15 Fascinating Lava Facts

Daily news often showcases images of the lava flows from Kilauea volcano in Hawaii. Terms that were once obscure, such as laze (a combination of lava and haze), vog (a mix of volcanic and smog/fog), and types of lava flows like pahoehoe and a'a, are now becoming common vernacular. But how well do you truly understand the molten rock? Here are 15 intriguing facts about lava.

1. LAVA IS MAGMA THAT REACHES THE SURFACE.

Magma refers to molten rock beneath the earth's surface, whereas lava is the term for magma once it erupts. While this distinction might seem minor, it matters—especially once the molten material cools. Both magma and lava give rise to igneous rocks, but magma underground cools more slowly, forming large mineral crystals in a category known as plutonic rocks. On the surface, lava cools quickly, resulting in smaller mineral crystals and a type of rock called volcanic. This shows how the same raw material can produce different types of rocks depending on where it cools. For example, granite and rhyolite are considered similar, but granite forms deep underground (plutonic), while rhyolite forms at the surface (volcanic).

2. THERE ARE VARIOUS TYPES OF LAVA...

Most lava falls into one of three categories: mafic, intermediate, or felsic. These are also known as basaltic, andesitic, and rhyolitic lavas, respectively. While other types exist, they are extremely rare. These three types are distinguished by their mineral composition, thickness (viscosity), and the volume of volcanic gases like water, carbon dioxide, and sulfur dioxide dissolved within the molten rock.

Around 90 percent of lava flows are mafic, containing about 50 percent silica (SiO2). This lava is characterized by its low viscosity and gas content, typically forming the classic bright-red flows we associate with lava. Intermediate lava, which contains roughly 60 percent silica, has higher gas content and viscosity, causing it to erupt explosively. Mount St. Helens' eruption was an example of an intermediate eruption. Even more volatile, though much rarer, are felsic lavas, which contain 70 percent silica and have the highest gas content and viscosity, often resulting in violent eruptions that produce fragments of rock called tephra.

3. … AND DISTINCT TYPES OF LAVA FLOWS.

Specifically, there are various types of mafic lava flows. The main surface types are a’a and pahoehoe, terms derived from Hawaiian. A’a flows rapidly, losing heat and increasing its viscosity, creating a rough, jagged surface as chunks of cooled lava break off. The term may come from the Hawaiian word for burn or stony. In contrast, pahoehoe is smooth and often likened to a twisted rope due to its slower movement and lower viscosity, which allows any breaks to quickly seal up. This term may come from the Hawaiian word for paddle, describing the smooth ripples paddles create in water. When an eruption occurs underwater, a third type, pillow lava, forms. Though it occurs beneath the ocean, pillow lava is often difficult to distinguish from pahoehoe.

4. A VOLCANO'S SHAPE DEPENDS ON THE TYPE OF LAVA IT CONTAINS.

Mafic lava, being more fluid, produces wide, gently sloping shield volcanoes like those found on the Hawaiian Islands. However, this type of lava can also create other volcanic features: Silica-rich mafic rocks can be ejected high into the air, landing back in the vicinity of the eruption to form spatter cones (where the lava stays liquid and welds together) or cinder cones (where solidified lava lands as rock). If the lava erupts through large fissures, it can form flood basalts, another name for mafic lava.

Intermediate and felsic lavas, which are more viscous, form stratovolcanoes (also called composite volcanoes), the classic, steep-sided volcanoes seen in popular depictions, such as Mount Fuji.

Highly felsic lava can create calderas, massive depressions formed when an eruption is so violent that the volcano collapses into the emptied magma chamber. One famous example is Yellowstone National Park, which sits atop a dormant supervolcano and contains a large caldera. Extremely felsic lava can also form lava domes, which occur when degassed lava piles up around the vent. According to the University of Oregon, these domes can appear in craters or along the sides of stratovolcanoes and calderas, or even far from any volcano.

5. HUMANS HAVE BEEN ENTHRALLED BY LAVA FOR THOUSANDS OF YEARS...

The earliest known depiction of a volcanic eruption dates back around 8500 years, found on a mural in the Neolithic settlement of Çatalhöyük, in present-day Turkey. (Some argue it’s not an eruption, but a leopard skin.) However, there may be evidence of an eruption even older. Cave paintings at Chauvet-Pont d'Arc, located 22 miles from France’s Bas-Vivarais volcanic field, are estimated to be around 37,000 years old. In addition to the usual animals depicted in the artwork, there are markings resembling sprays, leading some French researchers to speculate that these could be representations of a volcanic eruption previously unknown to history.

