Sea Level Change

Sea Level Change

An Investigation of Historical Sea Level Change

For eight weeks beginning in November 2009, off the coast of New Zealand, an international team of 34 scientists and 92 support staff and crew on board the scientific drilling vessel JOIDES Resolution (JR) were at work investigating sea-level change in a region called the Canterbury Basin. It proved to be a record-breaking trip for the research team.

The JR is one of the primary research vessels of an international research program called the Integrated Ocean Drilling Program (IODP). This research took place during IODP Expedition 317.

IODP is supported by two lead agencies, the U.S. National Science Foundation (NSF) and Japan's Ministry of Education, Culture, Sports, Science, and Technology.

10% of World Population Lives Below 10 Meters

At present 10 percent of the world's population lives within 10 meters of sea level. Current climate models predict a 50-centimeter to more than one-meter rise in sea level over the next 100 years, posing a threat to inhabitants of low-lying coastal communities around the world.

What Drives Sea Level Change?

To better understand what drives changes in sea level and how humans are affecting this change, scientists are "looking to our past for answers and digging back as far as 35 million years into the Earth's history to understand these dynamic processes," says Rodey Batiza of the NSF's division of ocean sciences.

Four Drilling Records

From November 4, 2009 to January 4, 2010, the IODP research team drilled four sites in the seafloor. One site marked the deepest hole drilled by the JR on the continental shelf (1,030 meters), and another was the deepest hole drilled on a single expedition in the history of scientific ocean drilling (1,927 meters).

Another record was broken for the deepest sample taken by scientific ocean drilling for microbiological studies (1,925 meters).

A fourth record was achieved when the team recovered sediment from the shallowest water site (85 meters) ever drilled for science by the JR.

"This was one of only two JR expeditions that have attempted to drill on a continental shelf--this was not a routine operation for this ship," says co-chief scientist Craig Fulthorpe of the University of Texas at Austin, who led the expedition with co-chief scientist Koichi Hoyanagi of Shinshu University in Japan.

The unstable, sandy composition of the sediments and the relatively shallow water of the shelf environment present unique challenges for a floating drilling platform like the JR, which relies on thrusters to maintain position and requires special technology to accommodate wave motion.

"We never expected we would be able to drill this deep in such a difficult environment," says Fulthorpe.

The Canterbury Basin

Canterbury Basin is part of a worldwide array of IODP drilling investigations designed to examine global sea level changes during Earth's "Icehouse" period, when sea level was largely controlled by changes in glaciation at the poles.

Before Canterbury, IODP sea level change studies included sites near the New Jersey coast, the Bahamas, Tahiti, and on the Marion Plateau off northeastern Australia.

Canterbury Basin was selected as a premier site for further sea level history investigations because it expanded the geographic coverage needed to study a global process. It displays similar sequence patterns to New Jersey studies.

Data from both the Canterbury Basin and the New Jersey shelf IODP expeditions will be integrated to provide a better understanding of global trends in sea level over time.

What Influences Sea Level Change?

Global sea level has changed in the Earth's past; these changes are influenced by the melting of polar ice caps, which increases the volume of water in the ocean.

Locally, relative sea level can also change as a result of tectonic activity, which causes vertical movement in the Earth's crust.

Together, glaciation and tectonic forces create a complex system that can be difficult to simulate with climate models. This necessitates field studies like the Canterbury Basin expedition, say geologists, to directly analyze samples.

A Sediment Record of Sea Level Change

The Canterbury Basin expedition set out to recover seafloor sediments that would capture a detailed record of changes in sea level that occurred during the last 10 to 12 million years, a time when global sea level change was largely controlled by glacial/interglacial ice volume changes.

The research team also recovered samples documenting changes in ocean circulation that began when movements in Earth's tectonic plates separated Antarctica from Australia, creating a new seaway between the two continents about 34 million years ago.

Canterbury Basin is one of the best sites in the world for this type of survey because it is located in a tectonically-active region and therefore has a relatively high rate of sedimentary deposition, which, like the pages of a book, record detailed events in Earth's climate history.

