Volcanic River Rock
And what appear to be newer volcanic flows capping it.
The dividing line for the two areas is around an altitude of 380 metres, approximately 130 metres below the climax level of Glacial Lake Penticton, which drained 10,000 years ago. The lake level, however, rose and fell several times over thousands of years. Here’s another view of what just might be an ancient river shore, perhaps that drained the lake, perhaps that was dry long before the lake came:
Pebbles in a Stream
Bigger than a house.
Ancient rivers in this region, that were filled in by volcanic flows, soon found their original beds. Once our valley glaciers cut through those renewed valleys and reshaped them, the water followed its old beds once more, and …
The shore of this river is clearly visible in this photograph, just above the vertical white seam. The ancient, pre-glacial valley floor is likely many hundreds of metres below, filled in by gravel. So things change, even though they stay the same.
This rock still stops water, however. Water still flows, just more slowly, in smaller volumes, like here:
Tree in a Post-Post Glacial Riverbed
Post-glacial gravels covered much of this river-smoothed rock, too, before they were trucked away for fill.
Rather than thinking of this as a desert, perhaps we should think of it as really wet country in a dry spell. A long dry spell.