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.
Permeable lenses of sand and gravel within till show a wide variation in bed thickness, grain size, and sorting of grains. Photograph showing unconsolidated deposits in North Dakota.
Public Domain.
