As the settlement of the pool got larger , portions of the shell began to slide backwards into the core pool area .
The majority of the upstream shell began to move into the reservoir , translating south and rotating slightly about the east abutment .
As the settlement of the pool got larger , portions of the shell began to slide backwards into the core pool area and the majority of the upstream shell began to move into the reservoir , translating south and rotating slightly about the east abutment .