Here's why:
* The schwa sound is represented by the symbol /ə/ and is a very common, neutral vowel sound in English. It's the sound you make in the unstressed syllables of words like "about" or "again".
* In the word "volcano", the first syllable "vol" is stressed, while the second syllable "ca" is unstressed. The "a" in the second syllable is pronounced with a schwa sound.
Therefore, the pronunciation of "volcano" is /vɒlˈkeɪ.noʊ/ with the schwa sound occurring in the second syllable.