India, Feb. 8 -- The search for Nancy Guthrie enters its seventh day mark on February 7. Authorities are confronting significant geographic and technical obstacles that pose new challenges in search efforts.

Nancy resides in the Catalina Foothills, a neighborhood northeast of Tucson that is full of residential properties tucked away in desert and elevated landscapes. Her home's surroundings are dangerous, expansive, and full of difficult terrain.

The 84-year-old mother of Savannah Guthrie, anchor of the Today show, disappeared from her Tucson, Arizona, home between January 31 and February 1.

The Catalina Foothills are a combination of federal and state-managed land and private residential property. These consist of portions of the Coro...