The Magma Could Kill Us All

They lie asleep, unchanged by the passage of time : two vast lumps of magma deep inside the Earth that seem to have survived intact since the birth of our planet. Once every fews ten of million years, one of them wakes up, sending a plume of super - hot material upwards. When it reaches Earth's surface, it erupts in a burst of volcanic activity on a truly awesome scale.

On one such such an episode probably helped kill off the large dinosaurs 66 million years ago. Another could one day do the same thing to our species.

On top of that, scientist sure know that the earth is bilions years old, but they also know that it is very active planet. The interior of the Earth may be difficult to study directly, but geologists suspect it is constantly churning away in a manner that alters it is chemistry - so that lava erupting at the surface generally seems chemically "young".

In 2010, scientists stumbled across an anomaly: lava in Greenland that, when it erupted 60 million years ago, was already very, very old. So old, in fact,that some of the chemical isotopes it contains seemed to date back to Earth's birth. The controversial suggestion was that somewhere, deep inside the earth, must be a blobs of hot magma that had escaped the churning process for that entire length of time.

Evidence has now emerged that the blobs have a sinister side.

Life on Earth suffers an occasional devastating mass extinction that wipes out most of the species alive at the time. Many of these extinction coincide with relativity short lived periods of intense volcanic activity on a scale that is difficult to imagine.

This volcanic activity can blanket millions of square kilometres - equivalent to all western europe, for instance - with hot lava. Geologists call these large expanses of lava "large igneous provinces". The most devastating mass extinction of the last 500 million years ago - the "end - Permian extinction" - coincided with the information of one of these large igneous provinces. Most of Siberia was smothered with lava during the end - Permian event.

Even the most famous extinction of them all might have been triggered in part by the formation of a large igneous province. The " end - Cretaceous extinction" event about 66 million years ago killed off all the dinosaurs except for one group - the birds. Although there is good evidence that an asteroid slammed into the Earth just as dinosaurs went extinct, there is also strong evidence of a vast outpouring of lava in west central india. It left lava deposits thatare 2 kilometre (1.2 miles) thick in places.

In 2011, the lavas in many of these large igneous provinces are chemically similar. And they seemed to contain the same ancient chemical isotopes associated with the blobs of unmixed hot magma found deep inside the Earth. For completely mysterious reasons - the blobs wake up and generate a devastating large igneous province with the potential to contribute to a mass extinction of life.

The idea is still very controversial - but if it proves correct, it could be very bad news for the fateof human civilization. That's because some geologists think the magma blobs still exist. Seismic surveys of Earth' s internal structure have revealed two large regions of the lower mantle. One massive blob lies 28oo kilometre below africa, while its twin lies at the same depth beneath the Pacific Ocean.

The suggestion is that these two blobs are the source of the unmixed ancient material that feeds the devastating large igneous provinces. If - or when - one of the two blobs wakes up again, the large igneous province it forms might it well trigger another mass extinction of life on Earth.