How Was the Gulf of Mexico Formed? Tectonic Rifting 150 Million Years Ago

The Gulf originated as a failed rift basin during the breakup of Pangaea:

1. ~150 Ma: North American and African plates begin separating (opening Atlantic).
2. Crust stretches, thins, and sinks, forming a deep basin.
3. Seawater floods in from the nascent Atlantic.
4. Rifting stops ~100 Ma; Gulf reaches present shape.

It is not a subduction or collision zone, but a relic of continental separation.