Explosive Materials

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 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

Pyroclastic flows

Pyroclastic flows

Hazards of Volcanoes• Lava flows- consume land unable to rebuild• Ash falls – smother towns and countryside; health

hazard• Pyroclastic flows – incinerate surrounding areas• Marine eruptions – tsunamis• Invisible gases – asphyxiation• Effect 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.

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