Chapter 5 Volcanoes in addition to Other Igneous Activity The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions

Chapter 5 Volcanoes in addition to Other Igneous Activity The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions www.phwiki.com

Chapter 5 Volcanoes in addition to Other Igneous Activity The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions The Nature of Volcanic Eruptions

Massey, Jamie, On-Air Personality has reference to this Academic Journal, PHwiki organized this Journal Chapter 5 Volcanoes in addition to Other Igneous Activity The Nature of Volcanic Eruptions Factors determining the “violence” or explosiveness of a volcanic eruption Temperature of the magma Composition of the magma Dissolved gases in the magma The above three factors actually control the viscosity of a given magma which in turn controls the nature of an eruption The Nature of Volcanic Eruptions Viscosity is a measure of a material’s resistance to flow Factors affecting viscosity Temperature – Hotter magmas are less viscous Composition – Silica (SiO2) content Higher silica content = higher viscosity (e.g., felsic lava such as rhyolite) Lower silica content = lower viscosity or more fluid-like behavior (e.g., mafic lava such as basalt)

John Marshall Law School US www.phwiki.com

This Particular University is Related to this Particular Journal

The Nature of Volcanic Eruptions Factors affecting viscosity continued Dissolved Gases Gas content affects magma mobility Gases exp in addition to within a magma as it nears the Earth’s surface due to decreasing pressure The violence of an eruption is related to how easily gases escape from magma The Nature of Volcanic Eruptions Factors affecting viscosity continued In Summary Fluid basaltic lavas generally produce quiet eruptions Highly viscous lavas (rhyolite or in addition to esite) produce more explosive eruptions Materials extruded from a volcano Lava Flows Basaltic lavas are much more fluid Types of basaltic flows Pahoehoe lava (resembles a twisted or ropey texture) Aa lava (rough, jagged blocky texture)

A Pahoehoe lava flow A Typical aa flow Materials extruded from a volcano Pyroclastic materials – “Fire fragments” Types of pyroclastic debris Ash in addition to dust – fine, glassy fragments Pumice – porous rock from “frothy” lava Lapilli – walnut-sized material Cinders – pea-sized material Particles larger than lapilli Blocks – hardened or cooled lava Bombs – ejected as hot lava

A volcanic bomb Bomb is approximately 10 cm long Volcanoes General Features Opening at the summit of a volcano Crater – steep-walled depression at the summit, generally less than 1 km diameter Caldera – a summit depression typically greater than 1 km diameter, produced by collapse following a massive eruption Vent – opening connected to the magma chamber via a pipe Volcanoes Types of Volcanoes Shield volcano Broad, slightly domed-shaped Composed primarily of basaltic lava Generally cover large areas Produced by mild eruptions of large volumes of lava Mauna Loa on Hawaii is a good example

Shield Volcano Volcanoes Types of Volcanoes continued Cinder cone Built from ejected lava (mainly cinder-sized) fragments Steep slope angle Rather small size Frequently occur in groups Sunset Crater – a cinder cone near Flagstaff, Arizona

Volcanoes Types of volcanoes continued Composite cone (Stratovolcano) Most are located adjacent to the Pacific Ocean (e.g., Fujiyama, Mt. St. Helens) Large, classic-shaped volcano (1000’s of ft. high & several miles wide at base) Composed of interbedded lava flows in addition to layers of pyroclastic debris A composite volcano Mt. St. Helens – a typical composite volcano

Mt. St. Helens following the 1980 eruption A size comparison of the three types of volcanoes Volcanoes Composite cones continued Most violent type of activity (e.g., Mt. Vesuvius) Often produce a nueé ardente Fiery pyroclastic flow made of hot gases infused with ash in addition to other debris Move down the slopes of a volcano at speeds up to 200 km per hour May produce a lahar, which is a volcanic mudflow

A nueé ardente on Mt. St. Helens Other volcanic l in addition to as long as ms Calderas Steep-walled depressions at the summit Size generally exceeds 1 km in diameter Pyroclastic flows Associated with felsic & intermediate magma Consists of ash, pumice, in addition to other fragmental debris Caldera

Massey, Jamie KNIX-FM On-Air Personality www.phwiki.com

Other volcanic l in addition to as long as ms Pyroclastic flows continued Material is propelled from the vent at a high speed e.g., Yellowstone plateau Fissure eruptions in addition to lava plateaus Fluid basaltic lava extruded from crustal fractures called fissures e.g., Columbia River Plateau Other volcanic l in addition to as long as ms Lava Domes Bulbous mass of congealed lava Most are associated with explosive eruptions of gas-rich magma A lava dome on Mt. St. Helens

Other volcanic l in addition to as long as ms Volcanic pipes in addition to necks Pipes are short conduits that connect a magma chamber to the surface Volcanic necks (e.g., Ship Rock, New Mexico) are resistant vents left st in addition to ing after erosion has removed the volcanic cone Formation of a volcanic neck Shiprock, NM – a volcanic neck

Deep-focus earthquakes occur along convergent boundaries Volcanoes in addition to climate Explosive eruptions emit huge quantities of gases in addition to fine-grained debris into the atmosphere which filter out in addition to reflect a portion of the incoming solar radiation Examples of volcanism affecting climate Mount Tambora, Indonesia – 1815 Krakatau, Indonesia – 1883 Mount Pinatubo, Philippines – 1991 End of Chapter 4

Massey, Jamie On-Air Personality

Massey, Jamie is from United States and they belong to KNIX-FM and they are from  Phoenix, United States got related to this Particular Journal. and Massey, Jamie deal with the subjects like Country Music; Entertainment

Journal Ratings by John Marshall Law School

This Particular Journal got reviewed and rated by John Marshall Law School and short form of this particular Institution is US and gave this Journal an Excellent Rating.