Canyon Passage | Official |

: The term is occasionally used in reconnaissance mission reports, such as those conducted by the USS Kitty Hawk over Laos.

: They can vary from narrow "keyhole" slots to massive galleries over 100 feet high. Canyon Passage

: These are typically formed by underground streams that erode downward through bedrock (often limestone). This process creates passages that are taller than they are wide , resembling narrow surface canyons with a cave ceiling. Characteristics : : The term is occasionally used in reconnaissance