Types of Lava

A'a lava

There are several different types of volcanoes: steep stratovolcanoes, wide shield volcanoes, and mounded lava domes. The shape of a volcano actually depends on the types of lava that it’s made up of. And so, there are several different types of lava.

The type of lava coming out of a volcano depends on its mineral content. Some lava is very thin, and can flow out of a volcano in great rivers that go for dozens of kilometers. Other lava is very thick, and only flows for a short distance before cooling and hardening. And some lava is so thick that it barely “flows” at all, and can plug up the plumbing of a volcano.

The main types of lava have been given Hawaiian names, because of the volcanic nature of the Hawaiian islands. You can find examples of different kinds of lava flows on the island.

A’a
Pronounced “ah-ah”, this is a basaltic lava that doesn’t flow very quickly. It looks like a slowly moving mass of hot jello, with cooler, rough surface. Once it hardens, the sharp spiny surface of a’a lava is extremely difficult to walk across. These types of lava erupt at temperatures above 1000 to 1100 degrees C.

Pahoehoe
Pronounced “pa-ho-ho”, this type of lava is much thinner and less viscous than a’a. It can flow down the slopes of a volcano in vast rivers. The surface of the lava congeals into a thin crust that looks very smooth. Pahoehoe lava can also form lava tubes, where the rock hardens around a fast-moving liquid core. When that core flows out of the tube, a long tunnel remains. Pahoehoe erupts at temperatures of 1100 to 1200 C.

Pillow Lava
Pillow lava is typically found erupting from underwater volcano vents. As soon as the lava contacts the water, it’s cooled down and forms a hardened shell. As more lava issues from the vent, the shell of lava cracks and more “pillows” come out of these cracks.

We have written many articles about volcanoes for Universe Today. Here’s an article about the temperature 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.

First Views of ISS at Full Length, Full Power

ISS at full length, taken from Discovery. Credit: NASA

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Space shuttle Discovery undocked from the ISS on Wednesday, providing the dramatic first views of the space station with its full company of solar arrays unfurled. “Discovery, Alpha, Godspeed,” ISS commander Mike Fincke radioed after the shuttle departed. “Thanks for making us symmetrical, giving us full power, and all the other wonderful things you did for us. You did great work. Come again.”

“Thanks for the great work as well,” shuttle commander Lee Archambault replied. “Have a good one, we’ll see you on the ground in about a month.”

The fly-around was timed to begin at orbital sunrise, to allow for good lighting for the much anticipated pictures. But everyone had to wait until later for a high-definition video replay on NASA TV. The shuttle’s KU-band television antenna didn’t have a good link with NASA’s relay satellites until after the fly-around was complete. The image above has been updated to show an official NASA image taken by the Discovery astronauts during the flyaround, and below are a few screenshots from the high-def replay, showing different views of the ISS, post undocking.

UPDATE: Video of the flyaround is now available, and can be seen below:


Screenshot of ISS flyaround by shuttle Discovery.  Credit: NASA TV
Screenshot of ISS flyaround by shuttle Discovery. Credit: NASA TV

ISS.  Credit: NASA TV
ISS. Credit: NASA TV

At a mission briefing after the undocking, mission managers expressed their excitement at seeing the images of the space station at full length, saying they felt an extreme amount of pride and joy for everyone involved with the ISS project.

“We’re getting ready to turn the station over to the research community,” said Dan Hartman, chairman of the space station mission management team, “and they will be challenged to keep the crew busy — and that’s a good thing. By the end of May (when the ISS crew size will increase to six), we’ll be ready to go.”

The Discovery crew took Sandy Magnus along with them, bringing her her home after her long-duration stay on the ISS, and left behind Koichi Wakata, Japan’s first long-duration astronaut.

The shuttle is scheduled to land on Saturday, March 28 with the first landing opportunity at 1:43 pm EDT.

What is the Temperature of Lava?

Lava fountain in Hawaii.

The temperature of lava when it is first ejected from a volcanic vent can vary between 700 and 1,200 degrees C (1,300 to 2,200 F).

As you probably know, lava is molten rock that comes out of a volcano during an eruption. Although the Earth’s mantle is solid, it’s so hot that puddles of molten rock can form between the mantle and the Earth’s crust. This lava is less dense than the surrounding rocks, and so it makes its way to the surface through cracks and faults in the Earth’s crust. Eventually, it erupts to the surface.

Even though lava is much thicker than water, it can flow great distances across the surface of the Earth before it cools and hardens. Some lava is very thin, and can flow many kilometers, while other lava is thick and doesn’t flow at all; it just piles up around the volcanic vent.

Whether lava is thick or thin doesn’t depend on the temperature of the lava. Instead it’s caused by the minerals in the lava. The coolest lava are felsic lavas, which can erupt at temperatures as low as 650-750 C. Next are the andesitic lavas, which erupt in the range of 750-950 C. Basaltic lavas typically erupt at temperatures above 950 C.

