Here's why:
* The asthenosphere is characterized by its physical properties, not its composition. It's a semi-molten, ductile layer that allows for slow, solid-state flow, making it important for plate tectonics.
* The asthenosphere is primarily composed of peridotite, a rock rich in olivine and pyroxene. However, the asthenosphere isn't a single solid rock formation; it's a zone with varying compositions.
So, while the composition of the asthenosphere is mainly peridotite, the type is defined by its physical state and behavior.
