The researchers presented a series of measurements indicating that the largest meteorite in
last million years has fallen on the territory of modern Laos. Geological
traces of this impact covers about one-tenth of the Land area, but the crater from
a long time could not find because it’s buried beneath the frozen
lava, write the scientists in the journal Proceedings of the National Academy of Sciences.
The impacts of large meteorites on the Earth not only lead to
large craters in place of direct contact with the surface, but also
initiate a series of geochemical processes such as the formation of impactites class
rocks formed in conditions of a sharp rise of temperatures and pressures. Often the finds of impactites at close Dating allow us to conclude about what happened the fall of the cosmic body even if the crater it is not detected.
One of the representatives of impactites are tektites —
melted pieces of natural glass that are characterized by homogeneous
structure and very low water content and other volatile substances. Tektites single
origin are not distributed randomly: they form a field scatter (strewn field),
which is associated with the decaying trajectory of the meteorite or
thrown out of the crater with debris.
About a hundred years ago geologists discovered the Australasian field
scatter of tektites, which occupies approximately 10 percent of the area of the entire earth
globe, making it the largest known. In the North it seizes Indochina,
and in the South goes beyond the shores of Australia. His age is approximately equal to 790 thousand
years, making it relatively young in geological terms. However
the most remarkable circumstance connected with the fact that associated with
this field tektite crater was not found. At the same time, age less than a million
years is not enough to erase traces of a large education natural
processes with normal speed.
Geologists from Singapore, USA, Thailand and Laos under the leadership of
Kerry si (Kerry Sieh) from Nanyang technological University came to the conclusion that is associated with the Australasian field, the crater is buried under layers
lava plateau territory Bolaven in the southern part of Laos. The argument
the authors relied on four lines of evidence: the Geochemistry of tektites, Dating local
basalts, the presence of gravitational anomalies, but also features limestone and
shale breccia, was found near the alleged crash site
The authors show that the specific composition of the Australasian
of tektites can be explained by mixing with the basalts of the plateau Boloven, which were already
in this region at the time of the fall, as the local volcanoes was active
before. Dating of frozen lava flows over an alleged crater and about
it all showed age less than 790 thousand years. Thus at a greater distance on
the surface are and older basalts.
Satellite data indicate the presence of negative gravitational anomalies in this region, that is, the presence of large quantities
the relatively light rocks. The authors attribute this to the rapid filling of the crater
light sedimentary rocks resulting from the collision. Held
the analysis speaks in favor of a crater size of 13 by 17 kilometers.
The latest evidence is related to the composition of exposed rocks,
located at a distance of 10 to 20 kilometers from the proposed center. These
education consist mainly of limestone and shale breccia with frequent
inclusions of quartz, which contain traces of impact metamorphism, which also confirms
the interpretation of the authors.
Previously, scientists have discovered the emergence of amorphous crusts of micro-organisms living on meteorite. Extraterrestrial bodies also attracted to explain the unusual composition of the most ancient breeds. Its ability to distinguish a meteorite from an ordinary earth rock, you can check in our test Laboratory”meteoritics”.