If you go to this sandcastle:
Make the camera perpendicular to the earth then zoom in quickly as far/fast as you can using the mouse wheel with the mouse over a 3D shape, you'll zoom through the earth about 10-20% of the time.
NOTE: It doesn't seem to happen nearly as often if the camera is on an angle, or if the mouse isn't over a shape.
It only seems to happen for me on Mac OS X and Ubuntu. It does not happen on Windows. I am able to reliably re-create the issue using OS X Sierra and Chrome 55.
My assumption is that it is somehow related to the scroll acceleration on OS X and linux. On windows the zoom steps are quite small, but on OS X they be come enormous if you zoom quickly. That's just a theory though.
This keeps happening to me all the time. Is this a known bug?