The SGC Stargate is active (glowing lights, closed iris) and General Hammond is anxiously waiting for an SG-1 signal even before Selmak, Carter and Martuf dial the address to return to Earth.
When Capt Carter, Jacob and Martouf are fleeing the vanishing tunnels, they ring to the surface of the planet to head for the Stargate. As the rings disappear, you can see their footsteps in the sand behind them leading into the ring area.