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    "segs": [ {
      "utf8": "In February of 1942, \nMexican farmer Dionisio Pulido"
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    "segs": [ {
      "utf8": "thought he heard thunder \ncoming from his cornfield."
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    "dDurationMs": 3778,
    "segs": [ {
      "utf8": "However, the sound wasn’t coming \nfrom the sky."
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  }, {
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    "dDurationMs": 5700,
    "segs": [ {
      "utf8": "The source was a large, smoking crack \nemitting gas and ejecting rocks."
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    "segs": [ {
      "utf8": "This fissure would come to be known as \nthe volcano Paricutin,"
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    "segs": [ {
      "utf8": "and over the next 9 years, its lava \nand ash would cover over 200 square km."
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    "segs": [ {
      "utf8": "But where did this new volcano come from,"
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    "segs": [ {
      "utf8": "and what triggered \nits unpredictable eruption?"
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    "segs": [ {
      "utf8": "The story of any volcano \nbegins with magma."
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    "segs": [ {
      "utf8": "Often, this molten rock forms \nin areas where ocean water"
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  }, {
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    "segs": [ {
      "utf8": "is able to slip into the Earth’s mantle \nand lower the layer’s melting point."
    } ]
  }, {
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    "segs": [ {
      "utf8": "The resulting magma typically remains \nunder the Earth’s surface"
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  }, {
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    "segs": [ {
      "utf8": "thanks to the delicate balance \nof three geological factors."
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    "segs": [ {
      "utf8": "The first is lithostatic pressure."
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    "segs": [ {
      "utf8": "This is the weight of the Earth’s crust \npushing down on the magma below."
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    "segs": [ {
      "utf8": "Magma pushes back with the second factor, \nmagmastatic pressure."
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    "segs": [ {
      "utf8": "The battle between these forces \nstrains the third factor:"
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  }, {
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    "dDurationMs": 3196,
    "segs": [ {
      "utf8": "the rock strength of the Earth’s crust."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Usually, the rock is strong enough \nand heavy enough"
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    "segs": [ {
      "utf8": "to keep the magma in place."
    } ]
  }, {
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    "segs": [ {
      "utf8": "But when this equilibrium is thrown off, \nthe consequences can be explosive."
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    "segs": [ {
      "utf8": "One of the most common causes \nof an eruption"
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    "tStartMs": 97421,
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    "segs": [ {
      "utf8": "is an increase \nin magmastatic pressure."
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    "segs": [ {
      "utf8": "Magma contains various elements \nand compounds,"
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  }, {
    "tStartMs": 103590,
    "dDurationMs": 3150,
    "segs": [ {
      "utf8": "many of which are dissolved \nin the molten rock."
    } ]
  }, {
    "tStartMs": 106740,
    "dDurationMs": 6327,
    "segs": [ {
      "utf8": "At high enough concentrations, compounds \nlike water or sulfur no longer dissolve,"
    } ]
  }, {
    "tStartMs": 113067,
    "dDurationMs": 3820,
    "segs": [ {
      "utf8": "and instead form \nhigh-pressure gas bubbles."
    } ]
  }, {
    "tStartMs": 116887,
    "dDurationMs": 2235,
    "segs": [ {
      "utf8": "When these bubbles reach the surface,"
    } ]
  }, {
    "tStartMs": 119122,
    "dDurationMs": 3198,
    "segs": [ {
      "utf8": "they can burst with the force \nof a gunshot."
    } ]
  }, {
    "tStartMs": 122320,
    "dDurationMs": 3630,
    "segs": [ {
      "utf8": "And when millions of bubbles \nexplode simultaneously,"
    } ]
  }, {
    "tStartMs": 125950,
    "dDurationMs": 4250,
    "segs": [ {
      "utf8": "the energy can send plumes of ash \ninto the stratosphere."
    } ]
  }, {
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    "dDurationMs": 5295,
    "segs": [ {
      "utf8": "But before they pop, they act \nlike bubbles of C02 in a shaken soda."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Their presence lowers \nthe magma’s density,"
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  }, {
    "tStartMs": 138355,
    "dDurationMs": 4743,
    "segs": [ {
      "utf8": "and increases the buoyant force \npushing upward through the crust."
    } ]
  }, {
    "tStartMs": 143098,
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    "segs": [ {
      "utf8": "Many geologists believe this process \nwas behind the Paricutin eruption"
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  }, {
    "tStartMs": 148191,
    "dDurationMs": 1820,
    "segs": [ {
      "utf8": "in Mexico."
    } ]
  }, {
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    "dDurationMs": 3507,
    "segs": [ {
      "utf8": "There are two known natural causes \nfor these buoyant bubbles."
    } ]
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    "tStartMs": 153518,
    "dDurationMs": 3170,
    "segs": [ {
      "utf8": "Sometimes, new magma \nfrom deeper underground"
    } ]
  }, {
    "tStartMs": 156688,
    "dDurationMs": 3970,
    "segs": [ {
      "utf8": "brings additional gassy compounds \ninto the mix."
    } ]
  }, {
    "tStartMs": 160658,
    "dDurationMs": 4148,
    "segs": [ {
      "utf8": "But bubbles can also form \nwhen magma begins to cool."
    } ]
  }, {
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    "dDurationMs": 5343,
    "segs": [ {
      "utf8": "In its molten state, magma is a mixture\nof dissolved gases and melted minerals."
