Complex sentence: The Haynesville Shale is an informal, popular name for a rock formation that underlies large parts of southwestern Arkansas, northwest Louisiana and East Texas at depths of 10,500 to 13,000 feet below the land's surface.
Split into simpler sentences: The Haynesville Shale is an informal, popular name for a rock formation that underlies large parts of southwestern Arkansas, northwest Louisiana, and East Texas. It lies depths of 10,500 to 13,000 feet below the land's surface.