 The tomb of Ramesses II returned to an early style, with a bent axis, probably due to the quality of the rock being excavated (following the Esna shale).Between 1998 and 2002, the Amarna Royal Tombs Project investigated the valley floor using ground-penetrating radar and found that, below the modern surface, the Valley's cliffs descend beneath the scree in a series of abrupt, natural "shelves", arranged one below the other, descending several metres down to the bedrock in the valley floor.The area of the Theban hills is subject to infrequent violent thunderstorms, causing flash floods in the valley.