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September 26, 2022

Are Rocks Living Things

featured image thumbnail for post Are Rocks Living Things

Although this sounds like the most boring topic in the world... it turns out rocks a pretty freakin cool!

As you probably already suspect, rocks are scientifically considered non-living things. Aka rocks are not alive and have never been alive.


Did you know there are rocks that GROW?

There are rocks that grow UP, and grow DOWN, and even rocks that grow IN WATER!

That's the really interesting part, rocks can grow but still not be considered living. Why is that?

Let's find out!

Why Is A Rock Not A Living Thing?

Pink Stacked Rocks

Pink Stacked Rocks

To be considered a living thing, there are a few requirements that need to be met.

  • Having an organised structure
  • Requires energy
  • Responds to stimuli
  • Capable of growth

At first glance it may seem like rocks don't meet any of these requirements... but they actually meet two!

Having An Organised Structure

The structure of a rock isn't nearly as organized as the structure crystal.

Rocks by their very nature can't be very structurally uniform because they are combination of lots of different materials.

Cave rocks are usually composed of minerals such as calcite, aragonite, opal, chalcedony and others.

But as far as natural systems go, the composition of rocks is fairly structured and therefore actually satisfies this requirement.

Capable of growth

We normally think of rocks as strating off HUGE and slowly erroding over time.

And while mountains and stones erode over many thousands and even millions of years, rocks grow at a very similar rate!

As Science Focus puts it:

"Limestone stalactites form extremely slowly – usually less than 10cm every thousand years – and radiometric dating has shown that some are over 190,000 years old. Stalactites can also form by a different chemical process when water drips through concrete, and this is much faster."

It's just that you can't feed them a bunch of cookies and expect to get a boulder.


What Rocks Can Grow?

Stacked Rocks & Sunshine

Stacked Rocks & Sunshine

There are 3 types of rocks that "grow."

Cave Rocks

If you've ever been in a cave before, you've probably seen rocks that can grow!

Rocks can grow in caves because water flowing along walls or dripping from the ceiling leaves behind minerals along the cave wall or floor.

If a rocks is formed by this dripping water grow DOWN then they are called stalactites. When they grow UP from the floor they are called stalagmites.

"These rocks MIGHT grow up taller than you!" <-- This is an easy way to remember that stalagmites are the ones that grow up from the floor.

Spring Rocks

There is a rock called Travertine grows at springs where water flows from underground onto the surface.

"Huge travertine formations are often found around hot springs because warmer water holds more minerals than cooler water" said Cory BlackEagle, a geologist at the University of Kentucky in Lexington.

It's unlikely that you've ever seen Travertine before. If you have, it was probably at Yellowstone National Park's famous Mammoth Hot Springs.

The springs are only about 8,000 years old, but its travertine deposits are over 239 feet thick and cover more than 1.5 square miles of land!

Coral Rocks

Coral is a bit tricky, because what most of us think of as rock is actually a dead animal.

Wild right?

As Florida's National Oceanic & Atmospheric Administration explains it

"With their hardened surfaces, corals are sometimes mistaken as being rocks. And, because they are attached, “taking root” to the seafloor, they are often mistaken for plants. However, unlike rocks, corals are alive. And unlike plants, corals do not make their own food. Corals are in fact animals.

The branch or mound that we often call “a coral” is actually made up of thousands of tiny animals called polyps. A coral polyp is an invertebrate that can be no bigger than a pinhead to up to a foot in diameter. Each polyp has a saclike body and a mouth that is encircled by stinging tentacles. The polyp uses calcium carbonate (limestone) from seawater to build a hard, cup-shaped skeleton. This skeleton protects the soft, delicate body of the polyp."

So while coral may FEEL like a rock, and even LOOK like a rock... it's not. But we wanted to include it in the section because most people think of it as a rock.

Do Rocks Have Living Organisms?

More Pink Stacked Rocks

More Pink Stacked Rocks

Rocks themselves don't have any living parts, and the things that live in rocks are far from any animals we'd recognise.

The most common organisms you'd find are called endoliths.

There are thousands of known species of endoliths, including members from Bacteria, Archaea, and Fungi.

Many endoliths are autotrophs. Autotrophs can make their own organic compounds by utilizing gas or dissolved nutrients from water moving through fractured rock.

Are Rocks Considered Dead?

Amazing Stacked Rocks

Amazing Stacked Rocks

Non-living is diffferent than being dead. If something is dead, then by definition it had to be alive at some point.

Since rocks and considered non-living, they can't die.

Rocks aren't considered dead because they've never been alive.

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