I would recommend you to use the camera in Program mode, it's more versatile than Auto because you can, in your case for example, compensate the exposure for glaciers because the camera is likely to underexpose them in Auto mode. Another mode you could use is Tv or Shutter Priority, with this mode you can select your preferred shutter speed to freeze the action.
Also, I really don't recommend using scene presets as these are very limited to certain situations, but if you really have trouble handling your camera's settings, I guess the preset scene modes wouldn't be too bad.
As for the High-speed Continuous, I'd recommend you not to use it all the time because you'd be able to capture only 1 second worth of action, but if you use it sparingly, you might get some pretty good photos.
And finally, using the default movie settings is fine, it should deliver optimal photos.
As my last piece of advice, I'd recommend you to experiment with your camera in P mode so you can get familiarized with this shooting mode which I believe is the best one you can use for most situations and the one you can get the best out of your camera.
_________________Gear: Canon SX20 IS, Canon Rebel T3i, Canon EF-S 18-55mm, Canon EF-S 55-250mm f/4-5.6 IS II
Wishlist: Canon 50mm f/1.8 II
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