Question 17

Roads and highways were blocked by ash.

The main result of the 1980 eruption of Mount St. Helens was the extensive blockage of roads and highways due to the significant ash fall that followed the eruption.

A) Roads and highways were blocked by ash.

This option is correct as the eruption produced a massive ash cloud that spread over a wide area, leading to the obstruction of numerous roads and highways. The ash deposits created hazardous conditions for transportation and significantly impacted accessibility in the region.

B) Homes and businesses were destroyed by earthquakes.

This option is incorrect. While the eruption did trigger seismic activity, the primary destruction was not directly due to earthquakes but rather the explosive eruption and the subsequent ash fallout. Homes and businesses were primarily affected by volcanic materials rather than seismic events.

C) Recreational areas were damaged by wildfires.

This option is incorrect. The eruption itself did not cause wildfires; rather, it was the ash and volcanic debris that impacted the natural landscape. The immediate aftermath involved volcanic effects rather than fire-related damage in recreational areas.

D) Agricultural fields were ruined by flooding.

This option is also incorrect. The eruption caused widespread ash deposition which adversely affected agriculture, but it did not primarily result in flooding. The damage was predominantly due to ash covering the fields rather than water-related issues.

Conclusion

The correct answer highlights the significant impact of ash from the Mount St. Helens eruption on infrastructure, particularly roads and highways. Other options fail to accurately capture the primary consequences of the eruption, which were related to volcanic activity and ash, rather than seismic events, wildfires, or flooding.