A time when the asthenoshere (or mantle) lost heat directly into atmosphere , then hydrosphere.

Mantle convection begins.

First attempts to form crust (hot, not very dense crust) subducted by fast moving shallow mantle convection.

Early mantle differentiation by mantle fractionation rather than plate tectonic which would not come about until the next period.

Based on the moon's geological record, the time before 4.0 BY was a time of massive meteorite impacts.

No rocks preserved from this period.

Oldest rocks are gneiss is 3.96 and 3.927 BY

Detrital zircon in archean sandstone and quartzite dates between 4.1 and 4.27 BY

Development of the Lithosphere begins. Heat lost from earth's surface differentiates into an upper lithosphere, somewhat cooler than the underlying asthenosphere, therefore more solid and more able to resists underlying mantle convection.

Crust, hotter-thinner and more buoyant than today's-formed from this lithosphere and broke into plates due to underlying mantle convection. Heat now lost mainly at plate margins.

Onset of oceanic hydrothermal activity (i.e., like modern black smokers) begins along with the first permanent formation of continental crust.

Rocks from this period are preserved in the following places

1. 3.8 BY Isua Group in Western Greenland
2. 3.5 BY mafic-ultramafic Jamestown ophiolite complex of the Barberton Belt in South Africa (syn-orogenic deposits such as turbidites, conglomerates and sandstones)
3. 3.5 BY tholeiitic komatiitic lavas and calc-alkaline pyroclastics of the Warrawoona Group in the Pilbara block (oceanic and island arc lavas) in Western Australia. Also has shallow water, passive margin deposits of stromatolitic evaporites)
4. 3.5 BY greenstone lavas of the Pietersburg belt in South Africa
5. Limpopo belt, Swaziland, South Arica (continental crust fragments)(also has shallow water, passive margin meta-quartzites, banded iron stone and meta-pelites)
6. Yilgarn block of Singhbhum craton of Western Australia (continental crust fragments)
7. Wyoming Province, USA (continental crust fragments)

Biochemical processes leave stromatolites, algal laminites, black chert, and microfossils)

Major Surge in Continental crust development recorded in abundat island arc greenstone deposits and in calc-alkaline orthogneisses of batholithic proportions.

With the development of continental plates began the formation of rifts, foreland basins, extension collapse orogens and onset of plate breakups by the end of this interval.

Continents developed in the following ways

Kaapvaal continent in South Africa

1. Intra-oceanic obduction (oceanic crust thrust upward and over oncoming plate) 3.7-3.2 BY
2. Amalgamation of oceanic terranes 3.3-3.2 BY
3. Progression of development types

1. passive margin types (Pongola Supergroup 2.94 BY)
2. cordilleran style accretion
3. Himlayan collision type (Limpopo Orogen 2.7 BY)
4. Foreland Basin (Witwatersrand 2.8 BY)
5. Extension basin collapse (Ventersdorp Supergroup 2.7 BY)
6. Continental stabilization (i.e., craton formation) (2.6 BY)

1. Shelf type sedimentation occurs yielding carbonates, quartzites, meta-pelitic mica schist and banded ironstone.

1. 3.05 BY Malene Supracrustals in western Greenland
2. Lewisian complex in Scotland
3. Western Yilgarn of Western Australia
4. Wyoming Province USA
5. Superior & Slave Provinces in Canada
6. Southern India

1. Final tectonic stage marked by continental flood basalts (2.77-2.69 BY Fortesque Group in Pilbara block in Western Australia) and a large number of intruded mafic dyke swarms (2.63 Matachewan swarm in Canada). These mark a failed attempt at continental plate development. Instead, these developments helped develop the continents by thickening and strengthening the continents in which they were emplaced.

1. This is a highly gradual and diachronous boundary.
2. No orogenic activity during this interval.
3. Extensive, stable supercontinent develps marking the end of the Archean Era
4. Margins of the supercontinent were passive margins while mafic dykes consolidated its at depth structure while, on its surface, sediments where laid down in its epicratonic basins and along lateral extensions forming the first platforms.
5. The change from the Archean to the Proterozoic is marked by the full development of large stable continents. These were thicker than before so that mantle heat flow was less than it was before. Also the composition of lavas changed from tholeiitic basalts mixed with salty seawater to calc-alkaline basalts implying a longer time of expose to mantle rocks. This is based on the sudden increase in the K₂O/Na₂O ratio (less Na and more K), the departure away from the mantle in ⁸⁷Sr/⁸⁶Sr ratio and other geochemical markers.

