What have been causes of Earth's major extinctions?

Answer 1

The 5 Major Extinctions
suffered by life on planet Earth (so far)



Here are details of the five worst mass extinctions in Earth’s history and their possible causes, according to paleobiologist Doug Erwin of the Smithsonian Institution’s National Museum of Natural History. Erwin said estimates of extinction rates are from the late John J. Sepkoski at the University of Chicago:
Cretaceous-Tertiary extinction, about 65 million years ago, probably caused or aggravated by impact of several-mile-wide asteroid that created the Chicxulub crater now hidden on the Yucatan Peninsula and beneath the Gulf of Mexico. Some argue for other causes, including gradual climate change or flood-like volcanic eruptions of basalt lava from India’s Deccan Traps. The extinction killed 16 percent of marine families, 47 percent of marine genera (the classification above species) and 18 percent of land vertebrate families, including the dinosaurs.

End Triassic extinction, roughly 199 million to 214 million years ago, most likely caused by massive floods of lava erupting from the central Atlantic magmatic province -- an event that triggered the opening of the Atlantic Ocean. The volcanism may have led to deadly global warming. Rocks from the eruptions now are found in the eastern United States, eastern Brazil, North Africa and Spain. The death toll: 22 percent of marine families, 52 percent of marine genera. Vertebrate deaths are unclear.

Permian-Triassic extinction, about 251 million years ago. Many scientists suspect a comet or asteroid impact, although direct evidence has not been found. Others believe the cause was flood volcanism from the Siberian Traps and related loss of oxygen in the seas. Still others believe the impact triggered the volcanism and also may have done so during the Cretaceous-Tertiary extinction. The Permian-Triassic catastrophe was Earth’s worst mass extinction, killing 95 percent of all species, 53 percent of marine families, 84 percent of marine genera and an estimated 70 percent of land species such as plants, insects and vertebrate animals.

Late Devonian extinction, about 364 million years ago, cause unknown. It killed 22 percent of marine families and 57 percent of marine genera. Erwin said little is known about land organisms at the time.

Ordovician-Silurian extinction, about 439 million years ago, caused by a drop in sea levels as glaciers formed, then by rising sea levels as glaciers melted. The toll: 25 percent of marine families and 60 percent of marine genera.

Answer 2

times change.
with the exception of those few spices living on earth now, every species of plant and animal ever has become extinct. always because the environment changed in such a way that they could not adapt. but there is probably a different specific reason for each one.
statistically speaking, humans have made no significant contribution.

Answer 3

Major tectonic or volcanic events,
Meteor impacts,
Climate change which may or may not be associated w/ the previous two,
Massive flooding events caused by tectonism or meteor impacts,
any combination of the above.....

Answer 4

...a Comet impact upon the Earth and Ted Kennedy driving around in his car.

Answer 5

Over-hunting, poaching, natural disasters, Ice Ages, urbanization/deforestation, destruction of natural habitat, failure to reproduce, out-numbered by predators.

Answer 6

Climate change. That's what lead to the lack of food, etc.

Answer 7

A super volcano in Siberia! Not only big meteors as we thought!

Answer 8

Meteors, poaching, viruses, lack of food, etc.