Book Name: GEOLOGICAL FIELD TECHNIQUES
Edited by : Angela L. Coe
Authors:
Angela L. Coe
Tom W. Argles
David A. Rothery
Robert A. Spicer
Department of Earth and Environmental Sciences,
The Open University, Walton Hall, Milton Keynes, UK
Rocks dating back 3.4 billion years from south-west Greenland’s Isua mountain range have yielded valuable information about the structure of Earth during its earliest stages of development. In these rocks, which witnessed the first billion years of Earth’s history, a French-Danish team led by researchers from the ‘Magmas and Volcanoes’ Laboratory (CNRS / Université Blaise Pascal / IRD) have highlighted a lack of neodymium-142, an essential chemical element for the study of Earth’s formation.
This deficit supports the hypothesis that between 100 and 200 million years after its formation, Earth was made up of an ocean of molten magma, which gradually cooled. The work, which was carried out in collaboration with the Laboratoire de Géologie de Lyon (CNRS / Université Lyon 1 / ENS de Lyon) and the University of Copenhagen, was published on 1 November 2012, in the journal Nature.
Earth is believed to have formed 4.58 billion years ago, by accretion of material in the Solar System. The heat produced by the accretion process, as well as by the decay of radioactive elements, caused this material to melt. As a result, 100 to 200 million years after its formation, Earth must have been made up of an ocean of molten magma, in the center of which a metallic core formed. The ocean gradually cooled. Earth’s crust then appeared, and the process of continental drift began. The crystallization of the molten magma is likely to have been accompanied by the chemical layering of Earth: concentric layers with distinct chemical compositions became differentiated. It is the signature of these primordial inhomogeneities that the researchers found in the Isua rocks.
The scientists were interested in a key chemical element, the isotope neodymium-142, formed by the decay of a now vanished radioactive isotope called samarium-146. The abundance of neodymium-142 is almost identical in all terrestrial rocks. Only two exceptions have been discovered to date, in Canada and Greenland, in certain rocks dating back 3.7 billion years. The composition of these rocks shows evidence of the primordial inhomogeneities that formed as the magma ocean crystallized.
In 2003, for the first time, two groups of French researchers observed an excess of neodymium-142 in certain rocks in the same region. If such excess can be found in some layers of the primordial Earth, it means that other layers must be depleted in this isotope. However, until these new findings by the French-Danish team, such neodymium-142 deficits remained hypothetical for nine years. Using a sophisticated method, thermal ionization mass spectrometry, the researchers carried out a very detailed analysis of the concentration of neodymium-142 in Isua rock samples. They discovered a neodymium-142 deficit of 10.6 parts per million, which lends weight to the ‘magma ocean’ theory.
These findings should help to improve models of the internal dynamics of Earth during its early stages of development. By discovering a neodymium-142 deficit in relatively young rocks, formed around a billion years after the crystallization of the magma ocean, the researchers have shown that the primordial inhomogeneities persisted longer than predicted before being eliminated by convective motion in Earth’s mantle. In order to obtain more comprehensive data, the scientists now intend to study the composition of other rocks of similar age outcropping for example in Canada, South Africa and China.
This study was mainly funded by an ERC Starting Grant.
The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archean rocks. Hanika Rizo, Maud Boyet, Janne Blichert-Toft, Jonathan O’Neil, Minik Rosing, Jean-Louis Paquette, Nature, 1 November 2012.
Note : The above story is reprinted from materials provided by Centre national de la recherche scientifique (CNRS).
–Book Name : Introduction to Mineral Exploration,Second Edition
– Edited by :
Charles J. Moon, Michael K.G. Whateley & Anthony M. Evans
– With contributions from:
William L. Barrett
Timothy Bell
Anthony M. Evans
John Milsom
Charles J. Moon
Barry C. Scott
Michael K.G. Whateley
Download Link >> http://www.mediafire.com/?pbybtkm7wuoa8fy
Book Name : Basic Geological Mapping , Fourth Edition
Author :
John W. Barnes
formerly of the Department of Earth Sciences,
University of Wales Swansea
with
Richard J. Lisle
Department of Earth, Ocean and Planetary Sciences
Cardiff University
Nestled within the vast and rugged landscape of the Vermilion Cliffs National Monument in northern Arizona lies a geological wonder that has captivated the imaginations of nature enthusiasts and adventurers alike – The Wave. This surreal and otherworldly sandstone formation is a testament to the awe-inspiring forces of nature that have shaped the American Southwest.
The Wave is a striking example of nature’s artistry, a sandstone formation that undulates in a wave-like pattern, creating an almost dreamlike landscape. Situated in the Coyote Buttes area of the Vermilion Cliffs, The Wave is renowned for its unique and colorful striations, resembling a painting crafted by the hand of a master artist. Its popularity has grown exponentially, drawing visitors from around the world eager to witness this geological masterpiece.
Understanding the geological origins of The Wave adds a layer of appreciation for its beauty. The formation is primarily composed of Jurassic-age Navajo Sandstone, deposited over 190 million years ago. Erosion, primarily by wind and water, has sculpted the sandstone into the undulating forms that we see today. The distinctive cross-bedding and layering tell a story of ancient dunes frozen in time, now revealed for all to marvel at.
“The Wave” consists of intersecting U-shaped troughs that have been eroded into Navajo Sandstone of Jurassic age. The two major troughs, which comprise this rock formation, are 19 meters wide by 36 meters long and 2 meters wide by 16 meters long. Initially, infrequent runoff eroded these troughs along joints within the Navajo Sandstone. After their formation, the drainage basin, which fed rainwater to these troughs, shrank to the point that the runoff became insufficient to contribute to the cutting of these troughs. As a result, the troughs are now almost exclusively eroded by wind as indicated by the orientation of erosional steps and risers cut into the sandstone along their steep walls. These erosional steps and risers are oriented relative to predominate direction of the wind as it is now naturally funneled into and through these troughs.
The Wave exposes large, eolian sets of cross-bedded sandstone composed of rhythmic and cyclic alternating grainflow and windripple laminae. The rhythmic and cyclic alternating laminae represent periodic changes in the prevailing winds during the Jurassic as huge sand dunes migrated across a sandy desert. The thin ridges and ribbing seen within The Wave are the result of the differential erosion of rhythmic and cyclic alternating grainflow and windripple laminae within the Navajo Sandstone. These laminae have differing resistance to erosion as they have been differentially cemented according to variations in the grain size of the sand composing them. The soft sandstone, including the ridges and ribbing, of The Wave is fragile. As a result, a person needs to walk carefully to not break the small ridges.
