Category: Astronomy

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Feel the ground. It’s nice and cool, right? Well, dig down a few kilometers and things really heat up. Once you’re down more than 30 km, and temperatures can reach more than 1,000 degrees C; that’s hot enough to melt rock. The melted rock is called magma, and it collects into vast chambers beneath the Earth’s surface. The molten rock is less dense than the surrounding rock and so it “floats” upwards through cracks and faults. When the magma finds its way to the surface, it erupts as lava, rock, ash and volcanic gases; this is a volcanic mountain.

A volcanic mountain starts out as a simple crack in the Earth called a volcanic vent. Magma erupts out of the ground as lava flows, clouds of ash, and explosions of rock. This material falls back to Earth around the vent, and piles up around it. Over time (and sometimes quite quickly) a volcanic mountain builds up, with the familiar cone shape.

There are different kinds of volcanic mountains. Cinder cone mountains are made up of material blasted out that rains back down. They don’t usually grow too large. Shield volcanoes are built up by many lava flows of low viscosity lava (low viscosity means that it flows more easily). The lava can flow for dozens of kilometers, and the volcano can be very wide. A stratovolcano or composite volcano is made up of many layers of ash, rock and hardened lava. Some of the largest, most impressive volcanoes in the world are stratovolcanoes (think about Mount Fuji or Rainier).

And we don’t just have volcanic mountains here on Earth. The largest mountain in the Solar System is Olympus Mons on Mars. This enormous shield volcano has grown to more than 21 km tall. There are also active volcanoes on Jupiter’s moon Io.

We have written many articles about volcanoes for Universe Today. Here’s an article about the biggest volcano in the Solar System, 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 interior of the Earth is hot enough to melt rock, and that’s just what happens. Melted rock squeezes together into vast pools of magma beneath the ground. Since it’s less dense than the surrounding rock, it makes its way upward to the surface. If the magma reaches the surface you get a volcano; with the ash, and the lava and the explosions. But if the magma pushes up but doesn’t actually crack through the surface, you can get a dome mountain.

Dome mountains don’t usually get as high as folded mountains because the force of the magma underneath doesn’t push hard enough. Over a long period, the magma cools to become cold, hard rock. The result is a dome-shaped mountain.

Over long periods of time, erosion wipes away the outer layers of the mountain, exposing the dome-shaped cooled magma of harder rock.

An example of a dome-shaped mountain is Half Dome in the Sierra Nevada range in California. It’s made of granite, and was once a large blob of magma pushed up through the Earth. Granite is much harder than other rock, and so it doesn’t erode as easily as the rest of the mountain. The softer layers of sedimentary rock were washed away, leaving the hard granite dome.

Other dome mountains aren’t so easy to spot. You need satellite images to see the circular shape in the Earth’s surface.

We have written many articles about the Earth for Universe Today. Here’s an article about how satellites can measure the movement of the Earth after an earthquake.

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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Some of the most dramatic mountains in the world are fold mountains. These are created when two of the Earth’s tectonic plates crash together – like in a head-on car crash. The edges of the two plates buckle and fold, and the peaks of these folds are mountains. Entire mountain ranges, thousands of kilometers long, are created during these slow motion collisions between tectonic plates.

Some famous examples of fold mountains are the Himalayan mountains in Asia and the Rocky Mountains in North America. Consider the fact that the Earth’s tectonic plates are moving very slowly, just a few centimeters every year. These folding collisions play out in incredibly slow motion, taking millions of years. The Indian subcontinent crashed into Asia 24 million years ago, and since then it has built up the Himalayan mountains – the tallest mountains in the world. In fact, the Himalayans are still growing.

Want to make your own folded mountain range? Take two flat strips of modeling clay and put them side to side. Then slowly push one strip into the other and you’ll see how one or both will crumple up under the pressure. You’ll make your own mini mountain range.

We have written many articles about mountains for Universe Today. Here’s an article about different types of mountains.

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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How were the famous “Pillars of Creation” formed? Perhaps only the shadow knows! New research suggests that shadows hold the key to how giant star-forming structures like the “Pillars” in the Eagle Nebula take shape.

The pillars are dense columns within giant clouds of dust and gas where massive stars form. Several theories have been proposed to explain why the pillars develop around the edge of ionized gas bubbles surrounding young, very hot stars. Using computer models, a group of astronomers from the Dublin Institute of Advanced Studies has found that partially-shadowed clumps of gas tend to creep towards darker areas, causing pile-ups behind dense knots of gas and dust that screen the intense ultraviolet light emitted by the stars.

Jonathan Mackey, who is presented the results at the European Week of Astronomy and Space Science in the UK said, “We created a simulation with a random distribution of lots of dense clouds with different sizes and shapes. We found that in certain cases a number of clouds can merge together in the shadows to form structures that look very like observed pillars. They are sufficiently dense to match the observations, can form in about 150,000 years and can survive for about 100,000 years. Although this is a preliminary study, we believe our results are quite robust and will be confirmed by more detailed modeling.”

The team, led by Dr. Andrew Lim, found that the configuration of clumps of gas had to be favorable for the pillars to form. Some age estimates put the Eagle Nebula pillars at no more than 100,000 years old, and models show that the shadow from a single clump would not attain the density to form a pillar in that relatively short timescale.

“Many of our models do not produce pillars that are as long and narrow as those in the Eagle Nebula, at least not at the observed gas density. It needs the right configuration of dense clumps of gas to form a long pillar. Unless the shadowed region is already very dense to begin with, it just takes too long to collect and organize the gas into a pillar,” said Lim.

The group plans to add increasing levels of realism to the model over the next couple of years, bringing in more accurate representations of the complex chemistry of interstellar gas, the effects of radiation from diffuse sources. Adding in the effects of gravity will also be important as the pillars contain dense gas condensations which are in the process of collapsing under their own weight to form the next generation of stars.

Mackey said, “Gravity is relatively unimportant when the pillars are forming, but there comes a point when they get very dense and it cannot be ignored any longer. We plan to include gravitation in future work so that we can study the next generation of stars which are forming in the pillars.”

Source: RAS

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Pelean eruptions, or Nuee Ardente eruptions occur when a large quantity of gas, dust, ash and lava fragments are blown out of a volcano’s central crater. This material falls back, and then travels down the side of the volcano at tremendous speeds – faster than 150 km/hour.

These eruptions are also known as pyroclastic flows, and they’re one of the most dangerous kinds of eruptions that volcanoes can do. Material blasted out in a Pelean eruption can tear through populated areas, killing thousands of people.

Pelean eruptions got their name from Mont Pelee, the volcano that caused tremendous destruction on Martinique, Lesser Antilles in 1902. The Pelean eruption and following pyroclastic flows killed more than 30,000 people in the worst volcanic disaster of the 20th century. The town of St. Pierre was effectively wiped off the map by a series of powerful eruptions.

We have written many articles about volcanoes for Universe Today. Here’s an article about Plinian eruptions, and here’s an article about Strombolian eruptions.

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.