A Sediment Record of 35 Million Years

Beyond breaking records, the IODP Canterbury Basin expedition achieved its goal of recovering a 10-million-year record of sea level fluctuations, with one drill hole extending back 35 million years.

Cores revealed cyclic changes in sediment type and physical properties (such as magnetic susceptibility) that are believed to reflect switches between glacial and interglacial time periods.

Even longer cycles were originally identified using seismic images generated using sound waves.

Understanding the relationship between these seismic "sequences" and global sea-level change is an important objective for post-expedition research, say expedition geologists.

The JR is operated by the U.S. Implementing Organization of IODP, which consists of the Washington, D.C.-based Consortium for Ocean Leadership, Texas A&M University, and Lamont-Doherty Earth Observatory of Columbia University.

Additional program support for the IODP comes from the European Consortium for Ocean Research Drilling (ECORD), the Australian-New Zealand IODP Consortium (ANZIC), India's Ministry of Earth Sciences, the People's Republic of China (Ministry of Science and Technology), and the Korea Institute of Geoscience and Mineral Resources .

source /http://geology.com/press-release/deepest-hole-in-oceanic-crust/

The Carbon Cycle Before Humans

Prerequisites for Geoengineering Earth's Climate

Geoengineering -- deliberate manipulation of the Earth's climate to slow or reverse global warming -- has gained a foothold in the climate change discussion. But before effective action can be taken, the Earth's natural biogeochemical cycles must be better understood.

Volcanoes Driving the Carbon Cycle

Two Northwestern University studies, both published online recently by Nature Geoscience, contribute new -- and related -- clues as to what drove large-scale changes to the carbon cycle nearly 100 million years ago. Both research teams conclude that a massive amount of volcanic activity introduced carbon dioxide and sulfur into the atmosphere, which in turn had a significant impact on the carbon cycle, oxygen levels in the oceans and marine plants and animals.

Oxygen Level Clues from Carbon-Rich Sediments

Both teams studied organic carbon-rich sediments from the Western Interior Seaway, an ancient seabed stretching from the Gulf of Mexico to the Arctic Ocean, to learn more about a devastating event 94.5 million years ago when oxygen levels in the oceans dropped so low that one-third of marine life died.

The authors of the first paper, titled "Volcanic triggering of a biogeochemical cascade during Oceanic Anoxic Event 2," reveal that before oxygen levels dropped so precipitously there was a massive increase in oceanic sulfate levels. Their conclusion is based on analyses of the stable isotopes of sulfur in sedimentary minerals from the central basin of the Western Interior Seaway, located in Colorado.

A Cascade of Biogeochemical Events

The researchers theorize that a massive amount of volcanic activity caused this sulfate spike, which triggered a cascade of biogeochemical events. More sulfate led to an abundance of the nutrient phosphorous, which allowed phytoplankton populations in the oceans to multiply. The phytoplankton thrived and then died. Their decomposing bodies depleted oxygen levels in the oceans, leading to the widespread death of marine animals.

The sedimentary burial of marine organic carbon during this event was so large, some prior studies hypothesized that it caused a decrease in atmospheric carbon dioxide levels. In the second Nature Geoscience paper, titled "Carbon sequestration activated by a volcanic carbon dioxide pulse during ocean anoxic event 2," the researchers tested the carbon dioxide drawdown prediction. By studying fossil plant cuticle material, they determined the amount of carbon dioxide in the atmosphere at the time the plants were growing. (The cuticle samples were collected from sites representing the western shore of the Western Interior Seaway, in present-day southwestern Utah.)

Ocean Anoxia and Atmospheric Carbon Dioxide

This work found that before the onset of ocean anoxia, the level of carbon dioxide in the atmosphere increased by approximately 20 percent. This significant increase is consistent with the volcanic activity invoked by the first Northwestern study (described above). The paleo-carbon dioxide reconstruction also detected two episodes of marked decrease in carbon dioxide levels -- up to 200 parts per million -- at the time of the early phase of marine carbon burial. This observation provides strong support for the carbon dioxide drawdown hypothesis.

