1) By a glacier 
[adv] - by a glacier
glacial, glacially 1. Relating to, referring to, or derived from a glacier. 2. Pertaining to those geological intervals characterized by cold climate conditions and advancing ice sheets and caps. 3. Suggestive of ice, extremely cold; frigid: such as, a glacial wind. 4. Devoid of warmth and cordiality: 'He had a glacial handshake.' 5. Coldly impe...
adverb by a glacier; `glacially deposited material`