Summarized: Key Takeaways
- Lava is classified into four main types based on its silica content: Felsic, Andesitic, Basaltic (Mafic), and Ultramafic.
- Felsic lava has the highest silica content (>63%) and is too viscous to flow, resulting in volcanic explosions and chunky rock formations.
- Andesitic lava has a silica content of 52-63%, is also very viscous, and has low aluminum but high iron and magnesium content.
- Basaltic lava has a silica content of 52-45%, is high in magnesium and iron oxide, and is responsible for the most common moving lava flows (AA, paehoehoe, and pillow lava).
- Ultramafic lava is extremely rare, runny, and produced only at extremely high temperatures. It has not been produced since before the time of the dinosaurs, as the Earth has cooled too much to produce it.
Lava is molten rock. It’s called magma when it’s under the surface of the Earth or another planet. Once it’s ejected onto the planet’s surface it is known as lava – and that’s when volcanic activity occurs.
Different types of lava exist, but it’s way more complicated than you think. Get to know the crazy world of lava and volcanoes below!
Decoding the Diversity: Understanding Lava Classification and The Main Types of Lava
Lava is classified by geologists into 4 groups. It is classified by how much silica it contains.
Silica is made of silicon and oxygen. It is a mineral composite that makes up 59% of the Earth’s crust. It’s also a key ingredient in glass!
Rhyolite and Dacite: The Two Faces of Felsic Lava
Felsic lava has the highest silica content, at >63%. It’s too viscous to flow so instead, it’s released by volcanic explosions as chunks. This rhyolitic rock below is made from felsic lava.
There are two types of felsic lava: rhyolite and dacite.
Andesitic Lava: The Iron-Magnesium Treasure
Andesitic lava has a silica content of 52-63%. It’s still very viscous. It’s low in aluminum but high in iron and magnesium. This type of lava doesn’t flow much.
Most Observable Lava: The Iron-rich Basaltic or Mafic Lava
Basaltic lava has a silica content of 52-45%. Most moving lava flows we see are this type. It’s high in magnesium and iron oxide. This type of lava includes AA, paehoehoe, and pillow lava.
The Long Gone Ultramafic Lava
Ultramafic lava was the runniest lava. This lava has not been produced since before the time of the dinosaurs. The Earth has now cooled too much to produce it. It is only produced by extremely high temperatures.
The image above is an example of a rock made by ultramafic lava a very long time ago in the Archean period of Earth’s formation. It’s called komatite.
Unveiling the 5 Common Types of Basaltic Lava
So, when we’re looking at a magnificent and terrifying volcanic eruption, we are most often seeing basaltic lava flows. This type of lava is not as viscous as andesitic and felsic lava and contains less silica.
This means it can flow down the side of a volcano or out of a similar break in the Earth’s crust.
There are three main types of basaltic lava and two types with a different chemical composition. See if you can spot them all!
AA Lava: The Coolest Form of Basaltic Variety
AA lava is the thickest type of basaltic lava. It forms at cooler temperatures and further away from the source of an eruption. It is sharp and crusty looking, with a jagged surface that doesn’t look friendly!
AA is pronounced ‘ah-ah’ and comes from the native Hawaiian word for this lava. AA lava is in the lower temperature range of 1200-1170° C.
Check out this video of an AA lava flow from Mt. Etna
Pahoehoe: The Smooth-Surfaced Lava Flow
Named by native Hawaiians, pahoehoe lava, pronounced as “pay-hoy-hoy,” means “runny lava”.
This lava flows like syrup with a thin skin on top. It’s often only a few inches thick and can look like smooth ropes. It forms close to the source of an eruption, where the temperature is hottest.
Paehoehoe lava forms when lava runs down a gentle slope quite slowly. It retains its heat for longer this way, so it stays syrupy. Often this type of lava comes from shield volcanoes.
Check out this video footage of pahoehoe lava flowing:
Pillow Lava: The Underwater Wonder
This type of lava is actually the most common form of lava. It’s hard to spot, however, as most of it is produced underwater on the sea bed. It is a submarine form of lava.