"Our research highlights the previously unappreciated role that the sulfur cycle plays in regulating nutrient cycling, the carbon cycle and climate," said Matthew Hurtgen, assistant professor of Earth and planetary sciences in the Weinberg College of Arts and Sciences at Northwestern and lead researcher of the first study.

Accelerating the Modern Carbon Cycle

"These two complementary studies provide a much clearer picture of how the Earth's carbon cycle was dramatically affected by catastrophic natural events long ago," said Bradley Sageman, professor and chair of Earth and planetary sciences at Northwestern and a co-author of both papers. "Although these events played out over hundreds or thousands of years, the magnitude of the changes, in carbon dioxide levels for example, are similar to those of the last 150 years resulting from human influence on the carbon cycle. The evidence demonstrates that the modern carbon cycle has been accelerated by orders of magnitude."

The Author Team

The sulfur work reported in the paper "Volcanic triggering of a biogeochemical cascade during Oceanic Anoxic Event 2" was conducted by Derek D. Adams, a doctoral candidate in Hurtgen's research group. Adams is first author of the paper; Hurtgen and Sageman are the paper's other authors.

Richard S. Barclay, a doctoral candidate in Sageman's research group, is the first author of the "Carbon sequestration activated by a volcanic carbon dioxide pulse during ocean anoxic event 2" paper. Sageman also is an author, and the third author is Jennifer McElwain, a professor from University College Dublin who co-advises Barclay's research and is one of the originators of the cuticle analysis method.

source http://geology.com/press-release/carbon-cycle-before-humans/

How Old are the Andes Mountains

 

Earlier Fault Activation

The geologic faults responsible for the rise of the eastern Andes mountains in Colombia became active 25 million years ago-18 million years before the previously accepted start date for the Andes' rise, according to researchers at the Smithsonian Tropical Research Institute in Panama, the University of Potsdam in Germany and Ecopetrol in Colombia.

The Eastern Range is the Oldest

"No one had ever dated mountain-building events in the eastern range of the Colombian Andes," said Mauricio Parra, a former doctoral candidate at the University of Potsdam (now a postdoctoral fellow with the University of Texas) and lead author. "This eastern sector of America's backbone turned out to be far more ancient here than in the central Andes, where the eastern ranges probably began to form only about 10 million years ago."

Zircon and Pollen Analysis

The team integrated new geologic maps that illustrate tectonic thrusting and faulting, information about the origins and movements of sediments and the location and age of plant pollen in the sediments, as well as zircon-fission track analysis to provide an unusually thorough description of basin and range formation.

As mountain ranges rise, rainfall and erosion wash minerals like zircon into adjacent basins, where they accumulate to form sedimentary rocks. Zircon contains traces of uranium. As the uranium decays, trails of radiation damage accumulate in the zircon crystals. At high temperatures, fission tracks disappear like the mark of a knife disappears from a soft block of butter. By counting the microscopic fission tracks in zircon minerals, researchers can tell how long ago how long ago rocks began to be uplifted, or exhumed toward the earth surface.

Classification of nearly 17,000 pollen grains made it possible to clearly delimit the age of sedimentary layers.

The use of these complementary techniques led the team to postulate that the rapid advance of a sinking wedge of material as part of tectonic events 31 million years ago may have set the stage for the subsequent rise of the range.

Information for Oil and Gas Exploration

"The date that mountain building began is critical to those of us who want to understand the movement of ancient animals and plants across the landscape and to engineers looking for oil and gas," said Carlos Jaramillo, staff scientist from STRI. "We are still trying to put together a big tectonic jigsaw puzzle to figure out how this part of the world formed." 

This work was published in the Geological Society of America Bulletin in April 2009.

STRI, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Web site: www.stri.org.

Funding for this study: German Academic Exchange Service, Deutsche Forschungsgemeinschaft, Potsdam University, Universidad Nacional de Colombia, Instituto Colombiano de Petroleo, Smithsonian Tropical Research Institute.

