Io Afire With Volcanoes Under Juno’s Gaze

An amazingly active Io, Jupiter’s “pizza moon” shows multiple volcanoes and hot spots in this photo taken with Juno’s infrared camera. Credit: NASA / JPL-Caltech / SwRI / ASI / INAF /JIRAM / Roman Tkachenko

Volcanic activity on Io was discovered by Voyager 1 imaging scientist Linda Morabito. She spotted a little bump on Io’s limb while analyzing a Voyager image and thought at first it was an undiscovered moon. Moments later she realized that wasn’t possible — it would have been seen by earthbound telescopes long ago. Morabito and the Voyager team soon came to realize they were seeing a volcanic plume rising 190 miles (300 km) off the surface of Io. It was the first time in history that an active volcano had been detected beyond the Earth. For a wonderful account of the discovery, click here.

Linda Morabito spotted the puzzling plume off Io’s limb in this photo, taken on March 8, 1979, three days after Voyager 1’s encounter with Jupiter. It really does look like another moon poking out from behind Io. A second plume over the terminator (border between day and night) catches the rays of the rising Sun. Credit: NASA / JPL

Today, we know that Io boasts more than 130 active volcanoes with an estimated 400 total, making it the most volcanically active place in the Solar System. Juno used its Jovian Infrared Aurora Mapper (JIRAM) to take spectacular photographs of Io during Perijove 7 last July, when we were all totally absorbed by close up images of Jupiter’s Great Red Spot.

Io is captured here by NASA’s Galileo spacecraft. Deposits of sulfur dioxide frost appear in white and grey hues while yellowish and brownish hues are probably due to other sulfurous materials. Bright red materials, such as the prominent ring surrounding Pele (lower left), and “black” spots mark areas of recent volcanic activity. Credit: NASA / JPL / University of Arizona

Juno’s Io looks like it’s on fire. Because JIRAM sees in infrared, a form of light we sense as heat, it picked up the signatures of at least 60 hot spots on the little moon on both the sunlight side (right) and the shadowed half. Like all missions to the planets, Juno’s cameras take pictures in black and white through a variety of color filters. The filtered views are later combined later by computers on the ground to create color pictures. Our featured image of Io was created by amateur astronomer and image processor Roman Tkachenko, who stacked raw images from this data set to create the vibrant view.

This map shows thermal emission from erupting volcanoes on Io. The larger the spot, the larger the thermal emission. Credit: NASA/JPL-Caltech/Bear Fight Institute

Io’s hotter than heck with erupting volcano temperatures as high as 2,400° F (1,300° C). Most of its lavas are made of basalt, a common type of volcanic rock found on Earth, but some flows consist of sulfur and sulfur dioxide, which paints the scabby landscape in unique colors.


This five-frame sequence taken by NASA’s New Horizons spacecraft on March 1, 2007 captures the giant plume from Io’s Tvashtar volcano.

Located more than 400 million miles from the Sun, how does a little orb only a hundred miles larger than our Moon get so hot? Europa and Ganymede are partly to blame. They tug on Io, causing it to revolve around Jupiter in an eccentric orbit that alternates between close and far. Jupiter’s powerful gravity tugs harder on the moon when its closest and less so when it’s farther away. The “tug and release”creates friction inside the satellite, heating and melting its interior. Io releases the pent up heat in the form of volcanoes, hot spots and massive lava flows.

Always expect big surprises from small things.

Astronauts Capture Great Views of Mount Etna Eruption

Mount Etna is Europe’s most active volcano, and it’s been spouting off since late February 2017. It spewed lava and gas with a rather big eruption last week, where 10 people were actually injured. The Expedition 50 crew on board the International Space Station have been able to capture both day and nighttime views of the activity from orbit.

The stunning view, above, was taken on March 17, 2017. The original photo, which you can see on NASA’s Gateway to Astronaut Photography of Earth website is actually a bit hard to make out. But space enthusiast Riccardo Rossi from Modena, Italy enhanced the original with color correction and increased the contrast with Photoshop. You can see the full version of Rossi’s enhancements on Flickr. .

ESA astronaut Thomas Pesquet took the image below on March 19, and shared it on Twitter, writing, “Mount Etna, in Sicily. The volcano is currently erupting and the molten lava is visible from space, at night! (the red lines on the left).”

A nighttime view from orbit of Mount Etna, erupting on March 19, 2017, taken by ESA astronaut Thomas Pesquet. The red streaks on the lower left are molten lava. See detail below. Credit: NASA/ESA.

This crop shows the glowing lava:

A crop of the above image, showing detail of the glowing lava at night from Mount Etna’s recent activity. Credit: NASA/ESA.

Mount Etna towers above the city of Catania on the island of Sicily. Scientists estimate it has been active for about 500,000 years. The first recorded eruption dates back to 1500 B.C., and it has erupted over 200 times since then.

