Spreading of the Red Sea floor over geological time

Red Sea Spreading Seafloor

The spreading of the seafloor under the Red Sea offers researchers a chance to study several important areas of science and apply what is learned to a better understanding of earth, earth's history, and perhaps other planets in the Solar System such as Mars. This paper reviews and examines existing science related to the tectonic plates (African and Arabian plates) beneath the Red Sea, the explanation for their movement apart and the dynamics of the hydrothermal activities that are part of the plate spreading itself. The Red Sea is of particular interest to scientists and this paper provides thorough reviews of the research conducted to date and why that research is of great value to science and to an understanding of how the Earth was formed.

INTRODUCTION:

The sea floor beneath the Red Sea is of great interest to geologists, oceanographers, seismologists and other scientists mainly because of the fact that the tectonic plates - that are the reason the Red Sea was formed in the first place - and are pulling apart ("separating") slowly but surely over geologic time. This dynamic is of great interest to the world of science in part because research into the formation of the oceans is important; what happens in one area of the world where plates are separating has vital implications for other areas of the world with similar geologic dynamics. Also, in an active tectonic region there is always the possibility of large earthquakes that could be generated within the tectonic region (and also the likelihood of a tsunami resulting from a large temblor. And moreover, the Red Sea is important to study because the seas and oceans are "inextricably interconnected" (www.ngsednet.org.oceans);theseas and oceans are sometimes seen as "indestructible" but they are not, and the more research that goes into the present day - and historical - issues associated with seas and oceans, the wiser the decisions mankind will be able to make through the process.

RED SEA GEOLOGIC EVOLUTION: ROBERT C. COLEMAN'S BOOK:

Author Robert C. Coleman (Geologic Evolution of the Red Sea) writes that hot brine pools were discovered on the seafloor of the Red Sea in 1966, which excited scientists. At that time the discovery of hot brine pools served as a "catalyst" in the sense of stimulating more collaborative research studies (Coleman p. 6); the evolving understanding of plate tectonics received a great boost when the Research Vessel (R/V) Glomar Challenger went into the Red Sea in 1972 and drilled into the seafloor at six sites around the "axial rift" (the separating tectonic plates under the Red Sea). The conformation soon followed that indeed, Coleman explains on page 6 of his book, the axial trough was "an active spreading center," which in fact was producing the "hot heavy metal brines." Still that drilling by the crew of the Glomar Challenger did not go deep enough to penetrate the "thick evaporite sequence along the edge of the axial trough" and hence, the nature of what lay beneath remained "enigmatic."

Among the "vexing problems" that has puzzled scientists trying to understand the Red Sea dynamics has been "trying to characterize the crust underlying the marginal trough and coastal plain" (Coleman, 7). In 1979 the U.S. Geological Survey and the Saudi Arabian Directorate General of Minerals conducted a research project - a "deep seismic refraction profile" - across western Saudi Arabia and well into the southeastern Red Sea. That research was discussed in a workshop involving some 46 seismologists from around the world; all 46 of these scientists had been given data from the USGS and Saudi Arabian research ahead of time. There were a variety of interpretations of this data, as might be expected, but the consensus among the scientists was that there was great concern by the fact that the "continental crust" (on land in Saudi Arabia) was 48 km deep while the oceanic crust dropped to just 17 km (Coleman, 7).

From that point on, the Red Sea has been considered (designated) a "key environment" because of its "great scientific and ecological importance," Coleman explains.

Some facts about the Red Sea: the Red Sea is an "elongate depression" that is more than 200 kilometers long; in the north, the shorelines are just 180 kilometers apart, while in the south of the Red Sea the shorelines - while much more irregular - are as far apart as 350 kilometers. There are volcanic centers within the axial zone, and the axial zone is surrounded by "fault terraces" that are nearly vertical and the walls rise up to 800 meters high from the bottom of the axial zone. At the time of the publishing of this book (1993) the rift was about four to five kilometers wide at about 2,000 meters deep into the Red Sea, Coleman explains (p. 18).

