Approximately 790,000 years ago, a meteorite crashed into the Earth with such force that the explosion covered approximately 10% of the planet with bright black pieces of rock debris.
Known as tectites, these glassy drops of melted terrestrial rock spread from Indochina to the Antarctica Eastern and from the Indian Ocean to the western Pacific. For more than a century, scientists sought evidence of the impact that created these boneless spots. But the location of the crater eluded detection, until now.
Geochemical analysis and local gravity readings told researchers that the crater was located in southern Laos on the Bolaven Plateau. The old impact was hidden under a cooled volcanic lava field that covers almost 2,000 square miles, scientists said in a new study.
When a meteor hits the Earth, land rocks at the impact site can be liquefied by the intense heat and then cooled in vitreous tectites, according to the Jackson School of Earth History Museum at the University of Texas. Scientists can observe the abundance and location of tectites to help locate an impact, even if the original crater erodes or hides, the study authors wrote. In this case, where there were many tectites, then where was the crater?
It is believed that the impact force created an edge that is over 300 feet high, according to the study. The impact tectites were larger and more abundant in the eastern part of central Indochina, but because the tectites were so widespread, previous estimates of crater size ranged between 9 miles (14.4 kilometers) in diameter and 186 miles (299.3 kilometers), and the precise position of the property remained uncertain. despite the fact that scientists spent decades searching.
For the new study, researchers first investigated several promising candidates for eroded craters in southern China, the north of Cambodia and the center of Laos, but soon they discarded those points. In all cases, the suspicious crater characteristics turned out to be much older and, instead, were identified as erosion in rocks dating from the Mesozoic era, about 252 million years ago and about 66 million years ago.
Was the crater buried? On the Bolaven Plateau in Laos, scientists found a site where volcanic lava fields could have hidden signs of an older meteorite impact. In a region that the researchers identified as a probable place for a crater, most lava flows were also in the correct age range: between 51,000 and 780,000 years.
The study authors observed below the surface of the lava taking gravity readings in more than 400 locations. Its resulting gravity map showed an area of ”particular interest” with a gravitational anomaly, a subsurface area less dense than the surrounding volcanic rock. According to the study, their measurements hinted at an elliptical “elongated crater” about 300 feet thick, about 8 miles wide and 11 miles long.
Together, all these clues suggested that “this thick pile of volcanic rocks really buries the impact site,” the scientists wrote.
The findings were published online on December 30 in the journal Proceedings of the National Academy of Sciences.
Originally posted in Live science.
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