Explosive Materials. The greater the explosivity, the greater the amount of fragmentation Lava & rock material sent into the air is called Tephra : ( Greek, for ash) is a generic term for any airborne pyroclastic accumulation - PowerPoint PPT Presentation
Explosive MaterialsThe greater the explosivity, the greater the amount of fragmentationLava & rock material sent into the air is called Tephra : (Greek, for ash) is a generic term for any airborne pyroclastic accumulationPyroclastic flows: (fire fragments) Individual eruptive fragments are called Tephra : Classified by size
ASH -- Very fine-grained fragments (< 2 mm), generally dominated by broken glass shards
LAPILLI -- Pea- to walnut-size (2 to 64 mm). They often look like cinders
BLOCKS AND BOMBS Fragments >64 mm
Pyroclastic flows move at speeds of over 60 miles per hour
reach temperatures of over 800 Degrees Fahrenheit (400 degrees Celsius). Pyroclastic flows
Hazards of VolcanoesLava flows- consume land unable to rebuildAsh falls smother towns and countryside; health hazardPyroclastic flows incinerate surrounding areasMarine eruptions tsunamisInvisible gases asphyxiationEffect on climate Tambora 1815; 1816 "year without Summer"When archaeologists began excavating Pompeii, they foundunusual spaces in the ash layer that, when filled with plaster,were casts of people that had been caught by the volcanic debris flow and could not escape.