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Volcanic Hazards!

Volcanic Hazards!. Volcanic Hazards!. Lava Flows. Lava Flows. Streams of molten rock Usually slow speed Only a few mph Can reach up to 60 mph Intermediate to mafic composition Most common Hawaiian hazard; leads to mostly destruction of property. Pu’u ‘O’o and Kupaianaha.

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Volcanic Hazards!

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  1. Volcanic Hazards! Volcanic Hazards!

  2. Lava Flows Lava Flows • Streams of molten rock • Usually slow speed • Only a few mph • Can reach up to 60 mph • Intermediate to mafic composition • Most common Hawaiian hazard; leads to mostly destruction of property

  3. Pu’u ‘O’o and Kupaianaha Pu’u ‘O’o and Kupaianaha • Started eruptions in 1983 • By 2002, 189 structures destroyed and 13 km of highway covered with up to 25m of lava Flow through 2002

  4. Pyroclastic Flows Pyroclastic Flows • Fluid avalanche of rock material, hot ash and gas • Can form when eruption columns collapse • Highly destructive • Typically faster than 80km/hr and up to 700°C • Can incinerate, burn, and asphyxiate people

  5. Lahars Lahars • Like pyroclastic flows, but with more water • 20-60% sediment: very turbulent • >80% sediment: smooth flow - much faster than turbulent - can float very large objects • Form from: • Snow/ice water mixed with debris • Pyroclastic flows mixed with river water • Rainfall on loose material (ash)

  6. Landslides Landslides • Large masses of earth that fall, slide or flow rapidly • Can trigger volcanic explosions, lahars, and tsunamis • • Formed by weakening of slopes from volcanic activity • - Magma intrusion, earthquakes, eruptions, intense rainfall • Large scale landsliding on south flank of Kilauea causing south side of Hawaii to fall into the sea

  7. Tephra Tephra • Airborne volcanic rock • Consists of wide range of rock types • Larger rocks fall closer to volcano; ash can travel thousands of kilometers • Bombs (>64mm), lapilli (2-64mm) and ash (>2mm) Reticulite Pele’s hair

  8. Volcanic Gases Volcanic Gases • Gases released: H20 vapor, CO2, SO2, HCl, HF, H2S, CO, H2, NH3, CH4 and SiF4 • Formation of acid rain (from SO2) can cause water contamination and plant damage • Prevailing winds can blow gases thousands of kilometers away

  9. Earthquakes Earthquakes • Volcanic earthquakes: small; caused by eruptions and movement of magma within the volcano • Tectonic earthquakes: occur at base of volcano or deep within the crust - larger and more destructive • April 2, 1868 – 7.9 magnitude earthquake; most destructive in Hawaiian history

  10. Ground cracks and settling • Cracks: ground cracks in the area of a new eruption as magma is forced upwards • Can be 6 ft wide and a mile long • Form within hours • Settling: occurs near end of the eruption • Subsurface magma drains away and causes ground to collapse • Cracks: ground cracks in the area of a new eruption as magma is forced upwards • Can be 6 ft wide and a mile long • Form within hours • Settling: occurs near end of the eruption • Subsurface magma drains away and causes ground to collapse

  11. Tsunamis Tsunamis • Giant ocean waves • Cause: earthquakes or giant landslides

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