The, Not So, Good Old Days 

As geologists we know that the Earth changes over time. If it didn't geology would not exist! But THIS ARTICLE gives some indication as to how much it has changed.

The author, a geochemist at Cambridge, describes her conclusions from analysing very old rocks from South West Greenland.

And she concludes that for a long period the Earth did not have a solid crust - it was an ocean of molten magma. The article describes the conclusions and tells us that these came from measuring isotopes of iron. You can read all about these in THIS PAPER. Some of you may understand it!

An important mineral in the paper, and the lower mantle, is bridgmanite - a mineral with which I was not familiar. Apparently it is what I knew as perovskite. Perovskite is a structure rather than a mineral and a mineral can only have a name if it exists on the surface of the Earth. Then it was found in a meteorite and it could be named! You can read all about it HERE.

The Earth is now composed of the inner core, the outer core, the lower mantle, the upper mantle, and the crust. AlexLMX/Shutterstock.

The very early Earth was not like this at all!