Historical clue formulations

• Like mud — 2018-10-24
• Like tar pits — 2015-07-21
• Like mud between one's toes, say — 2011-08-02
• Like wetlands — 2010-11-11
• Seeping — 2010-03-08
• Like slime — 2008-09-27
• Like mud — 2007-10-02
• Like mud — 2007-07-04
• Leaking goop — 2007-01-30
• Leaking — 2003-05-20
• Slimy — 1999-11-03
• Like mud — 1998-10-10
• Like mud — 1997-01-29