A month after showing signs of activity for the first time in years, a volcano in Nicaragua has again blasted plumes of ash, gas and lava on Jan. 3.

Located on the shores of Lago de Managua, the Momotombo volcano had been dormant for 110 years until it churned out hot rock and ash on Dec. 1 last year. Schools in the region were temporarily shut down because of the strong Strombolian eruption, in which the volcano produced continuous small explosions.

According to the Nicaraguan Institute for Territorial Studies, the Momotombo volcano on Sunday roared in activity before dawn, and subsided afterwards. No one near the volcano was reported to be hurt.

On Christmas day, some 20 minor earthquakes rattled the volcano at up to 3.0 on the Richter scale and at a depth of 6 miles.

Small tremors beneath volcanoes are usually part of the warning signs that scientists pay attention to in order to figure out whether a volcano is threatening to erupt or not.

How Scientists Monitor Volcanoes And Predict Eruptions

Volcanic eruptions are often unpredictable as they follow no typical time pattern before they erupt.

"There is no 'norm' for volcanoes, because it's all going to be up to the individual systems. Different volcanoes are going to have different periods of time based on all sorts of different things going on in the crust," said Erik Klemetti of Denison University.

Still, volcanologists pick up indications of the volcano's current and potential condition to help them prepare for any kind of danger.

Below are warning signs and key techniques that scientists use to predict volcanic eruptions.

1. When magma rises up from within the Earth, hundreds of minor earthquakes may begin to occur.

John Eichelberger of the United States Geological Survey (USGS) said rising magma causes solid rock to break and sends earthquake signals.

"This pushes the ground surface upward, and boils off hot gas that travels ahead of the magma," explained Eichelberger.

Through the use of seismometers and GPS networks found near volcanoes, USGS scientists detect volcanic earthquakes. They also utilize radar satellites to identify whether the ground has swelled by comparing visuals captured at different periods.

In October last year, researchers in Japan created an artificial earthquake to help them analyze data through hot water pools and 1.24-mile underground pathways. Doing so would contribute in predicting the next volcanic eruption in the country.

2. Temperatures around the volcano elevate as volcanic activity increase.

According to USGS, lava on the cooler side of volcanoes comes out at about 570 degrees Fahrenheit. Burning hot lava can reach up to 1,600 degrees Fahrenheit. When it is still inside the volcano, magma can burn up to 2,120 degrees Fahrenheit.

To detect heat around a volcano, scientists use satellite cameras and thermal imaging techniques.

3. Volcanoes on the verge of eruption release gases with high sulfur content.

The higher the sulfur content of volcanic gases, the closer the volcano is to erupt. Eichelberger said increases in the flow rate of carbon dioxide and sulfur dioxide denote impending magma flow.

With that, scientists take gas samples and use chemical sensors to measure levels of sulfur.

According to USGS, large amounts of sulfur can lead to volcanic air pollution. Sulfur dioxide undergoes a chemical reaction with oxygen, sunlight, water and dust particles to form vog, or volcanic smog.

Sulfur also affects the climate, warms the stratosphere, and cools the troposphere. Liquid drops of sulfuric acid also contribute to the destruction of the ozone layer.

Aside from that, plumes of volcanic ash and gases are bad news for airplanes. Clouds of ash are strongly dangerous for planes because they are often visibly similar to regular clouds. When ash is ingested into the engine, engine failure ensues.

4. Magma flow may help predict volcanic eruptions.

Scientists from the University of Utah found that the formation of magma on Mount Rainier may possibly help predict future volcanic eruptions.

Led by Phil Wannamaker, the team managed to identify and link the release of fluids at the top of the slab, the movement of the fluids into the overlying mantle wedge, to the melting and the transport of melt/fluid phase to a magma reservoir beneath Mount Rainier.

However, their findings won't help predict the specific time and date for future eruptions, they said.

5. Volcanologists measure the acidity and temperature of water.

During field observations, scientists use advanced equipment to monitor and predict possible volcanic eruptions. They measure the temperature and pH levels of water.

However, Eichelberger said measuring water is only a little helpful because while water is the most abundant gas in magma, the atmosphere contains too much of it that it does not help in forecasting.

Photo : Jorge Mejía Peralta | Flickr

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