Ref:  Mauricio Parra, Andres Mora, Carlos Jaramillo, Manfred R. Strecker, Edward R. Sobel, Luis Quiroz, Milton Rueda and Vladimir Torres. Eastern Orogenic wedge advance in the northern Andes: Evidence from the Oligocene-Miocene sedimentary record of  the Medina Basin, Eastern Cordillera, Colombia.  Geological Society of America Bulletin. 2009:

source http://geology.com/press-release/age-of-the-andes-mountains/   

Carbonatite Lava Flows

 

 

East African Rift Volcanoes

Science has unearthed the secret to what might have been alchemy at Oldoinyo Lengai volcano in Tanzania.

There, in the ancient East African Rift at a place known to local Maasai people as the Mountain of God, Oldoinyo Lengai spews forth carbon dioxide-laden lavas called carbonatites. The carbonatites line the volcano's flanks like snowballs.

The World's Only Carbonatite Eruptions

Oldoinyo Lengai is the only place on Earth where carbonatites currently erupt--and where carbon dioxide from a volcano doesn't vanish into thin air as a gas.

In a paper published this week in the journal Nature, scientists report the results of a study of Oldoinyo Lengai's volcanic gas emissions, sampled by the team during a carbonatite lava eruption.

How Carbonatite Magma is Produced

"We now know the origin of one of the most peculiar magmas on Earth," said William Leeman, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.  "These scientists have found that, based on new studies of the chemistry of gas emissions at Oldoinyo Lengai, a very small amount of melting of Earth's mantle, akin to that beneath mid-ocean ridges, can produce carbonatites."



The carbonatites consist of high amounts of carbon dioxide, some 30 percent. Unlike most lavas that are liquid at temperatures above 900 degrees Celsius (1,652 F), carbonatites are much cooler and erupt at only 540 degrees Celsius (1,004 F). However, they're extremely fluid, with a viscosity like that of motor oil.

Sampling Volcanic Gases

"We were able to collect pristine samples of the volcanic gases because Oldoinyo Lengai was erupting and under tremendous magma pressure at the time," said Tobias Fischer, a volcanologist at the University of New Mexico and lead author of the paper.  "There was minimal air contamination."

"The gases reveal that the carbon dioxide comes directly from the upper mantle, just below the East African Rift," said David Hilton, a geochemist at the Scripps Institution of Oceanography.

"These samples of mantle gases allow us to infer the carbon content of the upper mantle where the carbonatites are produced."

It's about 300 parts per million, a concentration virtually identical to that measured below mid-ocean ridges.

Nephelinite Magmas

The finding is significant, said geochemist Bernard Marty of the CNRS-CRPG (Centre National de la Recherche Scientifique-Centre de Recherches Pe'trographiques et Ge'ochimiques in France), "because it shows that these extremely bizarre lavas and their parent magmas, called nephelinites, were produced by melting of typical upper mantle minerals--which don't have a high carbon dioxide content."

Previous research, mainly based on laboratory experiments, suggested that a higher carbon dioxide content is needed to produce nephelinites and carbonatites.

High Sodium Magmas

"Oldoinyo Lengai magmas also contain an unusually high amount of sodium, up to about 35 percent," said Pete Burnard, a geochemist at CNRS-CRPG.

"It's this sodium content that makes the Lengai carbonatites solid rather than gas at the surface. At all other volcanoes on Earth, carbon dioxide 'degasses' into the atmosphere without forming the sodium-rich carbonatite magmas of Oldoinyo Lengai."

Not all Oldoinyo Lengai's carbon dioxide becomes carbonatite, however. Like other volcanoes, Oldoinyo Lengai does emit carbon dioxide into the atmosphere as a gas.

The scientists conclude that the upper mantle below the continents and the oceans is a uniform and well-mixed reservoir in which the compositions and abundances of carbon dioxide and other gases like nitrogen, argon and helium are essentially the same.

Hilton, Marty and Burnard are co-authors of the Nature paper.

The University of New Mexico Research Allocations Committee (RAC), Institut National des Sciences de l'Univers, Centre National de la Recherche Scientifque (INSU-CNRS), and Programme Intérieur de la Terre also funded the research.

source http://geology.com/press-release/carbonatite-lava-at-oldoinyo-lengai/ :/

Volcanic Tremors

Volcanic Tremors and Forecasting

 

    

   Eruptions

 

A New Explanation for Volcanic Tremors

University of British Columbia geophysicists are offering a new explanation for seismic tremors accompanying volcanic eruptions that could advance forecasting of explosive eruptions such as recent events at Mount Pinatubo in the Philippines, Chaiten Volcano in Chile, and Mount St. Helens in Washington State.

