Archean felsic volcanic rocks often causes pyroclastic flow (hot, dense gas with volcanic fragments) instead of fluid lava flow. However, if the rhyolitic lava is still molten during eruption, it can behave and flow like fluid flow. Felsic lava flow and lava dome are the two common types of underwater deposits formed by Archean felsic volcanic rocks (Fig. 4). Documented Archean lava structures are distinctive from post-Archean felsic lava because underwater eruptions are so rare in post-Archean. The dacitic or rhyolitic lava flows are quenched right after the eruption. When water is in touch with the flow, the lava quickly cools down. Finally, The
Archean felsic volcanic rocks ultramafic and mafic units make up the major volume of the volcanic units. The remaining volcanic units are extensive but thin felsic volcanic layers, such as Duffer Formation of the Warrawoona Group. The greenstone belts may be subsequently intruded by dome-shaped magma chambers. The intrusion deformed the felsic volcanic rocks along with the volcano-sedimentary sequences. Observing modern volcanic processes is relatively easier than observing Archean volcanism, because erosion constantly started removing earlier formed materials. So, studying the Archean supracrustal rocks back in deep time may be subjected to sampling bias. The meaning of "felsic" refers to high silica (SiO) content