It ’s been around 100,000 years since California ’s Long Valley supervolcano experienced a major eruption , but this purportedly sleeping caldera has been act a bit queerly over the retiring four decennary . New enquiry propose 240 three-dimensional miles of magma still exist within this supervolcano , but thankfully , a major eruption stay improbable .
The Long Valley Caldera , locate near Mammoth Mountain in eastern California , has been quiet for millennium , but its history is one of tremendous force . Around 760,000 years ago , this supervolcano experienced a stupendous six - day eruption that mail lava flows 30 miles ( 50 kilometer ) away and falling ash as far as Nebraska . The collapse of this vent ’s magma sleeping room resulted in the formation of the Long Valley Caldera , which experienced many subsequent eruptions during the following years , but nothing major for the retiring 100,000 years ; a volcano forms a depression , called a caldera , after expel the majority of its magmatic material .
Today , this dormant volcano features a stadium - shaped caldera about 20 miles long and 0.6 miles ( one kilometer ) deep , but it ’s not as quiet as it appear . Since 1978 , the dome of this caldera has been growing steady high — an watching which suggests Modern magma is leaking into the source , or that it ’s entering into its final level , with the recent upthrust related to the expulsion of its last remain stores of liquid magma . But these are theories . Prior to the new subject area , scientist were n’t completely sure about the caldera ’s exact forcible machine characteristic , despite across-the-board investigation over the past 40 years ; previous research let out small geological feature at very shallow depths , and very expectant feature article at deeper astuteness , create a blindspot in the mid - crustal regions .
A fresh study led by Ashton F. Flinders from the U.S. Geological Survey ’s California Volcano Observatory in Menlo Park , California , is now offer up the most detailed description of the Long Valley Caldera to date . The newresearch , release in the science journal Geology , suggests the reservoir contain over 240 three-dimensional nautical mile ( 1,000 three-dimensional kilometers ) of semi - liquified magma . Of this total , approximately 27 percent is in a fluid State Department — and give thanks goodness for that . At least 50 percent of the magma within a caldera needs to be in a liquid state to facilitate a big - scale superintendent - bang , according to the researchers .
“ We estimate the reservoir currently contains enough melt to tolerate another supereruption comparable in sizing to the caldera - forming eruption [ 767,000 years ago ] , ” write the source in the study . “ However , this intensity and a comparatively gamey melt fraction in no way insure that the magma is eruptible . ”
Phew . Despite these Holy Scripture of confidence , the researcher do n’t know how the melted magma is distribute within the reservoir , which could think of that “ normal ” eruptions , i.e. non - tiptop - eruptions , persist a distinguishable possible action . As this latest research suggests , this vent may not be as dormant as we ’ve been lead to believe .
“ While supervolcanoes like Long Valley are rarified , understanding the intensity and concentration of melting in their magma reservoir is decisive for determining their potential jeopardy , ” the researchers write .
Flinders and his colleague perform this work by psychoanalyze seismic data roll up for the preceding 26 years at locations within 95 miles ( 150 kilometers ) of the caldera . They calculated the shear - moving ridge velocity of the caldera ’s internal structure using the historical quake imaging data ( a technique in which x - shaft of light are used to display a hybridization - department through a solid body , like the Earth ’s crust ) , where mellow shear - waving velocity point low amplification of seismic waves and downcast shear - wave speed represented areas experiencing acute amplification . The lower the shear - waving speed , the more unstable the material .
Armed with this data , the researcher create a 3D look-alike of the caldera ’s interior , which they used to estimate the amount of liquified and semi - molten magma within the chamber , include the 240 three-dimensional mi of magma detected within a zone at the crust ’s middle regions .
As for the bit by bit ascend dome , the research worker say it ’s potential the supervolcano buy the farm through its end throes , as its magma stores slowly metamorphose into hearty rock and squeegee out the remain lava . The Long Valley Caldera may still be open of unleash ordinary - sized volcanic eruption , but nothing on the plate of what happened hundreds of thousands of years ago .
deplorably , the same can not be say for another California caldera — the Yellowstone supervolcano , which is tamp down with about 2,400 three-dimensional miles ( 10,000 cubic kilometers ) of magma . It could be decennium or even centuries before , or even if , this supervolcano erupt , so Californians can cool down for now .
[ Geology ]
GeologymagmaScience
Daily Newsletter
Get the ripe technical school , scientific discipline , and culture word in your inbox day by day .
News from the future tense , deliver to your present .
You May Also Like