1. Mainly examples of mature and fractionated sediments forming rocks (orthoquartzite, orthoconglomerates, sandstones) overlain by carbonates (dolomite, stromatolitic dolomite).
2. These sediments were lain down in passive margin or rifts tectonic settings. These settings can only occur where continents are splitting.
3. Between 2.4 and 1.9BY first free oxygen develops in the atmosphere, The is seen in several ways.

1. change from red matrix (i.e., thorough marine oxidation) to red coated grains (i.e., rusting in the air)
2. development of hematite-rich paleosols
3. hematite rich ores on banded ironstones

1. Abundant evaporites after 1.9 BY
2. Presence of continents and changes in the atmosphere and hydrosphere mark reconrd from here on.

1. Continental growth through accretionary orogens is the source of continental growth. These orogens are made up of island arc and accretionary prism deposits.
2. Collisional orogens also aid in formation of supercontinent.
3. Volcanic and plutonic rocks derived directly from new mantle material rather than re-worked Archean rocks.
4. Accretionary orogens also contain high percentage of post-orogenic rocks remelted from rocks formed during the orogeny (granites from deep contiental crust). This helped thicken and consolidate growing continents.

1. On single large continent, sedimentation outside rift zones was non-marine.
2. Transgressions resulted in marine deposits along single continent's margins.
3. Mantle material rising held beneath beneath supercontinent reheat bottom of the continental crust yielding anorthosites, crustal melt granites and rhyolite ash flow fields. Reheating and mobilization of low continental crust by mantle material trapped beneath it is referred to as anorogenic magmatism.
4. Supercontinent made up of tectonic plates named as follows.

1. Siberia
2. Baltica
3. Amazonia
4. Arequipa-Belen massif
5. the West African craton
6. the Rio de la Plata craton
7. Laurentia
8. East Gondwana
9. the Elsworth/Whitmore mountain block of west Antarctica
10. Kalahari craton
11. Congo craton

1. Oceans at this time were as follows.

1. Adomaster Ocean
2. Brazilide Ocean
3. Mozambique Ocean

1. Subduction closures result in huge orogen in what is now eastern North America.
2. Island arc development was followed by various kinds of crustal thickening followed by extensional collapse.
3. Passes from North America to what is now Scotland as the Moine orogen, then to what is now Scandanavia as the Sveconorwegian orogen.

1. Proterozic supercontiental plates cluster around the South Pole.
2. Breakup of supercontinent gave rise to the separation of Baltica, Laurentia, most of Gondwana and Siberia from the remain tectonic plates. Continental shelf deposits develop on margins of Laurentia and Baltica.
3. Mozambique Ocean Also created. Its closing results in orogens that formed a second supercontinent.

1. Mozambique orogenic belt of East Africa
2. Dahomeyide orogen of West Africa
3. Braziliano orogen of South America

1. Many island arcs amalgamated by peripheral orogenies into the Arabian-Nubian Shield and the Avalonian-Cadomian Belt along the exterior margins of the supercontients.
2. Oxygen increases in the atmosphere and hydrosphere allows for several events in the evolution of life.

1. eukaryotes diversify
2. stromatolites decline
3. metazoa appear
4. later development of animals with hardparts

6.) Cluster of tectonic plates, hence the supercontinents, aropund the South Pole fosters glaciation episodes.

1. Proterozoic Supercontinents break up at the outset of the Phanerzoic.
2. Tectonic plates migrate and are welded together by several orogens yto form a new Supercontinent called Pangaea surrounded by a world ocean called Pahthalassa.
3. Supercontinent breaks up first into Gondwana and Laurasia, then into the various tectonic plates that are recognized today.

Convergence of many tectonic plates at the North Pole and Antartcia at the South Pole stimulates the development of the past glaciation.