NASA’s Suomi NPP satellite also spotted nighttime activity from orbit. The image was acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS), using its “day-night band,” which detects light in a range of wavelengths and uses filtering techniques to observe signals such as gas flares, city lights, and reflected moonlight. In this image, it detected the nighttime glow of molten lava.

A view of Sicily and Mount Etna during the dark morning hours of March 16, 2017, taken by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite. Credit: NASA.

Further reading:
NASA Image of the Day
NASA Earth Observatory

Meteorite Confirms 2 Billion Years of Volcanic Activity on Mars

Color Mosaic of Olympus Mons on Mars

Mars is renowned for having the largest volcano in our Solar System, Olympus Mons. New research shows that Mars also has the most long-lived volcanoes. The study of a Martian meteorite confirms that volcanoes on Mars were active for 2 billion years or longer.

A lot of what we know about the volcanoes on Mars we’ve learned from Martian meteorites that have made it to Earth. The meteorite in this study was found in Algeria in 2012. Dubbed Northwest Africa 7635 (NWA 7635), this meteorite was actually seen travelling through Earth’s atmosphere in July 2011.

A sample from the meteorite Northwest Africa 7635. Image: Mohammed Hmani
A sample from the meteorite Northwest Africa 7635. Image: Mohammed Hmani

The lead author of this study is Tom Lapen, a Geology Professor at the University of Houston. He says that his findings provide new insights into the evolution of the Red Planet and the history of volcanic activity there. NWA 7635 was compared with 11 other Martian meteorites, of a type called shergottites. Analysis of their chemical composition reveals the length of time they spent in space, how long they’ve been on Earth, their age, and their volcanic source. All 12 of them are from the same volcanic source.

Mars has much weaker gravity than Earth, so when something large enough slams into the Martian surface, pieces of rock are ejected into space. Some of these rocks eventually cross Earth’s path and are captured by gravity. Most burn up, but some make it to the surface of our planet. In the case of NWA 7635 and the other meteorites, they were ejected from Mars about 1 million years ago.

“We see that they came from a similar volcanic source,” Lapen said. “Given that they also have the same ejection time, we can conclude that these come from the same location on Mars.”

Taken together, the meteorites give us a snapshot of one location of the Martian surface. The other meteorites range from 327 million to 600 million years old. But NWA 7635 was formed 2.4 billion years ago. This means that its source was one of the longest lived volcanoes in our entire Solar System.

This false color X-ray of NWA 7635 shows the meteorite’s mineralogy mineral textures. O, olivine; P, plagioclase (maskelynite); C, clinopyroxene (augite). Chemical compositions: Fe (purple), Mg (green), Ca (blue), Ti (magenta), and S (yellow). Purple colors in the mesostasis represent Fe-rich augite. You’re welcome, mineral nerds. Image: Lapen et. al.

Volcanic activity on Mars is an important part of understanding the planet, and whether it ever harbored life. It’s possible that so-called super-volcanoes contributed to extinctions here on Earth. The same thing may have happened on Mars. Given the massive size of Olympus Mons, it could very well have been the Martian equivalent of a super-volcano.

The ESA’s Mars Express Orbiter sent back images of Olympus Mons that showed possible lava flows as recently as 2 million years ago. There are also lava flows on Mars that have a very small number of impact craters on them, indicating that they were formed recently. If that is the case, then it’s possible that Martian volcanoes will be visibly active again.

A colorized image of the surface of Mars taken by the Mars Reconnaissance Orbiter. The line of three volcanoes is the Tharsis Montes, with Olympus Mons to the northwest. Valles Marineris is to the east. Image: NASA/JPL-Caltech/ Arizona State University
A colorized image of the surface of Mars taken by the Mars Reconnaissance Orbiter. The line of three volcanoes is the Tharsis Montes, with Olympus Mons to the northwest. Valles Marineris is to the east. Image: NASA/JPL-Caltech/ Arizona State University

Continuing volcanic activity on Mars is highly speculative, with different researchers arguing for and against it. The relatively crater-free, smooth surfaces of some lava features on Mars could be explained by erosion, or even glaciation. In any case, if there is another eruption on Mars, we would have to be extremely lucky for one of our orbiters to see it.

But you never know.

Astronomy Cast Ep. 433: Volcanoes on Mars

So if you’ve been to Yellowstone National Park, you’ve seen one of the most amazing features of the natural world – geysers. In today’s episode, we’re going to talk about geysers on Earth, and where they might be in the solar system.

Visit the Astronomy Cast Page to subscribe to the audio podcast!

We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.

What are Volcanoes?

A volcano is an impressive sight. When they are dormant, they loom large over everything on the landscape. When they are active, they are a destructive force of nature that is without equal, raining fire and ash down on everything in site. And during the long periods when they are not erupting, they can also be rather beneficial to the surrounding environment.

