Living Stalactites and Other Geological Surprises

Dripstones in caves can be made by microbes, some speleologists find.  That’s among several recent geological surprises.

Living Stalactites

Every tourist who has visited a limestone cave has been told that stalactites form when dripping water from the ceiling loses dissolved limestone.  What they haven’t considered seriously till now is the work of microbes in the process.  In Science Daily, new work by Swedish speleologists is reported showing that living cells have much more to do with cave formations than previously thought.  Microbes don’t just live on the dripstones; they actively participate in their formation.

According to traditional textbooks, dripstones are created by geological or geochemical processes with no influence from living organisms. But now scientists report that formation of dripstones can be a lot more complex than that: Sometimes microbes are responsible for the formation of these geological features.

The researchers from Denmark, Sweden and Spain have investigated dripstone formation in a Swedish cave and conclude that microbes play an active part in their formation.

Astrobiology Magazine reprinted the story.  The articles wandered off into space from there, wondering if life might exist in Martian caves.  Nothing was said about whether microbes speed up the process of dripstone formation.  The scientists have not asserted that all cave formations are worked on by microbes.  The extent and influence of microbial action, though, will have to be included as a factor in future explanations of speleothems (cave formations).

Learning from Giant Crystals

Those “mind-blowing” giant spears of gypsum in a Mexican cave named Naica are the subject of an article on PhysOrg about crystal shapes.  Juan Manuel García-Ruiz, a researcher from Spain, makes the argument in a new documentary that geological processes alone can create complex shapes once thought only possible by living organisms.

“For many years, it was believed that living organisms and crystalline minerals belonged to two separate worlds of symmetry, because life is able to create complex shapes with continuous curvature that were considered impossible as the product of mineral precipitation,” he explained.

So morphology has traditionally been used as a tool for biogenesis when searching for the oldest remnants of life on the planet or elsewhere—can we find evidence, in other words, of ancient biological molecules based on the morphology of shapes seen in the fossil record.

“We’ve demonstrated, however, that under similar conditions to the primitive earth, silica interacts with carbonates to form complex self-assembled purely inorganic structures with shapes that are indistinguishable from those considered to be remnants of the oldest life on Earth,” García-Ruiz said.

“This means that morphology alone can’t be used as the sole criterion for biogenecity,” he added. “We need to develop new analytical tools to reveal when life appears in this planet and if whether or not there is life elsewhere.”

Garcia-Ruiz thinks that inorganic crystallization might have led to life, but that is pure speculation.  Maybe, based on the first story (above), he should not so quickly discount the role of microbes in the crystals he studied.

Canyon Vanishing Act

A gorge created by a dam breach in Taiwan may be gone in 50 years, New Scientist says.  Right now, it’s 25 meters wide and 17 meters deep, but it’s changing fast.  This “vanishing river gorge shows geology in fast forward” —

Blink and this gorge will be gone. Normally, erosion takes thousands of years, but this river valley could vanish just 50 years after it formed, thanks to a new and rapid process called “downstream sweep erosion”.

The gorge a few decades from now will look like just a meandering river plain.  The article spoke of processes taking centuries or thousands of years, but did not mention millions of years.

The speed of the erosion is unusual, because geology is normally slow. A few geological events do happen quickly, such as islands forming after volcanic eruptions, landslides and floods from glaciers. But while the erosion of a gorge would normally take centuries, in Daan it will happen within a human lifetime. “It lets us monitor and study it in great detail,” says Cook.

Speaking of fast geology, Iceland is quaking with the possibility of an imminent volcanic eruption, the BBC News reported.

How long have scientists been studying caves without considering the possibility of microbial action?  This is a story some geologists not enslaved to gradualism may wish to look into.  Any physical or geological process can be sped up under the right circumstances.  What can we learn from giant crystals and other geological upsets?  We can learn that we need to unlearn some things textbooks say.