6. ... AND HAVE SOUGHT TO HALT IT FOR CENTURIES.

The first recorded attempt to stop a lava flow occurred in 1669, when Mount Etna erupted on the island of Sicily. Diego Pappalardo of Catania led a group to cut a hole in the hardened lava, hoping to divert the flow away from their town. Initially, this worked—for Catania’s residents. But it soon became a disaster for the people of Paterno, who realized that the redirected flow was now threatening their town. They drove Pappalardo and his men away, and the hole they had made eventually clogged, allowing the lava to resume its course toward Catania, where it collided with the city wall. The wall held for a few days before it eventually failed, and lava entered the city. Sicilians had more success in 1983 and 1992 when they managed to divert lava from Mount Etna using earthen banks and concrete blocks, with moderate success. Similarly, in 1973, Iceland diverted lava flow from an eruption by spraying it with seawater to contain the damage.

7. WE ATTEMPTED TO BOMB LAVA INTO SUBMISSION.

In 1935, the U.S. Army tried bombing a lava channel on Mauna Loa in Hawaii to divert the flow threatening Hilo. The attempt failed. They tried again in 1942 during another eruption of Mauna Loa, but once again, it didn't work. However, just a few days after the 1942 bombing, a natural collapse on the volcano occurred, which brought the lava flow to a halt. The theory behind bombing the channel was that it might slow down the lava, reducing its potential damage to cities, since lava moves fastest when confined to a channel or a lava tube. Lava that spreads out in a broad fan is much slower and cools more quickly.

This idea led to further experiments in 1975 and 1976, when the Air Force dropped bombs on ancient lava fields on Mauna Loa to observe the effects. They discovered that spatter cones were particularly susceptible to bombing. In their report, the Air Force stated, "Modern aerial bombing has a substantial probability of success for diversion of lava from most expected types of eruptions on Mauna Loa's Northeast Rift Zone, if Hilo is threatened and if Air Force assistance is requested." Despite this, the method has never been used again.

8. THE CAUSE OF HAWAII'S VOLCANIC ACTIVITY REMAINS A MYSTERY.

Typically, volcanoes form along the edges of tectonic plates as a result of plate movements, but Hawaii is located thousands of miles from any plate boundary. To explain this anomaly, geologists developed the "hot spot" theory, suggesting that a plume of exceptionally hot material rises from the boundary between the core and mantle, punching through the crust to form islands like Hawaii. Later refinements to this theory proposed that this plume remains stationary, and as the Earth's crust moves over it, it generates features such as the Hawaiian island chain.

However, as Earth magazine points out, this theory has been easy to propose but extremely difficult to verify. Critics argue that as contradictory evidence has emerged, the hot spot hypothesis has become so adaptable that it no longer holds much value. In response, a new theory connects these mid-plate features to plate tectonics. Specifically, in the case of Hawaii, because the Pacific plate is subducting, or moving beneath, other tectonic plates in Asia and parts of North America, it's starting to fracture. Local mantle conditions then cause the Hawaiian volcanoes to form. While eruptions make the news regularly, the cause of volcanic activity in Hawaii remains a topic of ongoing debate.

9. ESCAPING A LAVA FLOW IS EASIER THAN YOU MIGHT THINK …

In a study conducted last year, researchers from the University of Bristol analyzed volcanic fatalities between 1500 and 2017. Of the over 214,000 deaths recorded, only 659 were attributed to lava flows. As they noted, "lavas usually move slowly, allowing people to escape." According to the USGS, typical mafic lava on a gentle slope flows at less than 1 mph, and this speed increases on steeper slopes or in lava tubes.

The Bristol researchers also cautioned that the real danger lies in volcanic explosions. "Sudden eruptions of highly fluid lava can lead to fatalities," they stated. "Most deaths and injuries occur when escape routes are blocked or from small explosions caused by interactions with water, vegetation, or fuel."

