Nicolas Desmarest - Scientist of the Day

Nicolas Desmarest, a French geologist and cartographer, was born Sep. 16, 1725. When Desmarest began his work, it was thought that basalt formations, such as the Giant’s Causeway in Ireland, were some sort of sedimentary deposits. In 1763, Desmarest began mapping the Auvergne region of central France, which contains most of that country’s mountains. He noticed that the mountains were not at all like the Alps, but had the shapes and features of volcanoes, even though no active eruptions had ever been recorded in France. And he found basalt formations everywhere, the source of which he was able to trace to the volcano-like craters.

In 1771, Desmarest presented a geological map of the Auvergne region to the Paris Academy of Sciences, locating all the craters and basalt formations, and in the accompanying memoir, he argued that the mountains of the region were once volcanic, and that basalt is a volcanic, or igneous, rock. Desmarest was really the first to suggest that volcanoes had been important forces in shaping the face of the earth in the deep past, and that wherever we see basalt, we are observing the remains of past volcanic action. We displayed Desmarest’s map in our 2004 exhibition, Vulcan’s Force and Fingal’s Cave; the online version shows a detail of the map. The complete map is shown above, as well as two other details. The last one shows the map legend, and indicates that Desmarest understood fully that one can distinguish ancient lava flows from more recent ones, and that the “prismes de basalt” (columnar basalts) were clearly related to the lava flows.

Dr. William B. Ashworth, Jr., Consultant for the History of Science, Linda Hall Library and Associate Professor, Department of History, University of Missouri-Kansas City


Stunning Electric-Blue Flames Erupt From Volcanoes - Olivier Grunewald.

Sulfur combusts on contact with air to create stunning blue lava-like rivers of light in the Kawah Ijen crater on the island of Java.Kawah Ijen is one of several volcanoes situated in a 20 km radius in East Java, Indonesia. The caldera of Kawah Ijen harbors a kilometer-wide, turquoise colored, acidic crater lake that leaks sulphurous gases. At night the hot gases burn to emit an eerie blue glow that is unique to Kawah Ijen. The gases emerge from the cracks in the volcano at high pressure and temperature, up to 600°C, and when they come in contact with the air, they ignite, sending flames up to 16 feet high. Some of the gases condense into liquid sulfur, and continues to burn as it flows down the slopes giving the feeling of blue lava flowing.

Klyuchevskoy Eruption

The Russian peninsula of Kamchatka is a land of volcanoes. During my journey there between October 14 to 26, 2013, I visited the active volcanoes Klyuchevskoy and Sheveluch.

The former erupted for the first time in three years. During its strongest eruptive phase (shown above), lava fountains rose up to 0.6 mi (1 km) above the summit dome, and explosions could be heard at a distance of 19 mi (30 km) away.

Note the funnel shaped cloud of steam and smoke above Klyuchevskoy’s concealed, volcanic cone. Photo taken on October 16, 2013, at a distance of approximately 9.5 mi (15 km). - Marc Szeglat

What’s up with all those giant volcanoes on Mars?

Mount Everest is an enormous and awe-inspiring sight, towering 9 kilometres above the Earth’s surface. But if you were to stick it on Mars right next to Olympus Mons, the largest volcano in the solar system, it would look foolishly small—Olympus Mons triples the height of Everest and spans the state of Arizona.

Mars is sprinkled with huge volcanoes, hundreds of kilometres in diameter and dozens of kilometres tall. The largest volcano on Earth, on the other hand, is Mauna Loa in Hawaii, which rises only 4 km above sea level.

So why is Mars blessed with these monsters of the solar system? Why doesn’t Earth have any massive lava-spewing structures?

Geology, my friends.

Earth’s crust is split up into plates that move and collide. Usually, volcanoes are formed at the boundaries where two plates meet, and one subducts below the other and melts in the heat below the surface. This melt rises as magma and causes volcanism.

But in some places on Earth, there are “hot spots” in the middle of plates, where magma rises up from the core-mantle mantle in plumes. When this magma is spewed up onto the surface, it cools and solidifies into rock, and over the years, the rock builds up and up. When plumes open out in the middle of the ocean, the magma builds islands.


