Did you know that the Earth’s longest mountain range is underwater? The Mid-Ocean Ridge system, shown above snaking its way between the continents, is more than 56,000 kilometers (35,000 mi) long. This series of mountains and valleys marks where the Earth’s crustal plates are moving apart. This is where most hydrothermal vents are located. The Extreme 2001 dive site is in a vent field at 9°N latitude and 105°W longitude. Map adapted from NOAA.