Pillow lava does what it says on the tin and forms domes or bulbous pillow-like structures. You wouldn’t want to use lava as a pillow, though!
Pillow lava flows out slowly – it has a low effusion rate. This means it has time to solidify on all sides. Because of this it doesn’t spread out to form a sheet of lava. It stays in its bubble shapes. This pillow lava mainly comes from Thailand.
Block Lava: The Glassy Vulcan Phenomenon
Block lava can be andesitic or a combination of andesitic and basaltic. It is much more viscous than basaltic lava, so it forms chunks that don’t move much. They look more ‘friendly’ than AA lava, with glassy, smooth surfaces rather than sharp and ragged chunks.
Block lava tends to form thick, steep flow fronts.
Rhyolite and Dacite Lava: Volcanic Ash and Pumice Producers
Rhyolite lava has a different chemical composition as it has a lot more silica. This means it exploded out of volcanic areas in chunks!
Rhyolite lava can be from 10-100 meters (33 – 328 ft) thick. It is very slow-moving!
Dacite lava is also in this same category. Dacite lava tends to form lava domes, which are big piles of extruded magma in chunks. When dacitic magma erupts, it often showers the surrounding area in ash and pumice.
Pumice is also the stone you can buy to rub dead skin off your feet.
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Spotlight on Some of the World’s Most Astounding Lava Flows
Lava flows can be measured several ways. Here are a few of the most impressive lava flows known to science.
Prehistoric Giant Flow
A long time ago in prehistory, the Deccan volcanic area from India to Rajahmundry experienced five enormous mega flows of lava. These each traveled over 1500 km (932.1 mi).
Four of these flows happened just before a mass extinction known as the Cretaceous-Tertiary boundary (KTB) extinction event.
Longest Lava Flow
The longest lava flow in recorded history was from the volcano Laki in S.E. Iceland in 1783. It was 60-73 km (40-43 mi) long. It was a mixture of pahoehoe lava and AA lava.
However, it’s hard to measure a lava flow just on length. This is because it depends on the terrain the lava is flowing over.
Deepest lava flow
In the case of the Greenstone Lava Flow on Passage Island, the huge amount of lava didn’t travel far as it fell into a deep valley. It poured in until the valley was 500 meters (1,640 ft) deep in lava!
Basically, lava flows can be measured in length, volume, thickness or distance traveled from the vent.
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Top Sights for Volcano Enthusiasts: Experiencing the Phenomenon of Lava Flows Across the Globe
Here’s some of the best places to go to see this amazing lava flows around the world.
1. Volcanoes National Park, Hawaii
This Hawaiian National Park is home to Mauna Loa, the biggest active volcano in the world, and Kilauea, one of the most active. They are both shield volcanoes, with smooth low gradients and lots of lovely runny paehoehoe lava.
In Hawaiian tradition, this was the wrath of the goddess Pele. You can see a phenomenon known as “Pele’s Hair,” which consists of fine fragments of volcanic glass raining down from the sky!
You can view the hot lava pouring into the steaming sea from the viewing area 900 ft (274 m) away.
2. Mt. Etna & Mt. Stromboli, Italy
Mt. Etna in Sicily, Italy is one of the highest volcanoes in Europe and one of the most active worldwide. It is 3,329 m (2.069 mi) tall. There are usually old and new lava flows to see.
To see them, you can take a cable car, the ‘Funivia’ from Rifugio Sapienza. Or take a half or full day tour from Catania, Messina or Taormina.
The Funivia will get you 2,500 m (1.553 mi) up. After that, it’s either a guided hike up to the crater or a Jeep ride. You can join a 4-hour guided hike to the constantly glowing crater.
Mt. Stromboli gave its name to the Strombolian type eruption. It is named “The Lighthouse of the Mediterranean” due to its constant glow!
Moreover, it has erupted almost continuously for the last 2,500 years! It is one of 7 volcanic islands in the Aeolian archipelago.
You can also lie on the black volcanic sand beaches.
3. Erte Ale, Ethopia
Erte Ale volcano’s home is the Danakil Depression in Ethiopia. This land is infamous for being one of the harshest environments on Earth. This volcano’s other name is “The Gateway To Hell.”
