What is the difference between magma and lava?

They are the same molten rock. It is called magma while it is underground and lava once it reaches the surface.

Why are Hawaiian eruptions usually less explosive?

Hawaiian volcanoes erupt basalt, which is hot, runny and low in silica, so gas escapes easily rather than building up pressure. Explosive eruptions are more typical of thicker, gas-rich magmas, although Kīlauea has had explosive episodes in the past.

What is the difference between pāhoehoe and ʻaʻā?

Pāhoehoe has a smooth, ropy or billowy surface, while ʻaʻā is rough and covered in sharp, broken clinker. They can come from the same eruption; the difference depends on how fast the lava moves, how much it has cooled and how much gas it has lost.

Can scientists predict volcanic eruptions?

Not precisely, but they can often forecast them. Earthquakes, swelling ground and changes in gas emissions can show that magma is on the move, giving warnings of hours to months, though some eruptions come with little notice.

Can I explore a volcano in the app?

Yes. You can land on a volcanic landscape modelled on Kīlauea and explore its black lava fields, glowing lava flows and steaming vents in interactive 3D.

Black lava, glowing rivers of rock and the ground being made anew

Volcano

3D landscape · Kīlauea, Hawaiʻi

Land here and explore →

A volcano is a place where magma, molten rock from deep below, reaches the surface. Once it erupts it is called lava. Volcanoes can be gentle, sending rivers of lava slowly across the land, or explosive, blasting ash high into the sky. In this app you can land on a volcanic landscape modelled on Kīlauea in Hawaiʻi and explore its fresh black lava fields, glowing flows and steaming vents in interactive 3D.

Kīlauea, on the south-east side of the Island of Hawaiʻi, is one of the most active volcanoes on Earth and one of the most closely studied. Its eruptions are usually effusive, meaning lava pours out rather than exploding, which makes it a natural laboratory for scientists. The same forces that shaped Hawaiʻi have built Iceland, the Andes, Japan and much of the ocean floor.

Key facts

Model volcano: Kīlauea, HawaiʻiA shield volcano within Hawaiʻi Volcanoes National Park
Volcano type: Shield volcanoBroad, gently sloping and built from runny basalt lava
Lava temperature: ≈ 1,100–1,200°CTypical for erupting basalt in Hawaiʻi
Main lava types: Pāhoehoe and ʻaʻāBoth Hawaiian words, now used by geologists worldwide
Recent big event: 2018 eruptionLava destroyed hundreds of homes in the lower East Rift Zone
Biggest neighbour: Mauna LoaEarth's largest active volcano by volume; last erupted in 2022
Potentially active volcanoes: About 1,350 on landUSGS estimate, not counting most of those on the sea floor
Ring of Fire: Most of the world's active volcanoesOften quoted as about three quarters
World Heritage: Since 1987Hawaiʻi Volcanoes National Park is a UNESCO site

How volcanoes form

Most volcanoes grow where Earth's tectonic plates meet. Where plates pull apart, as along the Mid-Atlantic Ridge, the mantle rises, partly melts and fills the gap with new crust. Where one plate dives beneath another, water carried down with it lowers the melting point of the rock above, and the magma that forms feeds chains of volcanoes such as those around the Pacific Ring of Fire.

Hawaiʻi is different. It sits in the middle of the Pacific Plate, far from any boundary, above a hotspot: a long-lived plume of unusually hot material rising from deep in the mantle. As the plate slides slowly north-west over the hotspot, new volcanoes form and older ones drift away, go extinct and erode. The result is a chain of islands that gets older towards the north-west, with the youngest volcanoes, Kīlauea and Mauna Loa, at the south-east end and a new undersea volcano, Kamaʻehuakanaloa (formerly Lōʻihi), growing offshore.

Shield volcanoes and stratovolcanoes

The shape of a volcano depends largely on its magma. Basalt, low in silica, is hot and runny, and gas escapes from it easily. It spreads out in thin flows that build broad, gently sloping shield volcanoes, named because they resemble a warrior's shield lying on the ground. Mauna Loa, measured from its base on the sea floor, is taller than Mount Everest is above sea level, yet its slopes are gentle enough to walk up.

Magmas richer in silica, such as andesite and dacite, are thicker and trap more gas. They tend to erupt explosively and build steep, cone-shaped stratovolcanoes, or composite volcanoes, from layers of lava, ash and rock fragments. Mount Fuji, Mount St Helens and Mount Vesuvius are classic examples. Their eruptions can produce pyroclastic flows, fast-moving avalanches of hot gas and ash, which are among the deadliest volcanic hazards.

Calderas

When a magma chamber empties, the ground above can collapse into a large basin called a caldera. Kīlauea's summit caldera dropped dramatically during the 2018 eruption, and Halemaʻumaʻu crater within it deepened by hundreds of metres.

Pāhoehoe, ʻaʻā and lava tubes

Hawaiian basalt usually forms one of two kinds of lava. Pāhoehoe has a smooth, billowy or rope-like surface; it forms when hot, fluid lava moves slowly and a thin skin cools on top while the lava beneath keeps flowing. ʻAʻā is rough, jagged and covered in sharp, broken clinker. It forms when lava cools, loses gas or flows faster and more turbulently, and it is notoriously hard to walk across. A single flow can begin as pāhoehoe and turn into ʻaʻā further downhill.

