I was recently out on a hike and came across a dry waterfall in a deep ravine. There was a viewing platform, and I took several shots.
The problem is, that everything was flattened. The enormity of the gorge just wasn't there. (This is understandable, we're projecting a 3d space onto a 2d sensor)
What techniques or lenses should I use to capture the depth?
The primary thing that gives two dimensional photographs "three dimensional" depth is the angle(s) of the lighting source(es) that reveal(s) textures via the interplay between light and shadow. The amount of light, the angles relative to the subject and to the camera, the 'hardness' or 'softness', etc. are what define the 'depth' of a photo.
In the context of landscape photography one is often at the mercy of the weather and time of day. Waiting for the right light can be a painstaking process. In some cases, one might need to plan ahead for months to get the best angle of light provided by the sun on a particular scene. Then one must hope that the weather cooperates as well. If the weather isn't right today, it might be right tomorrow at the same time (give or take a few minutes) when the sun is in the same spot in the sky.
In a deep ravine the problem is compounded by the often flat lighting when everything is in shade and illuminated by diffused light from above. The limited time during the day when the sun is shining directly into the gorge, if there is such a time, can be the best or worst possible time to capture an image. It all depends on the particulars of that location.
As far as the enormity of the gorge goes, including something in the frame that people will recognize and understand to be a more or less "standard" size for that thing will help to give a sense of scale to the image.
Use aerial perspective to give the impression of greater distance.
Aerial perspective is the blue tint that distant objects have due to atmospheric haze.
We interpret the colour information to help us perceive distance. The contrast is also not so great as it is with objects close to us which appear warmer.
Remove the UV or Haze filter covering your lens to "protect" it. The increased haze and decreased contrast might be just enough to introduce a natural appearing image approximating sight rather than a crisp high-contrast picture.
Some factors that affect perception of depth in photos, along with suggestions you can try:
Stereoscopic vision. Take stereoscopic pairs. (Clouds photo presented as R/L/R. Use the pair that corresponds with your viewing method.)
Lighting. Presence of shadows and highlights. Use more directed lighting, as opposed to "flat" lighting.
Depth of field with foreground or background objects that are out of focus. Include foreground or background objects.
Overlapping objects. Change the composition to show objects overlapping.
Objects of varying sizes, especially a reference object of known size. Include people in your photo. (In the right-most clouds image, notice how the drawn in person affects the apparent scale of the image.)
Distortion. Images from perfectly corrected rectilinear lenses look "flat". Use a fish-eye lens.
Perspective I. Distance between objects and the camera. Use a wide-angle lens or take multiple images to stitch together.
Perspective II. Converging and diverging lines. Get close to an object and angle the camera along the object.
It is a problem, but using a wide angle lens, with something near (at a few feet) in the foreground will help to separate the distances. Then assuming an adjustable camera, stopping down and focusing at the hyperfocal distance will help that depth of field substantially (a tiny phone camera probably already has a lot of depth of field). See my site at https://www.scantips.com/lights/dof.html#hyper about hyperfocal.
