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 where the team could observe the lava dome from above. Inside the Caliente dome, magma and gas were steadily rising. Before an eruption, the vent at the top of the dome is sealed. This traps the magma and gases. As gas builds up, pressure builds up. Eventually, the seal breaks.
When the seal breaks, gas and magma shoot upward. Lava flows down the volcano. Ash spews skyward, hundreds of meters above the vent. When all the pressure has been released, some of the material resettles over the vent.
The vent seals again. Then the pressure begins to build until the next eruption.