We have written many articles about volcanoes for Universe Today. Here’s an article about the recent eruption of Alaska’s Redoubt volcano, and here’s an article about the biggest volcano on 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.

Stratovolcano

Mount Fuji - a composite volcano

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Stratovolcanoes, or composite volcanoes, are some of the largest, most familiar mountains on Earth. Perhaps you’ve heard of Mount Fuji, Mount Kilimanjaro, or Mount Rainier? These are stratovolcanoes. They’ve got that familiar shape with the gently sloping lower sides and then the sharp cone shape at the top. They make up 60% of the Earth’s individual volcanoes.

They typically have a layered or stratified appearance, with alternating lava flows, mudflows, fallen ash, and other debris. They usually form along the margins of the Earth’s tectonic plates, where one plate is pushing beneath another, or they’re sliding together. This creates weaknesses in the Earth’s crust, where magma from beneath the surface can escape.

Stratovolcanoes will usually have a central caldera, or crater, at the top, but they will also have a network of vents. They can have many lava domes and smaller vents where eruptions can occur; not just from the top. The lava flows out of them is extremely thick, and sometimes it barely flows at all. This lava plugs up the plumbing in stratovolcanoes, allowing them to build up tremendous amounts of pressure.

Of all the volcanoes on Earth, stratovolcanoes are the most dangerous. They can erupt with little warning, releasing enormous amounts of material. And they don’t always erupt nicely from their tops. As we saw with Mount Saint Helens, they can blast out material from the side, creating pyroclastic flows the hurtle down the volcano’s flanks at enormous speeds. Some classic eruptions of stratovolcanoes include the island of Krakatoa, which detonated in 1883, sending ash 80 km into the atmosphere.

We have written many articles about volcanoes for Universe Today. Here’s an article about how a volcano triggered a lightning storm. And here’s an article about the largest 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.

Lava Domes

Lava Dome

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Not all volcanoes are the familiar cone-shaped mountains with lava spewing out of the top. Sometimes you can get a very slow eruption, underneath the ground, where a mound of earth rises up above the surroundings. These are called lava domes.

Lava domes form when you have slow eruption of very thick lava, or multiple eruptions of different kinds of lava. Instead of breaking through to the surface, the material builds up underneath the ground, causing the huge lava dome mound to form. It’s so thick that the lava can’t flow very far at all, it just hardens quickly, extruding new material around the vent. They can grow for months or years, eventually building up to several hundred meters in height. Large composite volcanoes can have hundreds of lava domes across their flanks.

The sides of lava domes are very steep, and can cause rockslides around because of the extrusion of new lava. This can bury the surrounding landscape, and even start forest fires if the rocks are still hot. The surfaces of lava domes are rough and blocky because of the fragmentation of rock shell as the dome grows.

As you can probably guess, this buildup of lava and gas can be dangerous. Although people can avoid the growth of a lava dome, they can be a problem for buildings that can’t be moved. But an even more dangerous problem with lava domes is the fact that they can explode violently, without warning, releasing pyroclastic flows of ash and mud for more than 20 km around the dome itself. In 1902, an eruption from a dome on Mont Pelee in Martinique killed 30,000 people with high-velocity ash flow and poisonous gasses.

We have written many articles about volcanoes for Universe Today. Here’s an article about how a volcano in Chile triggered a lightning storm, and here’s an article about cinder cone 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.

Don’t ‘Supermassive’ Me: Black Holes Regulate Their Own Mass

black-hole
Crowded star field around GRS 1915 and its close-up (inset). Credits: X-ray: NASA/CXC/Harvard/J. Neilsen et al. Optical: Palomar DSS2.

Stellar-mass black holes, between 7 and 25 times the Sun’s mass, are  called  “micro-quasars” when they spawn powerful jets of particles and radiation, miniature versions of those seen in quasars. Stellar-mass black holes are on the small end of the scale opposite supermassive black holes, including those in quasars, which weigh millions to billions of times the mass of the Sun.

The micro-quasars’ jets may be part of a secret weapon for keeping their petite figures, according to new research.

Continue reading “Don’t ‘Supermassive’ Me: Black Holes Regulate Their Own Mass”

This Week’s Where In The Universe Challenge

where-in-the-universe-482
It’s Wednesday, so that means its time for another “Where In The Universe” challenge to test your visual knowledge of the cosmos. See if you can name where in the Universe this image is from, and give yourself extra points if you can name the spacecraft responsible for the image. Make your guess and post a comment. Check back sometime on Thursday to find the answer and see how you did. And remember, no posting links to the answer!! (that’s for RapidEye, who needed a reminder….)

UPDATE: The answer has now been posted below.
Continue reading “This Week’s Where In The Universe Challenge”

How Are Volcanoes Formed?

