Volcanoes Facts for Kids
Explosive facts about volcanoes and geology
Obsidian is a volcanic glass formed when lava cools so quickly that crystals have no time to form. Its edge can be sharper than surgical steel, and it was used by ancient peoples around the world to make knives and arrowheads.
When magma meets water β from the sea, a lake, or underground β it can trigger a phreatomagmatic eruption, which is especially explosive because the water turns instantly to steam. These eruptions can blast out huge craters and produce fine, glassy ash.
Volcanic soil is among the most fertile in the world because it is rich in minerals that plants need to grow. Many of the world's most productive farming regions, including parts of Italy, Indonesia, and Central America, are located on the slopes of volcanoes.
Iceland sits directly on the Mid-Atlantic Ridge where two tectonic plates pull apart, making it one of the most volcanically active places on Earth. With around 130 volcanoes, Iceland produces about a third of all the lava that erupts on land worldwide.
The 1815 eruption of Mount Tambora in Indonesia was the most powerful volcanic eruption in recorded history. It caused so much ash to enter the atmosphere that 1816 became known as 'the Year Without a Summer', with frost and crop failures reported in Europe and North America.
Fumaroles are vents in the Earth's surface that release steam and volcanic gases, and they are found in areas of geothermal activity near volcanoes. They can smell of sulphur, which some people compare to the smell of rotten eggs.
A caldera is a large depression formed when a volcano's magma chamber empties and the ground above collapses. Calderas can be enormous β Toba in Indonesia has a caldera about 100 kilometres long, now filled with a beautiful lake.
Large volcanic eruptions can generate spectacular lightning within the eruption cloud, caused by the collision of ash and ice particles producing static electricity. This phenomenon, known as volcanic lightning or 'dirty thunderstorms', has been photographed in dramatic detail.
The majority of the world's volcanic activity actually happens under the ocean, along underwater mountain ranges called mid-ocean ridges. Scientists estimate there may be over a million undersea volcanoes on the ocean floor.
Pyroclastic flows are fast-moving currents of hot gas, ash, and volcanic rock that race down a volcano's slopes at speeds of up to 700 kilometres per hour. They are one of the most deadly volcanic hazards because there is almost no way to outrun them.