EARTH

Columbia: the First Supercontinent

~1.8 to 1.4 billion years ago

Proterozoic · Paleoproterozoic · Statherian

Columbia, also called Nuna, is the earliest supercontinent that can be mapped, a single landmass formed when continental blocks welded together between 1.8 and 1.4 billion years ago.

A supercontinent is a single mass that gathers nearly all the world's land. Columbia, also called Nuna, is the earliest one that geologists can map coherently. Continental blocks collided and welded together along mountain belts, called orogens, and formed this mass between 1.8 and 1.4 billion years ago. Geologists suspect earlier assemblies, but these have left too little rock to reconstruct. Geologists reconstruct Columbia in two ways. They match orogens of the same age across blocks that are now separated. They also measure the direction of the magnetism that the rocks of each block acquired when they formed and have kept since. This direction records the latitude at which the block then lay.

Why it matters

Supercontinents have assembled and broken up repeatedly, a succession called the supercontinent cycle. Columbia is the first occurrence of this cycle that geologists can reconstruct. The cycle went on to pace climate, sea level and evolution for the rest of the planet's history.

Dating & uncertainty

The arrangement of the blocks varies between reconstructions, because palaeomagnetic poles are sparse for this age. Such a pole is the position of the magnetic pole deduced from old rocks. The reconstructions place the assembly between 1.9 and 1.58 billion years ago and the break-up around 1.45 to 1.38 billion years ago. Several cratons, old stable blocks of crust, remain unplaced.

Earth history as one day

14:29:049 h 31 min before midnight

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