Volcanoes from a distant world: The 1979 eruptions of Pele and Loki on Io

Figure 1. Volcanic eruptions on Io. Images are from NASA and were compiled by Lopes and Williams (2015).

Figure 1. Volcanic eruptions on Io. Images are from NASA and were compiled by Lopes and Williams (2015).

We will continue with our look at Revolutionary Eruptions in this post by traveling 365 million miles to an alien world, a world teeming with volcanic activity, a world where surface temperatures average 202˚F below zero, a world that looks a lot like a pizza. In doing so, we’ll see the importance of tying together the ethereal inquiry of scientific theory and the grounding truth of observation.

Volcanoes are not just confined to the habitable mass of silicates and iron we call Earth. Volcanism is ubiquitous throughout the solar system, and beyond. There is no better example of extraterrestrial volcanism than there is on Io (Fig. 1), one of four large moons of Jupiter known as Galilean satellites. Io was quite enigmatic for a period following its discovery by Galileo Galilei in 1610. Our understanding of Io took a great stride forward during the flybys of Voyager 1 and 2 spacecraft in 1979. Days before the first flyby, a landmark study argued that the gravitational influence of Jupiter and its other moons exert a massive tidal force on Io’s solid body. The tides have an amplitude of 330 ft! The authors of the study suggested that friction from the internal stretching of the moon results in astronomical heat production. The heat, they predicted, is vented by pervasive volcanism*.

Figure 2. Eruptions on Io. This picture, taken on March 8, 1979, was our first close view of Io. Two volcanic plumes (or billowing clouds of ash and gases), indicating concurrent eruptions of two volcanoes, are visible. Image is from NASA.

Figure 2. Eruptions on Io. This picture, taken on March 8, 1979, was our first close view of Io. Two volcanic plumes (or billowing clouds of ash and gases), indicating concurrent eruptions of two volcanoes, are visible. Image is from NASA.

Voyager 1 gave us our first close view of Io in March 1979 (Fig. 2). In the grainy first images relayed back to Earth, scientists at NASA discovered what looked like two billowing clouds of ash and gas called volcanic plumes. Thermal mapping of the surface of Io by Voyager 1 showed abnormally high temperatures in specific regions, one of which corresponding with a suspected plume. The images and thermal mapping together were strong evidence of vigorous volcanism on Io. Four months later, the flyby of Voyager 2 occurred. By this time, the eruption of one volcano, Pele, had ceased (Fig. 3). The eruption appeared to have deposit material that filled in an area of 10,000 km2!

Figure 3. Volcanic deposit on Io. The flyby of Voyager 2 occurred four months after Voyager 1. By this time, the eruption at Pele had ceased. The upper inset image shows Pele during the flyby of Voyager 1. The lower inset image, from Voyager 2, shows a large area surrounding the volcanic vent that has been filled in. Images are from NASA and were compiled by Lopes and Williams (2015).

Figure 3. Volcanic deposit on Io. The flyby of Voyager 2 occurred four months after Voyager 1. By this time, the eruption at Pele had ceased. The upper inset image shows Pele during the flyby of Voyager 1. The lower inset image, from Voyager 2, shows a large area surrounding the volcanic vent that has been filled in. Images are from NASA and were compiled by Lopes and Williams (2015).

There have been no fewer than 5 NASA missions that have informed our view of Io. Our picture of Io is coming in to focus, and we can now see that it is a world of the imagination. Io’s surface is pocked with volcanoes and stained an eerie hue of yellow from their activity (Fig. 4), testament to its status as the most volcanically active body in the solar system. Massive eruptions continuously reshape the surface (Fig. 5). Plumes can reach heights of nearly 190 mi, launching materials clear into space. Jupiter’s hulking mass emits an extraordinary magnetic field, which draws off 1 ton of gases and dust from Io’s atmosphere every second! Io is truly a remarkably unique presence in the solar system.

Figure 4. Surface of Io. In the time since Io’s discovery in 1610, our understanding of this bizarre world has grown with leaps and bounds. This map demonstrates our great progress.

Figure 4. Surface of Io. In the time since Io’s discovery in 1610, our understanding of this bizarre world has grown with leaps and bounds. This map demonstrates our great progress. Image is from NASA.

* Volcanoes are a great way to transport heat from the interior of a planet to the exterior. In fact, that’s why they exist. I will return to this idea in the next post.

Figure 5. Io surface changes.

Figure 5. Io surface changes. Image is from NASA.

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1980 Eruption of Mount St. Helens

In the Plinian phase of the infamous eruption of Mount St. Helens, 520 million tons of ash were hurled – upwards of 80,000 ft – into the air. That’s the mass of over 85 million African elephants (the big ones)! Imagine throwing 85 million elephants 80,000 feet into the air (with parachutes, of course). That would take a lot of energy (remember, one way to consider energy is the acceleration of a mass over a distance, which is known as work, a form of energy). In my first blog post, we compared the energy released from this eruption to that of a staggering 24 megatons of TNT. This week, before we get into the nuts and bolts of how volcanoes work, we’ll have a look at this case study – a specific event (i.e. the eruption of Mount St. Helens) that is used to inform a more general inquiry (i.e. how volcanoes work).

Image of the May 18 eruption of St. Helens. Source: USGS.

Image of the May 18 eruption of St. Helens. Source: USGS.

Fortunately, the eruption, as with most volcanic eruptions, came with warning. Earthquake swarms, the development of a bulge (that grew 5 ft per day), steam explosions, and high surface heat flow all hinted that St. Helens had awoken after a 123 year period of repose.