All Explosive Eruptions Preceded by  Tremors

All explosive volcanic eruptions are preceded and accompanied by tremors that last from hours to weeks, and a remarkably consistent range of tremor frequencies has been observed by scientists before and during volcanic eruptions around the world.

What Causes the Tremors?

However, the underlying mechanism for these long-lived volcanic earthquakes has never been determined. Most proposed explanations are dependent upon the shape of the volcanic conduit – the 'vent' or 'pipe' through which lava passes through – or the gas content of the erupting magma, characteristics that vary greatly from volcano to volcano and are impossible to determine during or after volcanic activity.

Published this week in the journal Nature, the new model developed by UBC researchers is based on physical properties that most experts agree are common to all explosive volcanic systems, and applies to all shapes and sizes of volcanoes.

"All volcanoes feature a viscous column of dense magma surrounded by a compressible and permeable sheath of magma, composed mostly of stretched gas bubbles," says lead author Mark Jellinek, an associate professor in the UBC Department of Earth and Ocean Sciences.

Tremors Caused by an Oscillating Magma Plug

"In our model, we show that as the center 'plug' of dense magma rises, it simply oscillates, or 'wags,' against the cushion of gas bubbles, generating tremors at the observed frequencies."

"Forecasters have traditionally seen tremors as an important – if somewhat mysterious – part of a complicated cocktail of observations indicative of an imminent explosive eruption," says Jellinek, an expert in Geological Fluid Mechanics. "Our model shows that in systems that tend to erupt explosively, the emergence and evolution of the tremor signal before and during an eruption is based on physics that are uniform from one volcano to another."

Understanding Problematic Tremor Origins

"The role of tremors in eruption forecasting has become tricky over the past decade, in part because understanding processes underlying their origin and evolution prior to eruption has been increasingly problematic," says Jellinek. "Because our model is so universal, it may have significant predictive power for the onset of eruptions that are dangerous to humans."

Research Leadership and Support

The research co-led by Prof. David Bercovici of Yale University and was supported by the Canadian Institute for Advanced Research, the Natural Sciences and Engineering Research Council of Canada, and the U.S. National Science Foundation.

Update 2011-02-25 4:00pm PST....
Sensational Headlines and Unnecessary Panic

Prof. Mark Jellinek says sensational headlines such as "Mt. Baker overdue to erupt" has taken his research out of context, potentially causing residents to panic over the "imminent" eruption of Mt. Baker.

"Mt. Baker is the youngest and second-most active volcano in the Cascade Volcanic Arc in Washington State. Based on its eruptive history, it is indeed overdue for an eruption, all Cascade volcanoes are," says Jellinek.

"However, in geological terms, 'overdue' does not equate 'tomorrow,' or 'next month.' Indeed, it could be 500 to 1,000 years before it's 'due' for an eruption."

"What's important for the public to note is that there are currently no precise ways of predicting such events, hence the relevance of our research into the mechanics underlying the the eruptive behaviour of volcanoes," says Jellinek 

.

source http://geology.com/press-release/volcanic-tremors/ :

