How Long Does Geology Take?
Geological change can occur quickly, if conditions are right, affecting life and civilization.
How long does it take for geological changes to occur? It depends on the type of change. Glaciers and continents move slowly, but a major asteroid strike could change a whole world instantly. Here are some news items to bear on the question of rapid vs slow change in geology and in a field dependent on geological change, biogeography.
Africa is splitting in two (Phys.org). Mention “geological time,” and what comes to mind? Usually, those charts with cumbersome names like Paleozoic, Pleistocene or Jurassic, with their side columns showing life evolving over millions of years. In Africa, though, geologists are watching a big, sudden change: “A large crack, stretching several kilometres has made a sudden appearance recently in south-western Kenya, as reported by BBC news.” The new rift is 50 feet deep and 50 feet wide, and still growing. More significantly, this article admits that geologists do not understand the forces behind plate tectonics. Live Science reporter Laura Geggel tries to fit the observation into conventional wisdom about plate tectonics, but an ounce of real-time observation is worth a pound of theory. Phys.org relays the thoughts of the lead geologist about the reliability of plate tectonics theory:
Dr. Lucía Pérez-Díaz, Postdoctoral Researcher, said: “The Earth is an ever-changing planet, even though in some respects change might be almost unnoticeable to us.
“Plate tectonics is a good example of this. But every now and again something dramatic happens and leads to renewed questions about the African continent splitting in two.”
The moyboy experts quoted in the article do not doubt slow geological change over “tens of millions of years.” The end of the article, though, mentions “sudden motorway-splitting faults or large earthquakes” as examples of “dramatic events” that have occurred. These having the advantage of eyewitness testimony. Nobody has witnessed a million years.
River’s evolution unfolds with fresh mix of dating techniques (Science Daily). Lab experiments with flumes (artificial channels where flow rates and sedimentation can be controlled) are changing ideas about river evolution. Even though the authors believe that the Lower Moulouya river in northeast Morocco took over a million years to achieve its present shape, there were surprises. Climate, for instance, was much less a factor than tectonic change. A big enough tectonic event could be quite rapid. The scientists determined that some deposits were younger than a million years old. This should be surprising in a world they believe is older by three orders of magnitude. The forces they describe could have taken place quickly:
At a regional scale, several indicators point to transient fluvial response resulting from major tectonic activity in this area, especially rock uplift in the Beni Snassen massif.
The latter strongly influenced drainage organisation, and therefore landscape evolution, in northeast Morocco.
The most striking feature of this drainage changes is the formation of a spectacular 30km-long gorge, which deeply cut the carbonate formations of the Beni Snassen massif, as a probable result of river piracy event(s), which made the Moulouya flow in its current direction towards the Mediterranean Sea.
Biogeographical and Ecological Change
Spider ‘Ballooning’ Flight With Silk Caught on Video (National Geographic). Spiders can be world travelers. We tend to think that a spider cannot migrate very far, but think again. Sarah Gibbons writes, “By releasing a silky sail, the crawlers can ‘balloon’ far distances—sometimes over entire oceans.” Tests of this phenomenon under controlled conditions showed that large numbers of spiders are jet setters:
The behavior Cho observed was “highly developed,” he says. He gathered that there are “big numbers of spiders doing this accurately.”
Before takeoff, the spiders prepared, like any good pilot would do.
Sticking out a front, hairy leg, the spiders tested wind speeds. In his lab, Cho was able to manipulate speeds and found that the spiders typically didn’t take off until speeds were lower than three meters per second.
Species hitch a ride on birds and the wind to join green roof communities (Science Daily). People who grow gardens on rooftoops and on high-rise buildings have found a surprise: species showing up they didn’t plant. This was surprising, given that the habitats are remote and harsh. “New research suggests that species that live on green roofs arrived by hitching lifts on birds or by riding air currents,” this article says. There seems to be a form of “aerial plankton” that allows mites, springtails (tiny insect-like creatures), bacteria and fungi and soil organisms to get up to these habitats, implying that they can also spread quickly over vast distances through these carriers.
Wildlife haven of Sulawesi much younger than first thought, according to new research (Phys.org). Another phenomenon gets dated down from previous assumptions (notice the Tontological headline?). Even using evolutionary assumptions, dates were off by an order of magnitude for the ecology of an island in southeast Asia.
The results reveal that though each species most likely arrived on what is now the island of Sulawesi at different times over the past 13 million years, all of them began to spread across the island simultaneously about 1-2 million years ago. This timing exactly coincides with geological evidence for the emergence of the arms of the island from the ocean. This coincidence indicates that the highly biodiverse and endemic ecosystems of Sulawesi have been assembled over a far more recent time frame than previously thought.
Parts of the Amazon thought uninhabited were actually home to up to a million people (Science Daily). This update to a surprise reported earlier (02 Sept 2008, 2 March 2017) provides another example of relatively rapid ecological change. The “untamed jungles” of legend, with primitive stone-age peoples inhabiting them, need to yield to new discoveries of complex civilizations that lived there not that many centuries ago. This was true in the Angkor Wat region of Cambodia, and is now turning out to be the case in Amazonia. Discoveries of earthworks called geoglyphs deep in the Amazon Basin are showing that “Parts of the Amazon previously thought to have been almost uninhabited were really home to thriving populations of up to a million people, new research shows.” One research team member says with Tontological spin, “Our research shows we need to re-evaluate the history of the Amazon.” See Live Science for some aerial photos of the “mysterious geoglyphs.”
Divided by DNA: The uneasy relationship between archaeology and ancient genomics (Nature). This thought-provoking article, which might be called “archaeology vs genomics,” has more to say about philosophical assumptions behind scientificclaims than the claims themselves. Reporter Ewen Callaway remembers how reluctant archaeologists were to embrace radiocarbon dating in the 1970s, when it upset conventional theories about dates of artifacts and civilizations. Is a similar battle happening now because of the next “transformative technology” of genomics? Genetic comparisons of people at archaeological sites is pointing to widespread migration and genetic mixing that was unexpected, sometimes indicating movements of whole populations over large distances. Archaeologists don’t want to be seen as Luddites rejecting these findings, but they also don’t like the attitude of some geneticists who think DNA answers every question. David Reich of Harvard, a pioneer of genetics research of archaeological remains, puts it this way with a cordial snicker:
Reich concedes that his field hasn’t always handled the past with the nuance or accuracy that archaeologists and historians would like. But he hopes they will eventually be swayed by the insights his field can bring. “We’re barbarians coming late to the study of the human past,” Reich says. “But it’s dangerous to ignore barbarians.”
Taking the long term view, we should recognize that Rome’s barbarians were supplanted by later migrants who were barbarians to them, and so on. So which barbarians have the whole truth? Will today’s civilized scientists be invaded by a new generation of barbarians in the future? Sometimes barbarians are wiser than the conquered.