Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock () or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Earthquakes at Mount St. Helens from 1980-2012, plot represents depth of earthquakes over time. Circle size relative to earthquake size.
Public Domain.
