EARTH

The Supercontinent Comes Apart

~201 to 135 million years ago

Phanerozoic · Mesozoic · Jurassic

The single landmass split along one rift after another, each announced by a flood of basalt: the Central Atlantic province at about 200 million years, the Karoo and Ferrar eruptions that opened the western Indian Ocean at 183, the Parana and Etendeka lavas at 135, just before the South Atlantic. The Atlantic unzipped from the middle outwards, and Gondwana came apart in pieces.

Why it matters

Every coastline that looks as though it would fit against another one dates from this. Splitting a continent also opens shallow seas, shifts currents and isolates whole faunas, which is why the plants and animals of the southern continents are related without being the same. Whether the basalt drove the splitting or merely came with it is still an open question.

Dating & uncertainty

Breakup is a sequence, not a date. The rifting that finally took Pangaea apart begins in the Triassic, after earlier episodes that failed; the Central Atlantic province erupts at about 200 Ma and the central Atlantic opens in the earliest Jurassic; the Karoo-Ferrar eruptions at 183 Ma open the western Indian Ocean; the Parana-Etendeka province at 135 Ma precedes the South Atlantic. The lavas tend to pile up away from where the ocean finally opens, which is what keeps their causal role in doubt.

Sources

1. Frizon de Lamotte et al. (2015), Tectonics · Style of rifting and the stages of Pangea breakup
2. Peace et al. (2020), Earth-Science Reviews · A review of Pangaea dispersal and large igneous provinces: in search of a causative mechanism
3. Stubblefield et al. (2023), Tectonophysics · Unzipping supercontinent Pangea: geologic, potential field data, and buried structures, and a case for sequential Atlantic opening

Earth history as one day

22:56:141 h 4 min before midnight

if Earth’s 4.54 billion years were compressed into a single day