But just what causes volcanoes? When it comes to our planet, they are the result of active geological forces that have shaped the surface of the Earth over the course of billions of years. And interestingly enough, there are plenty of examples of volcanoes on other bodies within our Solar System as well, some of which put those on Earth to shame!

Definition:

By definition, a volcano is a rupture in the Earth’s (or another celestial body’s) crust that allows hot lava, volcanic ash, and gases to escape from a magma chamber located beneath the surface. The term is derived from Vulcano, a volcanically-active island located of the coast of Italy who’s name in turn comes from the Roman god of fire (Vulcan).

The Earth's Tectonic Plates. Credit: msnucleus.org
Artist’s illustration of the Earth’s Tectonic Plates. Credit: msnucleus.org

On Earth, volcanoes are the result of the action between the major tectonic plates. These sections of the Earth’s crust are rigid, but sit atop the relatively viscous upper mantle. The hot molten rock, known as magma, is forced up to the surface – where it becomes lava. In short, volcanoes are found where tectonic plates are diverging or converging – such as the Mid-Atlantic Ridge or the Pacific Ring of Fire – which causes magma to be forced to the surface.

Volcanoes can also form where there is stretching and thinning of the crust’s interior plates, such as in the the East African Rift and the Rio Grande Rift in North America. Volcanism can also occur away from plate boundaries, where upwelling magma is forced up into brittle sections of the crust, forming volcanic islands – such as the Hawaiian islands.

Erupting volcanoes pose many hazards, and not just to the surrounding countryside. In their immediate vicinity, hot, flowing lava can cause extensive damage to the environment, property, and endanger lives. However, volcanic ash can cause far-reaching damage, raining sulfuric acid, disrupting air travel, and even causing “volcanic winters” by obscuring the Sun (thus triggering local crop failures and famines).

Types of Volcanoes:

There are four major types of volcanoes – cinder cone, composite and shield volcanoes, and lava domes. Cinder cones are the simplest kind of volcano, which occur when magma is ejected from a volcanic vent. The ejected lava rains down around the fissure, forming an oval-shaped cone with a bowl-shaped crater on top. They are typically small, with few ever growing larger than about 300 meters (1,000 feet) above their surroundings.

Cinder cone Paricutin. Image credit: USGS
Paricutin, an example of a cinder cone volcano. Credit: USGS

Composite volcanoes (aka. stratovolcanoes) are formed when a volcano conduit connects a subsurface magma reservoir to the Earth’s surface. These volcanoes typically have several vents that cause magma to break through the walls and spew from fissures on the sides of the mountain as well as the summit.

These volcanoes are known for causing violent eruptions. And thanks to all this ejected material, these volcanoes can grow up to thousands of meters tall. Examples include Mount Rainier (4,392 m; 14,411 ft), Mount Fuji (3,776 m; 12,389 ft), Mount Cotopaxi (5,897 m; 19,347 ft) and Mount Saint Helens (2,549 mm; 8,363 ft).

Shield volcanoes are so-named because of their large, broad surfaces. With these types of volcanoes, the lava that pours forth is thin, allowing it to travel great distances down the shallow slopes. This lava cools and builds up slowly over time, with hundreds of eruptions creating many layers. They are therefore not likely to be catastrophic. Some of the best known examples are those that make up the Hawaiian Islands, especially Mauna Loa and Mauna Kea.

Volcanic or lava domes are created by small masses of lava which are too viscous to flow very far. Unlike shield volcanoes, which have low-viscosity lava, the slow-moving lava simply piles up over the vent. The dome grows by expansion over time, and the mountain forms from material spilling off the sides of the growing dome. Lava domes can explode violently, releasing a huge amount of hot rock and ash.

Artist's impression of a what lies beneath the Yellowstone volcano. Credit: Hernán Cañellas/National Geographic
Artist’s impression of a what lies beneath the Yellowstone volcano. Credit: Hernán Cañellas/National Geographic

Volcanoes can also be found on the ocean floor, known as submarine volcanoes. These are often revealed through the presence of blasting steam and rocky debris above the ocean’s surface, though the pressure of the ocean’s water can often prevent an explosive release.

In these cases, lava cools quickly on contact with ocean water, and forms pillow-shaped masses on the ocean floor (called pillow lava). Hydrothermal vents are also common around submarine volcano, which can support active and peculiar ecosystems because of the energy, gases and minerals they release. Over time, the formations created by submarine volcanoes may become so large that they become islands.

Volcanoes can also developed under icecaps, which are known as subglacial volcanoes. In these cases, flat lava flows on top of pillow lava, which results from lava quickly cooling upon contact with ice. When the icecap melts, the lava on top collapses, leaving a flat-topped mountain. Very good examples of this type of volcano can be seen in Iceland and British Columbia, Canada.

