Which consequence results when tephra accumulation obstructs streams?

💡 Explanation

Lahars rapidly form because complete tephra blockage will suddenly fail causing a debris flow. The **plug failure** results in mobilized volcanic material from upstream accumulation; therefore, lahars, rather than slower processes or unrelated phenomena, are the key immediate risk.

• Which outcome is expedited when barrier island vegetation removal occurs?
• Which outcome results when stream avulsion shortens a river meander?
• Which outcome results when coastal upwelling weakens unexpectedly along the western coastline of South America?
• Which outcome results when strong currents erode sediment supporting coastal stacks composed of limestone?
• Which outcome occurs when a newly formed volcanic island destabilizes?
• Which impact on communities occurs during lahar flows?