East Africa's Great Rift Valley

Part I. The East African Rift System The East African Rift System (EARS) is one the geologic wonders of the world, a place where the earth's tectonic forces are presently trying to create new plates by splitting apart old ones. In simple terms, a rift can be thought of as a fracture in the earth's surface that widens over time, or more technically, as an elongate basin bounded by opposed steeply dipping normal faults. Geologists are still debating exactly how rifting comes about, but the process is so well displayed in East Africa (Ethiopia-Kenya-Uganda-Tanzania) that geologists have attached a name to the new plate-to-be; the Nubian Plate makes up most of Africa, while the smaller plate that is pulling away has been named the Somalian Plate (Figure 1). These two plates are moving away form each other and also away from the Arabian plate to the north. The point where these three plates meet in the Afar region of Ethiopia forms what is called a triple-junction. However, all the rifting in East Africa is not confined to the Horn of Africa; there is a lot of rifting activity further south as well, extending into Kenya and Tanzania and Great Lakes region of Africa. The purpose of this paper is to discuss the general geology of these rifts are and highlight the geologic processes involved in their formation. What is the East Africa Rift System? The oldest and best defined rift occurs in the Afar region of Ethiopia and this rift is usually referred to as the Ethiopian Rift. Further to the South a series of rifts occur which include a Western branch,  the "Lake Albert Rift" or "Albertine Rift" which contains the East African Great Lakes, and an Eastern branch that roughly bisects Kenya north-to-south on a line slightly west of Nairobi (Figure 2).  These two branches together have been termed the East African Rift (EAR), while parts of the Eastern branch have been variously termed the Kenya Rift or the Gregory Rift (after the geologist who first mapped it  in the early 1900's).  The two EAR branches are often grouped with the Ethiopian Rift to form the East Africa Rift System (EARS).  The complete rift system therefore extends 1000's of kilometers in Africa alone and several 1000 more if we include the Red Sea  and Gulf of Aden as extensions.  In addition there are several well-defined but definitely smaller structures, called grabens, that have rift-like character and are clearly associated geologically with the major rifts. Some of these have been given names reflecting this such as the Nyanza Rift in Western Kenya near Lake Victoria. Thus, what people might assume to be a single rift somewhere in East Africa is really a series of distinct rift basins which are all related and produce the distinctive geology and topography of East Africa. How did these Rifts form? The exact mechanism of rift formation is an on-going debate among geologists and geophysicists. One popular model for the EARS assumes that elevated heat flow from the mantle (strictly the asthenosphere) is causing a pair of thermal "bulges" in central Kenya and the Afar region of north-central Ethiopia.  These bulges can be easily seen as elevated highlands on any topographic map of the area (Figure 1). As these bulges form, they stretch and fracture the outer brittle crust into a series of normal faults forming the classic horst and graben structure of rift valleys (Figure 3).  Most current geological thinking holds that bulges are initiated by mantle plumes under the continent heating the overlying crust and causing it to expand and fracture. Ideally the dominant fractures created occur in a pattern consisting of three fractures or fracture zones radiating from a point with an angular separation of 120 degrees.  The point from which the three branches radiate is called a "triple junction" and is well illustrated in the Afar region of  Ethiopia (Figure 4), where two branches are occupied by the Red Sea and Gulf of Aden, and the third rift branch runs to the south through Ethiopia. The stretching process associated with rift formation is often preceded by huge volcanic eruptions which flow over large areas and are usually preserved/exposed on the flanks of the rift. These eruptions are considered by some geologists to be "flood basalts" - the lava is erupted along fractures (rather than at individual volcanoes) and runs over the land in sheets like water during a flood. Such eruptions can cover massive areas of land and develop enormous thicknesses (the Deccan Traps of India and the  Siberian Traps are examples). If the stretching of the crust continues, it forms a "stretched zone" of thinned crust consisting of a mix of basaltic and continental rocks which eventually drops below sea level, as has happened in the Red Sea and Gulf of Aden. Further stretching leads to the formation of oceanic crust and the birth of a new ocean basin. Part II. The East African Rift If the rifting process described occurs in a continental setting, then we have a situation