Examples on Other Planets:

Volcanoes can be found on many bodies within the Solar System. Examples include Jupiter’s moon Io, which periodically experiences volcanic eruptions that reach up to 500 km (300 mi) into space. This volcanic activity is caused by friction or tidal dissipation produced in Io’s interior, which is responsible for melting a significant amount of Io’s mantle and core.

Model of the possible interior composition of Io with various features labelled. Credit: Wikipedia Commons/Kelvinsong
Model of the possible interior composition of Io with various features labelled. Credit: Wikipedia Commons/Kelvinsong

It’s colorful surface (orange, yellow, green, white/grey, etc.) shows the presence of sulfuric and silicate compounds, which were clearly deposited by volcanic eruptions. The lack of impact craters on its surface, which is uncommon on a Jovian moon, is also indicative of surface renewal.

Mars has also experienced intense volcanic activity in its past, as evidenced by Olympus Mons – the largest volcano in the Solar System. While most of its volcanic mountains are extinct and collapsed, the Mars Express spacecraft observed evidence of more recent volcanic activity, suggesting that Mars may still be geologically active.

Much of Venus’ surface has been shaped by volcanic activity as well. While Venus has several times the number of Earth’s volcanoes, they were believed to all be extinct. However, there is a multitude of evidence that suggests that there may still be active volcanoes on Venus which contribute to its dense atmosphere and runaway Greenhouse Effect.

For instance, during the 1970s, multiple Soviet Venera missions conducted surveys of Venus. These missions obtained evidence of thunder and lightning within the atmosphere, which may have been the result of volcanic ash interacting with the atmosphere. Similar evidence was gathered by the ESA’s Venus Express probe in 2007.

3-D perspective of the Venusian volcano, Maat Mons generated from radar data from NASA’s Magellan mission.
3-D perspective of the Venusian volcano, Maat Mons generated from radar data from NASA’s Magellan mission. Credit: NASA/JPL

This same mission observed transient localized infrared hot spots on the surface of Venus in 2008 and 2009, specifically in the rift zone Ganis Chasma – near the shield volcano Maat Mons. The Magellan probe also noted evidence of volcanic activity from this mountain during its mission in the early 1990s, using radar-sounding to detect ash flows near the summit.

Cryovolcanism:

In addition to “hot volcanoes” that spew molten rock, there are also cryovolcanoes (aka. “cold volcanoes”). These types of volcanoes involve volatile compounds  – i.e. water, methane and ammonia – instead of lava breaking through the surface. They have been observed on icy bodies in the Solar System where liquid erupts from ocean’s hidden in the moon’s interior.

For instance, Jupiter’s moon Europa, which is known to have an interior ocean, is believed to experiences cryovolcanism. The earliest evidence for this had to do with its smooth and young surface, which points towards endogenic resurfacing and renewal. Much like hot magma, water and volatiles erupt onto the surface where they then freeze to cover up impact craters and other features.

In addition, plumes of water were observed in 2012 and again in 2016 using the Hubble Space Telescope. These intermittent plumes were observed on both occasions to be coming in the southern region of Europa, and were estimated to be reach up to 200 km (125 miles) before depositing water ice and material back onto the surface.

In 2005, the Cassini-Huygens mission detected evidence of cryovolcanism on Saturn’s moons Titan and Enceladus. In the former case, the probe used infrared imaging to penetrate Titan’s dense clouds and detect signs of a 30 km (18.64 mi) formation, which was believed to be caused by the upwelling of hydrocarbon ices beneath the surface.

On Enceladus, cryovolcanic activity has been confirmed by observing plumes of water and organic molecules being ejected from the moon’s south pole. These plumes are are thought to have originated from the moon’s interior ocean, and are composed mostly of water vapor, molecular nitrogen, and volatiles (such as methane, carbon dioxide and other hydrocarbons).

In 1989, the Voyager 2 spacecraft observed cryovolcanoes ejecting plumes of water ammonia and nitrogen gas on Neptune’s moon Triton. These nitrogen geysers were observed sending plumes of liquid nitrogen 8 km (5 mi) above the surface of the moon. The surface is also quite young, which was seen as indication of endogenic resurfacing. It is also theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar.

Here on Earth, volcanism takes the form of hot magma being pushed up through the Earth’s silicate crust due to convention in the interior. However, this kind of activity is present on all planet that formed from silicate material and minerals, and where geological activity or tidal stresses are known to exist. But on other bodies, it consists of cold water and materials from the interior ocean being forced through to the icy surface.

Color Mosaic of Olympus Mons on Mars
Color Mosaic of Olympus Mons on Mars. Credit: NASA/JPL

Today, our knowledge of volcanism (and the different forms it can take) is the result of improvements in both the field of geology, as well as space exploration. The more we learn of about other planets, the more we are able to see startling similarities and contrasts with our own (and vice versa).

