Historical clue formulations

• Underground rock — 2026-09-05
• Heat source for many hydrothermal vents — 2026-08-26
• Component that may emerge from Earth's asthenosphere — 2026-07-24
• It's bubbling below the surface — 2026-01-09
• Molten rock — 2025-04-21
• Heated pool? — 2024-01-25
• Underground rock? — 2023-02-16
• What lava is before an eruption — 2021-09-20
• Molten rock in a volcano — 2021-08-23
• Molten rock — 2021-06-15
• Underground rock? — 2021-03-20
• Obsidian, once — 2020-08-02
• Source of igneous rock — 2020-03-07
• Lava below the surface — 2019-01-23
• Molten rock — 2018-02-08
• Soft rock? — 2016-06-29
• Soft rock? — 2015-07-12
• Underground molten rock — 2013-05-20
• Eruption sight — 2012-01-22
• Molten rock — 2011-07-19
• Volcanic rock material — 2011-04-11
• Molten volcanic material — 2009-10-05
• Volcanic buildup — 2009-04-28
• Source of igneous rock — 2004-01-28
• Molten rock — 2002-09-30
• Igneous rock's source — 1995-09-06
• Molten matter — 1995-05-19
• Source of igneous rock — 1994-06-05