Blackwell Publishing
Precambrian Paleozoic Mesozoic Cainozoic
Cambrian 590 MYRBP Ordovician 438 MYRBP Silurian 438 MYRBP Devonian 408 MYRBP Carboniferous 360 MYRBP Permian 286 MYRBP

By the beginning of the Silurian the colonization of the land had begun. Crusts of algae at the water's edge had evolved into plants similar to modern mosses or liverworts. This had two important effects:

• the ground cover of plants protected the soil from erosion and enriched it with organic material.

• the chemical processes of many plants released oxygen into the atmosphere, opening up new possibilities for life out of water.

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