Lava Flow Facts For Kids
Lava flow is molten rock that comes from deep inside a planet and can pour out of a volcano or move through cracks, shaping land.
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Lava Flow Facts For Kids
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About this topic
Lava is molten, or partly molten, rock that comes from deep inside a planet or moon and reaches the surface. It can pour out of a volcano or squeeze through cracks in the ground. Lava can flow on land or under the sea, and sometimes it is thrown up into the air before falling back down as glowing pieces.
When lava cools and hardens, it becomes solid rock. People often call that solid rock “lava” too. Lava can look different depending on how hot it is, what it’s made of, and how it flows.
Explore with ChatDinoWhen lava cools and hardens, it becomes solid rock. People often call that solid rock “lava” too. Lava can look different depending on how hot it is, what it’s made of, and how it flows.
Quick Facts
Key Points
Lava is very hot—usually between about 800 and 1,200 °C (roughly 1,470 to 2,190 °F).
Viscosity is a word that tells how sticky or runny lava is.
ʻAʻā is a type of basaltic lava that makes very rough, broken surfaces.
Pāhoehoe is a kind of lava that looks smooth, billowy, or like twisted ropes.
Block lava flows come from thicker, stickier lava that makes chunky, angular blocks on the surface.
Lava tubes form when a smooth layer of lava cools on top and makes a hard roof while liquid lava keeps flowing below.
Lava domes form when very thick, sticky magma pushes out slowly and piles up near the vent.
A cinder cone is a small, steep hill that forms when bits of hot rock and glassy ash fly out of a volcano and pile up around the vent.
Lava can cover buildings and fields, so some towns have been badly damaged or lost.
Photos of Lava Flow
Arenal Volcano, Costa Rica, is a stratovolcano.
Shiprock, New Mexico, United States: a volcanic neck in the distance, with a radiating dike on its south side
Block lava at Fantastic Lava Beds near Cinder Cone in Lassen Volcanic National Park
Lava entering the sea to expand the big island of Hawaii, Hawaiʻi Volcanoes National Park
Lava fountain at Kīlauea
Glowing ʻaʻā flow front advancing over pāhoehoe on the coastal plain of Kīlauea in Hawaii, United States
📘 Eruption And Heat
Lava is very hot—usually between about 800 and 1,200 °C (roughly 1,470 to 2,190 °F). It reaches the surface when pressure or cracks let it escape. Sometimes lava flows out gently, and other times it is thrown up before landing again.
Lava can travel far because a thin crust forms on top as the surface cools. That crust acts like an insulating blanket, keeping the inside lava hot so it keeps moving. Lava also needs a bit of a push to start flowing; scientists call this behavior a Bingham fluid, which means it won’t move until force overcomes a tiny sticking point.
Go deeperLava can travel far because a thin crust forms on top as the surface cools. That crust acts like an insulating blanket, keeping the inside lava hot so it keeps moving. Lava also needs a bit of a push to start flowing; scientists call this behavior a Bingham fluid, which means it won’t move until force overcomes a tiny sticking point.
🔎 How Lava Flows
Viscosity is a word that tells how sticky or runny lava is. Most molten lava is about as thick as ketchup and is 10,000 to 100,000 times thicker than water. Hotter lava and some kinds of rock make it runnier, while cooler lava and different minerals make it thicker.
Lava doesn’t always shear smoothly. Often it flows with most of the motion in a thin layer near the surface. This is called plug flow, and it is like squeezing toothpaste from a tube—the outside moves slower while a chunk of the middle slides along more quickly.
Go deeperLava doesn’t always shear smoothly. Often it flows with most of the motion in a thin layer near the surface. This is called plug flow, and it is like squeezing toothpaste from a tube—the outside moves slower while a chunk of the middle slides along more quickly.
🧭 ʻaʻā Lava: Rough, Rubble Flows
ʻAʻā is a type of basaltic lava that makes very rough, broken surfaces. As it moves, the top breaks into jagged pieces called clinker. These sharp pieces ride along on the flow and push forward as the lava keeps moving.
Under the clinker there is a denser, still-hot interior. At the front, chunks tumble and get buried, so the flow builds up layers of broken rock on top and bottom. Sometimes bits stick together into round clumps called accretionary lava balls, which can grow as large as about 3 metres—about the height of a tall person. ʻAʻā is usually thicker and rougher than smoother pāhoehoe lava.
Go deeperUnder the clinker there is a denser, still-hot interior. At the front, chunks tumble and get buried, so the flow builds up layers of broken rock on top and bottom. Sometimes bits stick together into round clumps called accretionary lava balls, which can grow as large as about 3 metres—about the height of a tall person. ʻAʻā is usually thicker and rougher than smoother pāhoehoe lava.
💡 Pāhoehoe: Smooth, Ropy Lava
Pāhoehoe is a kind of lava that looks smooth, billowy, or like twisted ropes. It usually comes from runny, basalt lava that spreads out in thin sheets. As the front cools, small lobes and “toes” push forward and break out from a thin crust. This makes the surface look like big ropes or wrinkles—lava sculpture that artists might admire.
Because pāhoehoe stays hot and runny (often more than one thousand degrees Celsius), it can travel far. If it cools and becomes thicker, it can change into a rougher type of lava called ʻaʻā. Some pāhoehoe flows are short, but a few have flowed tens of kilometres.
Go deeperBecause pāhoehoe stays hot and runny (often more than one thousand degrees Celsius), it can travel far. If it cools and becomes thicker, it can change into a rougher type of lava called ʻaʻā. Some pāhoehoe flows are short, but a few have flowed tens of kilometres.
