Which hazard causes widespread crop failure following large pyroclastic eruption?

💡 Explanation

Aerosol optical depth increases because volcanic ash and sulfates from the pyroclastic flow block sunlight, driving cooling and reduced photosynthesis; therefore, A is correct rather than other effects which are localized or less significant for agriculture.

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• Which horizon development occurs as clay minerals migrate?
• Which atmospheric mixing results locally when enhanced differential heating induces convergence zones?
• Which risk increases when a coastal city's earthquake early warning system depends exclusively on shallow crustal seismic sensors?