South of Tricouni Peak are andesite and dacite lava flows that form two non-overlapping sequences. |
These are called tension gashes and formed as the dacite split open allowing the quartz fluid to fill in the cracks. |
These are overlain by flows of rhyolite, dacite, and andesite totalling about 900 m in thickness. |
They are marked by eruptions of cooler, stickier lavas such as andesite, dacite and rhyolite. |
The lava dome is made of dacite, a fine-grained volcanic rock that contains a sprinkling of larger, visible crystals, like chopped fruit in a cake. |
Four common volcanic rock types are basalt, andesite, dacite, and rhyolite. |