Hudson Volcano in Chile began to erupt, depositing volcanic ash over 150,000 square kilometres (58,000 sq mi).

Hudson Volcano is the most active volcano in the southern part of the Southern Volcanic Zone of the Andes Mountains in Chile, having erupted most recently in 2011. It was formed by the subduction of the oceanic Nazca Plate under the continental South American Plate. South of Hudson is a smaller volcano, followed by a long gap without active volcanoes, then the Austral Volcanic Zone. Hudson has the form of a 10-kilometre-wide (6-mile) caldera filled with ice; the Huemules Glacier emerges from the northwestern side of the caldera. The volcano has erupted rocks ranging from basalt to rhyolite, but large parts of the caldera are formed by non-volcanic rocks.

Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes Mountains and the Pacific Ocean. Chile had a population of 17.5 million as of the latest census in 2017 and has a territorial area of 756,102 square kilometers (291,933 sq mi), sharing borders with Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage to the south. The country also controls several Pacific islands, including Juan Fernández, Isla Salas y Gómez, Desventuradas, and Easter Island, and claims about 1,250,000 square kilometers (480,000 sq mi) of Antarctica as the Chilean Antarctic Territory. The capital and largest city of Chile is Santiago, and the national language is Spanish.

Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products, including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere. The force of the gases shatters the magma and propels it into the atmosphere where it solidifies into fragments of volcanic rock and glass. Ash is also produced when magma comes into contact with water during phreatomagmatic eruptions, causing the water to explosively flash to steam leading to shattering of magma. Once in the air, ash is transported by wind up to thousands of kilometres away.