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  }, {
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    "segs": [ {
      "utf8": "As the molten rock hardens, some of those \nminerals solidify into crystals."
    } ]
  }, {
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    "dDurationMs": 4000,
    "segs": [ {
      "utf8": "This process doesn’t incorporate \nmany of the dissolved gasses,"
    } ]
  }, {
    "tStartMs": 179621,
    "dDurationMs": 3291,
    "segs": [ {
      "utf8": "resulting in a higher concentration \nof the compounds"
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  }, {
    "tStartMs": 182912,
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    "segs": [ {
      "utf8": "that form explosive bubbles."
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    "segs": [ {
      "utf8": "Not all eruptions are due \nto rising magmastatic pressure—"
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    "segs": [ {
      "utf8": "sometimes the weight of the rock \nabove can become dangerously low."
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  }, {
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    "segs": [ {
      "utf8": "Landslides can remove massive quantities \nof rock from atop a magma chamber,"
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  }, {
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    "segs": [ {
      "utf8": "dropping the lithostatic pressure \nand instantly triggering an eruption."
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  }, {
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    "segs": [ {
      "utf8": "This process is known as “unloading”"
    } ]
  }, {
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    "segs": [ {
      "utf8": "and it’s been responsible \nfor numerous eruptions,"
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    "dDurationMs": 4722,
    "segs": [ {
      "utf8": "including the sudden explosion \nof Mount St. Helens in 1980."
    } ]
  }, {
    "tStartMs": 215544,
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    "segs": [ {
      "utf8": "But unloading can also happen \nover longer periods of time"
    } ]
  }, {
    "tStartMs": 219114,
    "dDurationMs": 2648,
    "segs": [ {
      "utf8": "due to erosion or melting glaciers."
    } ]
  }, {
    "tStartMs": 221762,
    "dDurationMs": 3470,
    "segs": [ {
      "utf8": "In fact, many geologists \nare worried that glacial melt"
    } ]
  }, {
    "tStartMs": 225232,
    "dDurationMs": 4490,
    "segs": [ {
      "utf8": "caused by climate change \ncould increase volcanic activity."
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  }, {
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    "segs": [ {
      "utf8": "Finally, eruptions can occur when \nthe rock layer is no longer strong enough"
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  }, {
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    "segs": [ {
      "utf8": "to hold back the magma below."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Acidic gases and heat escaping from magma"
    } ]
  }, {
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    "segs": [ {
      "utf8": "can corrode rock through a process \ncalled hydrothermal alteration,"
    } ]
  }, {
    "tStartMs": 244568,
    "dDurationMs": 3880,
    "segs": [ {
      "utf8": "gradually turning hard stone \ninto soft clay."
    } ]
  }, {
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    "dDurationMs": 3640,
    "segs": [ {
      "utf8": "The rock layer could also be weakened \nby tectonic activity."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Earthquakes can create fissures \nallowing magma to escape to the surface,"
    } ]
  }, {
    "tStartMs": 256777,
    "dDurationMs": 3012,
    "segs": [ {
      "utf8": "and the Earth’s crust \ncan be stretched thin"
    } ]
  }, {
    "tStartMs": 259789,
    "dDurationMs": 3478,
    "segs": [ {
      "utf8": "as continental plates \nshift away from each other."
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  }, {
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    "segs": [ {
      "utf8": "Unfortunately, knowing \nwhat causes eruptions"
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  }, {
    "tStartMs": 266217,
    "dDurationMs": 2400,
    "segs": [ {
      "utf8": "doesn’t make them easy to predict."
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  }, {
    "tStartMs": 268617,
    "dDurationMs": 3220,
    "segs": [ {
      "utf8": "While scientists can roughly determine \nthe strength and weight"
    } ]
  }, {
    "tStartMs": 271837,
    "dDurationMs": 1390,
    "segs": [ {
      "utf8": "of the Earth’s crust,"
    } ]
  }, {
    "tStartMs": 273227,
    "dDurationMs": 3780,
    "segs": [ {
      "utf8": "the depth and heat of magma chambers \nmakes measuring changes"
    } ]
  }, {
    "tStartMs": 277007,
    "dDurationMs": 3380,
    "segs": [ {
      "utf8": "in magmastatic pressure very difficult."
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    "segs": [ {
      "utf8": "But volcanologists are constantly \nexploring new technology"
    } ]
  }, {
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    "dDurationMs": 2547,
    "segs": [ {
      "utf8": "to conquer this rocky terrain."
    } ]
  }, {
    "tStartMs": 286844,
    "dDurationMs": 2905,
    "segs": [ {
      "utf8": "Advances in thermal imaging \nhave allowed scientists"
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  }, {
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    "dDurationMs": 2660,
    "segs": [ {
      "utf8": "to detect subterranean hotspots."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Spectrometers can analyze \ngases escaping magma."
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  }, {
    "tStartMs": 295839,
    "dDurationMs": 6264,
    "segs": [ {
      "utf8": "And lasers can precisely track the impact \nof rising magma on a volcano’s shape."
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    "segs": [ {
      "utf8": "Hopefully, these tools will help us better\nunderstand these volatile vents"
    } ]
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    "dDurationMs": 2206,
    "segs": [ {
      "utf8": "and their explosive eruptions."
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