On first inspection, this is a large rock slope failure that has transitioned into a rock and debris avalanche. There has been no indications that there was a trigger event, such as intense rainfall or an earthquake. It will be interesting to see whether the slope had been subjected to mining or quarrying. Note the very steep, planar surface at the rear of the landslide scar, and also on the left side. This suggests to me that the landslide has mobilised existing planes of weakness in the rock mass.