About the year 1150 AD, the empire of Tiwanaku disappears. No one knows for sure what caused this collapse.
There are different opinions.
One which handles a great theory about it is Arthur Posnansky. Why the tiwanakotas have not completed their great works? He said that both the first time as the second succumbed by a seismic cataclysm that brought the flooding of Lake Titicaca.
The remains found in a totally chaotic way, mixing equipment, tools, pottery, human bones, animal bones, etc., suggested that a natural phenomenon, such as floods and earthquakes, were a disaster in cities and ended the lives of its inhabitants.
Posnansky doesn’t share the idea that a large-scale war activity was the cause of the destruction of an entire civilization because there is no evidence of burials of combatants and their horses. Rather, the layers where incomplete skeletons found show signs of having been transported and deposited by the force of water and covered with earth.
To destroy an entire civilization must have happen a cataclysm of large-scale, sudden, and certainly at night, which took the unsuspecting city dwellers.
Few were saved, those who reached the heights of nearby hills, but insignificant in number as to reconstruct the whole civilization.
The researcher José Bellido Huidobro, aligns with Posnansky theory, but goes further and suggests that the reason for its disappearance was a great flood that affected not only the Tiwanaku empire but to all of America.
Ponce Sanjinés has a different view of these two researchers. He indicates that the disappearance of Tiwanaku was due to a military confrontation with Mollo culture, which became important in the area, and with crop failures associated with long periods of drought, climate change, contributed to the decline of Tiwanaku and subsequent emergence of regional lordships.
Documents you can find on the internet:
Periods of its history
Who built Tiwanaku
An advanced civilization
The area of Tiwanaku
The culture evolution
Diversity of names and meanings
Sequence of historical events
What leaves us Tiwanaku
A brief summary of Tiwanaku