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.
Example of ceiling boxwork in Wind Cave. As the cave formed, calcite-filled veins in the brecciated (fractured) limestone bedrock dissolved more slowly than the original host limestone, leaving behind the fracture filling as boxwork.
Public Domain.