In places, The Wave exposes deformed laminae within the Navajo Sandstone. These laminae were deformed prior to the lithification of the sand to form sandstone. Judging from their physical characteristics, this deformation likely represents the trampling and churning of these sands by dinosaurs right after their deposition. Dinosaur tracks and the fossil burrows of desert-dwelling arthropods, such as beetles and other insects, have been found within the Navajo Sandstone within the North Coyote Buttes Wilderness Area.
The Wave’s popularity comes with a caveat – access is strictly regulated. The Bureau of Land Management (BLM) issues a limited number of permits each day to preserve the delicate environment and ensure a peaceful experience for visitors. Securing one of these coveted permits has become a challenge in itself, adding an element of exclusivity to the journey. However, the effort required to obtain a permit only amplifies the anticipation and excitement for those fortunate enough to embark on this adventure.
Access to The Wave involves a moderate to strenuous hike, adding a sense of adventure and accomplishment to the visit. The journey begins at the Wire Pass Trailhead, leading hikers through a maze of slickrock and sandy terrain. Navigating the path, often marked only by small cairns, enhances the feeling of discovery and exploration. The final approach to The Wave unveils the iconic formation, a reward for those who have ventured into the heart of the Coyote Buttes.
One of The Wave’s most enchanting features is its vibrant color palette. The interplay of reds, oranges, yellows, and whites creates a mesmerizing display, especially during the golden hours of sunrise and sunset. The varying hues are a result of mineral deposits in the sandstone, with iron and manganese producing the warm tones that dance across the undulating surfaces. Photographers, in particular, find The Wave to be a captivating subject, with every angle revealing a new perspective of its kaleidoscopic beauty.
While the surrounding desert may appear harsh and barren, The Wave supports a surprising diversity of flora and fauna. Hardy desert plants, adapted to the arid conditions, cling to life in crevices and pockets of soil. The resilient desert tortoise and the elusive bighorn sheep are among the native inhabitants, showcasing the remarkable ability of life to thrive in seemingly inhospitable environments.
The fragility of The Wave’s ecosystem and its popularity among visitors have prompted conservation efforts to protect this natural wonder. Leave No Trace principles are emphasized, urging visitors to minimize their impact on the delicate environment. Education about responsible hiking practices and adherence to established trails help preserve The Wave for future generations, ensuring that its beauty endures.
Beyond its visual appeal, The Wave has inspired artists, writers, and creatives across disciplines. Its surreal forms and timeless beauty have been the muse for countless works of art, literature, and even scientific studies. The intersection of art and nature is vividly apparent in this remote corner of the American Southwest.
The popularity of The Wave has not been without challenges and controversies. The delicate balance between accessibility and preservation has led to ongoing discussions about visitor limits, permit systems, and the overall impact of human presence on this fragile landscape. Striking the right balance is crucial to ensuring the long-term sustainability of this natural treasure.
In conclusion, The Wave, Arizona, stands as a testament to the raw beauty and geological wonders that grace the American Southwest. Its surreal landscapes, vibrant colors, and the sense of exclusivity granted by limited permits make it a destination like no other. The journey to The Wave is not merely a physical one; it is a voyage into the heart of Earth’s history, where the forces of time and nature have collaborated to create a masterpiece that transcends the ordinary.
As visitors marvel at the undulating sandstone and vibrant hues, The Wave remains a beacon of inspiration, reminding us of the profound beauty that can be found in the most unexpected corners of our planet. Whether captured through the lens of a camera or etched into the memory of those fortunate enough to experience it firsthand, The Wave leaves an indelible mark, inviting all who encounter it to contemplate the wonders of our natural world.
Event Time
2012-10-28 03:04:10 UTC
2012-10-27 20:04:10 UTC-07:00 at epicenter
2012-10-28 05:04:10 UTC+02:00 system time
Location
52.769°N 131.927°W depth=17.5km (10.9mi)
Nearby Cities
139km (86mi) S of Masset, Canada
202km (126mi) SSW of Prince Rupert, Canada
293km (182mi) SW of Terrace, Canada
556km (345mi) NW of Campbell River, Canada
635km (395mi) SSE of Juneau, Alaska
The October 28th, 2012 (October 27 at the location of the epicenter) M 7.7 earthquake south of Masset, Canada, occurred as a result of oblique-thrust faulting near the plate boundary between the Pacific and North America plates. At the location of this event, the Pacific plate moves approximately north-northwest with respect to the North America plate at a rate of approximately 50 mm/yr.
This earthquake is likely associated with relative motion across the Queen Charlotte fault system offshore of British Columbia, Canada. Studies of tectonics in this region suggest plate motions are taken up by strike slip faulting parallel to the plate boundary, accompanied by lesser amounts of thrust motion to accommodate the oblique nature of the plate motion vector between the two plates with respect to the orientation of the main plate boundary fault structure. This oblique component of plate motion may involve either underthrusting of the western edge of the Pacific Plate beneath North America, or be taken up on crustal faults within the North America plate. The October 28th earthquake is consistent with either scenario. Its rupture extended approximately 100-150 km along strike, along the shallow extent of the source fault. Slip amounts reached approximately 5m, in a patch to the south of the epicenter. Aftershocks delineate the rupture well, as shown here.
This region of the Pacific:North America plate boundary has hosted 7 earthquakes of magnitude 6 or greater over the past 40 years – the largest of which was a M 6.6 earthquake in 2009, 80 km to the south east of the 2012 earthquake. In 1949, a M 8.1 earthquake occurred closer to the Pacific:North America plate boundary, likely as a result of strike-slip faulting, approximately 100 km northwest of the October 28th earthquake, near the northern extent of Haida Gwaii region (formerly Queen Charlotte Islands).
A new Rice University-led study finds that a deep connection about 50 miles underground can explain the enigmatic behavior of two of Earth’s most notable volcanoes, Hawaii’s Mauna Loa and Kilauea. The study, the first to model paired volcano interactions, explains how a link in Earth’s upper mantle could account for Kilauea and Mauna Loa’s competition for the same deep magma supply and their simultaneous “inflation,” or bulging upward, during the past decade.
The study appears in the November issue of Nature Geoscience.
The research offers the first plausible model that can explain both the opposing long-term eruptive patterns at Mauna Loa and Kilauea — when one is active the other is quiet — as well as the episode in 2003-2007 when GPS records showed that each bulged notably due to the pressure of rising magma. The study was conducted by scientists at Rice University, the University of Hawaii, the U.S. Geological Survey (USGS) and the Carnegie Institution of Washington.