🌟 Blocky Lava Flows
Block lava flows come from thicker, stickier lava that makes chunky, angular blocks on the surface. These flows are common on steep, cone-shaped volcanoes. Instead of smooth ropes, the top of the flow breaks into strong, blocky pieces with sharp edges and flat faces.
Under the broken surface, hot molten rock keeps moving. The flow pushes forward slowly as the new lava slides over the pile of broken blocks at the front. Because the lava is thicker, block lava moves much more slowly than runny types like pāhoehoe.
Go deeperUnder the broken surface, hot molten rock keeps moving. The flow pushes forward slowly as the new lava slides over the pile of broken blocks at the front. Because the lava is thicker, block lava moves much more slowly than runny types like pāhoehoe.
🧩 Lava Tubes: Underground Lava Tunnels
Lava tubes form when a smooth layer of lava cools on top and makes a hard roof while liquid lava keeps flowing below. The hardened roof acts like a blanket, keeping the lava underneath hot and able to travel far from its source. Over time this can make long tunnel-like passages underground.
When the eruption ends or the lava slows, the tunnels can drain and leave open caves. People have explored many tubes safely with guides. Some modern examples are found at Kīlauea in Hawaii, and older tubes exist in places like North Queensland, Australia.
Go deeperWhen the eruption ends or the lava slows, the tunnels can drain and leave open caves. People have explored many tubes safely with guides. Some modern examples are found at Kīlauea in Hawaii, and older tubes exist in places like North Queensland, Australia.
🗺️ Lava Domes And Thick Dome Flows (coulées)
Lava domes form when very thick, sticky magma pushes out slowly and piles up near the vent. Instead of flowing far, this lava balloons into a rounded, bumpy mound that can grow taller and wider. As it inflates, the dome’s surface often cracks and becomes covered by broken rock and ash.
If a dome grows on a slope, parts can squeeze out in short, thick streams called coulées (dome flows). These flows travel only a few kilometres but are tall and chunky instead of thin and runny. Famous dome-forming events include domes that grew after eruptions at places like Mount St. Helens.
Go deeperIf a dome grows on a slope, parts can squeeze out in short, thick streams called coulées (dome flows). These flows travel only a few kilometres but are tall and chunky instead of thin and runny. Famous dome-forming events include domes that grew after eruptions at places like Mount St. Helens.
🔬 Types Of Lava Hazards
A cinder cone is a small, steep hill that forms when bits of hot rock and glassy ash fly out of a volcano and pile up around the vent. These bits are called tephra (rock and ash pieces). Cinder cones can throw out hot fragments that fall nearby and make loose, crumbly slopes that are unsafe to walk on.
A spatter cone grows when molten blobs of lava land close together and weld into a mound. Spatter cones can make fast, rough lava that flows a short distance and can burn or cover nearby land. Both cone types can block rivers or roads and bury fields, so they are dangerous to people and towns close by.
Go deeperA spatter cone grows when molten blobs of lava land close together and weld into a mound. Spatter cones can make fast, rough lava that flows a short distance and can burn or cover nearby land. Both cone types can block rivers or roads and bury fields, so they are dangerous to people and towns close by.
📘 Towns Damaged By Lava Flows
Lava can cover buildings and fields, so some towns have been badly damaged or lost. In the 1700s a thick lava flow from Tseax Cone in British Columbia buried the Nisga'a villages of Lax Ksiluux and Wii Lax K'abit.
Other places show different outcomes. Garachico in Tenerife was destroyed by lava in 1706 but later rebuilt. Keawaiki, Hawaii, was covered in 1859 and was abandoned. San Sebastiano al Vesuvio, near Mount Vesuvius, was destroyed in 1944 and later rebuilt. Koae and Kapoho in Hawaii were buried in a 1960 Kīlauea eruption and were abandoned. Sometimes people rebuild; other times the land is too changed.
Go deeperOther places show different outcomes. Garachico in Tenerife was destroyed by lava in 1706 but later rebuilt. Keawaiki, Hawaii, was covered in 1859 and was abandoned. San Sebastiano al Vesuvio, near Mount Vesuvius, was destroyed in 1944 and later rebuilt. Koae and Kapoho in Hawaii were buried in a 1960 Kīlauea eruption and were abandoned. Sometimes people rebuild; other times the land is too changed.
🧠 Take the Quiz about Lava Flow
Frequently asked questions
What is lava?
Lava is molten, or partly molten, rock that comes from deep inside a planet or moon and reaches the surface. It can pour out of a volcano or squeeze through cracks in the ground. When lava cools and hardens, it becomes solid rock.
How hot is lava, and how does it reach the surface?
Lava is very hot—usually between about 800 and 1,200 °C. It reaches the surface when pressure or cracks let it escape, and sometimes it flows out gently or is thrown up before landing again.
Why can lava travel far even after the surface cools?
A thin crust forms on top as the surface cools, and that crust acts like an insulating blanket, keeping the inside lava hot so it keeps moving.
What does viscosity mean for lava?
Viscosity is a word that tells how sticky or runny lava is. Most molten lava is about as thick as ketchup and is 10,000 to 100,000 times thicker than water. Hotter lava and some kinds of rock make it runnier, while cooler lava and different minerals make it thicker.
What is pāhoehoe lava like?
Pāhoehoe is a kind of lava that looks smooth, billowy, or like twisted ropes. It usually comes from runny, basalt lava that spreads out in thin sheets.
What is ʻaʻā lava like?
ʻAʻā is a type of basaltic lava that makes very rough, broken surfaces. As it moves, the top breaks into jagged pieces called clinker.