A lahar is a type of volcanic mudflow or debris flow that occurs when volcanic materials mix with water, often from heavy rainfall or melting snow. These flows can be extremely dangerous, as they can travel quickly down the slopes of a volcano, carrying rocks, ash, and other debris with them. Lahars can occur during or after a volcanic eruption, posing a significant risk to nearby communities. Lahars can vary in size and speed, depending on the amount of water and volcanic material involved. They can travel at speeds of up to 60 miles per hour and can reach several meters in thickness. Areas near active volcanoes, such as Mount St. Helens or Mount Rainier, are particularly vulnerable to lahars, making monitoring and preparedness essential for local populations.