“We know both volcanoes are fed by the same hot spot, and over the past decade we’ve observed simultaneous inflation, which we interpret to be the consequence of increased pressure of the magma source that feeds them,” said lead author Helge Gonnermann, assistant professor of Earth science at Rice University. “We also know there are subtle chemical differences in the lava that each erupts, which means each has its own plumbing that draws magma from different locations of this deep source.
“In the GPS records, we first see inflation at Kilauea and then about a half a year later at Mauna Loa,” he said. “Our hypothesis is that the pressure is transmitted slowly through a partially molten and thereby porous region of the asthenosphere, which would account for the simultaneous inflation and the lag time in inflation. Because changes in pore pressure are transmitted between both volcanoes at a faster rate than the rate of magma flow within the porous region, this can also explain how both volcanoes are dynamically coupled, while being supplied by different parts of the same source region.”
Gonnermann said the transmission of pressure through the permeable rock in the asthenosphere is akin to the processes that cause water and oil to flow through permeable layers of rock in shallower regions of Earth’s crust.
“When we fitted the deformation, which tells us how much a volcano inflates and deflates, and the lava eruption rate at Kilauea, we found that our model could simultaneously match the deformation signal recorded over on Mauna Loa,” said James Foster, co-author and assistant researcher at the University of Hawaii School of Ocean and Earth Science and Technology. “The model also required an increase in the magma supply rate to the deep system that matched very nicely with our interpretations and the increased magma supply suggested by the jump in CO2 emissions that occurred in late 2003.”
Mauna Loa and Kilauea, Earth’s largest and most active volcanoes, respectively, are located about 22 miles apart in the Hawaii Volcanoes National Park on the island of Hawaii. They are among the planet’s most-studied and best-instrumented volcanoes and have been actively monitored by scientists at USGS’s Hawaiian Volcano Observatory (HVO) since 1912. Kilauea has erupted 48 times on HVO’s watch, with a nearly continuous flank eruption since 1983. Mauna Loa has erupted 12 times in the same period, most recently in 1984.
“To continue this research, we submitted a proposal to the National Science Foundation (NSF) earlier this summer to extend our study back in time to cover the last 50 years,” Foster said. “We plan to refine the model to include further details of the magma transport within each volcano and also explore how some known prehistoric events and some hypothetical events at one volcano might impact the other. This work should help improve our understanding of volcanic activity of each volcano.”
Gonnermann said there has been disagreement among Earth scientists about the potential links between adjacent volcanoes, and he is hopeful the new model could be useful in studying other volcanoes like those in Iceland or the Galapagos Islands.
“At this point it is unclear whether Hawaii is unique or whether similar volcano coupling may exist at other locations,” Gonnermann said. “Given time and ongoing advances in volcano monitoring, we can test if similar coupling between adjacent volcanoes exists elsewhere.”
Study co-authors include Michael Poland and Asta Miklius, both of HVO; Benjamin Brooks of the University of Hawaii; and Cecily Wolfe of the University of Hawaii and the Carnegie Institution of Washington.
The research was supported by the USGS and the NSF. The Kilauea and Mauna Loa GPS networks are supported by grants from the USGS, NSF and NASA and operated in collaboration by the USGS, Stanford University and the Pacific GPS Facility at the University of Hawaii.
Note : The above story is reprinted from materials provided by Rice University. The original article was written by Jade Boyd.
Wadi Al-Hitan “Whales Valley” is a paleontological site in the Al Fayyum Governorate of Egypt, some 150 km southwest of Cairo. It was designated a UNESCO World Heritage Site in July 2005 for its hundreds of fossils of some of the earliest forms of whale, the archaeoceti (a now extinct sub-order of whales). The site reveals evidence for the explanation of one of the greatest mysteries of the evolution of whales: the emergence of the whale as an ocean-going mammal from a previous life as a land-based animal. No other place in the world yields the number, concentration and quality of such fossils, as is their accessibility and setting in an attractive and protected landscape. This is why it was added by the UNESCO to the list of protected World Heritage sites.
The fossils found at the site may not be the oldest but their great concentration in the area and the degree of their preservation is to the extent that even some stomach contents are intact. The presence of fossils of other early animals such as sharks, crocodiles, sawfish, turtles and rays found at Wadi El-Hitan makes it possible to reconstruct the surrounding environmental and ecological conditions of the time, adding to its justification to be cited as a Heritage site.
The first fossil skeletons of whales were discovered in the winter of 1902-3. For the next 80 years they attracted relatively little interest, largely due to the difficulty of reaching the area. In the 1980s interest in the site resumed as four wheel drive vehicles became more readily available. Continuing interest coincided with the site being visited by fossil collectors, and many bones were removed, prompting calls for the site to be conserved. The remains display the typical streamlined body form of modern whales, yet retaining some of the primitive aspects of skull and tooth structure. The largest skeleton found reached up to 21 m in length, with well-developed five-fingered flippers on the forelimbs and the unexpected presence of hind legs, feet, and toes, not known previously in any archaeoceti. Their form was serpentine and they were carnivorous. A few of these skeletal remains are exposed but most are shallowly buried in sediments, slowly uncovered by erosion. Wadi El-Hitan provides evidences of millions of years of coastal marine life.
Fossils are present in high numbers and often show excellent quality of preservation. The most conspicuous fossils are the skeletons and bones of whales and sea cows, and over several hundred fossils of these have been documented.
The fossils of whales vary from single bones to entire skeletons, and a number of partial skeletons are currently on display in the public part of the park. The two common whales are the large Basilosaurus, and the smaller (3 to 5 metre) Dorudon. At least two other species are known from rarer remains.
The whales possess small hind limbs, that are not seen in modern whales, and a powerful skull with teeth similar to those of carnivorous land mammals. Other mammals are represented by the skeletons of three species of sirenia or sea cows. These were fully marine like the whales, and likewise show primitive features not seen in modern species and possess teeth that suggest that they grazed on seagrasses and other marine plants.
Bones of the primitive elephant Moeritherium have also been recorded. Fossil reptiles are represented by fossils of crocodiles and sea turtles, and bones of sea snakes have also been recorded. There are many species of bony fish, sharks and rays represented, but most of the fossils are isolated small teeth and these are not often conspicuous. Larger fish fossils include the rostra and pegs of sawfish; a sawfish rostrum of 1.8 metres long is laid out in the park.
Fossil shells are not common in the main whale-bearing rocks, but are very common in other rocks; many fallen rocks can be seen to be full of a wide variety of fossil shells. Disc-shaped nummulite fossils are common in places, and often coat the desert floor. A large log is present in the park, and this is full of tubular shipworm fossils. Some fossil seagrasses are also known.
