Rock of ages

No one minds me calling a billion years an age, do they?

Earth, the third rock from the sun (I loved that show), is ~4.6 billion years old, the sun a bit older. (Exact estimates vary, of course.)  In that time, lots has happened.  The sun grew about 30% hotter (and it's not done).  The Earth cooled from the heat of collapse as it coalesced out of the primordial material of the pre-solar system. Oceans and atmosphere formed. Life emerged. In time, oxygen-producing life evolved and totally changed the atmosphere.

Interesting things keep happening. Radioactive decay keeps the core hot and drives plate tectonics. Carbon-bearing rock disappears into the inter-plate subduction regions, and is returned to the atmosphere by volcanic eruptions. Continents drift, also driven by plate tectonics. There's erosion, and mountain building, and sedimentation. Ice ages come and go.

Oh yeah: early in Earth's history, a Mars-sized object smashed into our planet, melted the top many miles of Earth's surface, and blasted enough stuff into space to re-coalesce as the moon. 

And on, and on. 

In short, Earth is a complicated place. Geoscience, this month's theme at the Year of Science, deals with this very complex amalgam of physics, biology, and chemistry. After I harped at the non-science of recent months' YoS themes, I'm happy to see a real science recognized this month. Check it out.

And don't miss this six-minute video that introduces geoscience and has some absolutely stunning imagery. Earth is a beautiful place.