The extinction of the archosaurians occurred throughout the finish of the Cretaceous period, around sixty-five million years ago, and caused the loss of up to seventy p.c of all life on the planet. though this event wasn't the sole mass extinction in Earth's history or the foremost severe, dinosaur extinction has spawned a spread of theories from the credible to the below believable.
geological period
If a geological period occurred during the Cretaceous amount a substantial quantity of the planet's water and huge areas of land would are barred in ice. Since dinosaurs were thought to be cold purebred they'd in all probability not be ready to upset such extreme conditions and their numbers would have eventually dwindled.
illness
illness is another suggestion for the extinction of the dinosaurs. it's troublesome to envision but however, but one disease may well be so prevailing to wipe out massive swathes of the animal population, travel immense distances and kill each land and marine species in addition to plant life.
temperature change
If a gradual change within the earth' climate occurred with a cooler, drier setting and an adapting plant life, presumably the archosaurians wouldn't be ready to adapt quickly enough to survive. The fossil records of dinosaur skulls show they may solely have had little brains. this means dinosaurs relied on automatic body responses instead of the cognitive, higher cognitive process responses heat purebred animals are acknowledged to make. thus a dynamic environment could have been troublesome for dinosaurs to adapt to and they might not have been able to vie effectively with warm-blooded animals.
star
A supernova could be a star that explodes with enough energy to stay our sun burning for 6 billion years. If the planet was hit by the ensuing radiation from a close-by star it might have destroyed all archosaurian life. there's no proof for a supernova inflicted the extinction of the dinosaurs, and it's troublesome to envision that something would have outlived such an event.
The Volcano Theory
it's acknowledged that volcanic activity was widespread throughout the Cretaceous era, and could be a credible reason why the dinosaurs became extinct. The Deccan Traps in western Asian nations and areas in the Pacific Basin are doubtless sites for inflated volcanic activity at this time.
the results of huge-scale volcanic activity would have led to a nuclear kind winter with ash and gasses additional to the atmosphere, depleting daylight and making troublesome conditions for archosaurian species. acid especially would have countermined the ozonosphere permitting harmful ultraviolet rays to penetrate the surface.
The high level of volcanic activity would even have emitted large volumes of greenhouse gasses equivalent to C02 and methane, increasing the Earth's temperature and drastically dynamical the planet's climate. the results on the archosaurians would be harmful as they struggled to acclimate to the dynamic conditions, and huge-scale extinction of dinosaur species would have been inevitable.
Cretaceous sediments support the speculation of volcanic activity as they contain above traditional concentrations of minerals and sodium, each related to volcanoes. Cretaceous sediments may also contain volcanic rock.
The Asteroid Theory
within the late 1970' Luis and director Alvarez and scientists from the University of American state were finding out rocks of the K-T boundary (or Cretaceous-Tertiary boundary) in Gubbio, Italy. Within the clay layer of the K-T boundary, they found concentrations of atomic number 77 thirty times above normal. the 2 natural sources of this rare element are asteroids and volcanic rock from the planet's core, that junction rectifier Luis and director Alvarez's team to 1st counsel an asteroid collided with the Earth inflicting archosaurian extinction. The Alvarez team calculable the asteroid would want to be 10 kilometers in diameter to contain enough iridium to cause the iridium concentrations within the clay layer.
additional proof to support an asteroid impact has emerged. The K-T boundary has two layers. The higher layer is 3 millimeters thick and includes soot that is believed to possess come back from world fires caused by the impact.
The lower level is 2 millimeters thick and contains ejecta from the asteroid impact site. This includes quartz crystals called shock crystals which are physically altered by high temperatures and intense pressure. The layer conjointly contains tektites and small tektites, which are typically products of amalgamated glass. aghast crystals and tektites are each closely related to asteroid impact sites.
In 1990 the individual Alan Hildebrand, once finding out information gathered by geophysicists searching for oil, detected a hoop structure referred to as Chicxulub off the peninsula in Mexico. Chicxulub could be a crater a hundred and eighty kilometers in diameter and dates from around sixty-five million