The geology of the valley gives rise to the scenery, with wind and water erosion producing spectacular cliffs and buttes. The rocks present at Wadi Al-Hitan are all Middle to Late Eocene in age and comprise three main rock units. The Gehannam Formation comprises open marine mudstones, which are largely present on the flatter ground to the East of the public park.
The rock unit that contains most of the whale fossils is the Birket Qarun Formation. This comprises yellowish open marine sandstones that form most of the cliffs and buttes. The monotony of these sandstones is broken by a white layer full of well preserved animal burrows (previously thought to be mangrove roots) and a layer of black mudstone above that. When the cliffs of the Birket Qarun Formation are followed to the East, they are replaced by Gehannam Formation mudstones, indicating a change in water depth from shallower to deeper in that direction. The tops of the higher cliffs are within the Qasr el Sagha Formation, which comprises dark mudstones alternating with limestones full of shells and represents a lagoonal environment.
Summers on the Norwegian archipelago of Svalbard are now warmer than at any other time in the last 1,800 years, including during medieval times when parts of the northern hemisphere were as hot as, or hotter, than today, according to a new study in the journal Geology.
“The Medieval Warm Period was not as uniformly warm as we once thought–we can start calling it the Medieval Period again,” said the study’s lead author, William D’Andrea, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “Our record indicates that recent summer temperatures on Svalbard are greater than even the warmest periods at that time.”
The naturally driven Medieval Warm Period, from about 950 to 1250, has been a favorite time for people who deny evidence that humans are heating the planet with industrial greenhouse gases. But the climate reconstruction from Svalbard casts new doubt on that era’s reach, and undercuts skeptics who argue that current warming is also natural. Since 1987, summers on Svalbard have been 2 degrees to 2.5 degrees C (3.6 to 4.5 degrees F) hotter than they were there during warmest parts of the Medieval Warm Period, the study found.
Researchers produced the 1,800 year climate record by analyzing levels of unsaturated fats in algae buried in the sediments of Kongressvatnet lake, in western Svalbard. In colder water, algae make more unsaturated fats, or alkenones; in warmer water, they produce more saturated fats. Like pages in a book, the unsaturation level of fats can provide a record of past climate. So far, most Arctic climate records have come from ice cores that preserve only annual layers of cold-season snowfall, and thus cold-season temperatures. But lake sediments, with their record of summertime temperatures, can tell scientists how climate varied the rest of the year and in places where ice sheets are absent.
“We need both ice core and lake sediment records,” said Elisabeth Isaksson, a glaciologist at the Norwegian Polar Institute who was not involved in the study. “Here, Billy has found something that tells a different, more detailed story.”
In looking at how summers on Svalbard varied, researchers also discovered that the region was not particularly cold during another recent anomalous period–the “Little Ice Age” of the 18th and 19th centuries, when glaciers on Svalbard surged to their greatest extent in the last 10,000 years and glaciers in many parts of Western Europe also grew.They suggest that more snow, rather than colder temperatures, may have fed the growth of Svalbard glaciers.
Evidence from tree rings and ice cores shows that southern Greenland and parts of North America were warmer from 950 to 1250 than today, with the Vikings taking advantage of ice-free waters to settle Greenland. Some regions also saw prolonged drought, including California, Nevada and the Mississippi Valley, leading some scientists to coin the term Medieval Climate Anomaly to emphasize the extreme shift in precipitation rather than temperature. A natural increase in solar radiation during this time was responsible for warming parts of the northern hemisphere, with a rise in volcanic activity from 1100 to 1260 causing milder winters, University of Massachusetts scientist Ray Bradley explained in a 2003 Perspective piece in Science. Bradley is a co-author of the Svalbard lake sediment study.
Western Svalbard began to gradually warm in 1600, the researchers found, when the northern arm of the Gulf Stream, known as the West Spitsbergen Current, may have brought more tropical water to the region. In 1890, the warming began to accelerate, with researchers attributing most of the warming since about 1960 to rising industrial greenhouse gas levels. Ice cores from Svalbard, by contrast, show a slight cooling over the last 1,800 years. The conflicting evidence suggests that temperatures may have fluctuated more sharply between winter and summer, said Anne Hormes, a quaternary geologist at the University Centre in Svalbard who was not involved in the study.
D’Andrea and his colleagues dated their lake cores by analyzing grains of glass spewed by volcanoes hundreds of miles away in Iceland. Those past eruptions– Snæfellsjökullin 170, Hekla in 1104 and Öræfajökull in 1362 — all left unique chemical time markers on Svalbard’s lake sediments. “We know fairly precisely when these eruptions occurred, which is rare in the geologic record,” said study co-author Nicholas Balascio, a scientist at University of Massachusetts, Amherst.
Recent temperature measurements show that the Arctic is warming twice as fast as the rest of the planet, with sea ice this summer shrinking to its smallest extent on record. Natural feedbacks are amplifying the warming as loss of reflective sea ice causes the ocean to absorb more of the sun’s energy, melting more sea ice, which causes more energy absorption, and so on. Climate models suggest that by 2100 Svalbard will warm more than any other landmass on earth, due to a combination of sea-ice loss and changes in atmospheric and oceanic circulation, according to the International Panel on Climate Change 2007 report. In a study published last year in the journal Advances in Meteorology, Norwegian researchers estimate that average winter temperature in Svalbard could rise by as much as 10 degrees C, or 18 degrees Fahrenheit.
The study was funded by the U.S. National Science Foundation and the Keck Geology Consortium.
Note : The above story is reprinted from materials provided by The Earth Institute at Columbia University.
The Farafra depression is the second biggest depression by size located in Western Egypt and the smallest by population, near latitude 27.06° North and longitude 27.97° East. It is located in the Western Desert of Egypt, approximately mid-way between Dakhla and Bahariya.
Farafra has an estimated 5,000 inhabitants (2002) mainly living in the town of Farafra and is mostly inhabited by the local Bedouins. Parts of the town have complete quarters of traditional architecture, simple, smooth, unadorned, all in mud colour. Local pride has also secured endeavours to secure local culture. Also located near Farafra are the hot springs at Bir Sitta and the El-Mufid lake.
The Antarctic Ice Sheet could be an overlooked but important source of methane, a potent greenhouse gas, according to a report in the August 30 issue of Nature by an international team of scientists.
