The split between South America and Africa 135 million years ago was quite the explosive event. A recent study shows this breakup released over 3.8 million cubic miles of magma, which can still be found as volcanic rock in both continents and beneath the Atlantic Ocean. In some parts of Namibia and Angola, these volcanic rocks are impressively thick, reaching up to 1 kilometer.
This fresh research, which pulls together data from various sources across the continents and the ocean floor, reveals that the primary volcanic activity happened between 135 and 131 million years ago, peaking around 134.5 million years ago. This timeline helps scientists understand the events that triggered the breakup and how it affected the climate.
Mohamed Mansour Abdelmalak, the lead researcher and a geologist at the University of Oslo, points out that this period saw some extinctions and climate changes. By pinpointing when the magma erupted, researchers can connect it to these significant events in Earth’s history.
The study also identified a "thermal anomaly" under what was once the southern part of the supercontinent Pangaea. Pangaea began breaking apart around 200 million years ago, with the South America-Africa split occurring later. This separation was gradual. North America didn’t split from Europe until about 55 million years ago. Previous studies suggested that a mantle plume—hot rock rising from deep within the Earth—might have played a role in this breakup by thinning the continental crust from below.
While Abdelmalak believes the thermal anomaly might be linked to such a mantle plume, he acknowledges that this is still a hotly debated idea. More rock samples, especially from the depths of the ocean near Argentina and Uruguay, are needed to solidify these claims.
There’s a modern parallel to this process in Iceland, where volcanic activity is ongoing due to a mantle plume beneath the Mid-Atlantic Ridge. That ridge continues to pull apart at a rate of about 2 to 5 centimeters each year, creating new land through volcanic eruptions.
Collecting new rock samples from deep beneath the ocean and in Africa could provide crucial insights into the magnitude of magma released during this ancient breakup. Typically, large eruptions release a lot of greenhouse gases, warming the climate. However, around 134 million years ago, there was a surprising cooling period. This might have been due to the rapid weathering of volcanic materials, which pulled carbon dioxide from the atmosphere.
These findings contribute to our understanding of how past geological events shape our planet’s climate. The full study is documented in the May issue of Earth-Science Reviews.
If you’re intrigued by this topic, check out more about mantle plumes and geological formations at Live Science.
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