Large open fissures appear in clusters along the extrusive zone," and those clusters break up the "silt-lava sequences" and at times "transect" the ancient volcanoes. The fact that the sediments are not very deep on the volcanic features of the axial zone is clear evidence, Coleman writes, of its "youthfulness" in geologic terms. The "most spectacular manifestation of volcanism" is found along the axial ranges that have been discussed earlier in this paper. But Coleman asserts that eruptions in the Late Oligocene period - continuing "sporadically" up to the Late Miocene epoch - formed an "apron" that was 40 kilometers wide and extended more than 100 kilometers along the axis.

Meantime the southern portion of the Red Sea reveals "many sub-parallel faults" which are very similar, Coleman explains (p. 89), to mid-ocean patterns of tectonic faulting and spreading. The Red Sea spreading centers were fairly straight zones roughly 30 to 50 kilometers long and 3 to 20 kilometers across. In the northern portion of the Red Sea seafloor though is a place where dramatically irregular faulting makes the spreading center very different from the trends in the south. The faults along the spreading in the north are marked by zigzagging; the lack of "obvious transform faults," the author goes on, is "puzzling"; but it also reveals to scientists that the Red Sea has a "diachronous history of spreading" (Coleman, 89). Diachronous means there are various and widely differing ages of rock in the same zone.

Although this paper has alluded to the Red Sea as a place where two tectonic plates are slowly being pushed apart by the upward surge of hot magma, Coleman, and other scholars, refer to the Red Sea as having a "triple junction" - the African (Nubian) and Arabian tectonic plates are interacting with the Gulf of Aden oceanic spreading centers. The Gulf of Aden oceanic spreading center enters the gulf of Tadjura, and meets with the north-moving East African rift system, according to Coleman.

On page 123 author Coleman points to the belief that in geologic reality, four, not three, rigid plates are interacting dynamically in the Red Sea region; as discussed, the Arabian plate and the African (Nubian) plate are part of the picture; and Coleman adds to that stew the Sinai and Somalia plates. There is certainly rifting and spreading under the Red Sea, but Coleman writes in his Epilogue (p. 151-152) that there was - at the time his book was published - "No geologic evidence" that supports the existence of a "large dome centered" under the Red Sea Basin during the initial stages of rifting. In other words, there is no known "initial hot spot" where a volcano blasted molten rock and ash up through the rift. What he can say with certainty though is that the Red Sea "will continue to grow" through a combination of volcanic activity and faulting (the volcanic activity he refers to is the upward pushing of magma from deep in the earth's core, not a blast of volcanic ash exploding up from the seafloor).

However, it is "reasonable" Coleman posits, to assume there will be "future seismic and volcanic events" under the Red Sea, which makes the Red Sea "a unique ecosystem" and offers an "unparalleled" opportunity for continuing research of oceanic spreading and tectonic plate movement. The author warns against attempts by nations or corporations to exploit the Red Sea for "heavy metal deposits" or "petroleum" within the axial trough - prior to additional research.

SPREADING SEAFLOOR DYNAMICS BENEATH the OCEANS & SEAS

Prior to delving into the specifics relative to the Red Sea seafloor, a review of the dynamics of seafloor spreading is worthy and timely. There is an impressive volume of information with reference to the spreading of a seafloors and the movement of tectonic plates that respond by spreading when pushed by magma. The outermost layer of earth, earth's crust that is also alluded to as the upper mantle, is technically called the lithosphere.

Rosanna L. Hamilton, a professional scientist at Los Alamos National Laboratory ("The Lithosphere & Plate Tectonics") (www.solarviews.com) explainsfirst of all that there are eight large tectonic plates (African, Antarctic, Eurasian, Indian-Australian, Nazca, North American, Pacific and South American plates), and "two dozen smaller ones that are drifting above the mantle at the rate of two to four inches a year."

Hamilton explains that while Continental Lithosphere is as much as 93 miles thick, the "Oceanic Lithosphere" is much thinner - up to perhaps six miles. Indeed, the oceanic crust makes up only 0.099% of earth's mass, according to Hamilton. Oceanic lithosphere is a product of the volcanic magma that pushes up to force tectonic plates aside. As new oceanic lithosphere is actually formed the heat that comes up with the magma "escapes the interior as this new lithosphere emerges from below" in the Red Sea and elsewhere where there are tectonic plates spreading.

