I like what you did with the last landscape study, dinosaur rock formations! You have some inventive work here, also your observational drawings show that you think of form, they came along well.
As far as critique goes, I'd say, PARAMOUNT, remember to draw Everything in Perspective! Even if the subject matter is abstract, Always think of it in perspective, and remember to think of the "General Shape" of anything you draw.
Everything is made of shapes ---> be it fluid water or smoke, or folding paper, a train, dented piece of crumbling architecture, an ice mass, there's no difference whatsoever between these.
Also remember to think of anything you draw as a 3D object, whatever it is, you must be able to take the object in the drawing, and draw it from any angle.
Check this out, see how the drawings are almost "sculpted", you can take any of these and make a 3d clay model:
and keep in mind symmetry of shape wherever it applies in your designs:
What I mean by this is, make sure you always check that the two identical parts of an object are symmetric to each other in perspective.
Lastly, when you draw from life, don't focus on drawing what it is you see, but "understand" the underlying shapes in what you see, especially when studying anatomy and landscapes! Overall shapes, perspective, and flow. 3D
Hope this helps.