I'm working on modeling a mountain range...

Totally a surfacing noob question perhaps?

So how's the best way to go about this... As I am stumped.

1 is the base

2 is the point I'm trying to extrude or loft or sweep or boundary boss surface to.

2017 SP5.0

Simplified file is attached so others can play with it. This will be 3D printed. I realize I need to start understanding surfacing to a better level as I don't surface contour often.