Transmute Rock to Mud {Wizard}

This spell turns natural rock of any sort into an equal volume of mud. The depth of the mud can never exceed one-half its length or breadth. If it is cast upon a rock, for example, the rock affected collapses into mud. Creatures unable to Levitate, Fly, or otherwise free themselves from the mud sink at the rate of ten feet per round and suffocate, except for light-weight creatures that could normally pass across such ground. Brush thrown atop the mud can support creatures able to climb on top of it. with the amount of brush required subject to the DM's discretion. The mud remains until a dispel magic spell or a reverse of this spell, mud to rock, restores its substance — but not necessarily its form. Evaporation turns the mud to normal dirt. at the rate of 1d6 days per ten cubic feet. The mud to rock can harden normal mud into soft stone (sandstone or similar mineral) permanently unless magically changed.

[Player's Handbook]

Reversible

School: Alteration
Level: 5
Rarity: Common

Range: 10 yards/ level
Components: V, S, M
Duration: Special
Casting Time: 5
Area of Effect: One 20-foot cube/level
Saving Throw: None

Material Components:
Rock to Mud: clay and water (consumed)
Mud to Rock: sand, lime, and water (consumed)