Lately, it seems like everything on Earth is aligned to kill us: hurricanes, fires, floods. That’s the short list. According to Howard Lee at Ars Technica, a host of scientists now believe that massive volcanic floods called Large Igneous Provinces, or LIPs, are the cause of most global mass extinctions. Scientists are trying to figure out how LIPs work and when — not if — another flood will destroy life on earth.
The article goes into fascinating geological detail about what science knows about this cataclysmic volcanism. Although the title, “When Will the Earth Try to Kill Us Again?” makes the process sound maliciously anthropomorphic, the idea of a hateful Earth, sick of humanity’s meddling, does add some welcome levity to a grave vision of our future.
Some scientists claim LIPs occur cyclically every 15 million years, and they think we’re overdue for one. Others admit we don’t understand them well enough to predict. Lee compares human activity on the earth’s surface to an LIP: We are filling the atmosphere with CO2, causing global warming and oceanic dead zones at a faster pace than LIPs. Although nobody can accurately predict when an LIP will destroy our species, we do know this: That vintage wine you’ve been saving in the basement for a rainy day? This is the rainy day. Pop the cork.
Even if LIPs are the “smoking gun” behind most mass extinctions, that still doesn’t tell us how they killed animals. It wasn’t the lava. Despite the moniker—flood basalts—these are not raging torrents. You could probably out-walk the lava from a Large Igneous Province. As vast as they were, they flowed in much the same way as lava in Iceland or Hawaii flows today, with glistening orange and grey lobes swelling, stretching, and spilling to make new lobes. An advancing front will typically move at about a kilometer or two in a day (the average person can walk that distance in 30 minutes).
Unfortunately, gas is deadlier than lava.
The 1783-4 Laki eruption in Iceland gave us a tiny taste of what to expect from a LIP. It bathed Europe in an acid haze for five months, strong enough to burn throats and eyes, scorch vegetation and tarnish metal, to kill insects and even fish. That may be a killer, but, as far as science can tell, the haze from a LIP on its own is unlikely to be sufficient to cause a mass extinction. The climate effects of volcanic gases are deadlier still. Stratospheric sulfur from Laki cooled the planet by 1.3 degrees Celsius for three years, triggering one of the most severe winters on record in Europe, North America, Russia, and Japan. Famines ensued in many parts of the world, and that may have planted the seeds for the French Revolution five years later.
A decade-long LIP eruption could cool the planet by about 4.5 degrees Celsius, although the climate would recover in 50 years. This would no doubt cause geopolitical and financial chaos, but it’s unlikely by itself to eradicate a significant percentage of species from the sea, given the time it takes to mix the oceans (about a thousand years) and their huge thermal inertia.