How the Panama Canal Locks Lift Ships Over the Continental Divide

A ship cannot climb a mountain. So how does one cross Panama’s Continental Divide? The canal’s answer is to float it uphill—then float it back down.

The route is not a sea-level trench from ocean to ocean. Engineers dammed part of the Chagres River to create Gatun Lake. Its surface sits about 85 feet above sea level, giving ships a high-water route across the divide. The locks are the water-filled stairs that connect that route to the seas.

Imagine a ship arriving from the Atlantic. It enters the first chamber at Gatun, and the gates close behind it. Valves open to let water from the higher side flow through large passages in the lock walls, then through openings in the chamber floor. As the water rises, the ship rises with it. Once the water levels on both sides of the next gate match, the gate can open and the ship moves ahead.

Gatun has three such steps. After the third, the ship crosses Gatun Lake and the cut through the divide. Heading toward the Pacific, it descends one step at Pedro Miguel and two at Miraflores. To lower it, operators let water drain from each chamber toward the lower side before opening the next gate.

Here is the surprising part: pumps do not hoist the ship. Gravity moves the water; the ship simply floats at the water’s new level. Electricity operates the gates and valves, but the lift comes from the lake above.

That is the canal’s elegant trick. Rather than force a ship through the land at sea level, it raises the ship to a passage over the divide—and lowers it safely into the other ocean.