Laurentian Abyss

From Transformers Wiki

The USS Shoup prepares to drop Megatron's corpse into the Laurentian Abyss, far far below the waves.

The Laurentian Abyss is an underwater depression off the eastern coast of Canada in the Atlantic Ocean, at least 6,000 meters in depth.

Fiction

2007 Transformers film

The United States government dropped all of the defeated Decepticons into the Laurentian Abyss. It was hoped that the extreme pressure and frigid temperature of the Abyss would destroy bodies of the Decepticons, hiding the evidence from the unknowing populace of Earth. Transformers

Revenge of the Fallen film

Things did not work out as the government had planned, as the Constructicons, Ravage and Scalpel dove down to Megatron's resting place and reactivated him with a piece of the AllSpark. Rapidly surfacing, Megatron rammed into and destroyed the USS Topeka, a submarine assigned to guard the area. Revenge of the Fallen

Notes

John Keller calls the abyss the deepest point on Earth... but in reality, this is untrue. The Mariana Trench is over twice as deep as the Laurentian.
In Alliance issue #2, the Decepticons are transported across the country to an aircraft carrier in San Diego. San Diego is on the coast of the Pacific Ocean. In the 2007 film, Keller reports that they are going to be dropped into the Laurentian Abyss. Which is in the Atlantic Ocean. Now, either the aircraft carrier with the Decepticons is going to cruise down the Panama Canal, and all the way back up north to the Abyss and drop them there like Keller said, or they will be dropped somewhere in the Pacific Ocean, like the Mariana Trench.