similar to what is now occurring in Kenya where the East African/Gregory Rift is forming. In this case it is referred to as "continental rifting" (for obvious reasons) and provides a glimpse into what may have been the early development of the Ethiopian Rift. As mentioned in Part I, the rifting of East Africa is complicated by the fact that two branches have developed, one to the west which hosts the African Great Lakes (where the rift filled with water) and another nearly parallel rift about 600 kilometers to the east which nearly bisects Kenya north-to-south before entering Tanzania where it seems to die out (Figure 2). Lake Victoria sits between these two branches. It is thought that these rifts are generally following old sutures between ancient continental masses that collided billions of years ago to form the African craton and that the split around the Lake Victoria region occurred due to the presence of a small core of ancient metamorphic rock, the Tanzania craton, that was too hard for the rift to tear through. Because the rift could not go straight through this area, it instead diverged around it leading to the two branches that can be seen today. As is the case in Ethiopia, a hot spot seems to be situated under central Kenya, as evidenced by the elevated  topographic dome there (Figure 1). This is almost exactly analogous to the rift Ethiopia, and in fact, some geologists have suggested that the Kenya dome is the same hotspot or plume that gave rise to the initial Ethiopian rifting. Whatever the cause, it is clear that we have two rifts that are separated enough to justify giving them different names, but near enough to suggest that they are genetically related. Other Points of Interest: What else can we say about the Ethiopian and Kenya Rifts? Quite a lot actually; even though the Eastern and Western branches were developed by the same processes they have very different characters. The Eastern Branch is characterized by greater volcanic activity while the Western Branch is characterized by much deeper basins that contain large lakes and lots of sediment (including Lakes Tanganyika, the 2nd deepest lake in the world, and Malawi). Recently, basalt eruptions and active crevice formation have been observed in the Ethiopian Rift which permits us to directly observe the initial formation of ocean basins on land. This is one of the reasons why the East African Rift System is so interesting to scientists. Most rifts in other parts of the world have progressed to the point that they are now either under water or have been filled in with sediments and are thus hard to study directly. The East African Rift System however, is an excellent field laboratory to study a modern, actively developing rift system. This region is also important for understanding the roots of human evolution. Many hominid fossil finds occur within the rift, and it is currently thought that the rift's evolution may have played an integral role in shaping our development. The structure and evolution of the rift may have made East Africa more sensitive to climate changes which lead to many alternations between wet and arid periods. This environmental pressure could have been the drive needed for our ancestors to become bipedal and more brainy as they attempted to adapt to these shifting climates (see Geotimes 2008 articles: Rocking the Cradle of Humanity by Beth Christensen and Mark Maslin, and Tectonic Hypotheses of Human Evolution by M. Royhan Gani and Nahid DS Gani). Conclusions: The East African Rift System is a complicated system of  rift segments which provide a modern analog to help us understand how continents break apart. It is also a great example of how many natural systems can be intertwined - this unique geological setting may have altered the local climate which may have in turn caused our ancestors to develop the skills necessary to walk upright, develop culture and ponder how such a rift came to be. Just like the Grand Canyon, the East African Rift System should be high on any geologist's list of geologic marvels to visit. About the authors: James Wood has a PhD from Johns Hopkins University and is currently Professor of Geology at the Michigan Technological University in Houghton, Michigan where he teaches Earth History, Geochemistry, Remote Mapping and conducts a field course every spring in East Africa. His main research interests are energy deposits, mainly gas and oil, and doing field work in rift valleys. More information on the East Africa field course can be found at www.geo-kenya.com. Alex Guth is currently a PhD candidate at Michigan Tech and is looking at the effects of climate on desert varnish on the exposed flows and alluvium in the East African Rift Valley. She assists Dr. Wood with the geology field camp. She recently produced a geologic map of the southern half of the Kenya Rift which may be found at www.geo-kenya.com. Her website can be viewed at: www.geo.mtu.edu/~alguth/ source  http://geology.com/articles/east-africa-rift.shtml

