The synthesis of ammonia is carried out in a closed, variable-volume container at a constant temperature:

\[ \text{N}_2\text{(g)} + 3\,\text{H}_2\text{(g)} \rightleftharpoons 2\,\text{NH}_3\text{(g)} \quad \Delta H^\circ < 0 \]

The graph below displays the forward reaction rate (solid curve) and the reverse reaction rate (dashed curve) as a function of time. At time \(t_1\), the volume of the reaction container is rapidly halved at constant temperature, and the system is allowed to reach a new equilibrium at time \(t_2\).

Which of the following best explains the immediate effect observed at \(t_1\) and the subsequent changes that occur until \(t_2\)?