Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

As waters clear, scientists seek to end a muddy debate

17.12.2007
Geologists have long thought muds will only settle when waters are quiet, but new research by Indiana University Bloomington and Massachusetts Institute of Technology geologists shows muds will accumulate even when currents move swiftly. Their findings appear in this week's Science.

This may seem a trifling matter at first, but understanding the deposition of mud could significantly impact a number of public and private endeavors, from harbor and canal engineering to oil reservoir management and fossil fuel prospecting.

"Mudstones make up two-thirds of the sedimentary geological record," said IU Bloomington geologist Juergen Schieber, who led the study. "One thing we are very certain of is that our findings will influence how geologists and paleontologists reconstruct Earth's past."

Previously geologists had thought that constant, rapid water flow prevented mud's constituents -- silts and clays -- from coalescing and gathering at the bottoms of rivers, lakes and oceans. This has led to a bias, Schieber explains, that wherever mudstones are encountered in the sedimentary rock record, they are generally interpreted as quiet water deposits.

"But we suspected this did not have to be the case," Schieber said. "All you have to do is look around. After the creek on our university's campus floods, you can see ripples on the sidewalks once the waters have subsided. Closely examined, these ripples consist of mud. Sedimentary geologists have assumed up until now that only sand can form ripples and that mud particles are too small and settle too slowly to do the same thing. We just needed to demonstrate it that it can actually happen under controlled conditions."

Schieber and IU graduate student Kevin Thaisen used a specially designed "mud flume" to simulate mud deposition in natural flows. The oval-shaped apparatus resembles a race track. A motorized paddle belt keeps water moving in one direction at a pre-determined speed, say, 26 centimeters per second (about 0.6 miles per hour). The concentration of dispersed sediment, temperature, salinity, and a dozen other parameters can be controlled. M.I.T. veteran sedimentologist John Southard provided advice on the construction and operation of the mud flume used in the experiments.

For their experiments, the scientists used calcium montmorillonite and kaolinite, extremely fine clays that in dry form have the feel of facial powder. Most geologists would have predicted that these tiny mineral grains could not settle easily from rapidly moving water, but the flume experiments showed that mud was traveling on the bottom of the flume after a short time period. Experiments with natural lake muds showed the same results.

"We found that mud beds accumulate at flow velocities that are much higher than what anyone would have expected," said Schieber, who, because of the white color of the clay suspensions, calls this ongoing work the "sedimentology of milk."

The mud accumulates slowly at first, in the form of heart- or arrowhead-shaped ripples that point upstream. These ripples slowly move with the current while maintaining their overall shapes.

Understanding how and when muds deposit will aid engineers who build harbors and canals, Schieber says, by providing them with new information about the rates at which mud can accumulate from turbid waters. Taking into account local conditions, engineers can build waterways in a way that truly minimizes mud deposition by optimizing tidal and wave-driven water flow. Furthermore, Schieber explains, the knowledge that muds can deposit from moving waters could expand the possible places where oil companies prospect for oil and gas. Organic matter and muds are both sticky and are often found together.

"If anything, when organic matter is present in addition to mud, it enhances mud deposition from fast moving currents," he said.

The finding feels like something of a vindication, Schieber says. He and his colleagues have (genially) argued about whether muds could deposit from rapidly flowing water. Schieber had posited the possibility after noting an apparent oddity in the sedimentary rock record.

"In many ancient mudstones, you see not only deposition, but also erosion and rapid re-deposition of mud -- all in the same place," Schieber said. "The erosive features are at odds with the notion that the waters must have been still all or most of the time. We needed a better explanation."

David Bricker | EurekAlert!
Further information:
http://www.indiana.edu

More articles from Earth Sciences:

nachricht Filling the gap: High-latitude volcanic eruptions also have global impact
20.11.2017 | Institute of Atmospheric Physics, Chinese Academy of Sciences

nachricht Antarctic landscape insights keep ice loss forecasts on the radar
20.11.2017 | University of Edinburgh

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>