As the lithosphere cools, it contracts and then "moves away from the ridge, traveling across the seafloor to subduction zones." This process is technically called "seafloor spreading." After the lithosphere has been on the Red Sea floor for a while, it thickens up, Hamilton writes, and as it becomes even denser than the mantle just below it, it sinks into the earth (called "subduction") at a "steep angle" which cools the interior below the tectonic plates.

As a side note to undersea spreading, Hamilton mentions that as a rule all continents drift laterally along the "...convecting system of the mantle away from hot mantle zones toward cooler ones"; this is called continental drift, and "most" continents are either moving toward cooler parts of the mantle of earth. Or they are sitting on a cooler part of the earth's mantle. Africa is the one exception to this geologic rule, Hamilton continues. Africa was at one time - several hundred million years ago - the "core" of Pangaea, the "supercontinent" that broke into the continents that make up the earth's main land masses today.)

Meantime, the New York Times reported in 1987 that information about the spreading of sea floors is easier to come by thanks to "remote-controlled instruments and a new generation of manned deep-diving vessels." These technological developments have helped - and will continue to help - scientists learn more about how oceans and continents are being split apart. The training for proper use of these technologies was given in the late 1980s to 3,500 scientists from 78 countries; during the training session it was projected by Rodey Batiza of Northwestern University that they may be "a million volcanic mountains on the floor of the Pacific Ocean," most directly related to tectonic plate movement and magma surging upwards.

Among the 3,500 scientists there was "wide agreement" that the energy that is pushing the tectonic plates apart under seas and oceans comes "chiefly from the heat of radioactive decay inside the earth." Moreover, two scientists (Dr. R.W. Girdler of the University of Newcastle-upon-Tyne in England and P.R.K. Simpson) stated that magnetic instruments have indicated that the Africa plate and Arabian plate are "an unusual case" in which a "sea-floor spreading penetrates deep into a continent" (more on this topic will be discussed later in the paper).

This article was written, and the conference was held, well before the confirmation of the split under the Red Sea; still, at the time of the conference the scientists reported that the rift under the Red Sea was spreading at the rate of "about one inch per year"; and the rifting continues north through the gulf of Aqaba into the Dead Sea rift valley; that spreading rate is only have of the rate under the Red Sea.

RED SEAFLOOR RUPTURING: RECENT RESEARCH

The National Sciences Foundation (NSF) (Fall, 2006) MARGINS Newsletter No. 17, reports on the rupturing continental lithosphere dynamics in the northern and central Red Sea. In the narrative references are made to a recent an initiative launched to better understand "continental expansion" and how that transcends into ocean spreading. In this report - with data gathered from scientists from Massachusetts Institute of Technology, Penn State University and the University of Kansas - scientists explain that before studying the rupturing issues beneath the seafloor of the Red Sea, logistical and political issues had to be ironed out. The scientific collaborations that had been planned for this project - with scientists from Egypt, Sudan, Jordan, Eritera, and Saudi Arabia, were not workable.

Unfortunately due to the current security situation and political climate in the Middle East, the NSF...could not longer consider U.S.-led marine geophysical experiments in the Red Sea at this time" (Reilinger, 2006). This political dilemma sheds light on the fact that there is a great deal of tension, first, between the Muslim states in the Middle East and the West in general, and secondly, the United States is engaged in a controversial war in Iraq - and the U.S. supports Israel of course - which contributes to the deep rift (not unlike the tectonic rift beneath the Red Sea) between the Arab / Muslim states and U.S. And unfortunately, science becomes involved even though the empirical studies proposed for the Red Sea had nothing whatsoever to do with politics or gathering intelligence.

Still several aspects of the geophysical dynamics under the Red Sea are explored in the 2006 NSF report, based on significant research conducted prior to the Red Sea region (not just the sea but the surrounding and bordering territories) being designated an "ancillary site." The beginning of the separation of the Arabia from the Nubia (African tectonic plate) is believed to have happened in the Miocene epoch. This separation was a kind of "counterclockwise rotation of Arabia relative to Nubia," Reilinger et al. report.

That counterclockwise rotation continues to this day, the report explains, and it directly results in "increasing spreading rates" and also a "total extension from north to south" in the Red Sea. The scientists in this report characterize the spreading as "characterized by the early stages of continental breakup." The mid-ocean ridge and the magnetic anomalies associated with the ridge is so well developed, the report continues, that it has become "an ideal location to study the transition from rupturing continental lithosphere to full ocean spreading."

