Magma that is blasted into the air and hardens forms volcanic bombs.

Here's why:

* Magma: Molten rock found beneath the Earth's surface.

* Blast: When magma is forcefully ejected from a volcano.

* Hardening: As the magma cools and solidifies in the air.

Volcanic bombs are fragments of ejected volcanic material that are larger than 64 millimeters (2.5 inches) in diameter. They can be a variety of shapes, depending on the way they cool and solidify in the air.