We have written many interesting articles about volcanoes here at Universe Today. Here’s 10 Interesting Facts About Volcanoes, What are the Different Types of Volcanoes?, How Do Volcanoes Erupt?, What Are The Benefits Of Volcanoes?, What is the Difference Between Active and Dormant Volcanoes?

For more information, be sure to check out What is a Volcano? at NASA Space Place.

Astronomy Cast has an episode on the subject – Episode 141: Volcanoes Hot and Cold.

Sources:

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:

Weekly Space Hangout – June 24, 2016: Dr. James Green

Host: Fraser Cain (@fcain)

Special Guest:
Dr. James Green is the NASA Director of Planetary Science.

Guests:

Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg)
Dave Dickinson (www.astroguyz.com / @astroguyz)
Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )

Their stories this week:

Evidence for volcanic history on Mars

Impact of Brexit on UK science uncertain

FRIPON: A New All-Sky Meteor Network

A Solstice Full Moon

Water on (under) Pluto???

Blue Origin conducts fourth launch, test

We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

You can also join in the discussion between episodes over at our Weekly Space Hangout Crew group in G+!

What is the Difference Between Lava and Magma?

Few forces in nature are are impressive or frightening as a volcanic eruption. In an instant, from within the rumbling depths of the Earth, hot lava, steam, and even chunks of hot rock are spewed into the air, covering vast distances with fire and ash. And thanks to the efforts of geologists and Earth scientists over the course of many centuries, we have to come to understand a great deal about them.

However, when it comes to the nomenclature of volcanoes, a point of confusion often arises. Again and again, one of the most common questions about volcanoes is, what is the difference between lava and magma? They are both molten rock, and are both associated with volcanism. So why the separate names? As it turns out, it all comes down to location.

Earth’s Composition:

As anyone with a basic knowledge of geology will tell you, the insides of the Earth are very hot. As a terrestrial planet, its interior is differentiated between a molten, metal core, and a mantle and crust composed primarily of silicate rock. Life as we know it, consisting of all vegetation and land animals, live on the cool crust, whereas sea life inhabits the oceans that cover a large extent of this same crust.

The Earth's layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com
The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust. Credit: discovermagazine.com

However, the deeper one goes into the planet, both pressures and temperatures increase considerably. All told, Earth’s mantle extends to a depth of about 2,890 km, and is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust. Although solid, the high temperatures within the mantle cause pockets of molten rock to form.

This silicate material is less dense than the surrounding rock, and is therefore sufficiently ductile that it can flow on very long timescales. Over time, it will also reach the surface as geological forces push it upwards. This happens as a result of tectonic activity.

Basically, the cool, rigid crust is broken into pieces called tectonic plates. These plates are rigid segments that move in relation to one another at one of three types of plate boundaries. These are known as convergent boundaries, at which two plates come together; divergent boundaries, at which two plates are pulled apart; and transform boundaries, in which two plates slide past one another laterally.

Interactions between these plates are what is what is volcanic activity (best exemplified by the “Pacific Ring of Fire“) as well as mountain-building. As the tectonic plates migrate across the planet, the ocean floor is subducted – the leading edge of one plate pushing under another. At the same time, mantle material will push up at divergent boundaries, forcing molten rock to the surface.

The Earth's Tectonic Plates. Credit: msnucleus.org
The Earth’s Tectonic Plates. Credit: msnucleus.org

Magma:

As already noted, both lava and magma are what results from rock superheated to the point where it becomes viscous and molten. But again, the location is the key. When this molten rock is still located within the Earth, it is known as magma. The name is derived from Greek, which translate to “thick unguent” (a word used to describe a viscous substance used for ointments or lubrication).

It is composed of molten or semi-molten rock, volatiles, solids (and sometimes crystals) that are found beneath the surface of the Earth. This vicious rock usually collects in a magma chamber beneath a volcano, or solidify underground to form an intrusion. Where it forms beneath a volcano, it can then be injected into cracks in rocks or issue out of volcanoes in eruptions. The temperature of magma ranges between 600 °C and 1600 °C.

Magma is also known to exist on other terrestrial planets in the Solar System (i.e. Mercury, Venus and Mars) as well as certain moons (Earth’s Moon and Jupiter’s moon Io). In addition to stable lava tubes being observed on Mercury, the Moon and Mars, powerful volcanoes have been observed on Io that are capable of sending lava jets 500 km (300 miles) into space.

Igneous rock (aka. "fire rock") is formed from cooled and solidified magma. Credit: geologyclass.org
Igneous rock (aka. “fire rock”) is formed from cooled and solidified lava. Credit: geologyclass.org

Lava:

When magma reaches the surface and erupts from a volcano, it officially becomes lava. There are actually different kinds of lava depending on its thickness or viscosity. Whereas the thinnest lava can flow downhill for many kilometers (thus creating a gentle slope), thicker lavas will pile up around a  volcanic vent and hardly flow at all. The thickest lava doesn’t even flow, and just plugs up the throat of a volcano, which in some cases cause violent explosions.

