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When It's Foggy...
When it's foggy you can hear the sound from the south tower instantly by telephone, 415-202-3809. Then, wait about 2 seconds to hear the sound waves reach your ears through the air, traveling a little faster than a jet airliner. The south tower foghorn sounds a deep, loud note for 2 seconds, then it repeats in 18 seconds. Another foghorn at midspan between the towers sounds a pair of high-pitched notes.
Fog is formed when the moist air over the ocean is cooled by cold water currents along Northern California's coast. The water vapor cools and condenses into tiny water droplets – fog.
Fog is most common in the summer, when the air over the interior land heats up more than over the ocean. Warm air is less dense and exerts less pressure than cooler air, allowing the cooler ocean air to push its way in through the Golden Gate.
Why does the fog come through the Golden Gate?
It is the only sea-level gap in the coastal mountain range for hundreds of miles. It is a canyon cut through the mountains by an ancient river. Water stored as ice melted as the last Ice Age ended, raising the sea level. Today, the bottom of that canyon is over 300 feet (90 meters) below the waves. |