First, start with a square aspect ratio pic in PS. Remember that white equals heighth in a terrain, and black is depth. Create a silhouette of the shape you want to make. Then create a gradient either with the gradient tool if convenient, or with the airbrush if you need a custom curve. For my example, I concentrated on one of the 'spikes'....

RosemaryR
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"This...this is magnificent!"
"Oh, yeah. Ooooo. Aaaaah. That's how it starts.
Then, later, there's ...running. And....screaming."