The term lava is usually used instead of lava flow. This describes a moving outpouring of lava, which occurs when a non-explosive effusive eruption takes place. Once a flow has stopped moving, the lava solidifies to form igneous rock. Although lava can be up to 100,000 times more viscous than water, lava can flow over great distances before cooling and solidifying.

The word “lava” comes from Italian, and is probably derived from the Latin word labes which means “a fall” or “slide”. The first use in connection with a volcanic event was apparently in a short written account by Franscesco Serao, who observed the eruption of Mount Vesuvius between May 14th and June 4th, 1737. Serao described “a flow of fiery lava” as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain.

Such is the difference between magma and lava. It seems that in geology, as in real estate, its all about location!

We have written many articles about volcanoes here at Universe Today. Here’s What is Lava?, What is the Temperature of Lava?, Igneous Rocks: How Are They Formed?, What Are The Different Parts Of A Volcano? and Planet Earth.

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.

The Moon’s Other Axis

A six degree True Polar Wander occurred on the Moon due to ancient volcanic activity. Image: University of Arizona/James Tuttle Keane

It’s tempting to think that the Moon never changes. You can spend your whole life looking at it, and see no evidence of change whatsoever. In fact, the ancients thought the whole Universe was unchanging.

You may have heard of a man named Aristotle. He thought the Universe was eternal and unchanging. Obviously, with our knowledge of the Big Bang, stellar evolution, and planetary formation, we know better. Still, the placid and unchanging face of the Moon can tempt us into thinking astronomers are making up all this evolving universe stuff.

But now, according to a new paper in Nature, the Moon’s axis of rotation is different now than it was billions of years ago. Not only that, but volcanoes may been responsible for it. Volcanoes! On our placid little Moon.

The clue to this lunar True Polar Wander (TPW) is in the water ice locked in the shadows of craters on the Moon. When hydrogen was discovered on the surface of the Moon in the 1990s by the Lunar Prospector probe, scientists suspected that they would eventually find water ice. Subsequent missions proved the presence of water ice, especially in craters near the polar regions. But the distribution of that water-ice wasn’t uniform.

You would expect to see ice uniformly distributed in the shadows of craters in the polar regions, but that’s not what scientists have found. Instead, some craters had no evidence of ice at all, which led the team behind this paper to conclude that these ice-free craters must have been exposed to the Sun at some point. What else would explain it?

The way that the ice in these craters is distributed forms two trails that lead away from each pole. They’re mirror images of each other, but they don’t conform with the Moon’s current axis of rotation, which is what led the team to conclude that the Moon underwent a 6 degree TPW billions of years ago.

The paper also highlights the age of the water on the Moon. Since the TPW, and the melting of some of the ice as a result of it, occurred some billions of years ago, then the water ice that is still frozen in the shadows of some of the Moon’s craters must be ancient. According to the paper, its existence records the “early delivery of water to the inner Solar System.” Hopefully, a future mission will return a sample of this ancient water for detailed study.

But even more interesting than the age of the ice in the craters and the TPW, to me anyways, is what is purported to have caused it. The team behind the paper reports that volcanic activity on the Moon in the Procellarum region, which was most active in the early history of the Moon, moved a substantial amount of material and “altered the density structure of the Moon.” This alteration would have changed the moments of inertia on the Moon, resulting in a TPW.

It’s strange to think of the Moon with volcanic activity viewable from Earth. I wonder what effect visible lunar volcanoes would have had on thinkers like Aristotle, if lunar volcanic activity had occurred during recorded history, rather than ending one billion years ago or so.

We know that events like eclipses and comets caused great confusion and sometimes upheaval in ancient civilizations. Would lunar volcanoes have had the same effect?

What Are The Benefits Of Volcanoes?

Volcanoes are renowned for their destructive power. In fact, there are few forces of nature that rival their sheer, awesome might, or have left as big of impact on the human psyche. Who hasn’t heard of tales of Mt. Vesuvius erupting and burying Pompeii? There’s also the Minoan Eruption, the eruption that took place in the 2nd millennium BCE on the isle of Santorini and devastated the Minoan settlement there.

In Japan, Hawaii, South American and all across the Pacific, there are countless instances of eruptions taking a terrible toll. And who can forget modern-day eruptions like Mount St. Helens? But would it surprise you to know that despite their destructive power, volcanoes actually come with their share of benefits? From enriching the soil to creating new landmasses, volcanoes are actually a productive force as well.