The new study demonstrates that old organic matter in sedimentary basins located beneath the Antarctic Ice Sheet may have been converted to methane by micro-organisms living under oxygen-deprived conditions. The methane could be released to the atmosphere if the ice sheet shrinks and exposes these old sedimentary basins.
Coauthor Slawek Tulaczyk, a professor of Earth and planetary sciences at UC Santa Cruz, said the project got its start five years ago in discussions with first author Jemma Wadham at the University of Bristol School of Geographical Sciences, where Tulaczyk was on sabbatical
“It is easy to forget that before 35 million years ago, when the current period of Antarctic glaciations started, this continent was teeming with life,” Tulaczyk said. “Some of the organic material produced by this life became trapped in sediments, which then were cut off from the rest of the world when the ice sheet grew. Our modeling shows that over millions of years, microbes may have turned this old organic carbon into methane.”
The science team estimated that 50 percent of the West Antarctic Ice Sheet (1 million square kilometers) and 25 percent of the East Antarctic Ice Sheet (2.5 million square kilometers) overlies pre-glacial sedimentary basins containing about 21,000 billion metric tons of organic carbon.
“This is an immense amount of organic carbon, more than ten times the size of carbon stocks in northern permafrost regions,” Wadham said. “Our laboratory experiments tell us that these sub-ice environments are also biologically active, meaning that this organic carbon is probably being metabolized to carbon dioxide and methane gas by microbes.”
The researchers numerically simulated the accumulation of methane in Antarctic sedimentary basins using an established one-dimensional hydrate model. They found that sub-ice conditions favor the accumulation of methane hydrate (that is, methane trapped within a structure of water molecules, forming a solid similar to regular ice).
They also calculated that the potential amount of methane hydrate and free methane gas beneath the Antarctic Ice Sheet could be up to 4 billion metric tons, a similar order of magnitude to some estimates made for Arctic permafrost. The predicted shallow depth of these potential reserves also makes them more susceptible to climate forcing than other methane hydrate reserves on Earth.
Coauthor Sandra Arndt, a NERC fellow at the University of Bristol, who conducted the numerical modeling, said, “It’s not surprising that you might expect to find significant amounts of methane hydrate trapped beneath the ice sheet. Just like in sub-seafloor sediments, it is cold and pressures are high, which are important conditions for methane hydrate formation.”
If substantial methane hydrate and gas are present beneath the Antarctic Ice Sheet, methane release during episodes of ice-sheet collapse could act as a positive feedback on global climate change during past and future ice-sheet retreat.
“Our study highlights the need for continued scientific exploration of remote sub-ice environments in Antarctica, because they may have far greater impact on Earth’s climate system than we have appreciated in the past,” Tulaczyk said.
Note : The above story is reprinted from materials provided by University of California – Santa Cruz.
PASADENA, Calif. — NASA’s Mars Curiosity has debuted the first recorded human voice that traveled from Earth to another planet and back.
In spoken words radioed to the rover on Mars and back to NASA’s Deep Space Network (DSN) on Earth, NASA Administrator Charles Bolden noted the difficulty of landing a rover on Mars, congratulated NASA employees and the agency’s commercial and government partners on the successful landing of Curiosity earlier this month, and said curiosity is what drives humans to explore.
“The knowledge we hope to gain from our observation and analysis of Gale Crater will tell us much about the possibility of life on Mars as well as the past and future possibilities for our own planet. Curiosity will bring benefits to Earth and inspire a new generation of scientists and explorers, as it prepares the way for a human mission in the not too distant future,” Bolden said in the recorded message.
The voice playback was released along with new telephoto camera views of the varied Martian landscape during a news conference today at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
“With this voice, another small step is taken in extending human presence beyond Earth, and the experience of exploring remote worlds is brought a little closer to us all,” said Dave Lavery, NASA Curiosity program executive. “As Curiosity continues its mission, we hope these words will be an inspiration to someone alive today who will become the first to stand upon the surface of Mars. And like the great Neil Armstrong, they will speak aloud of that next giant leap in human exploration.”
The telephoto images beamed back to Earth show a scene of eroded knobs and gulches on a mountainside, with geological layering clearly exposed. The new views were taken by the 100-millimeter telephoto lens and the 34-milllimeter wide angle lens of the Mast Camera (Mastcam) instrument. Mastcam has photographed the lower slope of the nearby mountain called Mount Sharp.
“This is an area on Mount Sharp where Curiosity will go,” said Mastcam principal investigator Michael Malin, of Malin Space Science Systems in San Diego. “Those layers are our ultimate objective. The dark dune field is between us and those layers. In front of the dark sand you see redder sand, with a different composition suggested by its different color. The rocks in the foreground show diversity — some rounded, some angular, with different histories. This is a very rich geological site to look at and eventually to drive through.”
A drive early Monday placed Curiosity directly over a patch where one of the spacecraft’s landing engines scoured away a few inches of gravelly soil and exposed underlying rock. Researchers plan to use a neutron-shooting instrument on the rover to check for water molecules bound into minerals at this partially excavated target.
During the news conference, the rover team reported the results of a test on Curiosity’s Sample Analysis at Mars (SAM) instrument, which can measure the composition of samples of atmosphere, powdered rock or soil. The amount of air from Earth’s atmosphere remaining in the instrument after Curiosity’s launch was more than expected, so a difference in pressure on either side of tiny pumps led SAM operators to stop pumping out the remaining Earth air as a precaution. The pumps subsequently worked, and a chemical analysis was completed on a sample of Earth air.
“As a test of the instrument, the results are beautiful confirmation of the sensitivities for identifying the gases present,” said SAM principal investigator Paul Mahaffy of NASA’s Goddard Space Flight Center in Greenbelt, Md. “We’re happy with this test and we’re looking forward to the next run in a few days when we can get Mars data.”
Curiosity already is returning more data from the Martian surface than have all of NASA’s earlier rovers combined.
“We have an international network of telecommunications relay orbiters bringing data back from Curiosity,” said JPL’s Chad Edwards, chief telecommunications engineer for NASA’s Mars Exploration Program. “Curiosity is boosting its data return by using a new capability for adjusting its transmission rate.”
Curiosity is 3 weeks into a two-year prime mission on Mars. It will use 10 science instruments to assess whether the selected study area ever has offered environmental conditions favorable for microbial life.
JPL manages the mission for NASA’s Science Mission Directorate in Washington. The rover was designed, developed and assembled at JPL. NASA’s DSN is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions
Mars Science Laboratory/Curiosity Mission Status Report
PASADENA, Calif. – Today, NASA’s Mars rover Curiosity fired its laser for the first time on Mars, using the beam from a science instrument to interrogate a fist-size rock called “Coronation.”
