Volcanoes Facts for Kids
Explosive facts about volcanoes and geology
Pumice is a volcanic rock so full of tiny air bubbles that it is the only rock that floats on water. It forms when lava cools very rapidly, trapping gas bubbles inside before they can escape.
Volcanic eruptions can create entirely new land, as lava flows harden into solid rock. The Hawaiian Islands were formed entirely by volcanic activity over millions of years as a tectonic plate moved over a hotspot in the mantle.
Beneath Yellowstone National Park in the USA lies one of the world's largest supervolcanoes, capable of eruptions thousands of times more powerful than a typical volcano. Its last massive eruption was around 640,000 years ago.
Stromboli, a volcanic island off the coast of Sicily, has been erupting almost continuously for at least 2,000 years. Sailors once used its regular bursts of light to navigate at night, earning it the nickname 'the Lighthouse of the Mediterranean'.
When Krakatoa volcano in Indonesia erupted in 1883, the explosion was so loud it was heard nearly 5,000 kilometres away β as far as Australia. It was one of the loudest sounds ever recorded in human history.
The word 'volcano' comes from Vulcano, a volcanic island off the coast of Sicily, which the ancient Romans believed was the forge of Vulcan, the god of fire and metalworking. They thought the eruptions were caused by Vulcan making weapons for the gods.
Shield volcanoes have broad, gently sloping sides because their lava is very fluid and spreads out over a wide area. Mauna Loa and Mauna Kea in Hawaii are classic examples of shield volcanoes.
Stratovolcanoes, also called composite volcanoes, have steep, cone-shaped sides built up from layers of ash and hardened lava from many eruptions. They are responsible for the most violent volcanic eruptions, including Mount St Helens and Mount Vesuvius.
In 79 CE, Mount Vesuvius in Italy erupted catastrophically, burying the Roman city of Pompeii under metres of ash and pumice in a matter of hours. The city was preserved almost perfectly under the ash and was rediscovered centuries later.
While most volcanoes form at the edges of tectonic plates, hotspot volcanoes form in the middle of plates above unusually hot regions of the Earth's mantle. Hawaii and Iceland are both the result of volcanic hotspots.