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A Colombian mountain range has lose its " beginning " — a chock of Earth ’s crust that once propped it up but has since " dripped " down into the mantle , a novel study paint a picture . It ’s long been a mystery as to how the peaks have manage to stay erect , but now , researcher are investigating the underlie geology .
The Sierra Nevada de Santa Marta , a cragged area in northwest Colombia with prime that remain firm over 18,700 foot ( 5,700 meters ) marvellous , has perplexed geologists since the 1970s , when measurements indicated the crust beneath the acme was unusually fragile .
The Sierra Nevada de Santa Marta mountains in Colombia stands more than 18,000 feet tall.
" raft regions typically have wooden-headed crustal roots that correct for the load of the mountains , " study lead authorDavid Quiroga , a geophysicist and former graduate researcher at the University of Alberta in Canada , assure Live Science in an email . Earth ’s crust is much lighter than theunderlying mantle , Quiroga said . Because mountain are so gruelling , the crustal beginning that sit beneath them are embedded in the mantle . The mass displaced within the mantle is larger than that of the crustal theme , and this form make up for the load piled on by quite a little that ride above .
geophysicist can determine the heaviness of Earth ’s crust using gravity anomalousness measure . " In general , there is high gravity in places where there is a passel of batch , and vice - versa , " Quiroga said . The presence of a crustal root in hilly regions usually produces negative gravity anomaly values , meaning the mass in this region is lower than expected . This reflect where the lighter cheekiness has displaced the enceinte blanket , unlike other places where the mantle is intact .
" However , in the event of the Sierra Nevada de Santa Marta , in Colombia , there is an elevated mass part with a high convinced solemnity unusual person , " Quiroga tell . " This means that rather of having a mess deficit , there is an excess of flock . "
The Sierra Nevada de Santa Marta mountain range sits atop a subduction zone, where the Caribbean tectonic plate slides beneath northern South America.
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The mountain range once had a crustal ascendent to make up for its huge load — but this base slowly oozed down into the drape over a period of 10 million years , according to the cogitation , which was published Jan. 7 in theJournal of Geophysical Research : Solid Earth .
Earth ’s insolence and the uppermost mantle form a set cuticle around our planet known as the geosphere . The low lithosphere may " drop " down in places where it is heavy and colder than the pallium below , Quiroga tell . The mantle then develop to fill the col and heat up the lower crust , which can trigger change in its composition that cause grownup circumstances of the incrustation to sink .
Previousresearchhas suggest lithospheric dripping may explicate strange geologic formations and dynamics in other regions — include the Puna Plateau in the Andes , the Sierra Nevada in California and the Wallowa mountains in Oregon . But Quiroga and his colleagues are " the first to nominate that such a mechanism is a plausible account for the Sierra Nevada de Santa Marta , " he said .
It ’s unclear how the Colombian mountain range has managed to remain upright despite its evident lack of support , but the Prince of Darkness could be in the details .
" The models in our study show that once the mint realm lose its crustal root it start sinking due to the loss of keep , " Quiroga said . " Because the mountain is still upright and improbable , this indicate that the removal episode must have occurred very of late and that there has not been enough time for the peck to give way . "
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The elevation may have lost their root as recently as 2 million year ago , Quiroga said . In the study , the researchers also suggest a possible window for dripping pass between 56 million and 40 million years ago , during the Eocene date of reference This posterior fourth dimension systema skeletale implies the mountains have remained upright for over 40 million year , which is inconsistent with example in the study that predicted collapse after just 5 million years .
But other factors not included in the model might have propped the mountains up over the eld . The fence lithosphere may be firm enough to leave the peaks support from either side , and the mantle may have risen to detain the mountains from break down , Quiroga say . The Caribbean tectonic home , which is slide beneath Colombia , should also be considered as a possible airscrew in future models , he add .
Until then , the mystery besiege the Sierra Nevada de Santa Marta lives on .