Wolf Volcano. Image credit: NASA

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Some of the most dramatic mountains in the world are volcanoes. Volcanoes can grow to enormous heights quickly, sometimes just a few years. But have you ever wondered, how are volcanoes formed?

As you probably know, you’re standing on the Earth’s crust; a relatively thin layer of solid Earth. Beneath this is the mantle, an extremely hot region just a few dozen kilometers beneath your feet. Although the mantle is almost entirely solid, it can form small pockets of liquid rock and hot gasses. It’s hard to think of this way, but the molten rock – called magma – is more buoyant than the surrounding solid rock. It slowly forces its way upward through weaknesses in the Earth’s crust. These become volcanoes.

When the magma reaches the surface, it wells out onto the surface forming a volcano. What kind of volcano forms depends on the size of the crack in the crust, and the kind of lava that comes out. Some lava is very fluid, and can flow for long distances. This kind of lava creates shield volcanoes, like in the Hawaiian islands. Other lava is very thick, and doesn’t travel very far, creating the more familiar cinder cone shaped volcanoes.

Some very energetic volcanoes will spew rock, ash and magma high into the air. This material falls back down around the vent, and this is how the volcano builds up. The volcano is like a big debris pile surrounding the volcanic vent.

The largest, most dramatic volcanoes in the world are composite volcanoes, or stratovolcanoes. These can have vast networks of volcanic vents and chambers, with many openings to the surface. They can be made up of lava flows and deposits of ash that build up into huge mountains over millions of years. Some of the most dramatic mountains in the world are composite volcanoes: Mt. Fuji, Mt Kilimanjaro, and Mt. Rainier, for example.

We have written many articles about the volcanoes for Universe Today. Here’s an article about the biggest volcano on Earth, and here’s the tallest volcano.

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.

ISS/Shuttle Crews Take Call from President Obama

Obama and friends chat with ISS astronauts. Image Credit: White House/Pete Souza

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The ten astronauts aboard the International Space Station chatted with US President Barack Obama – along with some school children and Congressmen (“big kids when it comes to talking to astronauts,” Obama said). Topics discussed during the 30 minute conversation included the new solar arrays installed by the STS-119 crew, extraterrestrial life, video games, space food and exercise. Obama got a big laugh in orbit and on the ground when said he was glad the astronauts were using a hands-free phone since they were cruising along at 17,500 mph. He also asked if the astronauts still drank Tang, which didn’t even merit a reply from space.

The president told the ISS crews and the visiting shuttle crew he was extraordinarily proud of them for their work the past week, and wanted details of how they installed the new solar panels.

“We’re investing back here on the ground a whole array of solar and other renewable energy projects and so to find out that you’re doing this up at the space station is particularly exciting,” Obama said.

Last week’s addition of the last set of solar wings doubled the amount of power available for science experiments and will help support a larger crew in a few months.

Obama also asked Sandy Magnus, who has been on board the ISS for several months, and the only woman on board, whether she was ever tempted to cut her hair, which floated around her head. She said no, and the president called it “a real fashion statement.”

Obama also noted the “international-ness” of the ISS and said, “One of the things about this that this is an international space station, and we hope this is an example of the sort of spirit of cooperation we can apply not just in space by here on the ground as well.”

To watch the complete interview, CollectSPACE has the video.

The space shuttle crew departed from the ISS on Wednesday.

IYA Live Telescope Today – The Jewel Box Cluster

If you didn’t get a chance to watch the IYA telescope “live” on Galactic TV today, don’t worry. We took a video capture for you. Step inside to enjoy today’s view of NGC 4755…

The Jewel Box (also known as NGC 4755 or Kappa Crucis Cluster) is an open cluster in the constellation of Crux. As Kappa Crucis, it has a Bayer designation despite the fact that it is a cluster rather than an individual star.

It is one of the finest open clusters discovered by Nicolas Louis de Lacaille when he was in South Africa during 17511752. This cluster is one of the youngest known, with an estimated age of only 7.1 million years. It has an apparent magnitude of 4.2, and is located 6,440 light years from Earth and contains around 100 stars. This famous group of young bright stars was named the Jewel Box from its description by Sir John Herschel as “a casket of variously coloured precious stones,” which refers to its appearance in the telescope. The bright orange star Kappa Crucis contrasts strongly against its predominantly blue, hot companions. Kappa Crucis is a very large (hence very luminous) young star in its red supergiant stage, which paradoxically indicates that its life is drawing to a close. The cluster looks like a star to the unaided eye and appears close to the easternmost star of the Southern Cross, (Beta Crucis), so is only visible from southern latitudes. (Information courtesy of Wikipedia)

Right now the IYA remote live telescope is a work in progress. Be aware that video recordings will be jerky until we get some of the system bugs worked out. As always, you can visit the remote telescope by clicking on the IYA “LIVE Remote Cam” Logo to your right. We’ll be broadcasting whenever skies are clear and dark in Central Victoria! Enjoy….