Daily Earth Science Geosphere Repost

Asteroids, dinosaurs, and mercury poisoning

We all learned in primary school that the dinosaurs went extinct due to a giant asteroid impacting the earth about 65 million years ago. But, there is a backstory about an already weakened biosphere that doesn’t get much press. That is the story of the Deccan Traps, a massive outpouring of flood basalts on the Indian continent.

The term “traps” describes flood basalt provinces. The term derives from the Swedish word “trappa” meaning stairs. It is a reference to the stair-like morphology of stacked basalt sheets when they erode. 

The volcanic events that create flood basalts are different from the more well-known volcanic mountain building we see today. Flood basalts occur when the crust of the earth splits open along massive fissures, and the molten core of an underlying mantle plume (hot spot) disgorges onto the surface of the planet. Literal ‘rivers of lava’ flow like water across the earth’s surface, filling in valleys with lakes of molting rock and traversing the topography like a flood from hell. Individual flows can travel hundreds of miles before they freeze into solid rock. 

Deccan Traps

The Deccan Traps formed for tens of thousands of years prior to the Chicxulub asteroid impact near the Mexican, Yucatán peninsula. The asteroid was the coup de grâce for an already weakened biosphere. The Deccan Traps eruptions resulted in about 600,000 cubic miles of liquid rock extruding onto the earth’s surface. It was, however, the volcanic gases and toxins that took their toll on the environment. 

The surface of the planet seems benign compared to what spews out from the bowels of the earth during volcanic eruptions. Carbon dioxide, methane, sulfur dioxide, mercury, and more pump into the atmosphere from volcanic vents. 

In April of 1815, Mount Tambora in Indonesia erupted, resulting in the deaths of 92,000 people. Ash from the explosion affected weather for the next year, and 1816 was the year without a summer due to temporary glbal cooling.

If one explosion affects global weather for a year, imagine what 30,000 years of continuous massive eruptions would do. Billions of tons of greenhouse gases would flood the atmosphere creating a global warming effect. Also other metals and toxins would enter into the biosphere. Analysis of fossil shells from 66 million years ago shows that significant global increases in mercury occurred during the formation of the Deccan Traps.

Thirty millennia of global warming, acid rain, ocean acidification, and toxic metal poisoning would have taken their toll on the biosphere before an unwelcome visitor from outer space rammed into the Yucatán Peninsula. Perhaps the dinosaurs were already exiting the stage before the Chicxulub impact. No stories are as simple as they seem on the surface. There is always a backstory in the interconnected web of life on our planet.


Mass Extinction Events: Life’s Struggle for Survival (Source: ArcheanWeb) – https://archeanweb.com/2019/12/01/mass-extinction-events-lifes-struggle-for-survival/ Also:


Flood basalts, mantle plumes and mass extinctions – https://www.geolsoc.org.uk/flood_basalts_1 Also:

Earth’s greatest killer finally caught (Becky Oskin – Live Science) – https://www.livescience.com/41909-new-clues-permian-mass-extinction.html Also:

Earth’s Atmosphere Had Terrifying Mercury Pollution Even Before The Killer Asteroid (Carly Cassella – Science alert) – https://www.sciencealert.com/earth-s-atmosphere-was-polluted-with-mercury-even-before-the-asteroid-that-killed-the-dinosaurs Also:

The epic volcano eruption that led to the ‘Year Without a Summer’ (Jack Williams – Washington Post) – https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/04/24/the-epic-volcano-eruption-that-led-to-the-year-without-a-summer/ Also:

Feature Image: Eruption at Fimmvörðuháls at dusk (Modified) – By Boaworm – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=10025261  

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.