Soil Enrichment:

Volcanic eruptions result in ash being dispersed over wide areas around the eruption site. And depending on the chemistry of the magma from which it erupted, this ash will be contain varying amounts of soil nutrients. While the most abundant elements in magma are silica and oxygen, eruptions also result in the release of water, carbon dioxide (CO²), sulfur dioxide (SO²), hydrogen sulfide (H²S), and hydrogen chloride (HCl), amongst others.

In addition, eruptions release bits of rock such as potolivine, pyroxene, amphibole, and feldspar, which are in turn rich in iron, magnesium, and potassium. As a result, regions that have large deposits of volcanic soil (i.e. mountain slopes and valleys near eruption sites) are quite fertile. For example, most of Italy has poor soils that consist of limestone rock.

The area around the volcano is now densely populated. Credit: Wikipedia Commons/Jeffmatt
The area around the volcano is now densely populated. Credit: Wikipedia Commons/Jeffmatt

But in the regions around Naples (the site of Mt. Vesuvius), there are fertile stretches of land that were created by volcanic eruptions that took place 35,000 and 12,000 years ago. The soil in this region is rich because volcanic eruption deposit the necessary minerals, which are then weathered and broken down by rain. Once absorbed into the soil, they become a steady supply of nutrients for plant life.

Hawaii is another location where volcanism led to rich soil, which in turn allowed for the emergence of thriving agricultural communities. Between the 15th and 18th centuries on the islands of Kauai, O’ahu and Molokai, the cultivation of crops like taros and sweet potatoes allowed for the rise of powerful chiefdoms and the flowering of the culture we associate with Hawaii today.

Volcanic Land Formations:

In addition to scattering ash over large areas of land, volcanoes also push material to the surface that can result in the formation of new islands. For example, the entire Hawaiian chain of islands was created by the constant eruptions of a single volcanic hot spot. Over hundreds of thousands of years, these volcanoes breached the surface of the ocean becoming habitable islands, and rest stops during long sea journeys.

This is the case all across the Pacific, were island chains such as Micronesia, the Ryukyu Islands (between Taiwan and Japan), the Aleutian Islands (off the coast of Alaska), the Mariana Islands, and Bismark Archipelago were all formed along arcs that are parallel and close to a boundary between two converging tectonic plates.

The island of Santorini, Greece. Credit: EOS/NASA/ Public Domain
The island of Santorini, Greece. Credit: EOS/NASA/ Public Domain

Much the same is true of the Mediterranean. Along the Hellenic Arc (in the eastern Mediterranean), volcanic eruptions led to the creation of the Ionian Islands, Cyprus and Crete. The nearby South Aegean Arc meanwhile led to the formation of Aegina, Methana, Milos, Santorini and Kolumbo, and Kos, Nisyros and Yali. And in the Caribbean, volcanic activity led to the creation of the Antilles archipelago.

Where these islands formed, unique species of plants and animals evolved into new forms on these islands, creating balanced ecosystems and leading to new levels of biodiversity.

Volcanic Minerals and Stones:

Another benefits to volcanoes are the precious gems, minerals and building materials that eruptions make available. For instance, stones like pumice volcanic ash and perlite (volcanic glass) are all mined for various commercial uses. These include acting as abrasives in soaps and household cleaners. Volcanic ash and pumice are also used as a light-weight aggregate for making cement.

The finest grades of these volcanic rocks are used in metal polishes and for woodworking. Crushed and ground pumice are also used for loose-fill insulation, filter aids, poultry litter, soil conditioner, sweeping compound, insecticide carrier, and blacktop highway dressing.

The roof of the Pantheon, as seen from nearby rooftops in Roe. Credit: Public Domain/Anthony Majanlahti
The roof of the Pantheon, as seen from nearby rooftops in Roe. Credit: Public Domain/Anthony Majanlahti

Perlite is also used as an aggregate in plaster, since it expands rapidly when heated. In precast walls, it too is used as an aggregate in concrete. Crushed basalt and diasbase are also used for road metal, railroad ballast, roofing granules, or as protective arrangements for shorelines (riprap). High-density basalt and diabase aggregate are used in the concrete shields of nuclear reactors.

Hardened volcanic ash (called tuff) makes an especially strong, lightweight building material. The ancient Romans combined tuff and lime to make a strong, lightweight concrete for walls, and buildings. The roof of the Pantheon in Rome is made of this very type of concrete because it’s so lightweight.

Precious metals that are often found in volcanoes include sulfur, zinc, silver, copper, gold, and uranium. These metals have a wide range of uses in modern economies, ranging from fine metalwork, machinery and electronics to nuclear power, research and medicine. Precious stones and minerals that are found in volcanoes include opals, obsidian, fire agate, flourite, gypsum, onyx, hematite, and others.

Global Cooling:

Volcanoes also play a vital role in periodically cooling off the planet. When volcanic ash and compounds like sulfur dioxide are released into the atmosphere, it can reflect some of the Sun’s rays back into space, thereby reducing the amount of heat energy absorbed by the atmosphere. This process, known as “global dimming”, therefore has a cooling effect on the planet.

