Here's how it works:
1. Magma rises: Molten rock (magma) rises from deep within the Earth's crust.
2. Gas buildup: As the magma ascends, the pressure decreases, causing dissolved gases (mainly water vapor) to expand rapidly.
3. Explosive eruption: The expanding gases create immense pressure, leading to an explosive eruption.
4. Rapid cooling: The erupted material (lava and ash) is ejected into the air and cools very quickly.
5. Gas bubbles trapped: The rapid cooling traps the expanding gases, creating numerous tiny air pockets within the solidifying lava.
6. Pumice formation: This porous, lightweight rock, filled with gas bubbles, is known as pumice.
Key takeaway: Pumice is essentially solidified lava foam, formed by the rapid cooling of lava with trapped gas bubbles.
