The Wormhole closing after the Chimeran tower is hit by a Terraformer.
After the events of Operation Black Eden, the detonation of the fission bomb at the Chicxulub crater created a massive power surge in the Chimeran tower network, which allowed the Chimera to open a wormhole over New York City which presumably leads to the Chimera's, or "Pure Chimera's" homeworld.
The wormhole is kept open by a Chimeran tower stationed in New York, which fires a particle beam to contact with another beam on the other side of the portal, causing a Lambda particle manifold, connecting two separate regions of space time. The Chimera managed to keep the beams perfectly in phase, factoring in the rotation and orbit of Earth.[1] The wormhole, furthermore, greatly accelerated the terraforming process of freezing Earth to make it more hospitable for the Chimera and wiping out the remnants of humanity in the process. It can be presumed that once Earth would reach its desired temperature and humanity was extinct, millions if not billions of "Pure Chimera" would have used the wormhole to instantly travel to Earth and reclaim it as their planet.[2]
However, with the destruction of the New York tower in 1957 caused by Joseph Capelli accompanied by Charlie Tent, both the terrafroming process and the wormhole have been permanently interrupted and shut down. As a consequence, this seems to be a major turning point as humanity seems to gain an advantage over the Chimera.
It is unknown how the Chimera responded to this event, but with the loss of the "hive mind" the Chimera presumably became disorganized and ultimately suffered many losses, leading to humanity's victory against the Chimera.