Yesterday, we went on a site visit to the Bamburgh Research Project. It is a very interesting archaeological project with two main foci at present. We filmed at Bamburgh Castle and at the Bradford Kaims, a Prehistoric site which already seems to be extremely interesting!
So it would have come as a shock to Darwin to think the movement of the Earth’s continental plates could have been a major driver of evolutionary change in all life.
In our research, published this month in Gondwana Research, we suggest that the regular collision of tectonic plates over the past 700 million years has been a prime driver of evolutionary change on Earth.The essentials for life
We used laser technology housed in the Earth Science laboratories at the University of Tasmania to analyse more than 4,000 pyrite grains from seafloor mudstone samples collected from around the globe.
This enabled us to determine how concentrations of trace elements in the oceans have varied over the 700 million years. Trace elementsincluded copper, zinc, phosphorus, cobalt and selenium, which are necessary for nearly all life – from marine phytoplankton through to humans – to function.
The most surprising finding was that there were certain periods in Earth’s history when nutrient trace elements were highly enriched in the oceans, and other periods when levels of these critical trace elements were very low.
The nutrient-rich periods promoted rapid plankton growth in the short term, and this appears to correlate with periods of increased evolutionary change. An example of this is the rapid rise in trace elements preceding the Ediacaran (635 to 542 million years ago) and Cambrian (541 to 485 mya) periods, a time when multicellular animal life took off in a big way.
The Cambrian explosion, around 540 million years ago, is when most major groups of living animals appeared. This corresponds to a time when essential trace elements were peaking in the oceans, thus nutrient levels were very high.
The nutrient-poor periods caused depletion of plankton and promoted a slow-down in rates of diversification and ultimately could have played a role in three major mass extinction events. These occurred at the end of the Ordovician, Devonian and Triassic periods.
Although several possible explanations are given for these extinctions events, depletion in oceanic trace elements might be another plausible factor. Work is currently underway demonstrating that these events are tied to rapid declines in certain essential trace elements, particularly selenium.Plate tectonics and nutrient cycles
Nutrients in the oceans ultimately come from weathering and erosion of rocks on the continents. Weathering breaks down the minerals in the rocks and releases the nutrient trace elements, which nourish life. Thus when weathering and erosion rates increase for extended periods, more nutrients are supplied to the oceans.
In the long term of geological history, erosion rates rise dramatically during mountain building events caused by the gradual collision of tectonic plates.
Geologists have known since the 1960s that collisions of tectonic plates lead to the formation of huge mountain ranges. The Himalayas were formed when India, drifting northwards after splitting off from the supercontinent of Gondwana, slammed into Asia and pushed up the Tibetan Plateau. These collisions are called called orogenic events and their timing through Earth’s history is now well established.
Continued erosion eventually depletes the surface of nutrients, causing a drop in the ocean’s nutrients. This might have lead to extinction events in the seas.
This is the first time nutrient trace element curves have been developed that demonstrate the relationship between tectonic collisions and the generation of cycles of nutrients.
While the link between these nutrient cycles as drivers of evolution and factors in mass extinction events remains to be proven, it really makes us think about evolution in a broad sense. Plate tectonics and evolution both operate on the same time scale of millions of years, and it seems logical that they could be causally related.
The relationship between increased nutrients in the oceans with bursts of evolutionary change are clearly correlated for the early part of the cycles, but less clear is the correlation with the evolution of advanced land animals.Life out of the oceans
The origin of the first land animals, tetrapods about 370 million years ago, corresponds with a decrease in oceanic nutrients and a series of mass extinction events in the oceans. This could explain why certain sarcopterygian fishes with robust limbs left the seas when they did in order to leave the nutrient-poor ocean and make out on land.
But the first appearance of dinosaurs and mammals in the early Triassic, about 225 million years ago, has no correlation with trace element abundance.
Perhaps the cycles pertain mainly to biodiversity in the oceans. There is certainly a close correlation with the drop in nutrients and some global oceanic mass extinctions. These events are being tested and explored further in further research on selenium, to be released soon.Written by:
Ross Large – Distinguished Professor of Geology at University of Tasmania
John Long – Strategic Professor in Palaeontology at Flinders University
Marine scientists from Duke University, North Carolina State University and the University of Oregon discovered the wreck on July 12 during a research expedition aboard the Woods Hole Oceanographic Institution (WHOI) research ship Atlantis.
They spotted the wreck while using WHOI’s robotic autonomous underwater vehicle (AUV) Sentry and the manned submersible Alvin. The team had been searching for a mooring that was deployed on a previous research trip in the area in 2012.
Among the artifacts discovered amid the shipwreck’s broken remains are an iron chain, a pile of wooden ship timbers, red bricks (possibly from the ship cook’s hearth), glass bottles, an unglazed pottery jug, a metal compass, and another navigational instrument that might be an octant or sextant.
The wreck appears to date back to the late 18th or early 19th century, a time when a young United States was expanding its trade with the rest of the world by sea.
“This is an exciting find, and a vivid reminder that even with major advances in our ability to access and explore the ocean, the deep sea holds its secrets close,” said expedition leader Cindy Van Dover, director of the Duke University Marine Laboratory.
“I have led four previous expeditions to this site, each aided by submersible research technology to explore the sea floor — including a 2012 expedition where we used Sentry to saturate adjacent areas with sonar and photo images,” Van Dover said. “It’s ironic to think we were exploring within 100 meters of the wreck site without an inkling it was there.”
“This discovery underscores that new technologies we’re developing to explore the deep-sea floor yield not only vital information about the oceans, but also about our history,” said David Eggleston, director of the Center for Marine Sciences and Technology (CMAST) at NC State and one of the principal investigators of the science project.
After discovering the shipwreck, Van Dover and Eggleston alerted NOAA’s Marine Heritage Program of their find. The NOAA program will now attempt to date and identify the lost ship.
Bruce Terrell, chief archaeologist at the Marine Heritage Program, says it should be possible to determine a date and country of origin for the wrecked ship by examining the ceramics, bottles and other artifacts.
“Lying more than a mile down in near-freezing temperatures, the site is undisturbed and well preserved,” Terrell said. “Careful archaeological study in the future could definitely tell us more.”
James Delgado, director of the Marine Heritage Program, notes that the wreck rests along the path of the Gulf Stream, which mariners have used for centuries as a maritime highway to North American ports, the Caribbean, the Gulf of Mexico and South America.
“The find is exciting, but not unexpected,” he said. “Violent storms sent down large numbers of vessels off the Carolina coasts, but few have been located because of the difficulties of depth and working in an offshore environment.”
Bob Waters of WHOI piloted Alvin to the site of the newly discovered shipwreck after Sentry’s sonar-scanning system detected a dark line and a diffuse, dark area which they thought could be the missing scientific mooring. Bernie Ball of Duke and Austin Todd of NC State were aboard Alvin as science observers.
The expedition has been focused on exploring the ecology of deep-sea methane seeps along the East Coast. Van Dover is a specialist in the ecology of deep-sea ecosystems that are powered by chemistry rather than sunlight, and Eggleston studies the ecology of organisms that live on the seafloor.
“Our accidental find illustrates the rewards — and the challenge and uncertainty — of working in the deep ocean,” Van Dover said. “We discovered a shipwreck but, ironically, the lost mooring was never found.”
- CBA History
- Support Us
- Group Publications