Erte Ale has a permanent lava lake. It isn’t tall as volcanoes go as it’s only 613 m (2,011 ft) high. It makes up for that with a vastly wide crater full of lava, which measures 600 x 1700 m (656 yd x 1.056 mi)!
The climb to the crater takes 2-3 hours. It’s best to go in the early morning or the evening due to the intense heat of the day.
4. Mt. Sakurajima, Japan
Sakurajima in Kagoshima Bay, Japan, is one of Japan’s most active volcanoes. It has three peaks, so check which one is the most active before you go.
In 1914, it erupted so powerfully, the volcano changed from being an island to being a peninsula! The lava from the eruption formed new land, making a land bridge to the mainland. You can go this way, but it’s easier to take a ferry from Kagoshima Port and the Sakurajima Ferry Terminal.
There’s lots of things to do at the ferry port, too. Such as foot baths, and a natural hot mineral spring called an onsen.
There’s also the Nagisa Lava Trali and the lava covered Kurakami Shrine Gate, which show just how powerful the 1914 eruption was.
Below is the Kurokami Shrine Gate, frozen forever in solidified lava.
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The Volcanoes-Lava Connection: How Different Volcano Types Influence Lava Flow Characteristics
There are different types of volcanoes. This can influence the type of lava produced more than you think! Below are some of the types of volcanoes.
Cinder Cone Volcanoes: Producers of Sharp-Edged AA Lava
Steep sided volcanoes of the Cinder Cone type, like Mt. Etna in Italy, produce more AA lava. This is because the lava flows faster down the steep sides of the cone, which means it cools quicker. The cooling lava then forms into the crusty, sharp-edged AA lava.
Cinder cone volcanoes are often formed of andesite magma.
The Shield Volcanoes: Laying Down a Path of Smooth Paehoehoe Lava
Shield volcanoes have slopes with a low gradient and are lower in height.
They are much more likely to produce paehoehoe lava as their slopes are gentle enough that the lava flows slowly. Ths means it retains its high temperature for longer, which forms the runny appearance of paehoehoe lava.
This shield volcano is Mauna Loa in Hawaii, which is infamous for its eruptions. Mauna Loa is the largest active volcano on Earth, with a volume of at least 75,000 km2 (46,603 mi2)! That’s if you include its submarine dimensions, too.
Shield volcanoes are often formed of basaltic lava.
What Is Lava Rock? The Solidified Remnant of Fiery Magma Eruptions
Lava rock is a type of igneous rock made when magma rises to the surface and solidifies. Once lava has cooled and solidified, it is then lava rock.
Igneous rocks come in many different types. You can recognize them by these features:
- It doesn’t react with acids – if you drop them in vinegar they won’t bubble and fizz!
- It doesn’t have obvious layers.
- It doesn’t contain fossils
- It can be made of different minerals.
- It can contain bubbles or holes.
- It often has a glassy, shiny appearance.
Granite, basalt, obsidian, and pumice are all igneous rocks. The image above is a necklace and a piece of polished obsidian. Obsidian was made into sacrificial knives by the Mayans and Aztecs!
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Looking Beyond Earth: Lava and Volcanic Activities On Other Planets Across the Solar System
There is evidence of volcanic activity on almost every planet and moon in the Solar System. The most volcanically active is Io, one of Jupiter’s moons.
Venus also has lots of erupting volcanoes. It’s the hottest planet and has a lethally poisonous atmosphere! Charming. The volcanoes on Venus and Mars are much bigger than the volcanoes on Earth.
Scientists are still debating whether Mars still has any active volcanoes. The Moon and the planet Mercury have ancient lava flows from extinct volcanoes.
Other planets and moons in the Solar System contain cryovolcanoes. They are a form of volcanic activity. Some of these volcanoes erupt ice!
Pluto has evidence of cryovolcanoes. Cryovolcanoes can erupt into a frozen environment. Their “lava” can consist of frozen gasses like methane and a slurry of ice.
Who Studies Volcanic Activity?
