Another birthday - Old As Dirt?

- A little science and reflection.

So, how old is dirt?

I wanted to know. After all if I was going to be thought of as being older than dirt I wanted to know how old that was.

First of all, Earth didn’t start off with dirt. Earth started off with rock. Everything melted and solidified as rock. No dirt. So, dirt is not 4.5 billion years old as the age of the Earth is thought to be.

To start with we need to understand just what dirt is. One definition I found says, “Dirt is another name for soil. Soil is a natural, constantly-changing substance that is made up of minerals, organic materials, and living organisms.” So, dirt can’t be that old. It is constantly being renewed.

For the first dirt to come into existence there had to be rock, then organic material which means that here had to be living things. But what about the stuff on the moon or Mars where no organic material exists? This fine powdery stuff isn’t like Earth’s soil. It is basically ground rock. The rock on these places was ground up by impacts. Things falling in from space at high rates of speed broke up the rock over and over again until it was pulverized into a fine powder. That process was going on as the planets formed, so as soon as the planet was cool enough to stop melting the minerals the “dirt” started to accumulate. That “dirt” is about 4.5 billion years old.

But when saying “older than dirt” we are talking about Earth’s dirt. That’s different stuff. True, impacts had a part in making Earth dirt, but Earth has weathering processes, glaciers, and plate tectonics, volcanoes and earthquakes, things that change the surface dramatically. The original dirt was remixed, reheated and compressed and made into new rocks. Our dirt isn’t as old as Mars’ dirt. And I’m not a Martian (I don’t think) so my dirt isn’t as old.

Even Earth’s rocks aren’t that old. The rocks constantly go through changes from heat and pressure. Really old rocks are hard to find. The oldest rock found supposedly is a zircon crystal dated to 4.4 billion years found in Australia. Pretty rare. Most rocks just aren’t that old.

Dirt or soil is being made new everyday. Just like humans are new every day. So, yeah, I’m old as dirt. And so are you. So there!.

....and, for the picky, I know, it's not "dirt" without organic matter, so, no, the stuff on Mars is not technically dirt.