Also included in the MARGIN Newsletter No. 17 (Fall 2006) is a report by scientists (Stocki, et al., 2006) that points out there has been "Limited knowledge of how extensional strain is spatially and temporally distributed along the continental margins" of the rift under the Red Sea. That is to say, the story of how the rift technically and specifically took place has been hampered by the "scarcity of datable...volcanic rocks," and the gathering of this information has been hampered by fact that the "post-rift sedimentary rocks" are buried deeply with the rift.

Meanwhile, the Saudi Arabian Geological Survey has cooperated with the National Science Foundation (notwithstanding the prevention [because of political tensions] of addition research into the Red Sea mentioned earlier in this paper) to launch a "comprehensive low-temperature thermochronometric investigation...to determine the timing, origin, and geometry of extensional faulting and rift flank exhumation." This research was done primarily along the central and northern portion or the Red Sea that is actually within the territory of Saudi Arabia.

This is important, recent research, and the report indicates that more than 400 samples were taken (thermochronometric samples) to attempt to solve the puzzle of when the faulting (rifting) actually occurred. The results of those samples have not been released, but the detailed narrative that describes the process and the importance of this science adds to the theme of this paper that indeed the seafloor and its rifting beneath Red Sea is one of the most fascinating and important geological resources on the planet.

RED SEA HYDROTHERMAL PROCESSES: LINK to LIFE & LINK to MARS

The study of the Red Sea's hydrothermal dynamics - processes that occur as a result of the spreading of the seafloor and continue within the process of rifting / spreading - is proving to be useful as scientists study the history of the planet Mars. According to an article in the Australian Journal of Earth Sciences (Pirajno, et al., 2005), of all the tectonic plates on earth that might be somewhat similar to the "one-plate" geologic formation on Mars, the African plate is the "closest analogue" to Mars. Indeed, Africa has been "stationary" for about 65 million years, Pirajno writes on page 348 of his journal article. That length of time in one fairly stationary place among the planet's plates means for science that the crustal uplifts, the rifts and the "intraplate volcanism have not been recycled by convergent margin tectonics." And that fact would help scientists in their research on why Mars went from a planet with plenty of rivers and oceans and likely some form of life to a hot, dry, wasteland as it is today.

The East African Rift System, Pirajno continues, could well be an "analogue for the great rift system of Valles Marineris on Mars." Finding an example on earth that matches up well with what astrophysicists and geologists believe to be a great rift system on Mars allows the research related to another planet in the Solar System to continue right here on Earth. Indeed recent Mars rovers have discovered crystalline hematite and sulfate deports on Mars; this is factual geologic data that points to the fact that at one time Mars had hot-springs / hydrothermal processes, much like those processes under the Red Sea.

Why would it be important to find a geologic dynamic on earth that seems to resemble the history of Mars? "Knowledge of terrestrial hydrothermal systems is of paramount importance in the investigation of hydrothermal processes on Mars," Pirajno and associates assert (p. 347). There is no dispute among scientists as to whether or not there was water on Mars; there are numerous examples of geomorphological features like valley networks, outflow channels, and "giant polygonal patterned terrains" that clearly indicate the flow of water. The research to date indicates that Mars had a warmer climate, and "abundant liquid water"; the many of the riverbeds and drainage channels on Mars seem to have been formed by "spring sapping" rather than surface runoff.

Some of the features on Mars remind scientists of the hydrothermal activity that is consistent with the hydrothermal action under the Red Sea and in other mid-ocean ridges. Internal heat energy - like that which is pushing the African and Arabian plates farther apart under the Red Sea due to upwelling magmas - "must have had an important role in the inception of hydrothermal convection" on Mars, the writers suggest. The water on Mars today is generally believed to be "ground ice and permafrost"; and there are known polar regions on Mars "characterized by layered terrains" not unlike those under the Red Sea.

In summarizing the key points in this scholarly article, it is fair to say that studies focusing on "analogue processes" and on the "potential for hydrothermal systems on other planetary bodies in the Solar System" are vitally important. That is because these recent studies of earthly hydrothermal systems (such as the Red Sea spreading activity) will play "a crucial role" not only in future missions to the Planet Mars and the "search for extraterrestrial life," but these studies will also offer "new insights and new dimensions" on certain instances of hydrothermal activity on earth."

