Nevado Del Ruiz

When the concept of volcanic catastrophe is brought to mind, most people envision large-scale plinian eruptions such as Mt. St. Helen’s famous lateral blast, or Pinatubo’s majestic VEI-6 eruption in 1991.

Large eruptions in theory do pose a greater risk to local inhabitants than small eruptions would, but that doesn’t necessarily mean you need a large eruption to cause a catastrophe. In 1985, this concept was proven when Nevado Del Ruiz woke up with a VEI-3 eruption that is responsible for one of the greatest natural disasters in history.

Background on Ruiz’s Recent History

Around the time of 1984, Nevado Del Ruiz had started to see an incline in overall activity, including increased seismicity, increased sulphur emissions, and bursts of small phreataic eruptions. By November 1985, Ruiz reached a tipping point and finally erupted. Geologists noticed a cluster of long-period earthquakes prior to it’s signature eruption, but unfortunately failed to identify it as a tell-tale precursor of an eruption.

The 1985 eruption was not particularly large on a geologic scale. VEI-3 events happen almost every year, and sometimes may occur multiple times within a single year. The problem with Ruiz is that it doesn’t require large eruptions to devastate the surrounding landscape. Much like Mt. Rainier, the most notable facet to the Ruiz summit is the massive glacier that sits on top.

Aftermath of the 1985 Armero Lahar ( Image Wikimedia Commons.)

Aftermath of the 1985 Armero Lahar ( Image Wikimedia Commons.

When Ruiz erupted in 1985, there was just enough heat to melt a large portion of the glacier perched on top of the summit, which created an unimaginably large lahar. This Lahar swept down the mountain’s slopes and wiped the community of Armero from the face of the earth. The event was so devastating, that only 1/4 of the community’s residents survived, leaving approximately 23,000 people dead within a very short period from the initial eruption.

Current Risk Mitigation

After the 1985 disaster, Colombian authorities knew what they were dealing with, and made it a point to actively prevent risk associated with another eruption. While residents still have the 1985 event in mind, it is estimated that around 500,000 people are still at risk if Ruiz were to suffer another eruption similar to the event in 1985. The primary issue authorities face is that Lahars can travel incredibly fast, and in an extremely short period of time, the Ruiz Lahars can reach a distance of over 75km from the summit of the volcano.

Thankfully, Ingeominas, the Colombian authority is much more prepared now for a potential eruption, and they have taken steps to reduce any possible tragedy that could occur.

Is another Eruption Imminent?

As of 2010, Ruiz once again started to experience activity similar to what started occurring in 1984 prior to the 1985 eruption. Earthquake swarms, increased sulphur emissions, and eventual phreatic eruptions caused authorities to evacuate residents in 2012, and eventually the volcano did experience a minor ash eruption which was likely caused by a phreatic explosion. After this event, the volcano briefly died down in activity before experiencing more vigorous activity as of April 2013.

In April 2013, a large earthquake swarm started in a zone approximately 6-7km below the Arenas crater. The swarm has yet to stop since early April, and has since risen from 6-7km deep to 3-5km in depth. Since the commencement of the swarm, there have been over 17 events that have registered larger than 2.5m in magnitude, including several events that registered 4.0.

Additional to earthquakes, deformation, increased sulphur deposition, and increased fumarolic activity has been noticed since the advent of the April earthquake swarm.

All these events point to the likelihood of a magmatic eruption, which hasn’t been seen at Ruiz since the 1985 event. Keep in mind, volcanoes are not predictable, and Ruiz could easily cool down and hold off on erupting at any time. Ingeominas currently has the volcano on yellow alert, although if the trend continues, it would seem logical for the volcano to be upgraded to an orange alert status if the swarm continues to rise.

One thing to note is that if a magmatic eruption were to occur in the coming months, that would represent an uncharacteristically short repose time between eruptions based off the brief eruptive history we’ve seen in the last 6000 years or so.

What To Expect if Ruiz Erupts?

Ruiz’s magma like many stratovolcanoes in Colombia is dacitic in nature. Dacitic magma is quite viscous, which traditionally leads to more explosive eruptions. For comparison, Mt. St. Helens and Pinatubo also are dacitic volcanoes, which partially explains their violent eruptive histories.

While Ruiz does have the magma for more explosive eruptions, it has been relatively benign in terms of eruptive power in the last 11,000 years. In the last 11,000 years, most of the eruptions of Ruiz have been similar to the 1985 eruption, with numerous VEI 2, 3, and an occasional VEI 4 eruption occurring. As was previously mentioned, most of the damage and destruction that has occurred in this period has been a result of landslides and glacial melting resulting in large-scale debris avalanches and lahars.

(Image: WIkimedia Commons )

The glacier clad Ruiz edifice is constructed over numerous caldera structures, some which are as large as 10km across. (Image: WIkimedia Commons )

While it’s most likely an eruption would be relatively similar to the 1985 eruption, Ruiz has had a very long past, and hasn’t always been so benign. Ruiz has gone through three separate periods in it’s 1.7 million year history, and the current period is relatively young in a geological time scale. The prior two eruptive periods were characterized by massive caldera forming eruptions, with multiple calderas (some as large as 10km across) that would indicate eruptions that would dwarf Mt. St Helens’ famous eruption. It would probably be a safe assumption to believe that Ruiz also experienced many smaller events during those time periods, but such smaller eruptions are difficult to spot and stratify, whereas massive eruptions are much easier to spot over long time periods.

One of the greatest risks that has a decent chance to occur would be some form of slope failure or edifice collapse. The Ruiz summit has been greatly destabilized by glaciation coupled with the greater hydrothermal system within the edifice, and there have been multiple instances of slope failures and landslides in the last 11,000 years.

