As they’re composed of mineral elements rather than DNA and cells, by definition, rocks can’t be considered living things, which suggests they’re also excluded from accepted living processes, such as reproduction, sensitivity, agency of motion, and growth.
Well, sure enough, the first three processes are strictly out of the question, but interestingly, the latter, growth, is something all rocks are capable of given the right circumstances — Amazing, right?
But that’s not to say they grow the way you or I do. For rocks, it’s a slow burn. Their growth can take millennia, or often even millions of years! How is this possible? Read on, and all stony secrets will be revealed.
How And Where Do Rocks Grow Larger?
There are a few different scenarios in which rocks will seemingly grow larger, so let’s break them down one by one!
Caves
The most astounding evidence of rocks growing taller and generally larger over time can be found in caves. You’ve heard of stalactites and stalagmites before, right?
You know the ones… those pointy rocks jutting from cave floors and ceilings; they look kind of like icicles.
These formations weren’t always present, rather, they developed, or “grew”, over eons of interaction with water. Now, that might raise more questions than it answers. For instance, how the heck does water help rocks to grow as if they’re blades of grass?
Well, the thing to understand about water is that it’s barely ever just good old H2O. As it flows over and through the Earth, it picks up trace elements of certain matter that it comes into contact with.
Eroded and dissolved, this matter hitches a ride in the water, which then, rather like a slug, leaves trails of the stuff in its wake.
The left behind remnants of these contaminants are known as deposits. Now, these deposits are extremely minimal, but over time, as long as water keeps flowing, they gradually build up, giving the impression of rock growth.
Water that drips from the ceilings and walls of caves forms stalactites, while water running across the cave floor produces stalagmites.
These intriguing rocks are composed almost exclusively of calcium carbonate picked up by water passing over limestone earlier in its journey.
Hot Springs
Rocks also appear to grow and thrive around hot springs. Once again, this is due to the interference of water.
The rocks in question are known as travertine, and they can be seen in jaw-dropping numbers anywhere that hot water flows from beneath the Earth onto the surface.
The prominence of their growth comes down, not simply to the presence of water, but the temperature of the water; allow me to elaborate…
Did you ever do that experiment in science class at school where you would time how long it took salt to dissolve in a beaker of cold water as opposed to a beaker of hot water?
Don’t worry if not; I’ll fill you in on the details now — The hot water wins! However, this isn’t just the case with salt, but pretty much any mineral.
What I’m saying here is that due to the heat of the water, it picks up an abundance of contaminants on its way to the surface, and once it breaches, exposure to air cools it, and the deposits are left behind, forming and building upon sprawling stretches of travertine.
The Bottom Of The Ocean
Flowing water doesn’t just pick up mineral particulates; it also eats away at metals as it plots its path of least resistance in accordance with gravity.
This metallic content of the sea or even fresh water can eventually precipitate (deposit in solid form from a solution), forming rocks referred to as nodules or concretions along the water bed.
Although this is a lesser-known fact, it’s not exactly an uncommon phenomenon — You’ll find iron, copper, cobalt, nickel, and manganese “cannonballs” on the floor of every ocean on the planet, as well as many riverbeds.
Much like pearls, they form layer after layer, steadily growing in mass.
But when I say “steadily,” I really mean steadily! For instance, nodules composed of manganese typically grow just shy of a centimeter every million years or so — Bonkers, right?
One of the most celebrated examples of the freshwater variant of concretion is found in numerous locations across southern Utah.
Known as the Moqui Marbles, oftentimes these magnificent formations are composed of a sandstone core surrounded by expanding shells of iron ore.
There are even confirmed microscopic spherical concretions on the surface of Mars, playfully referred to as blueberries.
How And Where Do Rocks Grow Stronger And Heavier?
When we grow, we don’t just get taller (or wider if it’s the holiday season), we also get stronger and heavier, and if conditions are just right, rocks can also become stronger and heavier.
This only occurs across the metamorphic rock class (one of the three primary rock types), as it’s this very process that categorizes them as metamorphic formations.
These rocks are defined by their transition from one form of igneous, sedimentary, or initial metamorphic rock into another rock type.
The engine of this miraculous transformation is intense heat, pressure, hot mineral-dense water, or a combination of these factors.
Exposure to these extremes over extended periods of time essentially forces the minerals involved closer together, the pressure eventually increasing the density of the formation.
This means that the new formation is heavier and more robust than the original rock, but it will have actually gotten a little smaller due to the compression of atoms.
Why Do Rocks Grow In My Yard?
If you spend an inordinate amount of time fishing rocks from your lawn and growing beds only to find new ones emerge the following year, don’t worry; you’re not going crazy, and you’re not alone.
People all over the world find that they have somehow grown rocks alongside their vegetables each harvest.
However, this sudden influx of rocks isn’t due to the formation of new specimens. It’s actually just the emergence of those that already existed below the Earth’s surface.
This process is known as uplift, and it’s simply the consequence of the shifting sections of Earth’s crust. Sometimes they pull apart, sucking in particulate matter of weathered stones, and other times they squeeze together, forcing stones back to the surface.
You can essentially think of this as very small-scale orogeny, which is the natural building of mountains.
Final Thoughts
As you now know, rocks do indeed grow, mostly due to the deposits left by flowing water, but they can also grow heavier and stronger when exposed to extreme heat or pressure; however, all rock growth takes place over a much longer time frame than the living world.