Hawaiian Islands Hawaiian Islands Teprha Teprha
Hawaiian IslandsHawaiian Islands
TeprhaTeprha
Source for photos and explantions on the web
• http://volcanoes.usgs.gov/Products/Pglossary/pglossary.html
Plinian Eruption Column
• TEPHRA: Any volcanic product ejected into the air.
• Includes pumice, ash, spatter and more!
Volcanic Ash
PUMICE
• Tephra may either be shot into the air ballistically or carried upwards by the convecting column and blown downwind
Eruption Column and Cloud
• Ballistically ejected particles like blocks, bombs, and spatter tend to land near the vent and build cones.
Ballistic Spatter Explosion at Night.
Notice the Parabolic Path of the Spatter.
• Convectively carried material like ash, pele’s hair, light pumice blocks, and reticulite are carried far from the vent by the ash cloud. Deposits from ash clouds get finer away from the vent.
VOLCANIC ASH
Tephra is blown by Winds
• The explosivity of a volcano is related to gas expansion and the viscosity of the magma.
• Abundant gas that expands rapidly provides the force
• Viscosity of magma is the container. If the bubbles escape easily there is little fragmentation. Trapped bubbles explode causing fragmentation.
Explosivity Index
TEPHRA: PYROCLASTIC PRODUCTS
Pyroclastic Products are Called Tephra
Tephra are named first for size, then for texture.
>64 millimeters: Bombs and Blocks (Ballistic)(includes ribbon bombs, teardrop bombs, spatter bombs, pumice bombs–blocks, lava blocks, and lithic blocks)
2 to 64 millimeters: Lapilli(includes pumice, cinder, scoria, reticulite, pele’s tears, pele’s hair, limu o Pele, accretionary lapilli, and lithic lapilli)
<2 millimeters: Ash (includes ash, pele’s hair, limu o Pele,)
• Most of the gas that drives eruptions is water that turns to steam bubbles. The water may either be inside the magma or groundwater mixed into the magma as it rises to the surface.
Hawaiian style eruptions
• Generally fairly gentle as the magma is very fluid and allows the bubbles to pass through without causing violent explosions.
Hawaiian Fire Fountain
Reticulite
Reticulite––lapilli
Reticulite Bomb
Pele’s Hair
Cinders
Cinder lapilli at Pu‘u Puai
Pele’s Tears––Lava droplets
Low Fountain and Tephra Cone––Pu‘u ‘Ō‘ō
Dome Fountain
Spatter Bombs in Flight
Spatter Deposits
Pele’s Hair From Skylight
Strombolian style eruptions
These eruptions are marked by bursts of gas that are more explosive than Hawaiian eruptions due to the greater viscosity of the magmas that keeps gas from escaping easily.
Builds cinder cones like those seen on Mauna Kea, Hualālai, Haleakala, etc.
Cinder Cone
Kohala Mountains
Cinders and Bombs
Volcanic Bomb––Mauna Kea
Small Volcanic Bombs––really lapilli!!
Pumice Bomb at Pu‘u Waa Waa
• Explosive Hawaiian eruptions that make ash are all driven by groundwater or seawater mixing with the magma.
Ballistic Spatter at Ocean Entry
Large Lithc Block in Spatter Field at Ocean Entry––
Related to Collapse of Bench and Large
Steam Explosion
Spatter and Steam Cloud
Ballistic Spatter and Steam Cloud
Limu o Pele bubble bursting
Limu o Pele
Limu O Pele
Coarse Littoral Ash from Steam Plume
Footprints in Ash
Accretionary Lapilli
Accretionary Lapilli in Keanakako`i Ash near Footprints
Diamond Head is made of ash and accretionary lapilli.
Koko Head
Pumice
Volcanic Ash––Electron Microscope Photo