The mission’s Chemistry and Camera instrument, or ChemCam, hit the fist-sized rock with 30 pulses of its laser during a 10-second period. Each pulse delivers more than a million watts of power for about five one-billionths of a second.
The energy from the laser excites atoms in the rock into an ionized, glowing plasma. ChemCam catches the light from that spark with a telescope and analyzes it with three spectrometers for information about what elements are in the target.
“We got a great spectrum of Coronation — lots of signal,” said ChemCam Principal Investigator Roger Wiens of Los Alamos National Laboratory, N.M. “Our team is both thrilled and working hard, looking at the results. After eight years building the instrument, it’s payoff time!”
ChemCam recorded spectra from the laser-induced spark at each of the 30 pulses. The goal of this initial use of the laser on Mars was to serve as target practice for characterizing the instrument, but the activity may provide additional value. Researchers will check whether the composition changed as the pulses progressed.
If it did change, that could indicate dust or other surface material being penetrated to reveal different composition beneath the surface. The spectrometers record intensity at 6,144 different wavelengths of ultraviolet, visible and infrared light.
“It’s surprising that the data are even better than we ever had during tests on Earth, in signal-to-noise ratio,” said ChemCam Deputy Project Scientist Sylvestre Maurice of the Institut de Recherche en Astrophysique et Planetologie (IRAP) in Toulouse, France. “It’s so rich, we can expect great science from investigating what might be thousands of targets with ChemCam in the next two years.”
The technique used by ChemCam, called laser-induced breakdown spectroscopy, has been used to determine composition of targets in other extreme environments, such as inside nuclear reactors and on the sea floor, and has had experimental applications in environmental monitoring and cancer detection. Today’s investigation of Coronation is the first use of the technique in interplanetary exploration.
Curiosity landed on Mars two weeks ago, beginning a two-year mission using 10 instruments to assess whether a carefully chosen study area inside Gale Crater has ever offered environmental conditions favorable for microbial life.
ChemCam was developed, built and tested by the U.S. Department of Energy’s Los Alamos National Laboratory in partnership with scientists and engineers funded by the French national space agency, Centre National d’Etudes Spatiales (CNES) and research agency, Centre National de la Recherche Scientifique (CNRS).
NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Science Laboratory Project, including Curiosity, for NASA’s Science Mission Directorate, Washington. JPL designed and built the rover.
More information about Curiosity is online at http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl/ .
Research led by scientists at the American Museum of Natural History shows that ammonites-an extinct type of shelled mollusk that’s closely related to modern-day nautiluses and squids-made homes in the unique environments surrounding methane seeps in the seaway that once covered America’s Great Plains. The findings, published online this week in the journal Geology, provide new insights into the mode of life and habitat of these ancient animals.
Geologic formations in parts of South Dakota, Wyoming, and Montana formed as sediments were deposited in the Western Interior Seaway-a broad expanse of water that split North America into two land masses-during the Late Cretaceous, 80 to 65 million years ago. These formations are popular destinations for paleontologists looking for everything from fossilized dinosaur bones to ancient clam shells. In the last few years, groups of researchers have honed in on giant mounds of fossilized material in these areas where, many millions of years ago, methane-rich fluids migrated through the sediments onto the sea floor.
“We’ve found that these methane seeps are little oases on the sea floor, little self-perpetuating ecosystems,” said Neil Landman, lead author of the Geology paper and a curator in the Division of Paleontology at the American Museum of Natural History. “Thousands of these seeps have been found in the Western Interior Seaway, most containing a very rich fauna of bivalves, sponges, corals, fish, crinoids, and, as we’ve recently documented, ammonites.”
In the Black Hills region of South Dakota, Landman and researchers from Stony Brook University’s School of Marine and Atmospheric Science, the Black Hills Museum of Natural History, Brooklyn College, the South Dakota School of Mines and Technology, and the University of South Florida are investigating a 74-million-year-old seep with extremely well-preserved fossils.
“Most seeps have eroded significantly over the last 70 million years,” Landman said. “But this seep is part of a cliff whose face recently slumped off. As the cliff fell away, it revealed beautiful, glistening shells of all sorts of marine life.”
Studying these well-preserved shells, the researchers tried to determine the role of ammonites in the unique seep ecosystem. By analyzing the abundance of isotopes (alternative forms) of carbon, oxygen, and strontium, the group made a surprising discovery. The ammonites at the seep, once thought to be just passersby, had spent their whole lives there.
“Ammonites are generally considered mobile animals, freely coming and going” Landman said. “That’s a characteristic that really distinguishes them from other mollusks that sit on the sea floor. But to my astonishment, our analysis showed that these ammonites, while mobile, seemed to have lived their whole life at a seep, forming an integral part of an interwoven community.”
The seeps, which the researchers confirmed through oxygen isotope analysis to be “cold” (about 27 degrees Celsius, 80 degrees Fahrenheit), also likely attracted large clusters of plankton Ð the ammonites’ preferred prey.
With these findings in mind, the researchers think that the methane seeps probably played a role in the evolution of ammonites and other faunal elements in the Western Interior Seaway. The seeps might have formed small mounds that rose above the oxygen-poor sea floor, creating mini oases in a less-hospitable setting. This could be a reason why ammonites were able to inhabit the seaway over millions of years in spite of occasional environmental disturbances.
“If a nearby volcano erupted and ash covered part of the basin, it would have decimated ammonites in that area,” Landman said. “But if these communities of seep ammonites survived, they could have repopulated the rest of the seaway. These habitats might have been semi-permanent, self-sustaining sites that acted as hedges against extinction.”
Isotope analysis of strontium also revealed an interesting geologic finding: seep fluids coming into the seaway were in contact with granite, meaning that they traveled from deep in the Earth. This suggests that the Black Hills, a small mountain range in the area, already were beginning to form in the Late Cretaceous, even though the uplift wasn’t fully complete until many millions of years later.
This research was supported by the American Museum of Natural History and a National Science Foundation Research Experience for Undergraduates grant for two students from Brooklyn College to participate in the field work.
Note : The above story is reprinted from materials provided by American Museum of Natural History.
Ancient pollen and charcoal preserved in deeply buried sediments in Egypt’s Nile Delta document the region’s ancient droughts and fires, including a huge drought 4,200 years ago associated with the demise of Egypt’s Old Kingdom, the era known as the pyramid-building time.
“Humans have a long history of having to deal with climate change,” said Christopher Bernhardt, a researcher with the U.S. Geological Survey. “Along with other research, this study geologically reveals that the evolution of societies is sometimes tied to climate variability at all scales — whether decadal or millennial.”
