STRATA
| Date | Clue |
|---|---|
| 2026-05-03 | Geological layers |
| 2025-12-18 | Levels |
| 2025-07-12 | Earth's crust and others |
| 2025-01-30 | Rock layers |
| 2024-07-30 | Geologic layers |
| 2022-07-01 | Sheets of rock |
| 2021-01-27 | Levels |
| 2020-03-30 | Layers of rock |
| 2018-11-28 | Echelons |
| 2017-10-03 | Rock bands? |
| 2016-10-25 | Geological layers |
| 2015-10-30 | Stacked beds |
| 2013-07-04 | Levels |
| 2012-12-02 | Levels |
| 2012-05-16 | Rock layers |
| 2011-12-21 | Geologic layers |
| 2011-01-09 | Layers |
| 2010-09-12 | Levels |
| 2009-10-20 | Levels of society |
| 2008-11-10 | Rock layers |
| 2008-03-24 | Layers |
| 2008-01-19 | Echelons |
| 2008-01-14 | Layers |
| 2007-07-18 | Rock bands? |
| 2006-02-04 | Sheets |
| 2005-04-03 | Levels |
| 2005-03-28 | Layers |
| 2005-02-26 | Sheets |
| 2004-01-19 | Layers |
| 2003-09-20 | Levels |
| 2003-06-07 | Geological formations |
| 2002-11-24 | Levels |
| 2001-08-26 | Geologists' studies |
| 2001-07-06 | Layers |
| 2001-01-30 | Layers |
| 1999-03-05 | Sheets |
| 1997-11-04 | Geologic layers |
| 1997-10-20 | Layers |
| 1996-02-23 | Layers |
| 1995-01-12 | Class levels |
| 1994-02-21 | Rock layers |