Why is evidence from the Precambrian era scattered and incomplete?
The Precambrian (pЄ) eon began 4.6 billion years ago and ended 541 million years ago. Despite lasting for 88% of geologic time, little is known about the eon for the following reasons:
Metamorphosing rocks: rocks underwent major metamorphosis due to extreme heat and pressure. These drastic changes make the origins of the rock hard to follow, often preventing a formal analysis.
The law of superposition: the older a layer of rock is, the further down it is located. Thus, Precambrian rock strata are located very far down and are difficult to access.
Volcanic activity: extremely hot magma and lava can melt the bottom of earth's crust, rendering difficult the examination of Precambrian rock.
Erosion: billions of years of erosion distorts and destroys Precambrian rocks and features.
Plate tectonics: the movement of continental plates can cause subduction (the pushing of a plate down into molten magma), destroying rock.
Lack of complex life for fossil evidence: multicellular life only began 600 million years ago. The lack of other soft-bodied organisms before this time impedes further discovery.