[Keneldil the Polka-dot]

but after it goes extinct and experiences some erosion, the plug (just below the crater) is exposed and gives the mountain a pointed top

Hmm... I didn't know that. Some erosion? Sounds like that much erosion would take a LONG time. Longer than from when Maedhros jumped in the fire to when the Lonely Mountain would have become a volcano and spewed up the Silmaril. Just how long would it be between those two events anyway, theoretically?