Author: Fraser Cain

[/caption]
The biggest volcano on Earth is Hawaii’s Mauna Loa, rising to an elevation of 4,169 above sea level and with an estimated volume of 75,000 cubic kilometers. But did you know that Mauna Loa is also the largest active volcano? Mauna Loa’s most recent eruption started on March 24, 1984 and lasted until April 15, 1984. An eruption that recent makes it a very active volcano.

Mauna Loa is the biggest volcano in the world because it’s so active. The enormous mass of the volcano is pushing down on the sea floor, creating a deep depression that it’s sinking down into. Furthermore, the mass of the volcano is causing it to further settle and flatten out. When volcanoes start out, the new eruptions cause them to gain elevation faster than they shrink through settling and erosion. But when a volcano gets really large, it has to erupt regularly to continue gaining elevation.

The size and shape of Mauna Loa is still changing; although, very slowly. The caldera at the summit of Mauna Loa recently opened up about 10 cm during a period of eruption in 1975, and it’s believed that the peak was lifted up by about 13 cm. But then in the 1984 eruption, the peak subsided at least 61 cm. Geologists expect that large portions of Mauna Loa’s flanks will slide off the mountain into the ocean. This will shrink the volcano somewhat, but it will still be the largest volcano in the world.

It’s still a very active volcano, having erupted 33 times since historical records were first kept.

We have written many articles about volcanoes for Universe Today. Here’s an article about the tallest volcano in the world, 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.

[/caption]
I just like to take a second and direct your attention to an amazing resource developed for Universe Today by our astronomy guide Tammy Plotner. It’s a guide to all 88 constellations in the sky. Each entry has a chart for the region of the sky, descriptions of the major objects you’ll find there, background mythology, and a guided tour through each constellation with binoculars or a telescope. I’m really grateful for Tammy’s work on this, and I hope you find it really helpful, whether you’re an experienced astronomer or want to start exploring the constellations. Of course, it’s totally free for you all to use.

Here’s the full list of all the constellations:

• Andromeda
• Antila
• Apus
• Aquarius
• Aquila
• Ara
• Aries
• Auriga
• Bootes
• Caleum
• Camelopardalis
• Cancer
• Canes Venatici
• Canis Major
• Canis Minor
• Capricornus
• Carina
• Cassiopeia
• Centaurus
• Cepheus
• Cetus
• Chamaeleon
• Circinus
• Columba
• Coma Berenices
• Corona Australis
• Corona Borealis
• Corvus
• Crater
• Crux
• Cygnus
• Delphinus
• Dorado
• Draco
• Equuleus
• Eridanus
• Fornax
• Gemini
• Grus
• Hercules
• Horologium
• Hydra
• Hydrus
• Indus
• Lacerta
• Leo
• Leo Minor
• Lepus
• Libra
• Lupus
• Lynx
• Lyra
• Mensa
• Microscopium
• Monoceros
• Musca
• Norma
• Octans
• Ophiuchus
• Orion
• Pavo
• Pegasus
• Perseus
• Phoenix
• Pictor
• Pisces
• Piscis Austrinus
• Puppis
• Pyxis
• Sagitta
• Sagittarius
• Scorpius
• Sculptor
• Scutum
• Serpens Caput
• Serpens Cauda
• Sextans
• Taurus
• Telescopium
• Triangulum
• Triangulum Australe
• Tucana
• Ursa Major
• Ursa Minor
• Vela
• Virgo
• Volans
• Vulpecula

[/caption]
The Hawaiian Island chain is a group of islands formed by the constant eruption of a volcanic hotspot underneath the Earth’s tectonic plates. The slow movement of the Pacific plate carries the islands away from the volcano hotspot, so the volcanoes go dormant and eventually extinct. The tallest volcano and the largest volcano in the world are located in Hawaii. Even the most active volcano in the world can be found in Hawaii. If you want to see volcanoes, it’s the place to go.

Hawaii Volcanoes

• Mauna Loa – This active shield volcano is the second tallest volcano in the world, but it’s thbiggest volcano in the world. It has erupted within the last century.
• Hualalai – The third most active volcano in Hawaii.
• Kohala – the oldest of the 5 shield volcanoes that make up the Big Island of Hawaii.
• Kilauea – An active volcano on the eastern side of the Island of Hawaii. It’s in an almost constant state of eruption.
• Mauna Kea – The tallest volcano in the world, located on the Big Island of Hawaii.

We have written many article about volcanoes for Universe Today. Here’s some information about shield volcanoes, the kind found in Hawaii.

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.

[/caption]
Scoria is a kind of rock produced by volcanic activity. Like pumice, it forms when lava which is rich in gas cools quickly. It forms when molten rock is rising in a volcanic pipe, the decreasing pressure allows the gas to expand out (like opening a can of soda releases carbon dioxide).

Scoria rocks can either form inside the volcano, and be ejected out in eruptions. Or it can erupt as lava that cools quickly before the gas bubbles can escape the rapidly cooling rock. Scoria is similar to pumice, in that it has bubbles of gas trapped within it, but the bubbles are much smaller. Unlike pumice, scoria doesn’t usually float in water.