Plumes are fixed, always pushing magma up to one spot, but the Earth’s plates don’t stop for anything. While the magma rises, the plates move over the hotspot—at a rate of only a few centimetres a year, but still, they move and take the newly-made volcanoes with them. So, gradually, the plates and volcanoes move on, while the plume remains in the same spot, building a whole new volcano on the next bit of the plate. As the plate moves on and on, the plume builds up a whole chain of islands, called island arcs. This is how the Hawaiian Islands were formed.


The island-volcanoes never get too big, because the plates keep moving onwards. On Mars, however, the volcanoes are enormous because the magma appears to keep rising, cooling and solidifying in the same place, taking its sweet time to build up colossal mounds of volcanic rock kilometres high.

So far, we’ve seen no volcanic arcs like we do on Earth, and this is generally taken as evidence that Mars has no tectonic plates.

Two separate eruptions from Mt. Hood - 220 years ago and about 1,500 years ago - have revealed that many volcanoes prefer cold storage of magma, as opposed to the traditional visual we have had of these monumental inferno towers resting atop a giant pool of -


liquid hot magma.

The crystals analyzed in Mt. Hood’s lava reveal a chronological and temperate history of wonders. These crystals have been trapped beneath the volcano for nearly 100,000 years at temperatures so cold, the lava was compared to that of “a jar of old honey from the fridge”, too sticky and slow to erupt. The research suggests that the liquid cut-off is around 50% crystals. Beyond this ratio, the magma becomes too thick to push through the fractures leading to the surface.

From the MNN article:

"This tells us that the standard state of magma for this system is that it can’t be erupted," said Kari Cooper, a geochemist at the University of California, Davis. "That means that having a magma that can erupt is a special condition. Our expectation is that there’s a lot of volcanoes that behave this way."

The results suggest that monitoring volcanoes for liquid magma could warn of coming eruptions. Not all kinds of volcanoes behave like Mount Hood — Hawaii, for instance, is built differently, atop a giant hot spot — but most of the world’s most active volcanoes are in similar settings.

"If you can see a body of magma that has a high amount of liquid, perhaps this magma is getting ready to erupt or at least has some potential to erupt," said study co-author Adam Kent, a geologist at Oregon State University. "It wouldn’t be a slam-dunk guarantee."

The reason why Mt. Hood is set up this way is due to it being a subduction zone volcano, or, a volcano formed due to tectonic plates converging (slowwwwwly) with another. One plate is forced upward toward the surface, the other, downward toward the mantle, causing boundary known as a subduction zone, whereby the fluids (released by the plate being forced toward the mantle) melt the rocks above, pushing them to the surface to form volcanoes.


Learn about “subduction zones” HERE. [image source]

Looking at the “Ring of Fire” around the Pacific Ocean reveals the link between subduction zones and volcanoes. Inland of each subduction zone lies a chain of spouting volcanoes called a volcanic arc, such as Oregon’s Cascades, Alaska’s Aleutian Islands and Indonesia’s 130 active volcanoes.

"We have partial data sets for other systems, and they all seem to behave remarkably similarly, where they spend most of the time cold," Cooper said.

An almost identical process to Mount Hood’s recent eruptions occurred in the early 1990s at Mount Pinatubo, Kent added. "People could see the arrival of this hotter magma from below, and it eventually initiated an eruption," he said.

Mount Hood’s chilly magma reservoir sits about 2.5 to 3 miles (4 to 5 kilometers) beneath the surface. Its temperature is usually 1,380 degrees Fahrenheit (750 degrees Celsius), according to an analysis of the crystals.

You can read the rest of the article via MNN.


Monitoring volcanoes with radar satellites

Radar satellites can detect surface movements down to the millimetre. Italy’s Phlegraean Fields – or Campi Flegrei – is a large, volcanic area near the city of Naples. Data from the Sentinel-1 mission will be employed to monitor this and other areas, helping us to understand the processes happening below Earth’s surface.

Source: esa.int

Scientists searching for what they thought to be a shipwreck in the Gulf of Mexico have found something entirely different. A flower-like formation, nicknamed a ‘tar lily’, that was created by an asphalt volcano. It’s the first of its kind spotted in the Gulf and is likely hundreds, if not thousands, of years old.

Read more: http://bit.ly/Q0tVa3 via The Blaze

through SA