Historical clue formulations

• Hydrologist's field: Abbr. — 2012-10-03
• Earth sci. — 2010-11-09
• Earth sci. — 2008-06-24
• Earth sci. — 2003-01-12
• One of the phys. sciences — 2001-10-12
• Seismologist's field: Abbr. — 2001-08-24
• Earth sci. — 1994-08-09