What is Mount Agung, the volcano in the Pacific that could erupt at any time?

BALI, INDONESIA - A general view of Mount Agung is seen from Lempuyang Temple in Lempuyang village of Karangasem Regency, Bali, Indonesia on September 28, 2017. After Mount Agung's alert phase reached critical, the tourist destination and the local Hindus praying place Lempuyang Temple is now deserted from tourists. (Photo by Mahendra Moonstar/Anadolu Agency/Getty Images)

Credit: Anadolu Agency

Credit: Anadolu Agency

BALI, INDONESIA - A general view of Mount Agung is seen from Lempuyang Temple in Lempuyang village of Karangasem Regency, Bali, Indonesia on September 28, 2017. After Mount Agung's alert phase reached critical, the tourist destination and the local Hindus praying place Lempuyang Temple is now deserted from tourists. (Photo by Mahendra Moonstar/Anadolu Agency/Getty Images)

More than 130,000 people have been evacuated from an area on the Indonesian island of Bali as an eruption of a volcano there seems imminent.

Scientists say tremors and smoke from the volcano -- Gunung Agung, or Mount Agung -- are signs that it could erupt at any time.

Several countries have issued travel warnings, and airlines have told passengers they will be monitoring the volcano's activity and will alter flight paths if necessary.
Volcanic activity in Indonesian is common, and Agung is no exception.

>> Read more trending news

Here's what is known about Mt. Agung now.

What is Mt. Agung?

Mt. Agung, at 9,944 feet, is the largest mountain on the island of Bali. It is one of many volcanoes in the Ring of Fire, an area in the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. 

What is happening with Mt. Agung?

Scientists say that in the past few days large tremors have been felt in the area. In addition, smoke has been seen coming from the volcano's crater. "I would definitely be following the advice to stay outside the exclusion zone," Heather Handley, an assistant Earth sciences professor at Sydney's Macquarie University told The Associated Press. The increase in tremors suggests an eruption is "imminent," she said.

Has Mt. Agung erupted before?

Agung last erupted in 1963, after remaining dormant for more than 100 years. The 1963 eruption killed more than 1,100 people.

When will Mt. Agung erupt?

It may not, according to Dr. Janine Krippner, a New Zealand volcanologist based in Pittsburgh. "You can't tell when a volcano will erupt. You can't tell how big it will be and you can't tell how long it will last," Krippner told the BBC.

Why do volcanoes erupt?

Volcanoes erupt because of pressure from magma, or molten rock, found beneath the surface of the Earth.

Magma rises through cracks in the Earth's crust. Pressure from the movement of the magma builds up inside of the Earth. The pressure is eventually released by, for instance, a movement in one of the Earth’s tectonic plates. The magma will then explode upward through the volcano, erupting into the atmosphere. Eventually, the lava (magma after it reaches the Earth’s surface) will cool and form a crust.