Mt. Fujiyama, Japan Volcanism & Extrusive Igneous Activity expulsion of molten rock (LAVA), gases and water onto the surface of the Earth. expulsion of molten rock (LAVA), gases and water onto the surface of the Earth active volcanoes > > Active = erupted in historic times. - - e.g. Mauna Loa and Kilauea (Hawaii) - - Mt. St. Helens (Washington) - - Mt. Pinatubo (Philippines) - - Mt. Fujiyama (Japan) - - Mont Serrat (Caribbean)

Dormant vs Extinct Volcanoes Dormant volcanoes - have not erupted recently, but may do > Mt. Vesuvius (Italy) Extinct or inactive volcanoes - > Dormant volcanoes - have not erupted recently, but may do so again. > Mt. Vesuvius (Italy) Extinct volcanoes - have not recently erupted nor do they give indications of erupting in the future. > Thousands of these types of volcanoes exist. Mt. Kilamanjaro (Tanzania,Africa)

Volcanoes, Craters, Domes, Calderas Conical mountains - - central vent where lava, gases, and pyroclastic materials are erupted. - - Craters - - circular opening at summit - - generally less than 1 km in diameter Calderas - - a collapsed volcanic summit - - greater in diameter - - have steep sides. Dome a large mound of viscous, felsic lava - commonly plugs the central vent

Unzen Volcano, Japan shown with Lava dome and lahars (volcanic debris flows)

Caldera

Bathymetry map of Crater lake, Oregon

Summit of Kilauea-inner crater

Volcanoes types

Olympus Mons, a shield volcano

A small shield volcano in Iceland

Composite Volcanoes a.k.a.- stratovolcanoes - - interbedded pyroclastics and lavas. - - typically andesitic to rhyolitic lava > > intermediate to felsic magma composition - - Found on continents and island arcs > > mostly associated with convergent plate boundaries (subductive) > > examples of composite Mt. St. Helens, Mt. Vesuvius, Mt. Pinatubo, Mt. Fujiyama, Mt. Kilamanjaro., Mt. Rainier (photo) Mt. St. Helens, Mt. Vesuvius, Mt. Pinatubo, Mt. Fujiyama, Mt. Kilamanjaro., Mt. Rainier (photo)

Stratovolcano formation

Composite Volcanoes Mayon volcano, Philippines, is a nearly symmetrical composite volcano. Mayon volcano, Philippines, is a nearly symmetrical composite volcano. View of Mount St. Helens, Washington in View of Mount St. Helens, Washington in 1978.

Cinder Cones Primarily cinder-sized ( mm) material. but may have other sizes too. Cinders fall to Earth and collect around the vent. have steep slopes up to 33 degrees smaller than shield volcanoes, usually less than 400 m tall Form on the flanks of larger volcanoes.

Cinders and volcanic ash

Development of Cinder Cone

Lava Types Pahoehoe lava (smooth & ropey) in Hawaii. Pahoehoe lava (smooth & ropey) in Hawaii. Aa lava (rough and blocky) also in Hawaii. Aa lava (rough and blocky) also in Hawaii.

Pillow Lavas These bulbous masses of pillow lava formed when lava erupted & cooled under water. These bulbous masses of pillow lava formed when lava erupted & cooled under water. 1 meter

Lava Fountain

Pyroclastic Ash Flow Pyroclastic ash- lava blown up into the air smaller stuff is ash, larger stuff are called "bombs" Pyroclastic Ash Flow extremely fast (100's m/sec) extremely hot - - sometimes glowing redhot extremely lethal - - many deaths associated with volcanic eruptions are related to these events > > e.g., Pompeii and Herculanum aka Nuee Ardentes ' '

Glowing Ash clouds- Nuee Ardentes

Ash plume from a stratovolcano eruption

Pyroclastic flow Nuee Ardente,

Lahars are mud flows that often occur after eruptions. Nuée ardentes are mobile dense clouds of incandescent ash that can move downhill at speeds up to 100 km/hr. Lahars & Nuee Ardentes, Mt Pelee destroyed St. Pierre on the island of Martinique, West Indies in 1902,

The effects of explosive volcanic activity

Gases and Magma Volcanic gases - - water vapor - carbon dioxide - - nitrogen - sulfur oxides - - hydrogen sulfide - chlorine Felsic magmas - - highly viscous : Si-rich - - inhibits the expansion of gases - - pressure builds up - - explosive eruptions, like Mt. St. Helens. Mafic magmas - - lower viscosity - - lower gas pressure - - erupt rather quietly, like Hawaiian Volcanoes.

Lake Nyos, a volcanic lake in Cameroon, Africa CO 2 emitted from the acidic lake killed 1700 villagers near the lake in 1986

Mt. St. Helens

Effects of Volcanic activity builds up mountains and new land; also destroys land - - (Lithosphere-aka. GEOSPHERE) destroys many living things - - (biosphere) ejects ash and gases into the air blocking sunlight Changes weather and climate patterns for several months to a year - - (atmosphere) Causes changes in drainage patterns, and pollutes many water sources - - (hydrosphere) (exosphere)

Distribution of volcanoes is not random related to plate tectonics commonly found along plate boundaries

Eruption types are a function of plate tectonic setting, magma composition and water/gas content.

Plinian eruption of Lascar Volcano in Chile

A Vulcanean eruption

Surtseyan eruption

Vesuvian eruption

Strombolian style eruption of Tungurahua Volcano, Ecuador

* VEI stands for Volcanic Explosivity Index Eruption styles and their relative explosiveness