Tag Archives: limestone

Comparison theory experiment.

The Pentagon is one huge pile of ancient bugs, but don’t start evacuating just yet

New research shows that several famous buildings including the Pentagon in the US or the British Museum in London are giant heaps of microbes. No, really.


Variations of size and sorting of ooids.
Image credits Batchelor et al., 2017, Scientific Reports.

The one thing these buildings have in common is that they were erected using a special kind of rock called oolithic limestone. It gets this name from the tiny carbonate (CaCO3) beads which make up the material — they resemble tiny eggs in shape, and the term ‘oolith‘ is drawn from the Greek word for egg. The rock resembles fish roe or tightly-packed styrofoam in texture and is a quality, highly appreciated building material. Its mineral composition lends the limestone hardiness, durability, and a pleasant color, while its oolithic texture makes it easy to cut and sculpt in any direction.

The traditional view is that these ooids form from grains rolling across ocean floors and collecting sediments as they go. When they grow too big for currents to move them along, these ooids stack and fuse together with carbonate material precipitated from the surrounding water. New research from the Australian National University (ANU), however, comes to propose a much buggier origin story for ooliths — using a mathematical model, scientists arrived at the conclusion that the ooids were made of mineralized microbes forming concentric layers.


Comparison theory experiment.

Comparison between the team’s simulated results and experimentally grown ooid.
Image credits Batchelor et al., 2017, Scientific Reports.

“Jurassic oolite in England has been used to construct much of the City of Bath, the British Museum and St Paul’s Cathedral,” said first author Bob Burne in a news release. “Mississippian oolite found in Indiana in the US has been used to build parts of the Pentagon in Virginia and parts of the Empire State Building in New York City.”

“We have proposed a radically different explanation for the origin of ooids that explains their definitive features. Our research has highlighted yet another vital role that microbes play on Earth and in our lives.”

The team used mathematical modeling to simulate how ooliths form and identify the most likely mechanism of their growth. The algorithms they used to simulate the process were based on systems designed to describe how brain tumors develop. The most likely process of oolith formation, the one that best explains their size and internal mineralization patterns, the team explains, is the mineralization or microbial biofilms — in short, the fossilization of microbes and bacteria.

This process would explain the strikingly ordered structures seen in ooids, with very cleanly-defined concentric layers around a central point. It would also explain why ooids have roughly consistent maximum sizes despite a plethora of different environmental condition across the world’s oceans — something which the previous hypothesis never really explained in a satisfactory manner. Burne thinks the results debunk the popular “snowball theory” that ooids were formed by grains rolling on the seafloor and accumulating layers of sediment.

The paper “A biofilm and organomineralisation model for the growth and limiting size of ooids” has been published in the journal Scientific Reports.

The ‘hottest’ 7 … hot springs

The idea for this article hit me while I was writing this post about awesome landscapes. I was doing some research, and when I found the amazing things hot water springs can create, it was obvious that this article had to come.

Grand Prismatic Spring

Measuring about 250×380 feet, and being the largest hot water spring outside of New Zealand, the Grand Prismatic Spring is definitely something worth gazing at.

It sits in Yellowstone, high on the top of a mound, and has some small terraces that highlight even better the amazing colours created by the bacteria inside the water.

The vivid colours are the result of pigmented bacteria; the colours range from green to red, depending on the amount of chlorophyll the bacteria has, as well as the temperature of the water.

Mammoth springs

While we’re still in Yellowstone, I just have to mention Mammoth springs.

The amazing springs that showcase terraces was formed due to the occurence of the typical elements: heat, water, limestone, and a fracture system.

Heat and water create the necessary force for the travertine terraces to appear (travertine is a form of limestone deposited by mineral springs and generally associated to hot springs).

Pamukkale springs

In Turkish, Pamukkale means “cotton castle” – and it’s quite easy to understand why.

It was created with pretty much the same elements as Mammoth Spring, but the aspect is not identical, because the deposition of the travertine depends on a number of factors, including weather, temperature, local geochemistry, etc.

Guelma spring

Located in Algeria, this hot water spring draws more and more people, despite the relatively remote area.

Here, you can practically see the travertine formations cascading down like waterfalls.

This happens because of the way it is formed. Initially, the mineral depositions are soft and jelly-ish (so to speak), but as time passes, they harden in whatever position they are left.

Blood Pond

The people who named it sure didn’t have to think a long time when they named it.

There are nine hot water springs in Beppu, and they’ve been nicknamed “hells”, due to the boiling water, and the Blood Pond is the “worst” of them. It’s also the nicest one to look at… at least if you ask me.

The Blue Lagoon

This Icelandic Blue Lagoon has been turned into a geothermal spa, due to the minerals in the water, such as silica and sulphur. These mineral rich waters are reputed to help people suffering from skin diseases.

Jigokudani Monkey Park

The name Jigokudani literally means Hell’s Valley – something with Japanese and hot water springs… can’t find a single one that’s not named hell.

The spring itself isn’t extremely spectacular, but the thing is, it’s famous due to a large population of Japanese Macaques, commonly known as snow monkeys. The smart rascals come down from the cold forests to take a warm bath… and who can blame them ?

Photo sources: 1 2 3 4 5 6 7 8 9 10 11 12 13