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New research provides insights into the dramatic separation of South America and Africa during the Pangaea breakup, approximately 135 million years ago. This continental split, a key event in Earth’s geological history, involved significant volcanic eruptions and reshaped the planet.
Volcanic Eruptions Mark Pangaea Breakup
A study reveals that the division between South America and Africa was characterized by intense volcanic activity. Around 135 million years ago, as these continents drifted apart, substantial magma flows occurred, leaving behind a substantial volume of volcanic rock.
The geological event resulted in the extrusion of over 3.8 million cubic miles (16 million cubic kilometers) of magma. Evidence of this massive eruption persists today in the form of volcanic rock formations across South America, Africa, and the floor of the Atlantic Ocean. In regions of Namibia and Angola, these layers of solidified lava reach thicknesses of up to 0.6 mile (1 kilometer).
Precise Timing of Magma Flows
The recent investigation, synthesizing existing data from South America, Africa, and the Atlantic seabed, has refined the timeline of these major magma discharges. Analysis indicates that the primary eruptions took place between 135 million and 131 million years ago, peaking around 134.5 million years ago. This enhanced understanding of the eruption chronology could assist scientists in determining the triggers for the continental split and assessing its consequences for the global climate.
According to Mohamed Mansour Abdelmalak, the study’s lead author and a geologist and geophysicist at the University of Oslo, Norway, “We observe some extinction events and climate disturbances” coinciding with the period around 134.5 million years ago. Pinpointing the precise age of the magma eruptions is crucial for linking these geological events to broader environmental changes.
Thermal Anomaly Beneath Pangaea
Furthermore, the research has uncovered indications of a “thermal anomaly” located beneath the southern portion of Pangaea. Pangaea, the ancient supercontinent, began its fragmentation approximately 200 million years ago, eventually giving rise to the continents we recognize today. The separation process was gradual; while South America and Africa parted ways 135 million years ago, the complete separation of North America from Europe occurred much later, around 55 million years ago. Previous research suggests that the breakup of southern Pangaea was partly initiated by a mantle plume – an upwelling of exceptionally hot rock originating from Earth’s mantle.
Abdelmalak suggests that the newly identified thermal anomaly, which contributed to the separation of South America and Africa, might be linked to this mantle plume activity. However, he acknowledged that this interpretation remains a subject of ongoing scientific debate.
Mantle Plume Hypothesis
“We lack sufficient samples to definitively confirm the relationship between this volcanism and the mantle plume,” Abdelmalak explained. He emphasized the need for rock samples from the area now situated under the deep ocean off the coasts of Argentina and Uruguay, regions that have seen limited deep-sea drilling expeditions.
Modern Analogues and Future Research
Iceland provides a contemporary illustration of mantle plume activity leading to magma outpourings, according to Abdelmalak. In Iceland, the Mid-Atlantic Ridge, a zone where tectonic plates are still diverging at a rate of 0.8 to 2 inches (2 to 5 centimeters) annually, is situated on land. The Iceland hotspot, believed to be fueled by a deep mantle plume, has shaped this landscape.
Acquiring more deep rock samples from Africa and the deep ocean is essential for researchers to quantify the volume of magma erupted during the Africa-South America split and to evaluate the eruptions’ impact on global climate patterns, Abdelmalak stated. While large volcanic eruptions typically cause global warming due to greenhouse gas emissions, the period around 134 million years ago experienced a cooling trend. This cooling could be attributed to the rapid weathering of erupted magma. Weathering, the process of rock breakdown and chemical reactions with the atmosphere, effectively removes carbon dioxide from the atmosphere.
The detailed findings of this study are published in the May issue of the journal Earth-Science Reviews.