Inside an Eruption
Magma rises from below Earth’s surface.
Rising gases put pressure on the sealed vent.
Gases explode, breaking the seal.
A hot column of volcanic ash and gas shoots into the air.
During large eruptions, pyroclastic flows made of gas and volcanic matter move at high speeds.
Lava flows slowly across the land.
Lahars, mixtures of water and ash, move rapidly down streams and rivers.
Once the gases have escaped, the explosion ends. The seal closes again.
magma and gas
How It Works
The plan was to hike to the top of Santa María. Here, the team could observe the lava dome from above.
Inside the Caliente dome, magma and gas were rising. Before an eruption, the vent of the dome is sealed. Magma and gases are trapped. Pressure builds. The seal breaks.
When the seal breaks, gas is released. Magma oozes out as lava. It flows like thick rivers. Ash is forced high into the sky.
Then some of the material resettles over the vent. The vent seals again. The pressure begins to build again until the next eruption.