A volcano becomes dangerous when it proposes a threat to human life. You won‚Äôt see any kind of reporting if a volcano erupts in a most uninhabited part of Kamchatka. However, even if a volcano starts showing any vicious sings of hot gasses in a highly populated area then many lives comes under a risk. Before the eruption, a volcano spreads harmful gasses around the nearby area. A volcanic eruption contains hot magma, dark ash, and dust. The magma after the explosion can travel up to 100 km/h, which makes it almost impossible to escape in a case of a sudden eruption. The effects of a volcanic eruption are not just limited to a certain area, it can have more disastrous consequences than you might imagine. In 1883 Indonesian volcano Krakatau erupted violently to the nearby area. However, the volcanic ash from the explosion reached up to a height of 80 km. As a result, this explosion darkened the sky worldwide for some time.