There are many more good reasons to study the undersea area beneath the Red Sea than the likely connection to Mars, of course. One reason that has not yet been raised in this paper is that there are life forms that are unique to the environment of a hydrothermal system such as that under the Red Sea. When sea floor exploration began in the 1970s, the research done around spreading centers revealed about 107 new "families" with "220 genera and 375 new species." Some of these recently discovered species include varieties of tubeworms, clams, shrimps and crabs. But more importantly, the exploration of the undersea floor where there is spreading and hydrothermal activities (like the Red Sea) gives scientists a sense that these places are "the ideal environment for the establishment of primitive life."

This is exciting for scientists because, as Pirajno writes on page 339 of his journal article, "the earliest microorganisms [on Earth] may have been hyperthermophiles," and those are being discovered in mid-ocean ridge spreading places. Scientists are constantly looking for clues to the origins of earth, and they believe (according to Pirajno's research) that there may be clues - or empirical evidence - within the dynamics of the hydrothermal actions below the Red Sea. On page 332 of the scholarly paper by Pirajno and colleagues they state that hydrothermal activity below the Red Sea produces sulfates, sulfides and oxides. Seawater percolates up through fractures in the crust (through the spreading between the African and Arabian tectonic plates), they note, and is heated; it then generates a "hydrothermal convection system" which in turn results in the "extraction of metals from the mafic rocks" that are part of the oceanic crust. These extracted metals then form "ore fluid."

This discovery about 30 years ago, the authors explain on page 332, has led to "very fruitful research." That is, the minerals on the seafloor that were produced by the process of spreading have a "direct application" to ore deposits onshore. Hence, the existence of previously unknown "ecosystems that thrive on anoxia and sulfur" leads logically to an assessment of "future and very valuable mineral resources." The study of those "previously unknown ecosystems" will offer insights into "the possible origin of life on earth," Pirajno writes.

Moreover, the authors point out that the spreading beneath the Red Sea results in the creation of minerals; indeed a category of "metalliferous deposits" which is typically associated with basins formed near "extensional tectonics and intracontinental rifts," can be found under the Red Sea. These minerals include "red Sea-type sulfide and oxide accumulations" as well as cu-rich stratabound disseminated sulfides." The bottom line here as far as the science is that some of the oxides and other deposits resulting from the hydrothermal action under the Red Sea are being linked as "possible modern analogues" to ancient SEDEX environments.

SEDEX is an acronym for "Sedimentary exhalative " which means sediments that are formed from "exhausts" like the hydrothermal exhaust escaping from the spreading seafloor. The SEDEX environments are actually ore deposits which are believed to have been formed by the release of ore-bearing hydrothermal fluids into an ocean or a sea, which then results in the precipitation of stratiform ore. Why is this important in studying the Red Sea's floor? The answer is that SEDEX deposits are considered, according to the authors, the most important source of lead, zinc and barite, a major contributor of silver, copper, gold, bismuth and tungsten. And the discovery of valuable minerals (including silver, gold, tungsten) could be meaningful to nations with jurisdiction within the Red Sea boundaries.

RECENT RED SEA SCIENCE: DISCUSSION

The most recent revelations regarding the Red Sea allows for a thoughtful discussion of what is happening today along the faults and cracks in the earth that are part of the tectonic activities of the African (Nubia) and Arabian plates. Indeed, the National Geographic reported in July, 2006, that scientists have determined "...a recent tear in Earth's continental crust near the [Red Sea] is the largest single rip seen since satellite monitoring began" (Lovgren, 2006)). The report explains that over the past 30 million or so years, the Arabian tectonic plate has been moving away from the African (also known as the "Nubian" plate) plate. This is a well-known part of the factual resume of the Red Sea and the Arabian and African tectonic plates. Within the area that the two plates are moving apart there is a "rift"; rifting is the process of the slow opening of a gap between two tectonic plates. Rising hot magma from the center of the earth drives up the Arabian plate and the African plate from below and they reportedly actually began drifting apart approximately 55 million years ago, according to sources reported by.