Geology And Geophysics


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Beautiful Yellowstone's active geo-thermal features make it like no other place on earth.  On March 1, 1872, President Ulysses S. Grant signed into law a bill which made the area of Yellowstone the nations first national park.  Scientists believed that the natural wonders of the park, such as its many geysers and hot springs, were remnants of an extinct volcano but a major earthquake in the park in 1959 changed their belief and would prove to awaken the scientific community to the existence of a geological time-bomb.

On August 17, 1959, a major earthquake occurred, causing a huge landslide and killing 28 people.  The quake was so large that the USGS decided to begin extensive studies on the area.  Geologist Bob Christiansen, was the first to find the caldera of a massive volcano inside the park.  Further studying of the area found a total of three large overlapping calderas.  Resurveying of the original 1923 benchmarks in 1970 revealed a three foot rise in the measurement of the land area.  The rising of the land brought the realization that the caldera was in fact active.  Christiansen's study of the surrounding rock and ash field proved that the volcano has a super-eruption approximately once every 600,000 years, although lava flows indicate a smaller eruption only 70,000 years ago.  It is estimated that 640,000 years have passed since the last big eruption, considered to be all the more reason to monitor the caldera closely.  The biggest worry of the geologist is the safety of the many visitors to the park each year who come to marvel at the natural wonders.

Yellowstone receives almost 3 million visitors a year with the majority being unaware of the super-volcano beneath their feet, which could quickly eject more than a trillion tons of rock and debris covering half the continent with ash in a matter of hours.  In 2003, new cracks suddenly opened in the area and the ground heated to such a degree as to cause the park service to close many of the trails to visitors.  The cracks allowed poisonous gas to be released, killing a group of bison.  This gas, contained in the magma beneath the surface is what makes Yellowstone so volatile, escaping through cracks and bubbling from the hot springs at any given moment.

The magma of the Yellowstone volcano contains large amounts of silica, a substance which causes vast amounts of explosive, poisonous gas to be caught within the magma itself and makes the possibility of a major eruption even more possible.  A super-eruption of Yellowstone would be a million times bigger than Hiroshima, killing millions and changing the climate of the earth itself.  Of the 20 super-volcano eruptions known in the history of the earth, half of those occurred within North America.  Many warnings appear before the eruption of a volcano, but the cycles of active times can be a guessing game.

During the imminent eruption of a volcano, areas of land will rise dramatically, and swarms of earthquakes occur as the magma gets closer to the surface, breaking the rock above its chamber.  The earthquakes will become stronger and can fracture the rock allowing the magma to shoot to the surface.  The USGS Yellowstone Volcano Observatory constantly monitors and records all activity in the Yellowstone park recording at least 2,000 to 2,500 earthquakes per year.  The YVO's seismic activity recordings for this year alone have already surpassed that count causing uneasiness within the scientific community especially during the months of January/February:

-January, 2010:  Large swarm of 1620 earthquakes recorded.  The largest swarm in total number of earthquakes to date.  Largest event, 3.8 magnitude, January 21, 2010.

-February, 2010:  Swarm of 244 earthquakes recorded.  Largest event, 3.1 magnitude, February 2, 2010.

-January/February Swarm:  1,809 earthquakes recorded with this swarm, 14 being greater than 3.0 magnitude.  Location:  The Madison Plateau, near the northwest margin of the caldera, previous swarms have occurred here in the last 30 years with this being the largest.  Swarm began on January 15, 2010 and continued until February 25, 2010.

-March, 2010:  66 earthquakes recorded.  Largest event, 2.7 magnitude, March 29, 2010.

-April, 2010:  117 earthquakes recorded.  Largest event, 3.3 magnitude, April 3, 2010.

-May, 2010:  118 earthquakes recorded.  Largest event, 2.5 magnitude, May 11, 2010.

Is Yellowstone a ticking time-bomb?  According to the rules of Geology, yes.  It happened before and it will happen again.  The "Beast", as the volcano has come to be called, has warranted constant monitoring with its abrupt changes and volatile,  unpredictable behavior.  New cracks, hot springs, geysers and hot mud pits appear without warning from this geo-thermal active area and although Christiansen and most geologists doubt another super-eruption will happen any time soon,  they agree that an eruption comparable to Mount St. Helens is a very real possibility. 


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