The Villarrica volcano erupts near Pucon, Chile, early Tuesday, March 3, 2015. (AP Photo/Aton Chile)

Of the estimated 1,500 active volcanoes on Earth, at least two dozen of them erupted in 2015.

Over the course of the year, more than 30,000 people have had to be evacuated from cities and towns surrounding volcanoes. Thousands of flights had to be canceled, stranding hundreds of thousands of travelers.

Some of the most notable eruptions were:

- Sicily’s Mount Etna, which erupted twice in December, one of which was its . Etna spewed lava and ash that even produced some lightning. The first blast sent fountains of lava into the air and jets of hot material as much as a mile above the volcano’s summit.

- Nicaragua’s Momotombo volcano erupted for in December.

- Hawaii's Mount Kilauea erupted in August, sending a ribbon of lava flowing into nearby forests. Additionally, a 3.8 magnitude earthquake occurred under the volcano.

- Afrom Indonesia's Mount Raung combined with ash from the Gamalama and Dukono mountains, the Sinabung volcano and Mount Karangetang to darken the skies in July. Airports were closed and 37 flights to and from Bali’s Ngurah Rai airport were canceled.

- The June eruption of Indonesia's Mount Sinabung leftmore than 3,000 people within a 4-plus mile radius of the volcano displaced from their homes.

- Chile's Villarrica volcanoerupted in March, causing numerous rivers in the area to rise as snow along the sides of the volcano melted. Authorities had to monitor four communities that were cut off from main roads when two bridges were destroyed by rising water from nearby rivers.

- In MarchMexico's Colima volcanoerupted twice in the same morning.

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A study was released suggesting that the speed at which the Earth spins . The belief is that the extra energy the sun uses to alter the speed of Earth’s spin, even by the smallest amount, can transfer hundreds of thousands of petajoules of energy into the subsurface, and that may trigger additional eruptions.

Some researchers have also blamed global warming. According to a 2012 study in the journal Geology, melting of land ice could relieve pressure off of continents, which could allow magma to surge up more easily, leading to a higher likelihood of more eruptions. However, the scientists of both studies agree that the ties between climate change and more eruptions aren't concrete, and more examination needs to be done before any conclusions can be drawn.

Above is a collection of photos from 2015’s volcanic eruptions.

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