Volcanism Extrusive Igneous Activity expulsion of molten rock
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Volcanism & Extrusive Igneous Activity • expulsion of molten rock (LAVA), gases and water onto the surface of the Earth. - 550 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) Mt. Fujiyama, Japan
Dormant vs Extinct Volcanoes • • Dormant volcanoes - have not erupted recently, but may do so again. > Mt. Vesuvius (Italy) Extinct or volcanoes • -Extinct inactive 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 - Dome - a large mound of viscous, felsic lava - commonly plugs the central vent • Calderas - a collapsed volcanic summit - greater in diameter - have steep sides.
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)
Stratovolcano formation
Composite Volcanoes Mayon volcano, Philippines, is a nearly symmetrical composite volcano. View of Mount St. Helens, Washington in 1978.
Cinder Cones Primarily cinder-sized (0. 25 -1. 0 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 of Cinder Cone Development Cinder Cone
Lava Types Pahoehoe lava (smooth & ropey) 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. 1 meter
Lava Fountain
Pyroclastic Ash Flow ' aka Nuee Ardentes 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
Glowing Ash clouds. Nuee Ardentes
Ash plume from a stratovolcano eruption
Pyroclastic flow , Nuee Ardente
, Lahars & Nuee Ardentes • 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. 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 - nitrogen - hydrogen sulfide - carbon dioxide - sulfur oxides - 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 (exosphere) • Changes weather and climate patterns for several months to a year - (atmosphere) • Causes changes in drainage patterns, and pollutes many water sources - (hydrosphere)
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
Eruption styles and their relative explosiveness * VEI stands for Volcanic Explosivity Index
- Mafic extrusive igneous rock
- Rhyolite mafic
- Obsidian rock
- Sedimentary rock song
- Luster streak
- Sedimentary deposition
- Intrusive vs extrusive igneous rocks
- Extrusive rocks
- Extrusive igneous rocks example
- Igneous rock to metamorphic rock
- Whats the rock cycle
- Meteorite
- Intraplate volcanism
- Magma formation concept map
- Expelled molten rock
- Intrusive igneous rock bodies are called
- Laccolith shape
- Igneous rock types
- Igneous rock
- Ignition rocks
- Pumice rock type
- Concept mapping of the different rock types
- Igneous rock colors
- Characteristics igneous rocks
- Igneous rock animation
- Pumice extrusive or intrusive
- What kind of rock is this
- Molten rocks underneath
- Igneous rock comic strip
- Igneous rock
- Igneous rock texture
- Non-banded grains
- How igneous rocks are formed
- Igneous rock
- Sedimentary rock concept map
- Igneous rock identification lab
- Rock cycle
- Igneous rock properties
- Igneous rock
- Is diorite aphanitic or phaneritic
- Characteristics of igneous rocks
- Composition of igneous rocks