Crater of Death update 2016

Scientists say they have a clue that may enable them to find traces of the asteroid that wiped out the dinosaurs in the very crater it made on impact.

This pointer takes the form of a nickel signature in the rocks of the crater that is now buried under ocean sediments in the Gulf of Mexico.

An international team has just drilled into the 200km-wide depression.

It hopes the investigation can help explain why the event 66 million years ago was so catastrophic.

Seventy-five percent of all life, not just the dinosaurs, went extinct.

One tantalising revelation is that the scientists observe a big nickel spike in the sediments immediately above what has become known as Chicxulub Crater.

This is an important marker that could lead on to the discovery of asteroid material itself.

Old Wellie Dr Sally Morgan was part of the team on the project.

http://www.bbc.co.uk/news/science-environment-38299804

The Earth stands on the brink of its sixth mass extinction

Life on Earth is in trouble. That much we know. But how bad have things become – and how fast are events moving? How soon, indeed, before the Earth’s biological treasures are trashed, in what will be the sixth great mass extinction event?

Rather than the nine extinctions among vertebrates that would be expected to have occurred in normal geological circumstances since 1900, their conservative estimate adds in another 468 extinctions, spread among mammals, birds, reptiles, amphibians and fish.


NOT THE FIRST TIME: Previous mass extinctions

Geological history includes many periods when species have died in large numbers. In each of the following, more than half the Earth’s species disappeared:

1 End-Ordovician, 443 million years ago.

This coincides with very rapid glaciation; sea level fell by more than 100 metres, devastating shallow marine ecosystems; less than a million years later, there was a second wave of extinctions as ice melted, sea level rose rapidly, and oceans became oxygen-depleted.

2 Late Devonian, c 360 million years ago.

A messy prolonged event, again hitting life in shallow seas very hard, and an extinction that was probably due to climate change.

3 Permian-Triassic mass extinction, c 250 million years ago.

The greatest of all, ‘The Great Dying’ of more than 95% of species, is strongly linked with massive volcanic eruptions in Siberia that caused, among other effects, a brief savage episode of global warming.

4 Triassic-Jurassic mass extinction, c 200 million years ago.

This has been linked with another huge outburst of volcanism.

5 Cretaceous-Tertiary mass extinction 65 million years ago.

This killed off the dinosaurs and much else; an asteroid impact on Mexico probably did the damage, but the world’s ecosystem may have been weakened by volcanic outbursts in what is now India.

Prof Mark Williams, Leicester University
For more information:
http://www.theguardian.com/environment/2015/jun/21/mass-extinction-science-warning

25 Biggest Turning points in Earth's History

Our planet has existed for 4.5 billion years, and it has been a busy few eons. Here are the 25 biggest milestones in Earth's history. From leaps forward in evolution to devastating asteroid impacts, these were the turning points that shaped our world.

http://www.bbc.com/earth/bespoke/story/20150123-earths-25-biggest-turning-points/index.html

KT BOUNDARY

The space rock that hit Earth 65m years ago and is widely implicated in the end of the dinosaurs was probably a speeding comet, US scientists say.

Researchers in New Hampshire suggest the 180km-wide Chicxulub crater in Mexico was carved out by a smaller object than previously thought.The space rock gave rise to a global layer of sediments enriched in the chemical element iridium, in concentrations much higher than naturally occurs; it must have come from outer space.

The team suggests that frequently quoted iridium values are incorrect. Using a comparison with another extraterrestrial element deposited in the impact - osmium - they were able to deduce that the collision deposited less debris than has previously been supposed.

The recalculated iridium value suggests a smaller body hit the Earth. So for the second part of their work, the researchers took the new figure and attempted to reconcile it with the known physical properties of the Chicxulub impact.

For more information follow the link:

http://www.bbc.co.uk/news/science-environment-21709229