An official website of the United States government
Here's how you know
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.
Grand Canyon Monitoring and Reseach Center scientists produce fact sheets that summarize decades of research. Click on the title of these fact sheets to get the PDF version.