Around 35 million years ago, the Arabian tectonic plate began colliding with its Eurasian counterpart, causing the prehistoric Tethys Ocean that once separated the supercontinents of Laurasia and Gondwana to shrink.

Laurasia would later morph into North America, Europe and parts of Asia, while Gondwana fragmented into South America, Africa, Antarctica, Australia and India. But the ancient sea did not disappear entirely, for a remnant of it survives today, in the form of the Strait of Hormuz.

Experts say the geological process that created the critical waterway – now an emergent new frontier in the US and Israel’s war with Iran – is the very same process which gave the region its oil riches in the first place.

According to National Geographic, as the Arabian plate began to move further under the Eurasian plate, the two plates crumpled together, creating the Zagros Mountains – an impressive stretch of peaks that still exist in Iran. The weight of these mountains depressed part of the Arabian plate, causing the strait to form.

For hundreds of millions of years before the Arabian plate collided into Eurasia, it sat below sea level, providing the perfect environment for crude oil to form, according to National Geographic.

That is because when animals and plants in marine environments die, their remains fall to the bottom of the seabed, slotting between layers of silt and sand. Then, over millions of years and under intense heat and pressure, these remains morph into what we call crude oil.

“No wonder the Assyrians called the Persian Gulf ‘The Bitter Sea’,” he wrote last month.