While the most likely risk for a magmatic eruption would be a mid-sized event that creates large lahars, Ruiz really has the potential to do anything she pleases, and can’t be discounted by the local residents and government.

Cbus20122

Update: Hazard map added so one can see how far from the volcano Armero really is.

Nevado del Ruiz hazard map, from Wright and Pierson

Nevado del Ruiz hazard map, from Wright and Pierson

Spica

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199 thoughts on “Nevado Del Ruiz

      • Good morning/ evening Renato. How’s things with you? Busy time I guess with end of year exams etc.
        Yup! Reykjanes Ridge and onto the peninsula is certainly rocking this morning!
        http://en.vedur.is/earthquakes-and-volcanism/earthquakes/
        off early to Hospital appt. Routine blood tests and a compulsory time for doing nothing but sitting and reading. I have my Kindle charged and ready 😀

        • Just a note. Hekla strain is dropping. The Reykjanes quakes show on the seismicity plot but not on the HEK strain. Why does a large quake in SE Asia show up there and not a local 3+ M Is it because 3+M really isn’t that big?
          (Again it’s a case of what I DON’T see that is interesting)

          • Diana, regarding STRAIN GRAPHS AROUND HEKLA.

            The strain changes accordingly to atmospheric pressure.

            Atmospheric pressure rising causing rising strain, and the other way around. Currently atmospheric pressure is lowering, thus you see the strain lowering in all 4 stations at same time! It is NOT because of something at Hekla rising and lowering tension. Unless the pattern only shows up at Hekla, and not the other stations.

            The waving motion up and down is related to tides, which occurs every 6 hours.

            That’s why the waves highs and lows occurs at same time in the four graphs, as well as the latest decreasing strain in all four stations, related to decreasing atmospheric pressure. The same pattern can also be seen in the Icelandic TREMOR GRAPHS! Which by the way are strongly affected by wind, car traffic, far away ocean waves, and other noise.

            However sudden slips in Hekla, which are not visible in other stations, indicate changes occuring at Hekla (a transient).

            And to make everyone a little bit more knowledgable: Burfell is a station near Hekla, some 15km northwest, which usually shows big changes before an eruption, but Burfell is outside of the proper volcanic system of Hekla. STO and Hella are quite far away, more than 25 km, so in principle they will only show something when an eruption has already started or it is about to do it. They are good spots to watch an eruption of Hekla, and are populated areas.

            These last two stations are within the SISZ, so they are more affected probably by tectonic behaviors such as large earthquakes. Although they are quite far away from the other edge of SISZ, further west, near Hengill. And probably do not show anything occuring there.

          • Yes, interesting question Diana!

            Icelandic SILS in general always show very big quakes occuring ijn the world, but never M3 quakes if they are quite “far away”, like a 150km distance between Reykjanes and Hekla.

            But if a M4 or M5 would occur in Reykjanes, they would certaintly pick a sign.

            Same thing for tremor linked to volcanoes. Small events like ocasional harmonic tremor at Katla, Grimsvotn, Hamarinn (something like a hydrothermal bump) only shows in SILS around that region but not everywhere else. An eruption however shows everywhere across Iceland, especially if its large.

            • Thank you so much Irpsit. That has answered my questions really well. I now understand a little more. A very concise and informative comment which could possibly be retained in the Dragon’s Hord. under ” What’s happening in Iceland”

            • The prophet of the Day award goes to Irpsit for saying that a M4 event would show on the strainmeters. A few minutes later it showed 🙂

      • Earthquakes in Reykjanes, especially small ones like a M3, CANNOT trigger anything on Hekla. Things have to be BIG to trigger something else far away.

        I can give examples of events that triggered other events, and events that did not triggered other events.

        Eyjafjallajokull eruption did not trigger anything at Katla, and this was a particualrly big one at Eyja.

        A large earthquake in SISZ in 2000 (if I am not wrong) triggered minor earthquakes all the way up to Langokull and all the way down to Reykjanes, including dramatic changes clearly visible in the lake at Krisuvik. That earthquake was a M6.5.

        Small earthquakes even up to M4 usually never triggered anything nearby. Earthquakes M5 can trigger small events not so far away from the spot of action, like in Tjornes, the event last year triggered minor quakes in neighbour fractures.

        Also in 1996, a large M5 suddently occured in Bardarbunga. Quickly swarms started in Grimsvotn and a few days later an eruption occurs there.

        Also the quake in south Iceland 2000 occurred a few months after an eruption of Hekla, but that could have been a coincidence too.

        However, a more interesting coincidence occurred in 1783. After Laki event, there was a very large M6 or M7 quake in southwest Iceland, in Thingvellir. In my opinnion, perhaps the Laki event triggered that fault which was already probably due to slap.

        Also, in 1975 eruptions started on and off in Krafla. In 1976 a big one quake occurred in Tjornes. I think the tectonic-volcanic events of Krafla probably triggered the events in Tjornes further north.

        These triggers are all a question of intensity and proximity.

        Quakes far out in the Atlantic cannot trigger anything in Iceland, unless they would be of a monster type of intensity.

        • Thanks for the feedback, Irpsit. I thought this swarm at Reykjanes ridge would last longer, as they usually do. They do affect tremor readings but aren’t strong enough to interfere with the strain meters. Cool.
          Morning Diana and everyone!

          • You are not a great prophet my friend!
            You just wrote that it did not happen and affect, and a new phase of the swarm started with a 4.1 that affected the strainmeters. 🙂

  1. Just had another big one, bigger than this morning. I’m at the airport and didnt feel it. I’m going to make me a makeshift quake alarm system. (A coin hanging from a rubberband up against a metal pipe.)

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