Magma vs Lava
Magma is molten rock that is still underground, stored in magma chambers and cracks in the crust. Once it erupts onto the surface it is called lava. They are the same material in different places — but where it cools changes the gases it holds, how fast it solidifies and what rock it becomes.
Last reviewed on 2026-10-03.
Quick Comparison
| Aspect | Magma | Lava |
|---|---|---|
| Location | Below the surface | On the surface (or erupted underwater) |
| Dissolved gases | Holds water vapour, CO₂ and sulfur gases under pressure | Most gas escapes; can leave bubbles (vesicles) |
| Cooling speed | Slow — insulated by surrounding rock (thousands of years or more) | Fast — exposed to air or water (hours to years) |
| Rock formed | Intrusive (plutonic) igneous rock | Extrusive (volcanic) igneous rock |
| Crystal size | Large, visible crystals | Small crystals, glass, or gas holes |
| Rock examples | Granite, diorite, gabbro | Basalt, andesite, rhyolite, obsidian, pumice |
Key Differences
1. Where Each Is Found
Magma forms where rock in the upper mantle or lower crust partially melts — above subduction zones, at mid-ocean ridges where plates spread apart, and at hotspots such as Hawaii. Being less dense than the surrounding rock, it rises and may collect in magma chambers a few kilometres below a volcano.
Lava is simply magma that has reached the surface through a vent or fissure, on land or on the sea floor. Most of Earth's lava erupts unseen along mid-ocean ridges.
2. Gases and Explosiveness
Underground, pressure keeps gases such as water vapour, carbon dioxide and sulfur dioxide dissolved in the magma, much like CO₂ in a sealed soda bottle. As magma rises and pressure drops, the gases form bubbles. In runny, low-silica magma they escape gently; in thick, silica-rich magma they can blast the magma apart into ash and pumice in an explosive eruption.
By the time it flows as lava, most of the gas has escaped, though frozen bubbles often remain as holes in rocks like scoria and pumice.
3. Temperature and Viscosity
Temperatures depend on composition. Basaltic (low-silica) lava typically erupts at about 1,100–1,200 °C and flows easily, as on Hawaii and Iceland. Andesitic and rhyolitic (silica-rich) lavas are cooler, roughly 650–1,000 °C, and much more viscous, forming steep domes and short, thick flows.
Hawaiian names are used for two basaltic flow textures worldwide: pāhoehoe, with a smooth, ropy surface, and ʻaʻā, with a rough, clinkery surface.
4. Different Rocks From the Same Melt
Magma that cools slowly underground grows large crystals, producing coarse-grained intrusive rocks such as granite. Lava cools quickly, producing fine-grained extrusive rocks such as basalt; if it cools almost instantly it forms volcanic glass (obsidian). Granite and rhyolite have similar chemistry, as do gabbro and basalt — the difference is mostly cooling speed. See igneous vs sedimentary vs metamorphic rock.
Examples
Magma
- Magma chambers beneath Yellowstone and other volcanoes
- Granite batholiths exposed today in places like Yosemite
- Dikes and sills: sheets of magma that cooled in cracks
Lava
- Lava flows from Kīlauea, Hawaii
- Fissure eruptions in Iceland
- Pillow lava formed on the sea floor
- Lava tubes left after flows drain
Frequently Asked Questions
Is magma hotter than lava?
Not necessarily. They are the same molten rock; lava starts cooling once it erupts, so a given flow gets cooler over time, but fresh lava erupts at roughly the temperature its magma had just below the surface, about 700–1,200 °C depending on composition.
When does magma become lava?
The moment it reaches Earth's surface — through a volcanic vent or fissure on land or on the ocean floor. The name changes; the material is the same.
What rock does magma form?
Intrusive (plutonic) igneous rocks such as granite, diorite and gabbro, which have large crystals because they cooled slowly underground.
What rock does lava form?
Extrusive (volcanic) igneous rocks such as basalt, andesite and rhyolite, plus glassy or bubbly rocks like obsidian, pumice and scoria.