Volcanoes Points to Be Covered on Volcanos Products

Volcanoes

Points to Be Covered on Volcanos • Products of eruptions • Lava properties vs composition • Fissure eruptions • Types of volcanoes • Distribution of volcanoes

World Famous Kilimanjaro Fujiyama Mt St Helens Mauna Loa

What do we expect in a volcanic eruption? • Solids lofted into atm • Lava flows from others (called some pyroclastics. Better • Range from mafic than fireworks? (e. g. basalt) to • You bet!!! felsic, like all ign rx • Rocks may form from • Water • Gases fusing of pyroclastics can range from dense (tuff) to light (pumice)

Volcanoes Vulcan’s Story • Magma/lava viscosity related to composition. • Less viscous lavas flow more easily. • This releases dissolved gases more easily. • Less likely to produce a violent eruption. • More likely to be distributed farther.

Gassy Volcanoes – Giving us atmosphere Sangay Paricutin Kilauea Stromboli

Volcanoes More on Water and Gases • What gas is overwhelmingly the most abundant volcanic gas? • Water vapor. Over (95%) • Isn’t that how we got our oceans, streams, etc. • Our hydrosph, yes. And our atm • Oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen sulfide (stinky), hydrogen chloride (? ? ), sulfur dioxide (bad guy? ), ammonia

Fissure Eruptions • Erupt basaltic lava. • Low viscosity, moves fast and far. • Where are these fissures? • The ocean floor in spreading centers. • Anywhere on land? • Yes, wherever rifting has occurred. • Check out the Colombia Plateau. Great thicknesses of basalt lava.

Fissure eruptions at Kilauea

Kilauea eruption

Shield Volcanoes • Buildup primarily from basalt flows. • Long, low-angle slopes. • Form of an inverted shield. Mauna Loa

Cinder Cones • Almost entirely pyroclastics. • Short, steep slopes. • Slopes at steepest angle possible for size of pyroclastics. • Usually depression at top of cone.

Cinder Cone

Stratovolcanoes (Composite Cones) • Pyroclastics build up. • Lava flows extend laterally. • Alternating lava and pyroclastics. Cotopaxi Mt Hood

Spectacular Volcanic Features Crater Lake

Mt St Helens

Sangay

Distribution of Volcanoes • Convergent plate boundaries Circum-Pacific Ring of Fire Alpine-Himalayan Belt Divergent plate boundaries: oceanic ridges Mid-Atlantic Ridge

Terms used in the study of volcanoes Technical Terms Cinder cone Convergent boundary Divergent boundary Fissure eruption Pyroclastics Rift Shield volcano Spreading center Stratovolcano (Composite cone) Non-technical terms Lava Viscosity

Student Responsibilities on Volcanoes • What are the products of volcanic eruptions? • How do we interrelate magma/lava viscosity, stored gases, violence of an eruption, and distance of transport of the volcanic products? • What are fisssure eruptions, shield volcanoes, cinder cones, and stratovolcanoes? • How do we explain the global distribution of volcanoes?