Here's why:

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

* Chamber: A large underground cavity where magma accumulates.

While the core of the volcano is made of solidified magma, it's important to note that:

* Magma chambers are not always solid: They can contain a mix of solid and molten rock, depending on the temperature and pressure.

* The "core" of the volcano is the central point where eruptions occur, but it's not a single, solid entity. The magma chamber is a complex system that can feed multiple vents and fissures.