This underwater volcano, located about 65 km north of Tonga's capital, Nuku'alofa, created a massive eruption that was heard as far away as Alaska and triggered a tsunami that affected numerous countries, including the United States and Japan. The eruption sent an enormous plume of ash, steam, and gas up to 20 km into the atmosphere, which resulted in the formation of an umbrella cloud that spread concentrically, distributing ash at an unprecedented rate. This event was also notable for the amount of water vapor it ejected into the stratosphere, estimated at around 146 teragrams, which is almost four times the water vapor that the 1991 Mount Pinatubo eruption in the Philippines lofted into the stratosphere. The Hunga Tonga-Hunga Ha'apai eruption was so powerful that it caused atmospheric pressure changes that were detected on the other side of the world, in Europe, and generated a sonic boom that circled the globe twice. The tsunami it triggered was observed across the Pacific Ocean, with waves reaching up to 30 cm in some areas. This eruption was one of the most explosive in the 21st century, with its effects being felt globally.