Mount Meager massif are covered with their eruptive products and serve as the surface expressions of intrusions. As a result, they provide a unique opportunity to study the relationships between magma chambers and their lavas. The mafic (rich in magnesium and iron), intermediate (between mafic and felsic) and felsic (rich in feldspar and quartz) volcanic rocks of the massif were erupted from at least eight volcanic vents. The Bridge River Vent is a relatively young volcanic crater that formed during an eruption about 2,400 years ago. This eruption ranged in character from explosive to effusive and involved lava dome extrusion, pyroclastic flows, lahars
Geology of Ascension Island same time as the Sister's Peak region 829,000 years ago. Bentmoreite scoria cones record evidence of mafic volcanism, although older rhyolite and trachye flows, domes and pyroclastic deposits point to felsic eruptions as well. The Central Felsic Complex (CFC), centers on Green Mountain and Middleton Ridge and is older than the Eastern Felsic Complex. Here, ash is typically welded together and breccia is laden with rhyolite and obsidian fragments. Middleton Ridge formed more than one million years ago and is accompanied trachyte and rhyolite flows. By comparison, Green Mountain formed as recently as 395,000 years ago with trachyte flows and