Magma and lava are essentially the same molten rock, but their location distinguishes them: magma is molten rock underground, while lava is molten rock that has erupted onto the Earth's surface.
Here's a breakdown of the key differences:
Location
This is the primary differentiating factor:
- Magma: Found beneath the Earth's surface, within the crust or mantle. It exists within magma chambers.
- Lava: Magma that has erupted onto the Earth's surface through volcanoes or fissures.
Composition and Properties
While the base composition is similar, exposure to the surface can alter lava's properties:
- Dissolved Gases: Magma typically contains dissolved gases (water vapor, carbon dioxide, sulfur dioxide, etc.). As magma rises and pressure decreases during an eruption, these gases are released, contributing to the explosive nature of some eruptions. Lava loses these gases, making it less volatile.
- Temperature: Both magma and lava have extremely high temperatures. However, lava cools more rapidly once exposed to the atmosphere.
- Crystallization: Crystallization processes can occur in both magma and lava. As magma cools underground, minerals can slowly crystallize, forming intrusive igneous rocks. Lava cools much faster on the surface, resulting in extrusive igneous rocks with smaller crystals or even a glassy texture.
- Pressure: Magma is under immense pressure from the surrounding rock. Lava experiences significantly less pressure once it reaches the surface.
Formation
- Magma: Magma forms when the Earth's mantle or crust partially melts due to:
- Increased temperature
- Decreased pressure
- Addition of water (which lowers the melting point)
- Lava: Lava is simply magma that has made its way to the surface, usually through a volcanic eruption.
Table Summarizing the Differences
| Feature | Magma | Lava |
|---|---|---|
| Location | Underground | On the Earth's Surface |
| Gases | Contains dissolved gases | Gases mostly released |
| Cooling Rate | Slow | Fast |
| Pressure | High | Low |
| Rock Formation | Intrusive Igneous Rocks | Extrusive Igneous Rocks |
In summary, the crucial distinction between magma and lava lies in their location. Magma is molten rock beneath the Earth's surface, while lava is molten rock on the Earth's surface after an eruption. This difference in location leads to variations in gas content, cooling rates, pressure, and ultimately, the type of igneous rock that forms.
