As population increases in the Pacific Northwest, areas near the volcanoes are becoming developed and more people and property are at risk. The principal hazards to people in the Pacific Northwest are from lahars and ash fall. Lahars (volcanic mudflows) can destroy buildings and infrastructure. Eruptions that include volcanic ash can be especially dangerous for aircraft, even at long distances from the volcano, because volcanic ash can clog and shut down their engines. –“Why Study Cascade Volcanoes?,”
USGS

What does this passage help to explain?

the step-by-step process that causes a volcano to erupt
what happened the last time a volcano erupted in the area
why people should be mindful of the danger volcanoes can pose
how the government responds after an active volcano erupts