Plate Tectonic Supercycle (Supercontinents)

Early Earth was a molten mass of rock that gradually cooled enough for a crust to form. This early crust was probably a single unbroken plate - like that of Venus.
The first appearance of plate tectonics was about 3 billion years ago. This is the time when the granite and the greenstone belts formed the building blocks of today's continents. The rise of the continents and the beginning of subduction was the start of the plate tectonic Supercycle (also known as the Wilson cycle).
The Plate tectonic Supercycle has become one of geology's most important concepts. The construction of supercontinents followed by their break-up and dispersal has influenced the timing of major events in Earth's evolutionary and climate history. This cycle has altered the composition of the geosphere, atmosphere, hydrosphere and biosphere over geologic time.

Cratons, Continents and Supercontinents

Cratons

Are stable masses of ancient continental crust that were formed mostly in the Archean. They consist of shield (see diagram below), where ancient rock is near the surface, and a platform, where sedimentary rock covers the shield. The stable interiors of today's continents are built from cratons therefore many calls them the continental building blocks.

Continents

Are areas of land often made up of several continental cratons as well as younger Phanerozoic fold belts have been added through plate convergence and collision. If a large area of land does not contain a craton, it is considered a continental fragment. An example of this is Madagascar, which has broken off from eastern Africa.

Supercontinents

Are giant landmasses composed of all or most of the Earth's continental continents. The most recent of these was Pangaea.

Stages of the Plate Tectonic Supercycle

Its formation is a repeating cyclic process.
Heat builds up under the supercontinent, causing doming and rifting that break the supercontinent apart.
The continents disperse a new ocean bases form and oceanic crust is subducted in other locations.
The continetn eventually reach maxiumum dispersal with wide oceans around the globe. The ocean contract, islands arcs collide with continents and continents amalgamate, forming fold mountains belts such at the Himalayas - the cycle begins again.
It appears that the cycle ranges from 500 million years to 700 million years.

The Plate Tectonic Supercycle and its Effect on the Climate

The links between stages of theis cycle and climate are numerous. Over the course of Earth's history, climate as classified as being either icehouse climate (cold climate continental glaciations and cold inland deserts) or greenhouse climate (warm climate). The connections between these two climates are in the table below. The period of cycle varies but it is approximately 440 million years long.

Past Supercontinents

Palaeomagnetic data shows how the continental cratons have moved about Earth and where they were located at different points in time. This gives us an indication of the several supercontinents that formed and broke apart before Pangaea.
The rocks offer evidence of events in the supercycle. Continental convergence at the end of the cycle leads to folded igneous and metamorphic rocks. Rifting during the break-up of a supercontinent leads to basalt dykes (columnar basalt). The folded remains of mountain belts are 50-100 million years older than the basalt dykes because the supercontinent had to form (folds) before it could rift apart (dykes).

From the palaeomagnetic and geological evidence, we know that at least 5 supercontinents formed in the past (see below) The original continent Ur, is not included in the list because many geologists do not consider it to be a supercontinent as it was smaller than the size of Australia.

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