Molten

''Rock and sand heats to its melting point, causing blisters and searing wounds for creatures in contact with the earthen ground. Concentrating, you cause the earth to burst open with smoky flames, incinerating those still around.''

This spell heats rock or sand to its melting point in a matter of rounds:
 * 1st Round Earth dries; rock or sand heats up. Creatures in contact with the ground take 4d8 points of fire damage (Reflex save for half damage).
 * 2nd Round Creatures in contact with earthen ground take 2d6 points of fire damage (Reflex save for half damage). Rock continues to heat up, increasing the damage to 8d6 points of fire damage (Reflex save for half damage). Sand liquefies into glass; any creature still standing in the area falls into the molten glass, taking 16d6 points of fire damage (no save). Creatures outside or above the area but within 10 feet take 1d6 points of fire damage (no save).
 * 3rd Round Earth bursts into smoky flames, and creatures in area take 10d6 points of fire damage (Reflex save for half damage). Rock melts into magma; any creature still standing in area falls into the lava, taking 20d6 points of fire damage (no save). Molten sand continues to burn immersed creatures. Creatures outside or above the area but within 10 feet take 2d6 points of fire damage (no save).

When you cease concentrating, the spell terminates, and the molten area begins to gradually cool. Every hour that passes, reduce the damage inflicted by stepping into the area by one die of damage. Eventually molten sand cools to solid glass, while scorched earth and molten rock cool into igneous rock and ash.