Chapter 4- Valcanos Flashcards
Atmosphere
Originally created from gasses released from volcanic eruption
Hydrosphere
Produced by condensation of volcanic water vapor.
Hydrosphere
Produced by condensation of volcanic water vapor.
Biosphere
Both positively✔️ and negatively❌️ influenced by volcanism
✔️-Lava flows and ash weather to produce fertile soils
❌️-Violent eruptions can destroy nearly all life in their paths.
❌️- Large amounts of ash and volcanic gasses in the atmosphere can trigger rapid climate changes and contribute to mass extinctions
Volcanism
Occurs when magma makes it’s way to the Earth’s surface
Volcanos
Landforms formed by the extrusion of lava
Volcanos
Landforms formed by the extrusion of lava
Lava
Produced when magma reaches Earth’s surface
Explosive eruptions
Produces rapidly cooled rock fragments called pyroclasts
Pyroclasts
Size can range from dust (ash) to boulders (blocks and volcanic bombs)
Effusive eruptions
Calm oozing of magma out of the ground (flowing lava) (volcanos in Hawaii)
Creation of land
Lava flows build up volcanic islands (Hawaii)
Geothermal Energy
Underground heat generated by igneous activity
Effect on Climate
Very large eruptions can result in measurable global cooling resulting in crop failures and famines.
Violence of eruptions is controlled by
-Dissolved gasses in magma
-Ease or difficulty of gasses escaping to atmosphere
Viscosity
A fluids resistance to flow
-higher silica contents produce higher viscosities
-Cooler lavas have higher viscosities
-Amount of dissolved gases, the more dissolved gases,the more fluid the lava.
Mafic Lava Flows
Low viscosity and flows easily
(Pahoehoe, A’a, Lava Tube)
Flood Basalts
Very low viscosity and flows very easily frome erupting fissures
Columnar Jointing
Parallel mostly six-sided vertical columns
Submarine Lava flows
Pillow structure formed as lava flows into water.
Intermediate and Felsic Lava Flows
Thicker viscous lavas that flow short distance
Pyroclastic Materials
Dust, ash, cinders, lapillus, blocks, and volcanic bombs
Pyroclastic Flows
Mixture of gas and pyroclastic debris that flows rapidly down slope.
Shield Volcanoes
-Broad and gently sloping
-Composed of solidified basaltic lava flows
-flows often contain lava tubes
Cinder cones
-Small and steeply sloping
-composed of a pile of loose cinders; basalt is common.
Composite Valcanoes
-moderately to steeply sloping
-constructed of alternating layers of pyroclastic debris and solidified lava flows
-composed primarily of intermediate composition volcanic rocks (Andesite)
-Most common type of volcano on convergent plate boundaries
-Mainly located around Pacific Ocean (Ring of fire) and Mediterranean sea.
Lava Domes
-extremely high viscosity
-degassed
-felsic lavas
(Often glassy, obsidian)
Calderas
-volcanic depression of at least 1km in diameter
-result of very violent eruptions
(Crater Lake in Oregon)
Volcanic hazards
-Pyroclastic flows: account for the largest number of deadly events (Pompeii)
-volcanic gases: Carbon dioxide (Nyos Cameroon)
-volcanic mudflow: Lahars
(Armero Colombia
-Indirect hazards: famine and lightning
-Eruption times correspond with largest mads extinction events
Volcanos status
Approximately 1,500 active volcanos worldwide
Active volcano
Currently or recently eruptive
(About 500 In world today)
Dormant volcano
Hasn’t erupted I’m thousands of years, but is expected to erupt in the future
Extinct volcano
Hasn’t erupted in many years and shows no signs of any future eruptions
Volcanic activity at divergent Boundaries
-decompression melting
-effusive eruptions of basalt magmas and pillow lavas
-formation of most of the sea floor
-mid-oceantic ridges, iceland
Volcanic activity at convergent boundaries
-Most large well known volcanoes
-explosive composite volcanoes
-viscous andesitic lavas
Within plate volcanic activity
-Mantle Plumes (hot spots): Hawaii, Yellowstone
-Basaltic magma/lava
