Transmute Rock to Mud {Priest}

This spell turns natural rock of any sort into an equal volume of mud. If it is cast upon a rock, for example, the rock affected collapses into mud. Magical or enchanted stone is not affected by the spell. The depth of the mud created cannot exceed 10 feet.
Creatures unable to Levitate, Fly, or otherwise free themselves from the mud sink at the rate of 1/3 of their height per round and eventually suffocate, save for lightweight 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 required decided by the DM. Creatures large enough to walk on the bottom can move through the area at a rate of 10 feet per round.
The mud remains until a successful dispel magic or transmute mud to rock spell restores its substance — but not necessarily its form. Evaporation turns the mud to normal dirt at a rate of 1d6 days per 10 cubic feet. The exact time depends on exposure to the sun, wind, and normal drainage.

Transmute Mud to Rock

The reverse, transmute mud to rock, hardens normal mud or quicksand into soft stone (sandstone or similar mineral) permanentJy unles magically changed. Creatures in the mud are allowed a saving throw to escape before the area is hardened to stone. Dry sand is unaffected.

Reversible

Sphere: Elemental (Earth, Water)
(Alteration)
Level: 5

Range: 160 yards
Components: V, S, M
Duration: Special
Casting Time: 8
Area of Effect: 20-foot cube/level
Saving Throw: None

Material Components:
clay and water (or sand, lime, and water for the reverse)