the siberian traps are considered to have erupted through numerous vents over a period of a million years or more, probably east and south of norilsk in siberia. the giant norilsk nickel-copper-palladium deposit formed within the magma flows in the main siberian traps. the presence of extensive tuff and pyroclastic deposits suggests that a number of large explosive eruptions occurred during or before the eruptions of basaltic lavas. the presence of silicic volcanic rocks such as rhyolite is also indicative of explosive eruptions.