Why are there no trees in the broad valleys in the Valles Caldera, unlike the Caldera’s verdant, forested slopes?
Consider that there were lakes in much of the Valles Caldera after the caldera collapsed 1.2 million years ago, since the bowl of the Caldera trapped precipitation over thousands of years that could not escape. Sediment in the water settled to the bottom of the lakes, rather than their sides. Once the water from the lakes was displaced over the wall of the Caldera by the formation of the ring fracture domes and the resurgent dome, and the lakes had fully drained away, the composition of the soil of the lakebed had been permanently changed. The soil of the valley floors had much more moisture and was much finer than the soil on the slopes due to the fact that they had been lakebeds. Trees prefer drier, rockier soil, so rather than growing in the broad valleys, the trees kept to the slopes. This effect, combined with the fact that colder air descends into the bottom of the valleys rather than the slopes, making it harder for trees to grow there, explains the lack of trees on the broad va