Another name for scoria is cinder, and it’s the primary component of cinder cones. These are relatively small volcanoes that appear suddenly, built up to a maximum height of a few hundred meters and then go extinct. The cone builds up from the scoria, rock and ash ejected from the volcano, which rains back down around it.

While pumice ranges in color from white to black, scoria is darker in color, ranging from dark brown, to black to red. The Easter Island statues were carved out of volcanic rock, and the red stones on top were carved out of a different type of scoria rock prized for its red color.

We have written many articles about volcanoes and rocks for Universe Today. Here’s an article about obsidian, a type of volcanic glass produced when lava cools quickly. And here’s an article about basalt, rocks formed from cooled 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.

[/caption]
Volcanoes have many ways to kill you, from hot lava, rocks blasted through the air, to poisonous gasses. But one of the most dangerous parts of a volcano are mud flows that can stream down their sides, following the path of river valleys. Volcano lahars have been the cause of many deaths in the last few centuries. With more people living close to or even on the flanks of steep volcanoes, even more deaths are certain.

Lahars are volcanic mudflows, and they don’t have to come directly from volcanic activity. They occur when huge amounts of volcanic ash, mixed with water flows down the side of a mountain. They can flow at speeds more than 100 km/hour, following the path of a river valley, but with the weight of concrete. Lahars are liquid when they’re flowing, and then harden almost solid when they stop. One cause of a volcano lahar is an eruption, when volcanic ash mixes with a volcano glacier, creating this muddy mixture. It’s also possible for a lahar to form when a lake or dam breaks, mixing water with ash already on the side of a volcano.

And they’ve caused terrible damage. The eruption of Nevado del Ruiz in Columbia in 1985 sent lahars down the mountainside, burying the city of Armero under 5 meters of mud and debris. A lahar coming off Mount Rainier in Washington sent a wall of mud 140 meters deep, covering a total area of 330 square kilometers – 300,000 people now live in the area covered by that lahar. In the recent eruption of Mount Pinatubo in 1991, 700 people were killed by the lahars that came down the mountain after the intense rainfall that followed the eruption.

The term lahar comes from the Indonesian word for “wave”.

We have written many article about volcanoes in Universe Today. Here’s an article about pyroclastic flows, and here’s an article Plinian eruptions which can cause pyroclastic flows.

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.

[/caption]
Mexico is known for its beaches and historical ruins, but did you know that Mexico has some of the most spectacular volcanoes in North America? It has the tallest volcano in North America (the third tallest mountain in North America), and islands formed from shield volcanoes.

Mexico Volcanoes

• Barcena – a volcano on the island of San Benedicto that wiped out all life on the island in 1952.
• Ceboruco – A volcano that had the largest eruption in Mexico in 930 AD.
• Chichinautzin – A volcanic field just outside Mexico City.
• Colima – An active volcano visible from Mexico City.
• El Chichon – A previously unknown lava cone that erupted in 1982, killing 2000 people.
• Jocotitlan Volcano – A distinct horseshoe-shaped volcano.
• Nevado de Toluca – A dormant stratovolcano and Mexico’s 4th highest peak.
• Paricutin – A volcano that appeared suddenly in a Mexican cornfield, rose to a height of more than 400 meters and then stopped growing.
• Pico de Orizaba – A dormant volcano that hasn’t erupted since the 17th century, it’s the third tallest peak in North America.
• Popocatepetl – An active volcano in Mexico, the 2nd tallest active volcano in North America.
• San Martin – A shield volcano near the Gulf Coast of Mexico.
• Socorro – a shield volcano that makes up the largest of the Revillagigedo Islands.
• Tacana – A tall stratovolcano that straddles the border between Mexico and Guatemala

We have written many articles about volcanoes for Universe Today. Here’s an article about Costa Rica volcanoes, and here’s a full list of famous volcanoes around the world.

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.

[/caption]
Jocotitlan is an stratovolcano located about 60 kilometers northwest of Mexico City. It rises to an elevation of 3,900 meters above sea level, but it’s isolated from any other mountains or peaks in the surrounding plains, rising up 1,300 meters above the Toluca basin.

One of its most prominent features is a horseshoe-shaped escarpment visible from the northeast; it formed when the northeast edge of the caldera collapsed. Whenever this event happened, it created an enormous landslide that buried 80 square kilometers of land to the northeast of the volcano.

Jocotitlan formed in the Pleistocene era (11,000 to 1.8 million years ago) primarily out of andesitic-to-dacitic lava flows. After that there was an obsidian dacitic eruptino and then the creation of a lava dome complex. The volcano produced regular lava flows, pumice-fall eruptions and pyroclastic surges. The last known eruption at Jocotitlan happened about 700 years ago, and produced block-and-ash flows and pyroclastic surges.

We have written many article about volcanoes for Universe Today. Here’s an article about other volcanoes in Mexico, and here’s an article about many famous 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.