Author: Fraser Cain

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Here on the surface of the Earth, the ground is cool and comfortable. But as you descend into the Earth, temperatures increase. By the time you get to the Earth’s mantle, temperatures can get more than 1000 degrees C. The high temperatures cause rocks to melt into magma. This magma collects together into large underground pools called magma chambers.

The molten rock in a magma chamber is under tremendous pressure. This pressure fractures the rock, and the magma seeps through these cracks, rising to the surface. When the magma finally reaches the surface, you get a volcanic eruption. What started out as magma inside the Earth becomes lava, ash, gas and volcanic rock.

Magma chambers are hard to detect. That’s because they can be deep underground. The magma chambers that scientists actually know about are only 1 to 10 km under the surface. Scientists can identify the location of magma chambers through seismology. They detect the minor earthquakes that happen as magma moves up through through the rock into and out of a magma chamber.

Once a volcano erupts, it empties out the magma chamber, causing the surrounding rock to collapse inward. If enough rock collapses, you can get a large depression at the surface of the Earth called a caldera.

In 2006, drillers in Hawaii accidently pierced into an active magma chamber. It was the first time that magma had ever been studied “in its natural habitat.” They were searching for geothermal energy sources at a depth of 2.5 km when their drill bit went into the magma chamber. Molten rock went back up the bore hole several meters and then solidified so the scientists could study it.

We have written many articles about volcanoes for Universe Today. Here’s an article about the difference between magma and lava. And here’s an article about different types 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.

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The material that erupts out of a volcano starts as magma deep underground. Much of this magma is rock, but it can also contain pockets of volcanic gas dissolved into it. As the magma rises up, these dissolved gasses begin to form tiny bubbles as the pressure gets lower. As it gets closer to the surface, the bubbles increase in number and size creating additional pressure inside the volcano.

The volcanic gas undergoes a tremendous increase in volume when the magma reaches the surface and erupts. This expansion can be the driving force of explosive eruptions.

The primary components in volcanic gas are water vapor, carbon dioxide and sulfur (either sulfur dioxide or hydrogen sulfide). But you can also find nitrogen, argon, helium, neon, methane, carbon dioxide and hydrogen. Approximately 60% of total emissions released by volcanoes is water vapor, and carbon dioxide accounts for 10 to 40% of emissions. Although that sounds like a candidate for greenhouse gases, volcanoes actually contribute only 1% of the carbon dioxide released into the atmosphere every year.

You might be surprised to know that poisonous gases were responsible for about 3% of all volcano-related deaths from 1900 to 1986. Some people were killed by acidic corrosion (ouch) while others were asphyxiated.

We have written many articles about volcanoes for Universe Today. Here’s an article about different types of volcanoes, and here’s an article about the biggest volcano in the Solar System.

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.

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Named after the volcano Stromboli in Siciliy, Strombolian eruptions are one of the most beautiful to watch; and fortunately, they’re one of the less dangerous types of eruptions. A Strombolian eruption has huge blobs of lava and hot rocks bursting from the volcano’s vent. As the lava hits on the sides of the volcano, it streams down the slopes in fiery rivers.

Strombolian eruptions occur when gas inside the volcano coalesces into bubbles, called slugs. These grow large enough to rise through the magma column. Once they reach the top of the magma column, they burst because of the lower air pressure, and throw magma into the air. Imagine a soap bubble popping, throwing soapy material everywhere. During an eruption, these gas bubbles can be popping every few minutes.

Since a Strombolian eruption doesn’t cause catastrophic damage to the volcano itself, they can keep going for years and years. In fact, Stromboli itself has been erupting this way for thousands of years. Another famous Strombolian volcano is Mount Erebus in Antarctica.

One of the best ways to experience a Strombolian eruption is to see it at night. That when the glowing blobs of magma are easily seen against the dark sky.

We have written many articles about volcanoes for Universe Today. Here’s an article about different types of volcanoes, and here’s an article about different types of lava.

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.

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Think about a classic volcanic eruption, with a huge cloud of volcanic ash rising up from a giant cinder cone. That’s a Plinian eruption, named after the Roman statesman Pliny the Younger, who witnessed the eruption of Italy’s Mount Vesuvius in 79 AD. As you probably know, that eruption desctroyed the downs of Pompeii and Herculaneum, killing thousands of people.

Plinian eruptions are associated with volatile-rich dacitic to rhyolitic lava, and they typically erupt from stratovolcanoes (think Mt. Fuji). A Plinian eruption can go on for hours or days, sustaining a giant eruptive column. The thrust of the expanding gases give the volcanic material an exit velocity of several hundred meters per second. Some of these eruptive columns can reach heights of 45 km.

What goes up has to come back down. The material thrown so high in a Plinian eruption rains back down over a large area, covering everything in a thick covering of ash. Cubic kilometers of ash can come down on the surrounding landscape.

Plinian eruptions can also generate one of the most dangerous events associated with volcanic eruptions: pyroclastic flows. This is where an eruptive column can collapse. Instead of flowing up high into the air, the hot gas, rock and ash coming from the volcano flows down its steep sides, reaching speeds of 700 km/hour. Everything in the path of the flow is destroyed by this high speed, superheated gas and rock. Pyroclastic flows have been known to travel hundreds of kilometers from an eruption site.

