Valley of the Kings rains. There is currently little year-round rain in this part of Egypt, but there are occasional flash floods that hit the valley, dumping tons of debris into the open tombs. The quality of the rock in the Valley is inconsistent, ranging from finely-grained to coarse stone, the latter with the potential to be structurally unsound. The occasional layer of shale also caused construction and conservation difficulties, as this rock expands in the presence of water, forcing apart the stone surrounding it. It is thought that some tombs were altered in shape and size depending on the types of rock the
Valley of the Kings 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. Recent studies have shown