Then on May 18, after two months of precursory activity, St. Helens lived up to its status as the most active volcano in the Cascades. The eruption began when a magnitude 5+ earthquake triggered a landslide on the north flank where the bulge had been building (Image B). The removal of the large mass of land allowed hot water within the system to expand and explode through the landslide scar (Image C). The massive blast, moving at >300 mi/hr, removed the top ~1000 ft of volcano and felled a dense forest of trees in a 6 mi radius arc. The magma (molten rock) below the volcano was stored at very high pressure, and the removal of the upper cone reduced the confining pressure, unleashing a torrent of rapidly ascending magma (similar to the way a soda bottle that’s been shaken “erupts” after removing the cap). Rapid expansion of hot gases fragmented the ascending magma, causing a massive plume of shattered magma (now, cooled to a glass) and hot gases to be hurtled into the air. Within minutes, the eruptive column reached heights of 15 mi and searing avalanches of hot gas and rocks – known as pyroclastic flows – poured out of the eruptive vent at speeds up to 80 m/hr.

Initiation of the eruption of the May 18 eruption. Source: modified after USGS images.

Initiation of the eruption of the May 18 eruption. Source: modified after USGS images.

The erupted ash traversed the US in 3 days, while the eruption waned, and in the 15 days it took the ash cloud to travel around the world, the eruption ended. The effects of the eruption were devastating. The lives of 57 people were swept away. Over 330 million cubic feet of timber was damaged or destroyed. And the economic impact was severe.

Image: USGS

This series of images show the aftermath of the eruption on the volcanic edifice. Most of the pre-1980 volcanic edifice was built in the last 3000 years, meaning that it was younger than the great pyramids of Egypt! Source: USGS.

I’d like to continue reviewing eruptions that have ushered in profound changes in Earth’s history, such as that of St. Helens. So, look forward to monthly posts on Revolutionary Eruptions. We’ll travel to Mexico in the ’40s, where a volcano emerged in the middle of a cornfield one day. Another eruption we’ll consider gave the northern hemisphere a “year without a summer”. We’ll see volcanic eruptions in distant worlds. And more!

Welcome!

Mt. St. Helens Eruption

Eruption of Mt. St. Helens on May 18, 1980. Photo: USGS

Volcanoes are one of the most beautiful and powerful geologic processes that shape the face of the Earth. The 1980 eruption of Mount St. Helens, a minor affair when put into a geologic perspective, released the energy of about 24 megatons of TNT – equivalent to the energy needed to circumnavigate the Earth in a car well over half a million times. Volcanic recycling of water has filled our oceans. Volcanoes have given birth to our continents. Every atom of carbon and hydrogen in your body (roughly 5 x 10^27, or 5 octillion, atoms, which is equivalent to 28% of our body by mass) has likely been erupted from volcano, perhaps several times, before becoming a building block of your body. Volcanoes are truly a source of intellectual inspiration, but they also have very tangible relevance. Volcanic hazards threaten over 500 million people worldwide, and eruptions are commonplace. At any given time, about 15 volcanoes are erupting*. Gaining a better understanding of how volcanoes operate is undeniably one of our most fundamental endeavors.

This blog is about discovering volcanoes. It’s about what volcanoes are, how they work, and why we study them. It’s my goal to explore volcanoes from the ground up. No background in geology will be required for the journey, but a healthy aptitude for science will be an asset. I hope to provide casual discussion on many fascinating aspects of the inner workings of volcanoes, which are informed by the most current, most cutting-edge research in the field.

A different, perhaps subsidiary, goal is to use this website as a platform for sharing Earth science educational resources. I have taught several geology labs and, as a result, have several teaching aids that I’d like to share.

Rasmussen_Lava

Me and some lava erupting from Kilauea volcano in Hawaii.

And you might be wondering about me, the author. Volcanoes have been the object of my research, excitement, and deepest curiosity for the last several years of my life. Currently, I’m pursuing a Ph.D. at Columbia University and Lamont-Doherty Earth Observatory. I research the transportation and storage of magma, the fuel for volcanoes, in the Aleutian Volcanic Arc, an archipelago of volcanic islands that stretches from Alaska to the Kamchatka peninsula in Russia, and it is for this reason – and my demonstrable claim that this is one of the most fascinating, most volcanically active regions on Earth – that I will commonly use Aleutian volcanoes as examples. Prior to my arrival at Columbia, I was an undergraduate at University of Oregon. I studied processes that generate magmas in the Lassen Peak area of the California Cascades. As a master’s student at New Mexico Tech, I worked on Antarctic volcanoes. I worked on understanding the pre-eruptive behavior of magmatic volatiles (a fundamental component of magma that controls many aspects of the volcanic process). My goal for this project is to share with you my enthusiasm for and knowledge of volcanoes.

Rasmussen_ORCascades

Me collecting explosively-erupted “tephra” near the summit of North Sister volcano in Oregon. Mt. Bachelor, South Sister, and Middle Sister (all volcanoes) look on.

*In future posts, I will return to many of the assertions in the first paragraph and explain them in more detail, but now, I wanted to have a quick discussion on what it means for a volcano to be “erupting”. You might think: erupting? Lava oozing? Ash clouds billowing? It’s true. Those processes can accompany eruptions, but here I define “eruption” as a volcano in a non-normal state. For example, earthquakes might be occurring at the volcano (potential signals of the underground movement of magma) or the volcano might have an abnormally high heat flow (possibly indicating the recent arrival of a shallow magma body). For more, look forward to posts on the volcanic process, the scale and style of volcanic eruptions, volatiles and volcanoes, and volcanoes through time.