Lava fountains and flows illuminate the area during the Mauna Loa volcano eruption in Hawaii, U.S. November 30, 2022.
Credit: © Go Nakamura, Reuters/Alamy Images

That’s a whole lotta lava! Mauna Loa, the world’s largest active volcano, erupted on November 27, 2022, and it hasn’t stopped. Mauna Loa is in Hawaii Volcanoes National Park on the island of Hawaii. It rises 13,677 feet (4,169 meters) from sea level to its peak. That is about 12 Eiffel Towers standing on top of each other! At the top is Mokuaweoweo, a crater. But wait, there is more! The Kilauea, a volcano that lies on the southeastern slope of Mauna Loa, is also erupting. The two volcanoes are creating a dual eruption that has continued since late November.

Mauna Loa, meaning long mountain, spans about half the surface of Hawaii’s Big Island. It covers 10.5 miles from the base to the summit. It hasn’t erupted in 38 years! Most volcanologists consider any volcano that has erupted in the last 10,000 years or so to be active. Some of them use the term dormant to describe an active volcano that is not currently erupting or showing signs of a coming eruption. Volcanologists label a volcano extinct if there is strong evidence it will never erupt again.

Mauna Loa’s continued eruption has shot lava into the sky and down the slope of the mountain. The lava flow is dangerously close to a pivotal highway on the Big Island. Daniel K. Inouye highway connects the eastern and western halves of the island. As the lava flow galumphed at a rate of 40 to 60 feet an hour, officials activated the National Guard to the scene on Tuesday, 9 days after the eruption began. Officials have a plan for shutting down the highway if the lava gets much closer.

Scientists can predict the behavior of volcanic eruptions by looking at past eruptions. There is plenty of data on Kilauea since it has erupted off and on since the mid-1950′s. Kilauea erupted in 2018 engulfing around 700 homes in lava and spewing volcanic ash 30,000 feet into the air. While scientists know what Kilauea is capable of, they do not have much information on Mauna Loa.

Mauna Loa’s longest eruption lasted 18 months in 1855-1856. Most of the lava produced by eruptions comes from rifts (cracks) in the mountain’s sides, not from the peak crater. In 1926, lava destroyed a coastal settlement. Parts of other settlements were buried in 1950. A 1984 eruption sent lava flowing to within 4 miles (6.4 kilometers) of the city of Hilo.

May 30, 2018

Earlier this month, on May 3, Kilauea, a large volcano on the “Big Island” of Hawaii, erupted violently and pumped dangerous lava flows near residential neighborhoods, prompting local officials to order emergency evacuations. Since then, dozens of fissures have opened up along the slopes of the volcano, oozing glowing lava or shooting fountains of it high into the air. The volcano has also produced massive columns of smoke and ash and a haze with varying amounts of poisonous gases. As of today, Kilauea’s eruption proceeds without any signs of stopping, and new lava fissures and cracks appear daily.

A massive column of ash and smoke billows from Hawaii’s Kilauea volcano on May 4, 2018, near Pahoa, Hawaii. Credit: U.S. Geological Survey

Volcanologists have used flying drones to monitor Kilauea’s flowing lava as it creeps towards homes and other buildings in the Leilani Estates neighborhood near the town of Pahoa. Hawaii Governor David Ige mobilized the Hawaii National Guard to assist with evacuations and security in the area. So far, 82 homes have been destroyed by lava and around 2,000 residents have been evacuated. Kilauea’s flows have also damaged several other structures, including the Puna Geothermal Venture, a conversion plant that uses heat from volcanic activity to generate electric power.

Lava erupts from a fissure in the Kilauea volcano on May 22, 2018, in Kapoho, Hawaii. Credit: © Mario Tama, Getty Images

Kilauea is one of the world’s most active volcanoes. The current eruption is only the latest of a highly active eruption cycle that began in January 1983. This month’s eruption was preceded by a swarm of small earthquakes caused by the movement of magma beneath Kilauea and the collapse of a volcanic vent in Kilauae’s crater floor. On May 3, 2018, hours after a magnitude-5.0 earthquake, steam and lava spewed from several surface cracks on the eastern side of Hawaii’s Big Island.

Kilauea rises 4,190 feet (1,227 meters) above sea level and constitutes about 14 percent of the land area of the Big Island. Kilauea and massive Mauna Loa are the stars of the area’s Hawaii Volcanoes National Park. Kilauea is a shield volcano, a volcanic mountain with broad, gently sloping sides. Shield volcanoes commonly erupt in fountains of lava. The fountains feed lava lakes within a caldera (large crater), and long, often slow-moving flows seep down the volcano’s sides. Repeated eruptions produce layer upon layer of flows. The layers gradually build the slope upwards and outward, forming a shallow, rounded cone. The name shield volcano refers to such a volcano’s broadly curved shape, which resembles a soldier’s shield. Kilauea’s summit caldera contains a lava lake known as Halema`uma`u. In Hawaiian mythology, the molten lake is the home of the volcano goddess, Pele.