We have written many articles about the Earth for Universe Today. Here’s an article about different types of volcanoes, and here’s an article about different types of lava.

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.

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The Earth’s mantle, just a few dozen kilometers beneath your feet is incredibly hot. The high temperatures cause rocks to melt and form magma that collects in vast chambers beneath the Earth’s surface. Since it’s lighter than the surrounding rock, this magma makes its way up through weaknesses in the rock until it reaches the Earth’s surface erupting as a volcano. The spot where it erupts is known as a volcanic vent.

A volcanic vent is that spot in the Earth’s crust where gases, molten rock, lava and rocks erupt.

Volcanic vents can be at the top of some of the largest volcanoes on Earth, like Hawaii’s Mauna Kea, or they can be openings in the Earth’s crust down at the bottom of the ocean. The shape of the volcanic vent can sometimes define whether the volcano is explosive or not. A fissure vent can be a few meters wide and many kilometers long. Lava pours out of fissure vents, creating lava channels, but they don’t usually explode.

The tall familiar cone shaped stratovolcano (like Mount Fuji) can have one volcanic vent at the top of the mountain, but also have many smaller volcanic vents across the flanks of the volcano where smaller eruptions occur. These large volcanoes can erupt explosively, posing a great danger to people living nearby.

In the case of very viscous (or thick) lava, you can get a slow buildup of material into a lava dome. The lava is so thick that it doesn’t move very far from the volcanic vent. Instead it just plugs it up, forming a bulging dome of material. These can also explode violently.

We have written many articles about volcanoes for Universe Today. Here’s an article about different types of volcanoes. And here’s an article about underwater 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.

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Here on the surface of the Earth, the ground is relatively cool. But as you descend into the Earth, things get hotter and hotter, eventually reaching hundreds or even thousands of degrees C. The hot temperatures inside the Earth’s mantle can melt rock; this is magma.

Magma collects in large pools underneath the surface of the Earth in vast magma chambers. Because it’s lighter than the surrounding rock, it makes its way upwards through weaknesses in the Earth’s crust until it reaches the surface. When the magma reaches the surface, it can extrude as lava, or even erupt violently throwing up ash and even rocks.

The temperature of magma can range between 700 and 1300 degrees Celsius depending on the chemical composition of the rocks. You might be surprised to know that the interior of the Earth is a solid, not liquid. The magma only forms in regions where the temperatures are high and the pressures are low; typically within a few kilometers of the surface of the Earth.

The melted magma comes from rocks under huge temperatures and pressures. Most rocks are a collection of different minerals, which can have different melting points. When one part of the rock starts to melt, the rest remains solid. This causes the melted material to squeeze out in small globules. These globules collect together to fill up the magma chamber underneath a volcano.

All igneous rock found on the Earth was originally formed as magma.

We have written many articles about the Earth for Universe Today. Here’s an article about the difference between magma and lava.

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.

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All lava isn’t the same. There can be tremendous differences in the viscosity (thickness), temperature and chemical composition of lava. The least viscous (least syrupy) lava is known as pahoehoe, and it can flow for many kilometers away from the source of a volcanic eruption. One of the longest flows ever recorded was an eruption from Mauna Loa that was 47 km long.

In fact, when you think of an erupting volcano, with vast rivers of lava flowing out, that’s pahoehoe – it’s a Hawaiian term. It’s a basaltic lava that once hardened has a smooth, ropy surface. In fact, it can have such beautiful shapes that people call it lava sculptures. The strange shapes happen because the front of the lava flow forms a thin shell, and then blobs continually break out from the crust. These cool and then more lava breaks out from that.

Once the pahoehoe lava flows finally cool, the resulting rock is incredibly smooth; they’re smooth down to a scale of just a few millimeters. This is very different to aa lava flows, which feel like jagged glass once they harden. Pahoehoe is smooth and nice to walk across, while a’a lava will ravage your shoes and give you a nasty cut if you happen to fall on it.

We have written many articles about the Earth for Universe Today. Here’s an article about all the different types of lava, and here’s an article about a’a lava.

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.

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If you’ve ever visited the Big Island of Hawaii, you’ll get a chance to see one of nature’s most amazing formations: a lava tube. Lava tubes are natural tunnels where lava flows underneath the ground, sometimes for many kilometers. After the eruption is over, you can be left with a long empty tunnel that seems almost man made.

A lava tube happens when low viscosity lava forms a continuous hard crust that gets thicker and thicker, while lava is flowing inside it. Eventually the lava forms a thick hard crust above, but low viscosity lava continues to flow inside. In fact, the thick sides act like insulation to keep the inner lava hot and molten. When the eruption finally ends, the lava flows out of the tube, emptying it out.

Lava tubes can be many meters wide, and typically run several meters below the surface. One tube on Mauna Loa starts at the eruption point and then flows about 50 km to the ocean. Inside the tube there can be various formations, like lava stalactites known as lavacicles (named after icicles). You can also get pillars that stretch from the top to the bottom of the lava tube.

Some of the most well known lava tubes are Thurston Lava Tube in Hawaii Volcanoes National Park, and Lava Beds National Monument in Northern California.

We have written many articles about the Earth for Universe Today. Here’s an article about different types of lava. And here’s an article about lava flows in general.

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.