Stratovolcanoes or composite volcanoes are characterised by their steep slopes. Some famous volcanoes like Mount St Helens, Mount Tambora and Krakatoa are some examples of stratovolcanoes. Read on to know interesting facts about stratovolcanoes.
Grand and steep sided
Many large volcanoes on earth are stratovolcanoes. They are steep-sided and have alternating layers of lava, volcanic ash and, cinders. These volcanoes have smooth lower slopes, but much steeper upper slopes, creating a concave cone upwards. Their crater is also usually small.
These volcanoes usually lead to pyroclastic flows that move at speeds faster than 100 km/h. Their speeds can also reach 700 km/h. One of the most destructive stratovolcano was Mount Vesuvius that destroyed the city of Naples, Italy in 79 A.D. Their eruption can cause eruptions of lava containing basalt, dacite, or andesite. Their eruptions are also known as Plinian eruptions, named after Pliny the younger, who described the eruption of Mount Vesuvius. Ash and dust from mount Vesuvius ascended up to 40 kilometers high in the atmosphere.
They take 10,000 to 100,000 years to form
Most known stratovolcanoes are between 10,000 to 100,000 years old. Some can even be a million years old. Mount Rainier is a volcano at least a million years old. It last erupted about 1,000 years ago.
Their lava cools down quickly
Although their lava flows out at high speeds, most of it cools down and solidifies quickly before spreading to other places.
Long rest between eruptions
The interval between two consecutive eruptions of these volcanoes is longer than most other volcanoes.
Formed at convergent plate borders
Many stratovolcanoes exist along the Pacific rim and also the ring of fire. They are formed when one plate descends underneath another plate. This is why many of them are found along the ring of fire. Ring of fire is where the Oceanic plate meets the contenental plate. Some famous stratovolcanoes situated on the Pacific rim or the ring of fire are Mt. Fuji (Japan), Mt St Helens (USA), Paricutin (Mexico), and Mt Pinatubo (Philippines).