolian explosive activity at SE crater at around 9.p.m. Lava overflowed the eastern rim of SE crater and fed a flow that moved toward the western wall of the Valle del Bove (Valley of the oxen), an ancient huge uninhabited depression on the NE side of the volcano.

The Sicilian communities near the volcano were not threatened by this latest fascinating eruption. Best place to watch the fascinating eruptions of Mount Etna is the town of Taormina, nestled on a hill at 220 meters / 722 feet above the sea level and at a safe linear distance of approx. 28 Km / 17,4 miles from the top craters of the Sicilian volcano.”

Fearsome lava eruptions spewing from Mt Etna on Jan. 11, 2011

A few years back, I visited Mt Etna and was incredibly lucky to witness this spectacle of nature myself. It was an unforgettable experience to see the glowing red-orange colored lava flowing out from the bowels of the Earth. It was like a living being with circulating blood.

In the excitement, I did something that in retrospect was incredibly stupid. I stood on a ledge, perhaps 50 cm thick, right above the porthole of the scalding hot lava erupting from the earth beneath my feet. Many others did too.

Sicily is a lovely place of manmade and natural wonders. Don’t pass up an opportunity to see Etna aflame

Look at Etnaweb (in Italian, but Universal) for a fantastic collection of local photos and webcams of the eruption.

Volcanic eruptions are breathtaking events to behold. The residual plumes of smoke and ash can stay aloft for many years and can also effect how we see other astronomical events such as our view of solar and lunar eclipses.

For a more tranquil view of Earth and inspiration from Carl Sagan, click here

NASA’s Spirit robot is positioned next to an ancient and extinct volcanic feature on Mars. Learn more here

Can you envision a place hotter than Etna ? … A scorching, molten hellish world where the temperatures are unimaginably hot

Read about a newly detected Earth-sized planet with lava flows vastly hotter than Etna – or anywhere on Earth for that matter – in this story about a historic new discovery from NASA’s Kepler space telescope

Comment or send me your photos and eyewitness accounts of erupting Mt Etna

Signs of activity at the summit of Mount Etna, Europe’s most active volcano.
Water vapor and other volcanic gases overflow Etna’s summit craters, spilling out over the volcano’s upper slopes. A steam plume rises from a collapse pit that formed in late 2009, the newest volcanic feature on Etna. Dark lava flows from recent eruptions cover the peak, overlaying lighter, weathered flows from hundreds or thousands of years ago. (Numbers on the image indicate when a flow was erupted.) The oldest lavas are covered by green vegetation. Eruptive cones and fissures also dot the landscape. Frequent explosions deep within the Northeast Crater, which may presage an upcoming eruption, are audible at the summit. These explosions were occurring sporadically every few minutes, as recorded by nearby seismometers. This natural-color satellite image was acquired by the Advanced Land Imager (ALI) aboard (EO-1) on September 26, 2010.
Mt Etna photographed by astronauts aboard the International Space Station on August, 2, 2006.
One of the most consistently active volcanoes in the world, Sicily’s Mount Etna has a historical record of eruptions dating back to 1500 BC. This astronaut photograph captures plumes of steam and possibly ash originating from summit craters on the mountain: the Northeast Crater and Central Crater, which includes two secondary craters (Voragine and Bocca Nuova). Locals heard explosions coming from the rim of the Northeast Crater on July 26, 2006, and the plumes shown in this image are likely a continuation of that activity. Credit: NASA.