Volcanoes

Question 1

What are Lahars (secondary hazard of volcanoes)

Answer 1

When rainfall mobilizes volcanic ashes forming volcanic mudflows
Occurs at subduction zone at composite volcanoes

Question 2

Effects of lahars

Answer 2

1) deposits thick layers of sediment, damaging bridges,infrastructures and towns causing long-term disruption in transport/ electricity

2) long term environmental impacts e.g. soil degradation and altered river courses, threatening local ecosystems.

Question 3

Mount St. Helens case study ( for primary and secondary hazards)

Answer 3

1) began w/ a massive explosive event that produced a colossal cloud, reaching a altitude of 24km spreading across several states.
2) formed lahars due to the melting of snow and ice mixing with volcanic debris
3)formed pyroclastic flows (primary)
4) thus, the eruption of this is a classic eg of how a single volcanic event can produce both immediate primary hazards and enduring secondary hazards, illustrating the widespread and complex nature of volcanic activity.

Question 4

What are pyroclastic flows

Answer 4

Very large, dense clouds of hot ash and gas (600º)

Their erratic nature makes it challenging to predict when they’ll occur, increasing the risk to life and ecosystems.

Question 5

Effects of pyroclastic flows

Answer 5

1) the Mount St. Helens triggered pyroclastic flows that surged down the volcanoes slopes at high speeds, incinerating everything in their path which formed a large debris avalanche that engulfed the surrounding landscape.

2) fine volcanic ash produced can cause severe respiratory damage / suffocation if inhaled.