When a volcano erupts, it explosively releases lava, ash, and gases that have been building up under enormous pressure deep inside the Earth. The ground shakes, the mountain rumbles, and suddenly molten rock shoots into the sky. In 79 AD, Mount Vesuvius erupted so violently that it buried the Roman city of Pompeii under volcanic ash.

But erupt isn't only for volcanoes. The word describes any sudden, powerful burst or outbreak. A crowd might erupt in cheers when their team scores the winning goal. An argument can erupt when tensions that have been simmering finally explode into angry words. Your little brother might erupt in laughter at something ridiculous. Even a rash can erupt on your skin, appearing suddenly.

The word captures that sense of something breaking through with force, whether it's molten rock breaking through the Earth's crust or joy breaking through someone's usual calm. An eruption (the noun form) suggests power and suddenness: emotions erupting like geysers, violence erupting in a peaceful place, or applause erupting in an auditorium.