Bernhardt conducted this research as part of his Ph.D. at the University of Pennsylvania, along with Benjamin Horton, an associate professor in Penn’s Department of Earth and Environmental Science. Jean-Daniel Stanley at the Smithsonian Institution also participated in the study, published in July’s edition of Geology.
“Even the mighty builders of the ancient pyramids more than 4,000 years ago fell victim when they were unable to respond to a changing climate,” said USGS Director Marcia McNutt. “This study illustrates that water availability was the climate-change Achilles Heel then for Egypt, as it may well be now, for a planet topping seven billion thirsty people.”
The researchers used pollen and charcoal preserved in a Nile Delta sediment core dating from 7,000 years ago to the present to help resolve the physical mechanisms underlying critical events in ancient Egyptian history.
They wanted to see if changes in pollen assemblages would reflect ancient Egyptian and Middle East droughts recorded in archaeological and historical records. The researchers also examined the presence and amount of charcoal because fire frequency often increases during times of drought, and fires are recorded as charcoal in the geological record. The scientists suspected that the proportion of wetland pollen would decline during times of drought and the amount of charcoal would increase.
And their suspicions were right.
Large decreases in the proportion of wetland pollen and increases in microscopic charcoal occurred in the core during four different times between 3,000 and 6,000 years ago. One of those events was the abrupt and global mega-drought of around 4,200 years ago, a drought that had serious societal repercussions, including famines, and which probably played a role in the end of Egypt’s Old Kingdom and affected other Mediterranean cultures as well.
“Our pollen record appears very sensitive to the decrease in precipitation that occurred in the mega-drought of 4,200 years ago,” Bernhardt said. “The vegetation response lasted much longer compared with other geologic proxy records of this drought, possibly indicating a sustained effect on delta and Nile basin vegetation.”
Similarly, pollen and charcoal evidence recorded two other large droughts: one that occurred some 5,000 to 5,500 years ago and another that occurred around 3,000 years ago.
These events are also recorded in human history — the first one started some 5,000 years ago when the unification of Upper and Lower Egypt occurred and the Uruk Kingdom in modern Iraq collapsed. The second event, some 3,000 years ago, took place in the eastern Mediterranean and is associated with the fall of the Ugarit Kingdom and famines in the Babylonian and Syrian Kingdoms.
“The study geologically demonstrates that when deciphering past climates, pollen and other micro-organisms, such as charcoal, can augment or verify written or archaeological records — or they can serve as the record itself if other information doesn’t exist or is not continuous,” said Horton.
This study, Nile delta response to Holocene climate variability, was published in the July edition of Geology, and was authored by Christopher Bernhardt, USGS; Benjamin Horton, Penn; and Jean-Daniel Stanley, Smithsonian Institution. Support for the work came from the University of Pennsylvania, the U.S. Geological Survey, and the Smithsonian Institution.
Note : The above story is reprinted from materials provided by United States Geological Survey.
A new study has successfully reconstructed temperature from the deep sea to reveal how global ice volume has varied over the glacial-interglacial cycles of the past 1.5 million years.
Scientists have announced a major breakthrough in understanding Earth’s climate machine by reconstructing highly accurate records of changes in ice volume and deep-ocean temperatures over the last 1.5 million years.
The study, which is reported in the journal Science, offers new insights into a decades-long debate about how the shifts in Earth’s orbit relative to the sun have taken Earth into and out of an ice-age climate.
Being able to reconstruct ancient climate change is a critical part of understanding why the climate behaves the way it does. It also helps us to predict how the planet might respond to human-made changes, such as the injection of large quantities of carbon dioxide into the atmosphere, in the future.
Unfortunately, scientists trying to construct an accurate picture of how such changes caused past climatic shifts have been thwarted by the fact that the most readily available marine geological record of ice-ages — changes in the ratio of oxygen isotopes (Oxygen 18 to Oxygen 16) preserved in tiny calcareous deep sea fossils called foraminifera — is compromised.
This is because the isotope record shows the combined effects of both deep sea temperature changes, and changes in the amount of ice volume. Separating these has in the past proven difficult or impossible, so researchers have been unable to tell whether changes in Earth’s orbit were affecting the temperature of the ocean more than the amount of ice at the Poles, or vice-versa.
The new study, which was carried out by researchers in the University of Cambridge Department of Earth Sciences, appears to have resolved this problem by introducing a new set of temperature-sensitive data. This allowed them to identify changes in ocean temperatures alone, subtract that from the original isotopic data set, and then build what they describe as an unprecedented picture of climatic change over the last 1.5 million years — a record of changes in both oceanic temperature and global ice volume.
Included in this is a much fuller representation of what happened during the “Mid-Pleistocene Transition” (MPT) — a major change in Earth’s climate system which took place sometime between 1.25 million and 600 thousand years ago. Before the MPT, the alternation between glacial periods of extreme cold, and warmer interglacials, happened at intervals of approximately 41,000 years. After the MPT, the major cycles became much longer, regularly taking 100,000 years. The second pattern of climate cycles is the one we are in now. Interestingly, this change occurred with little or no orbital forcing.
“Previously, we didn’t really know what happened during this transition, or on either side of it,” Professor Harry Elderfield, who led the research team, said. “Before you separate the ice volume and temperature signals, you don’t know whether you’re seeing a climate record in which ice volume changed dramatically, the oceans warmed or cooled substantially, or both.”
“Now, for the first time, we have been able to separate these two components, which means that we stand a much better chance of understanding the mechanisms involved. One of the reasons why that is important, is because we are making changes to the factors that influence the climate now. The only way we can work out what the likely effects of that will be in detail is by finding analogues in the geological past, but that depends on having an accurate picture of the past behaviour of the climate system.”
Researchers have developed more than 30 different models for how these features of the climate might have changed in the past, in the course of a debate which has endured for more than 60 years since pioneering work by Nobel Laureate Harold Urey in 1946. The new study helps resolve these problems by introducing a new dataset to the picture — the ratio of magnesium (Mg) to calcium (Ca) in foraminifera. Because it is easier for magnesium to be incorporated at higher temperatures, larger quantities of magnesium in the tiny marine fossils imply that the deep sea temperature was higher at that point in geological time.
The Mg/Ca dataset was taken from the fossil record contained in cores drilled on the Chatham Rise, an area of ocean east of New Zealand. It allowed the Cambridge team to map ocean temperature change over time. Once this had been done, they were able to subtract that information from the oxygen isotopic record. “The calculation tells us the difference between what water temperature was doing and what the ice sheets were doing across a 1.5 million year period,” Professor Elderfield explained.