As a pāhoehoe flow continues, its surface can harden into a roof while molten lava keeps running beneath, forming a lava tube. The rock roof insulates the lava, so it can travel many kilometres without cooling much. When the eruption ends and the lava drains away, an empty tunnel may remain. Nāhuku, also known as the Thurston Lava Tube, is a well-known example that visitors can walk through in Hawaiʻi Volcanoes National Park.

Pele's hair and tears

Wind can stretch droplets of lava into fine golden threads of volcanic glass called Pele's hair, and small droplets can cool into glassy beads called Pele's tears. Both are named after Pele, the Hawaiian goddess of volcanoes and fire.

Fumaroles and volcanic gases

Magma contains dissolved gases that escape as it rises, much as bubbles appear when a fizzy drink is opened. The most abundant is water vapour, followed by carbon dioxide and sulphur dioxide, with smaller amounts of hydrogen sulphide, hydrogen chloride and other gases. Fumaroles are vents where these gases escape, often surrounded by yellow crusts of sulphur and other minerals. In the 3D landscape, the steaming vents represent these openings.

In Hawaiʻi, sulphur dioxide reacts in sunlight and air to form a hazy mix of fine particles and gas called vog, short for volcanic smog, which can affect people with breathing problems. Carbon dioxide is heavier than air and can collect in low-lying hollows. Scientists measure changes in the amount and mix of gases because they can signal that fresh magma is moving towards the surface.

How life returns to lava

Fresh lava is sterile, black and very hot, yet life begins to return remarkably quickly. Wind brings spores and seeds, and in wet parts of Hawaiʻi, lichens, mosses and ferns can appear in cracks within a few years. One of the first trees to take hold is the ʻōhiʻa lehua, with its red, brush-like flowers, which can root in cracks in young lava and is a vital part of Hawaiian forests.

How fast a lava field turns green depends mainly on rainfall and the type of lava. Rough ʻaʻā traps water and windblown material in its gaps and is often colonised faster than smooth pāhoehoe. On the wet windward side of the island, forest can develop within decades or centuries, while dry lava fields may stay largely bare for much longer. Some insects and spiders live on the newest flows, feeding on other insects blown in by the wind.

Monitoring, hazards and volcanoes elsewhere

The USGS Hawaiian Volcano Observatory, founded in 1912, watches Kīlauea and its neighbours with seismometers, tiltmeters, GPS stations, gas sensors, cameras and satellite radar. Rising magma causes swarms of small earthquakes and makes the ground swell measurably. These signals cannot predict the exact time of an eruption, but they often give warning that one is becoming more likely. Hazards include lava flows, volcanic gases, ash, ground cracking and, at explosive volcanoes, pyroclastic flows and mudflows called lahars.

Iceland is one of the best places to see volcanoes elsewhere, because it sits on both the Mid-Atlantic Ridge and a hotspot. The 2010 eruption of Eyjafjallajökull sent ash into the skies over Europe and grounded flights for days, and since 2021 a series of eruptions on the Reykjanes Peninsula has sent lava towards the town of Grindavík. Other notable volcanoes include Etna in Sicily, Nyiragongo in the Democratic Republic of the Congo with its lava lake, and Tambora in Indonesia, whose 1815 eruption helped cause the cold 'year without a summer' in 1816.

Surprising facts about Volcano

Measured from its base on the ocean floor, Mauna Loa is taller than Mount Everest is above sea level.
The words pāhoehoe and ʻaʻā come from the Hawaiian language and are now standard terms used by geologists around the world.
Lava from Kīlauea has added new land to the Island of Hawaiʻi, building out the coastline into the sea.
A new Hawaiian volcano, Kamaʻehuakanaloa, is already growing on the sea floor south-east of the island, though it may take tens of thousands of years to reach the surface.
Some lava tubes are long enough to carry lava many kilometres from the vent while keeping it hot.
Wind can spin lava into fine golden threads of glass known as Pele's hair.

Frequently asked questions

What is the difference between magma and lava?: They are the same molten rock. It is called magma while it is underground and lava once it reaches the surface.
Why are Hawaiian eruptions usually less explosive?: Hawaiian volcanoes erupt basalt, which is hot, runny and low in silica, so gas escapes easily rather than building up pressure. Explosive eruptions are more typical of thicker, gas-rich magmas, although Kīlauea has had explosive episodes in the past.
What is the difference between pāhoehoe and ʻaʻā?: Pāhoehoe has a smooth, ropy or billowy surface, while ʻaʻā is rough and covered in sharp, broken clinker. They can come from the same eruption; the difference depends on how fast the lava moves, how much it has cooled and how much gas it has lost.
Can scientists predict volcanic eruptions?: Not precisely, but they can often forecast them. Earthquakes, swelling ground and changes in gas emissions can show that magma is on the move, giving warnings of hours to months, though some eruptions come with little notice.
Can I explore a volcano in the app?: Yes. You can land on a volcanic landscape modelled on Kīlauea and explore its black lava fields, glowing lava flows and steaming vents in interactive 3D.

Keep exploring

The landscapes in Ember’s Universe are procedural 3D scenes modelled on real places. The landforms, plants and light follow the real thing, but the details are generated, not mapped.

Sources