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The most violent eruption registered in history was that in the La Garita Caldera in the United States. It occurred 2.1 million years ago and formed a 35 x 75 km crater, drastically changing the climate on Earth. Fortunately, these eruptions are rare: they occur every 50,000 or 100,000 years.
Composite volcanoes have very sticky and thick lava, which can make them very explosive when they erupt: gas bubbles that are trapped in the magma chamber find it hard to escape through the viscous rock. They can also spurt lots of hot ash and rocks into the air, making them extremely dangerous.
These explosive volcanoes also spew out eruptions of small rock and ash, which gets deposited on the sides of the volcano. Therefore, we see that composite volcanoes are composed of alternating layers of hardened lava, volcanic ash and rock fragments, which is why they are called ‘composite. Are composite volcanoes the most explosive?
Once St. Helens erupted, the gentle peak left a bowl-shaped depression – a caldera. Hot lava isn’t the only threat that composite volcanoes may pose – the ash that rises from them can have disastrous effects. Ash can remain suspended in the atmosphere and significantly impact the world’s climate.
When a volcano erupts, lava, gasses and fragments of rock travel right up the main vent and are thrown out through the crater. When the eruption finishes the lava may drop back down the pipe or form a lava lake in the crater. Lava Flow – When magma reaches the surface it is called lava (pronounced ‘larver’).
This is the most violent eruption of a volcano. Fine ash, thick lava, and glowing, gas-charged clouds are emitted, traveling downhill at a high rate of speed. Fierce rains often accompany eruptions because of the release of steam from the volcano, which will then condense on the atmosphere to form clouds.