the oldest dinosaur

Asilisaurus kongwe: the

 

 oldest dinosaur

 

 

This dinosaur-like creature lived 10 million years before

 dinosaurs.

Ten Million Years Before Dinosaurs

Paleontologists announced the discovery of a dinosaur-like animal — one that shared many characteristics with dinosaurs but fell just outside of the dinosaur family tree — living 10 million years earlier than the oldest known dinosaurs. The researchers conclude that dinosaurs and other close relatives such as pterosaurs (flying reptiles) might have also lived much earlier than previously thought.

The description of the new species Asilisaurus kongwe (a-SEE-lee-SOAR-us KONG-way) appears in the March 4, 2010 issue of the journal Nature in a paper lead-authored by Sterling Nesbitt, a postdoctoral researcher at The University of Texas at Austin's Jackson School of Geosciences. Nesbitt conducted the research with his colleagues while a graduate student at Columbia University's Lamont-Doherty Earth Observatory and the American Museum of Natural History.

Meat-Eaters Evolve into Plant-Eaters

The research also suggests that at least three times in the evolution of dinosaurs and their closest relatives, meat-eating animals evolved into animals with diets that included plants. These shifts all occurred in less than 10 million years, a relatively short time by geological standards.

Relationship Between Silesaurs and Dinosaurs

Asilisaurus is part of a sister group to dinosaurs known as silesaurs. Silesaurs are considered dinosaur-like because they share many dinosaur characteristics but still lack key characteristics all dinosaurs share. The relationship between silesaurs and dinosaurs is analogous to the close relationship of humans and chimps. Even though the oldest dinosaurs discovered so far are only 230 million years old, the presence of their closest relatives 10 million years earlier implies that silesaurs and the dinosaur lineage had already diverged from common ancestors by 240 million years ago. Silesaurs continued to live side by side with early dinosaurs throughout much of the Triassic Period (between about 250 and 200 million years ago).

This is the first dinosaur-like animal recovered  from the Triassic Period in Africa.

Physical Characteristics of Asilisaurus

Fossil bones of at least 14 individuals were recovered from a single bone bed in southern Tanzania making it possible to reconstruct a nearly entire skeleton, except portions of the skull and hand. The individuals stood about 0.5 to 1 meter (1.5 to 3 feet) tall at the hips and were 1 to 3 meters (3 to 10 feet) long. They weighed about 10 to 30 kilograms (22 to 66 pounds). Asilisaurus walked on four legs and most likely ate plants or a combination of plants and meat. They lived about 240 million years ago.

Silesaurs have triangular teeth and a lower jaw with a beak-like tip which suggest that they were specialized for an omnivorous and/or herbivorous diet. These same traits evolved independently in at least two dinosaur lineages. In all three cases, the features evolved in animals that were originally meat-eaters. Although difficult to prove, it's possible that this shift conferred an evolutionary advantage. An ecosystem can support far more plant eaters than meat eaters. So being able to eat plants might have opened up a broader range of habitats. Not counting modern birds, dinosaurs survived for about 180 million years.

This new species is found along with a number of primitive crocodilian relatives in the same fossil bed in southern Tanzania. The presence of these animals together at the same time and place suggests that the diversification of the relatives of crocodilians and birds was rapid and happened earlier than previously suggested. It sheds light on a group of animals that later came to dominate the terrestrial ecosystem throughout the Mesozoic (250 to 65 million years ago).

"Everyone loves dinosaurs," said Nesbitt. "But this new evidence suggests that they were really only one of several large and distinct groups of animals that exploded in diversity in the Triassic, including silesaurs, pterosaurs, and several groups of crocodilian relatives."

An Explostion of Triassic Silesaur Finds

Silesaurus, the first known member of the silesaur group was discovered in 2003. In just 7 short years, specimens of 8 other members have been unearthed from Triassic rocks across the globe.

"This goes to show that there are whole groups of animals out there that we've never even found evidence of that were very abundant during the Triassic," said Nesbitt. "It's exciting because it means there is still so much chance for discovery."

Naming Asilisaurus kongwe

The name Asilisaurus kongwe is derived from asili (Swahili for ancestor or foundation), sauros (Greek for lizard), and kongwe (Swahili for ancient).

The Author Team and Supporters

Co-authors of the Nature paper include an international team consisting of: Christian A. Sidor (Burke Museum and University of Washington), Randall B. Irmis (Utah Museum of Natural History and University of Utah), Kenneth D. Angielczyk (The Field Museum, Chicago), Roger M.H. Smith (Iziko: South African Museum, South Africa), and Linda A. Tsuji (Museum für Naturkunde an der Humboldt-Universität zu Berlin, Germany).

Funding for the research was provided by The National Geographic Society, The Evolving Earth Foundation, The Grainger Foundation, and The National Science Foundation.

More about Asilisaurus...

More information about Asilisaurus and images are available online.

For more information, contact: Marc Airhart, Geology Foundation, Jackson School of Geosciences, 512 471 2241.

source
http://geology.com/press-release/asilisaurus-kongwe/