Geologists, petrologists and volcanologists all study volcanic activity. The areas they study are a little different.
Geologists study the processes and materials that make up our Earth. They are especially interested in how the Earth changes over time.
Petrologists study certain rocks to find out how to best extract useful materials out of them.
They do a lot of outdoor fieldwork, traveling to locations to collect and analyze rocks. They test rocks with physical tests like the streak test. As well as with acids and chemicals.
Volcanologists collect data about volcanic activity. They usually need to travel to volcanic sites to take samples.
They use their findings to help predict future volcanic activity and keep local populations safe. They also study how volcanoes behave and work.
Is Blue Lava Real? A Spectacle of Illuminated Gases
Blue lava is not actually blue. It has been photographed on the slopes of Kawah Ijen, a volcano in Indonesia. The amazing pictures taken by Oliver Grunewald show glowing bright blue flows pouring from the volcano’s crater.
The blue color is caused by sulfur gasses that are pouring out with the lava. They are very hot, above 600° C. Once they are exposed to the oxygen in the air, these sulfurous gasses burn bright blue.
So it’s not the lava that is blue – it’s the gasses directly above it. The actual lava is a normal red orange color.
What Is a Lava Lake?
Lava lakes happen when a large volume of lava collects and stays in a volcanic crater or depression. The lava is usually basaltic. They are still called a lava lake if the lava is partly solidified!
Some of the most impressive lava lakes are in Africa. One is in the Danakil Depression (Erte Ale volcano) and one is on Mt. Nyiragongo in the Congo. Mt. Nyiragono crater lake is a whole 1 km (1,094 yd) wide!
Other good places to go to see lava lakes are Mount Erebus (Antarctica), Kilauea (Hawaii) and Ambrym and Mount Yasur (Vanuatu). These lava lakes are permanent, so you will definitely see lava!
How Hot Is Lava?
Lava temperature can range from 700° C to 1200° C. How hot it is depends on the type of lava.
Felsic lava tends to be the coolest lava. It is ejected in hard blocks at a temperature of 700° C.
Paehoehoe is the hottest type of lava. Its temperature is in the highest range of between 1100 -1200° C.
Andesitic lava has a temperature between these two extremes.
Magma vs Lava
Magma is molten rock that is under the Earth’s (or another planet or moon’s) crust.
It is called lava once it is ejected onto the surface of the Earth.
Magma comes from the vast area under the Earth’s crust called the mantle. Here, magma remains liquid or semi-liquid due to the vast pressure and temperature. It is composed of minerals, with a lot of silica, but also gasses such as carbon dioxide and water vapor.
Once lava has cooled, become rock and weathered, it can return to being magma if it is pushed back down to the hot temperatures beneath the crust. This is called the Rock Cycle.
From Lava to Loam: The Fertility of Volcanic Soils and Their Positive Impact on Agriculture
Lava rock eventually breaks down into volcanic soil, which is rich in nutrients that plants need.
Lava flows contain iron and magnesium, plus many other minerals. This means areas where lava has flowed become some of the most fertile soils on Earth!
New Zealand’s rich farmland comes from volcanoes. As does the fertile land around Naples in Italy, where all sorts of vegetables and fruit are grown. The soil is made from flows of ash and lava coming from Mt Vesuvius.
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Is a pyroclastic flow a lava flow?
A pyroclastic flow is not a type of lava flow. It is not made of molten rock. A pyroclastic flow is made of hot lava rocks, toxic gas and ash. It is much faster than a lava flow.
What’s the most common type of lava?
Pillow lava is the most common type of lava. You wouldn’t know this unless you could see under the ocean as this type of lava only appears on the sea bed underwater.
How fast does lava flow?
Most lava only moves at the walking speed of a human being. Or much less. The fastest lava flow front was in the 1950 Mauna Loa eruption. The front of the lava flowed at 9.7 km/h (6 mph). Once the channels of lava got going, the speed increased to 60 km/h (37 mph).
Is there anything that could live in lava?
Lava is so hot it would melt DNA and RNA, the building blocks of life. Even tardigrades, that can survive exposure to outer space, would not be able to survive being submerged in molten lava.