Anytime there's an eruption under a glacier there's a lot of potential for what Icelanders call a jokulhlaups. It's basically just a giant flood of water from a rapidly melting glacier.
It was found that the flood, coming from the modern glacier area of the source, was caused by breaking of ice-dam and coffer-dam lakes formed by blocking of river with glacier movement.
The study of Sanxingdui should take the investigation of weather three or four thousand years ago as the stand and analyze the durative drought, sudden flood and glacier movement.