Not
to be confused with Kennerland, a theme park (based on a toy company) I just
made up when I stumbled across the name of this supercontinent.
Kenorland
was one of the earliest supercontinents, having formed about 2.72 billion years ago. It accreted some
cratons that already existed, but also found some new continental crust to
merge with. Pieces of it would later become Laurentia (most of North America
and Greenland), Baltica (todays’ Scandinavia and Baltic regions), Yilgarn
(Western Australia), and Kalaharia (large portions of South America and
Africa).
It is
known that Kenorland sat in low latitudes until great underground magma surges
started to cause tearing of the crust about 2.48 billion years ago. At about
that time, Baltica straddled the equator and was connected to Laurentia
(Canadian Shield), Kola and Karelia (2 pieces that have since rejoined with
Baltica).
It is
thought that the breakup of Kenorland may have been when the Earth shifted from
tearing caused by magma plumes to the modern plate tectonics we know today.
However, the discovery of an earlier continent and a supercontinent may
indicate this transition occurred even earlier.
By
2.45 billion years ago, Yilgarn (Western Australia) was no longer connected to
the other cratons, and Kola and Karelia cratons were also drifting away.
Therefore, there was longer a supercontinent, and this was about the same time
as the Huronian glaciation, which lasted up to 60 million years. Indications
are that atmospheric oxygen rose from 0.1% to 1%. This increase in oxygen
caused the virtual disappearance of the gas methane, which was oxidized into
carbon dioxide and water.
Furthermore,
the breakup of Kenorland generally increased continental rainfall, reducing the
other greenhouse gas, carbon dioxide. Also, the solar output at that time was
less than 85% of its current power, and all these circumstances together
produced a runaway “Snowball Earth”, where average temperatures planet-wide
fell to below freezing.
Wow,
that’s a pretty drastic response to a supercontinent not being able to hold
itself together.
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