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Ancient Continental Breakup Triggered Massive Magma Eruptions
Scientists have recently discovered that a major continental breakup 135 million years ago – the separation of South America and Africa – led to significant geological events. This rifting event unleashed an immense outpouring of magma, estimated at 16 million cubic kilometers, evidence of which persists today as volcanic rock formations on both continents and across the Atlantic seabed. Volcanic rock layers, reaching thicknesses of up to one kilometer, are found in regions such as Namibia and Angola.
Eruption Timeline Refined
This new research, drawing upon a compilation of existing data from South America, Africa, and the ocean floor, reveals that the primary magma eruptions occurred between 135 and 131 million years ago, peaking approximately 134.5 million years ago. A refined timeline of these eruptions can offer researchers clearer insight into the causes of the continental split and its impact on the climate.
Thermal Anomaly and Continental Drift
Furthermore, the study identifies evidence of a thermal anomaly located beneath the former southern Pangaea, the supercontinent that began fragmenting 200 million years ago into the continents we know today. Continental separation occurred gradually. While South America and Africa rifted apart 135 million years ago, the break-up of North America wasn’t complete until around 55 million years ago.
Mantle Plume’s Role in Continental Separation
Research indicates that the breakup of southern Pangaea was partly driven by a mantle plume. A mantle plume is a massive upwelling of hot, buoyant material from Earth’s mantle, the layer beneath the crust. These plumes thin and weaken the overlying continental crust by inducing melting from below.
Ongoing Debate
Mohamed Mansour Abdelmalak, the study’s lead author and a geologist and geophysicist at the University of Oslo in Norway, indicated the new research suggests the thermal anomaly, which facilitated the separation of South America and Africa, is attributable to a mantle plume. However, this hypothesis remains contentious.
Abdelmalak noted that a lack of sufficient samples hinders definitive confirmation of the link between this volcanism and the mantle plume. He emphasized the necessity for samples, particularly from bedrock located deep beneath the ocean off Argentina and Uruguay, regions where deep-sea drilling has been minimal.
Need for Further Deep-Sea Sampling
Abdelmalak further explained that acquiring more deep rock samples, from both Africa and the deep ocean, would aid researchers in better understanding the volume of magma erupted during the Africa-South America split and the subsequent climate effects.
Climate Impact of Magma Eruptions
Large volcanic eruptions typically induce climate warming through the release of significant greenhouse gases. However, around 134 million years ago, a cooling period occurred, potentially due to the rapid breakdown or weathering of the erupted magma.
Cooling Period Paradox
Weathering, in geological terms, describes the breakdown of rocks and their chemical reaction with the atmosphere, a process that absorbs carbon dioxide.