How to Identify a Valley
A short field guide to reading the landscape when you're standing in (or driving through) one.
Start with the cross-section
Look across the valley, not down it. The shape between the two opposing hillsides is the fastest way to tell what carved it.
- V-shaped valleys have steep, straight walls that meet in a narrow bottom. Almost always cut by a river — the river is still doing the work.
- U-shaped valleys have a flat floor and steep parallel walls. Cut by a glacier. Yosemite Valley and most of Glacier National Park's main valleys are textbook examples.
- Flat, wide basins with mountains on both sides but no obvious drainage are usually structural — a graben or rift valley where the crust has dropped between two faults. Owens Valley, the Rio Grande Rift, and Death Valley all qualify.
Look for the tributaries
Side valleys tell you the history. When a smaller valley enters a main valley high on the wall, well above the current floor, it's a hanging valley — a sign the main valley was scoured deeper by ice than the tributary. Bridalveil Fall in Yosemite drops out of one.
Read the floor
A meandering river with oxbows and a broad floodplain means an old, low-gradient valley. Braided channels over gravel bars mean lots of sediment and a young, active system — common downstream of glaciers. A dry wash with rounded cobbles means it floods, just not today.
Use the app
Point your phone. Valley Landmarks Near Me will name the valley you're standing in and the ones around you, using GPS and your device compass. Combine that with the shape cues above and you can usually work out the story in a minute.