Volcanologists are worried about the many fissures that have opened along the eastern slope of Kilauea, spewing lava, smoke, and ash. Some flows reached the Pacific Ocean, where red-hot lava created huge clouds of steam laced with poisonous and stinky sulfur dioxide. Gases from Kilauea have collected into a toxic volcanic smog that has now drifted as far away as Guam and the Mariana Islands, where residents have been warned to limit outdoor activity.

May 4, 2012

Strange spirals discovered on the surface of Mars strongly suggest that fire, not ice, was responsible for the formation of a region that has puzzled scientists for more than a decade. The spirals–rock formations that look like coils of rope–were discovered by graduate student Andrew Ryan of Arizona State University in images of Athabasca Valles, a network of valleys near the Martian equator. The images were made by a high-resolution camera aboard NASA‘s Mars Reconnaissance Orbiter that can provide clear images of objects about the size of a beach ball at a distance of 185 miles (300 kilometers).

Athabasca Valles is a network of valleys about 185 miles long near the Martian equator. The region’s surface is covered by huge plates that have cracked and broken into thousands of irregularly shaped, multisided blocks. Ryan and his co-author Philip Christensen reported finding 269 spirals, ranging in diameter from 16 to 98 feet (5 to 30 meters), between the blocks.

(NASA/JPL/University of Arizona)

Some scientists have argued that the blocks in Athabasca Valles, which look like Arctic ice floes, formed as sheets of ice moved across the Martian surface. Others argued that the cracks formed because of volcanic activity. Mars has the largest volcanoes in the solar system, including gigantic Olympus Mons. Ryan and Christensen contend that the spirals provide strong evidence for the lava theory. They note that similar features can be seen in the smooth, slow-moving lava flows on Hawaii. There, the rubbery surface of the flows is twisted into coils as the liquid lava streams below move in different directions at different speeds. They argue that a similar process must have produced the spirals in Athabasca Valles. Some scientists, however, continue to argue that ice was responsible for the blocks in the region.

Additional articles in World Book:

• Hawaii Volcanoes National Park
• The Search for Water on Mars (a Special Report)

March 27, 2012

Sometimes things are not as simple as they appear. Take the planet Mercury, for instance. In a very short time, the smallest planet in the solar system (sorry Pluto, you’re no longer a planet) has gone from a simple hunk of rock, much like Earth’s moon, to one of the most unusual planets ever studied. For years, most astronomers thought that Mercury formed early in the solar system’s history and has since remained pretty much unchanged. New evidence shows a planet whose more recent history includes active volcanoes, a shifting crust, and other activities once thought to have ended billions of years ago. Some of these activities may result from the fact that Mercury is slowly shrinking. The shrinking would explain why the outer layer of the planet is buckling and cracking. A closer look at the surface also shows evidence of lava flows having occurred much more recently than previously thought.

The MESSENGER space probe has revealed surprising new findings about the smallest planet in the solar system. (Courtesy of NASA)

The planet’s surface is not the only surprise. Mercury may also have an internal structure like no other planet yet studied by scientists. Mercury appears to have a core consisting of three layers. Earth has only two such inner layers. Both Mercury and Earth have an inner core of solid metal surrounded by a second layer of liquid metal. Unlike Earth, Mercury appears to have a third layer made of solid iron and sulfur. Many scientists now speculate that this possible third layer of core explains one of the great mysteries concerning Mercury. Scientists have long wondered how the planet could be so small and yet have a much greater mass than the other inner planets–Venus, Earth, and Mars–for its size.

The new data on Mercury was collected by the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) space probe. Launched in 2004 by NASA, MESSENGER began a one-year mission orbiting Mercury in early 2011 (which NASA scientists have now extended). The probe reached the planet after a more than five-year tour of the inner solar system. The long, looping route involved three close fly-bys of Mercury along with close approaches to Venus and Earth.

Just how loopy was the route MESSENGER took? Mercury is only about 20 percent farther from Earth than Mars when those planets pass closest to Earth. Yet, a probe going to Mars travels for less than a year. By comparison, MESSENGER took more than five years to reach Mercury.

Additional World Book articles

• Probing the Planets (a special report)
• Space Exploration 2004 (Back in Time article)
• Space Exploration 2008 (Back in Time article)
• Space Exploration 2009 (Back in Time article)
• Space Exploration 2011 (Back in Time article)