The resulting picture shows that ice volume has changed much more dramatically than ocean temperatures in response to changes in orbital geometry. Glacial periods during the 100,000-year cycles have been characterised by a very slow build-up of ice which took thousands of years, the result of ice volume responding to orbital change far more slowly than the ocean temperatures reacted. Ocean temperature change, however, reached a lower limit, probably because the freezing point of sea water put a restriction on how cold the deep ocean could get.
In addition, the record shows that the transition from 41,000-year cycles to 100,000-year cycles, the characteristic changeover of the MPT, was not as gradual as previously thought. In fact, the build-up of larger ice sheets, associated with longer glacials, appears to have begun quite suddenly, around 900,000 years ago. The pattern of Earth’s response to orbital forcing changed dramatically during this “900,000 year event,” as the paper puts it.
The research team now plan to apply their method to the study of deep-sea temperatures elsewhere to investigate how orbital changes affected the climate in different parts of the world.
“Any uncertainty about Earth’s climate system fuels the sense that we don’t really know how the climate is behaving, either in response to natural effects or those which are man-made,” Professor Elderfield added. “If we can understand how earlier changes were initiated and what the impacts were, we stand a much better chance of being able to predict and prepare for changes in the future.”
Note : The above story is reprinted from materials provided by University of Cambridge, via EurekAlert!, a service of AAAS. The original story is licensed under a Creative Commons license.
A type of fault formed when the hanging wall fault block moves up along a fault surface relative to the footwall. Such movement can occur in areas where the Earth’s crust is compressed. A thrust fault, sometimes called an overthrust if the displacement is particularly great, is a reverse fault in which the fault plane has a shallow dip, typically much less than 45o.
For years, many scientists had thought that plate tectonics existed nowhere in our solar system but on Earth. Now, a UCLA scientist has discovered that the geological phenomenon, which involves the movement of huge crustal plates beneath a planet’s surface, also exists on Mars.
“Mars is at a primitive stage of plate tectonics. It gives us a glimpse of how the early Earth may have looked and may help us understand how plate tectonics began on Earth,” said An Yin, a UCLA professor of Earth and space sciences and the sole author of the new research.
Yin made the discovery during his analysis of satellite images from a NASA spacecraft known as THEMIS (Time History of Events and Macroscale Interactions during Substorms) and from the HIRISE (High Resolution Imaging Science Experiment) camera on NASA’s Mars Reconnaissance Orbiter. He analyzed about 100 satellite images — approximately a dozen were revealing of plate tectonics.
Yin has conducted geologic research in the Himalayas and Tibet, where two of Earth’s seven major plates divide.
“When I studied the satellite images from Mars, many of the features looked very much like fault systems I have seen in the Himalayas and Tibet, and in California as well, including the geomorphology,” said Yin, a planetary geologist.
For example, he saw a very smooth, flat side of a canyon wall, which can be generated only by a fault, and a steep cliff, comparable to cliffs in California’s Death Valley, which also are generated by a fault. Mars has a linear volcanic zone, which Yin said is a typical product of plate tectonics.
“You don’t see these features anywhere else on other planets in our solar system, other than Earth and Mars,” said Yin, whose research is featured as the cover story in the August issue of the journal Lithosphere.
The surface of Mars contains the longest and deepest system of canyons in our solar system, known as Valles Marineris (Latin for Mariner Valleys and named for the Mariner 9 Mars orbiter of 1971-72, which discovered it). It is nearly 2,500 miles long — about nine times longer than Earth’s Grand Canyon. Scientists have wondered for four decades how it formed. Was it a big crack in Mars’ shell that opened up?
“In the beginning, I did not expect plate tectonics, but the more I studied it, the more I realized Mars is so different from what other scientists anticipated,” Yin said. “I saw that the idea that it is just a big crack that opened up is incorrect. It is really a plate boundary, with horizontal motion. That is kind of shocking, but the evidence is quite clear.
“The shell is broken and is moving horizontally over a long distance. It is very similar to the Earth’s Dead Sea fault system, which has also opened up and is moving horizontally.”
The two plates divided by Mars’ Valles Marineris have moved approximately 93 miles horizontally relative to each other, Yin said. California’s San Andreas Fault, which is over the intersection of two plates, has moved about twice as much — but Earth is about twice the size of Mars, so Yin said they are comparable.
Yin, whose research is partly funded by the National Science Foundation, calls the two plates on Mars the Valles Marineris North and the Valles Marineris South.
“Earth has a very broken ‘egg shell,’ so its surface has many plates; Mars’ is slightly broken and may be on the way to becoming very broken, except its pace is very slow due to its small size and, thus, less thermal energy to drive it,” Yin said. “This may be the reason Mars has fewer plates than on Earth.”
Mars has landslides, and Yin said a fault is shifting the landslides, moving them from their source.
Does Yin think there are Mars-quakes?
“I think so,” he said. “I think the fault is probably still active, but not every day. It wakes up every once in a while, over a very long duration — perhaps every million years or more.”
Yin is very confident in his findings, but mysteries remain, he said, including how far beneath the surface the plates are located.
“I don’t quite understand why the plates are moving with such a large magnitude or what the rate of movement is; maybe Mars has a different form of plate tectonics,” Yin said. “The rate is much slower than on Earth.”
Earth has a broken shell with seven major plates; pieces of the shell move, and one plate may move over another. Yin is doubtful that Mars has more than two plates.
“We have been able to identify only the two plates,” he said. “For the other areas on Mars, I think the chances are very, very small. I don’t see any other major crack.”
Did the movement of Valles Marineris North and Valles Marineris South create the enormous canyons on Mars? What led to the creation of plate tectonics on Earth?
Yin, who will continue to study plate tectonics on Mars, will answer those questions in a follow-up paper that he also plans to publish in the journal Lithosphere.
Reference:
A. Yin. Structural analysis of the Valles Marineris fault zone: Possible evidence for large-scale strike-slip faulting on Mars. Lithosphere, 2012; 4 (4): 286 DOI: 10.1130/L192.1
A type of fault in which the hanging wall moves down relative to the footwall, and the fault surface dips steeply, commonly from 50o to 90o. Groups of normal faults can produce horst and graben topography, or a series of relatively high- and low-standing fault blocks, as seen in areas where the crust is rifting or being pulled apart by plate tectonic activity. A growth fault is a type of normal fault that forms during sedimentation and typically has thicker strata on the downthrown hanging wall than the footwall.
