"Eruption" starts with a short accompanied intro with Alex Van Halen on drums and Michael Anthony on bass.
"Eruption" was played on the Frankenstrat, with an MXR Phase 90, an Echoplex, a Univox echo unit and a 1968 Marshall 1959 Super Lead tube amp.
Initially, "Eruption" was not considered as a track for the Van Halen album as it was just a guitar solo Eddie performed live in the clubs.
'"[8] "Spanish Fly", an acoustic guitar solo on Van Halen II, can be viewed as a nylon-string version of "Eruption", expanding on similar techniques.
Similarly, it was suggested by Templeman for inclusion on the album after he heard Eddie Van Halen playing a classical guitar.