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

The link between volcanic eruptions and global cooling has been the subject of scientific study for decades. In that time, several dips have been observed in global temperatures after large eruptions. And though most ash clouds dissipate quickly, the occasional prolonged period of cooler temperatures have been traced to particularly large eruptions.

Because of this well-established link, some scientists have recommended that sulfur dioxide and other  be released into the atmosphere in order to combat global warming, a process which is known as ecological engineering.

Hot Springs And Geothermal Energy:

Another benefit of volcanism comes in the form of geothermal fields, which is an area of the Earth characterized by a relatively high heat flow. These fields, which are the result of present, or fairly recent magmatic activity, come in two forms. Low temperature fields (20-100°C) are due to hot rock below active faults, while high temperature fields (above 100°C) are associated with active volcanism.

Geothermal fields often create hot springs, geysers and boiling mud pools, which are often a popular destination for tourists. But they can also be harnessed for geothermal energy, a form of carbon-neutral power where pipes are placed in the Earth and channel steam upwards to turn turbines and generate electricity.

Steam rising from the Nesjavellir Geothermal Power Station in Iceland. Credit: Gretar Ívarsson/Fir0002
Steam rising from the Nesjavellir Geothermal Power Station in Iceland. Credit: Gretar Ívarsson/Fir0002

In countries like Kenya, Iceland, New Zealand, the Phillipines, Costa Rica and El Salvador, geothermal power is responsible for providing a significant portion of the country’s power supply – ranging from 14% in Costa Rica to 51% in Kenya. In all cases, this is due to the countries being in and around active volcanic regions that allow for the presence of abundant geothermal fields.

Outgassing and Atmospheric Formation:

But by far, the most beneficial aspect of volcanoes is the role they play in the formation of a planet’s atmosphere. In short, Earth’s atmosphere began to form after its formation 4.6 billion eyars ago, when volcanic outgassing led to the creation of gases stored in the Earth’s interior to collect around the surface of the planet. Initially, this atmosphere consisted of hydrogen sulfide, methane, and 10 to 200 times as much carbon dioxide as today’s atmosphere.

After about half a billion years, Earth’s surface cooled and solidified enough for water to collect on it. At this point, the atmosphere shifted to one composed of water vapor, carbon dioxide and ammonia (NH³). Much of the carbon dioxide dissolved into the oceans, where cyanobacteria developed to consume it and release oxygen as a byproduct. Meanwhile, the ammonia began to be broken down by photolysis, releasing the hydrogen into space and leaving the nitrogen behind.

Another key role played by volcanism occurred 2.5 billion years ago, during the boundary between the Archaean and Proterozoic Eras. It was at this point that oxygen began to appear in our oxygen due to photosynthesis – which is referred to asthe “Great Oxidation Event”. However, according to recent geological studies, biomarkers indicate that oxygen-producing cyanobacteria were releasing oxygen at the same levels there are today. In short, the oxygen being produced had to be going somewhere for it not to appear in the atmosphere.

Roughly 2.5 billion years ago, towards the end of the Archaean Era, oxidation of our atmosphere began. Credit: ocean.si.edu
Roughly 2.5 billion years ago, towards the end of the Archaean Era, oxidation of our atmosphere began. Credit: ocean.si.edu

The lack of terrestrial volcanoes is believed to be responsible. During the Archaean Era, there were only submarine volcanoes, which had the effect of scrubbing oxygen from the atmosphere, binding it into oxygen containing minerals. By the Archaean/Proterozoic boundary, stabilized continental land masses arose, leading to terrestrial volcanoes. From this point onward, markers show that oxygen began appearing in the atmosphere.

Volcanism also plays a vital role in the atmospheres of other planets. Mercury’s thin exosphere of hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor is due in part of volcanism, which periodically replenishes it. Venus’ incredibly dense atmosphere is also believed to be periodically replenished by volcanoes on its surface.

And Io, Jupiter’s volcanically active moon, has an extremely tenuous atmosphere of sulfur dioxide (SO²), sulfur monoxide (SO), sodium chloride (NaCl), sulfur monoxide (SO), atomic sulfur (S) and oxygen (O). All of these gases are provided and replenished by the many hundreds of volcanoes situated across the moon’s surface.

As you can see, volcanoes are actually a pretty creative force when all is said and done. In fact, us terrestrial organisms depend on them for everything from the air we breathe, to the rich soil that produces our food, to the geological activity that gives rise to terrestrial renewal and biological diversity.

We have written many articles about volcanoes for Universe Today. Here’s an article about extinct volcanoes, and here’s an article about active volcanoes. Here’s an article about volcanoes.

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

Astronomy Cast also has relevant episodes on the subject Earth, as part of our tour through the Solar System – Episode 51: Earth.