The majority of fatalities were due to "pyroclastic density currents"—essentially hot gas, ash, and rocks moving at incredible speeds—which caused approximately 60,000 deaths. Volcano-triggered tsunamis claimed a similar number of lives. Another 50,000 people lost their lives due to lahars, or volcanic mudflows of water and debris. The remaining deaths were from secondary lahars (which can happen years after an eruption), tephra, avalanches, landslides, gas, flying rocks known as ballistics, and, in nine instances, lightning.

10. … BUT LAVA STILL POSES A SIGNIFICANT THREAT.

The largest lava-related loss of life occurred in the Democratic Republic of Congo in 2002, when an estimated 100 to 130 people were killed by lava from the Nyiragongo eruption. Located near the city of Goma, the eruption forced the displacement of 250,000 people (with another 150,000 remaining), as the lava flowed through city streets, cutting off parts of the town, including covering about 80 percent of the airstrip at the local airport. Nyiragongo is particularly dangerous due to its proximity to a major city, and it's thought to produce some of the fastest lava on Earth. In a 1977 eruption, lava—an extremely low-viscosity mafic type—traveled at an estimated 40 mph. The 2002 flow is believed to have been slightly slower.

11. BLUE LAVA DOESN'T EXIST …

Images of "blue lava" from the Indonesian volcano Kawah Ijen are commonly shared on social media. Unfortunately, the striking blue glow is not real lava. It's actually caused by sulfuric gases that emerge at high temperatures and ignite, sometimes flowing down as glowing liquid sulfur. Blue flames, caused by ignited methane gas from burning plant matter, are also being seen in Hawaii.

12. … BUT BLACK LAVA DEFINITELY EXISTS.

The coolest lava in the world is found at Ol Doinyo Lengai in Tanzania. Lava typically ranges in temperature from 1300°F to 2300°F (700°C to 1250°C) depending on its composition. However, the lava at Ol Doinyo Lengai is only around 1000°F. It is also the only known active carbonatite volcano in the world, with a carbonatite being an igneous rock primarily made of carbonate minerals. Instead of flowing red, this lava is black and solidifies into white. The exact origin of this unusual lava is still debated, but due to its role in producing much of the world's rare-earth elements, it's increasingly studied for its economic value.

13. THERE'S A RESTAURANT THAT COOKS FOOD USING LAVA.

If you're ever on the island of Lanzarote in the Canary Islands and looking for a unique dining experience, you can visit El Diablo. This restaurant is distinctive because its grill sits above a 6-foot deep hole filled with lava (though it's considered safe, as the last eruption occurred in 1824). Dining here might be a safer option than attempting to roast marshmallows over a volcanic vent—something the USGS strongly advises against. Even if it weren't dangerous to be near a vent, the sulfur dioxide and hydrogen sulfide emissions would make your marshmallow taste terrible.

14. MARS MAY HAVE LAVA CHANNELS.

The debate over whether the deep channels on Mars' surface were shaped by lava or water remains a hot topic among scientists. While it might seem straightforward to distinguish between the two, a 2010 study on a lava flow from 1859 in Hawaii revealed features strikingly similar to what was once believed to be water-carved channels on Mars. Researchers concluded that fast-moving, low-viscosity lava could form these channels, challenging the assumption that they were created by water. A 2017 study on another part of Mars reached a similar conclusion, suggesting that what was traditionally thought to be evidence of rivers and lakes could actually be explained by lava flooding channels and filling old impact craters.

15. REMOVING LAVA CAN TAKE YEARS—IF IT EVEN HAPPENS.

Restoring a landscape after a volcanic eruption can be a daunting task. If ash has accumulated, it's crucial to dispose of it safely at designated sites, all while avoiding inhalation of hazardous substances like glass, fine silica dust, and toxic gases, which can lead to serious health issues. Lava removal is even more challenging. According to Accuweather, contractors seldom fully remove hardened lava, as it can take years to cool completely. Even when it does, removing it requires specialized equipment. University at Buffalo volcanologist Greg Valentine explained to Digital Trends, "In the Hawaii case, we are talking about lava that is incredibly sticky and viscous, and that is nearly 2000°F. No house can stand up to that, and even if it could, it would be partly or completely buried when everything is over." Because of these obstacles, most people choose to start over rather than attempting to remove the lava.