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Salts included in the Earth's early ocean

We all know that salt is a big part of the ocean water today. Two things help scientists figure out what chemicals may have been part of the Earth's early oceans. Igneous rocks are made of iron, aluminum, silicon, and magnesium (the silicates), and these components are easily destroyed by acids. There are very little sedimentary rocks of ages older than 2.5 billion years (see geologic time). (The absence of sedimentary rocks leads scientists to a number of hypothesis, either
  • 1.) there must have been mostly igneous rocks at the beginning of time
  • 2.) maybe the Earth was covered with water everywhere such that change of igneous to sedimentary rock took a long time (turbulent action in rivers and streams is required to break igneous rock apart).
  • 3.)possibly sedimentary rocks were destroyed by metamorphism in the early days rather than as today by erosion.
So igneous rocks must have been the only rocks around.)

Anyway, in an environment with no oxygen such as that of the early Earth, the waste products of erosion by acid, namely chlorine and iron from the rocks and the acid, had no where to go but to accumulate in the ocean. Thus the early ocean was full of chrorine and iron.

What induced a change into this environment was the introduction of free oxygen due to the photosynthetic activity of early bacteria. Free oxygen is an agent of change, ready to attack other molecules and react with them. In the early ocean environment, oxygen attacked iron.

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