The Earth Story

Earth’s early impacts

Today, asteroids large enough to cause global effects only hit the planet Earth once during a period of tens or hundreds of millions of years. However, when the solar system was younger, there was much more debris around and it was likely stirred up by occasional big motions of the giant planets. Although geologic processes have removed many of the craters from these early impacts, scientists are gradually finding evidence like these rocks for their existence.

These rocks come from one of many drill cores taken in Western Australia. Australia preserves some of the Earth’s oldest crust in an area called the Pilbara Craton. This craton is filled with large granitic plutons and metamorphosed sedimentary rocks stretched around them, a remnant of the formation of Earth’s earliest continental crust. The sedimentary rocks are over 3 billion years old and therefore also preserve chemical remnants of the environment when life was first evolving and diversifying. To investigate these processes, scientists have taken a series of drill cores through the sediments that give them intact stratigraphic sequences through these Archean aged rocks.

This rock comes from one of those drill cores. Its age is constrained by dating of other rocks in this drill core to be 3.46 billion years old. The small grains you see are spherules, small bits of molten rock splashed out by an impact. They are found in a drill core through different layers of chert, a silica-rich rock that is common in Archean sediments; the different colors come from different parts of the surrounding unit.

To establish that these were produced when an asteroid hit Earth, a team of researchers led by a scientist at Geoscience Australia characterized their textures and chemistry. They found elevated levels of platinum group elements, things like platinum, palladium, gold, and iridium, in addition to other elements like nickel and sulfur that are rare on Earth (they’re locked in the core) but abundant in meteorites. They also found angular particles (impact debris) and occasionally spherules that were broken and injected with quartz, illustrating the violence of their formation.

This spherule layer is the 17th impact spherule layer known from either South Africa or Australia. Those impacts occurred over hundreds of millions of years, so life would have had time to recover from them, but discovering so many of these layers shows that Earth was truly much more of a shooting gallery in the Archaean and surviving this environment would have been difficult for many species.

Interpreting this history is also complicated for geologists; because the rocks are metamorphosed and difficult to date precisely, some of those impacts could be correlated between the continents, but that’s hard to tell. For example, a few meters above the main spherule-bearing layer there is a second layer containing spherules. Because the rocks are metamorphosed, the scientists can’t tell if that layer actually represents a second impact or instead just a sedimentary reworking of spherules from the lower layer.

-JBB

Image credit and reference: Glickson et al., 2016 (Precambrian Research) http://bit.ly/25aGpBm

References: http://www.psu.edu/dept/spacegrant/ABDP/ http://bit.ly/23VUQmW

EARLY EARTH MAY HAVE BEEN KEPT WARM BY HYDROGEN-NITROGEN COLLISIONS

Many theories have been explored over the years as to how the Earth stayed warm during the first two billion years of its development, as even though it was warm enough to support life, it was not from heat provided by the Sun. Earth at that time only received 70 percent of the solar radiation that it receives today and its average temperature was up to 25 °C colder. There is geological evidence that Earth had liquid water at this time, despite the average surface temperature being around -10 °C. Robin Wordsworth and Raymond Pierrehumbert, geologists at the University of Chicago, have suggested in a paper published in the journal Science that it was collisions between hydrogen and nitrogen molecules in the atmosphere that kept early Earth warm.

Previous work had focused on the hypothesis that it was methane released by organisms consuming hydrogen that was acting as a greenhouse gas, trapping the small amount of heat coming from the Sun. In this new study however, Wordsworth and Pierrehumbert suggest that collisions between hydrogen and nitrogen molecules create "dimer" molecules that wobble when hit by infrared light from the Sun. This wobbling would allow for heat capture for Earth’s atmosphere. Evidence for this theory would be indications that there was more hydrogen in Earth’s atmosphere in the past than there is today.

The two researchers reference new work by others which suggests that that is the case: there are some calculations that show that early Earth’s atmosphere may have contained as much as 30 percent hydrogen. According to Wordsworth and Pierrehumbert, if the early Earth had as much as 10 percent more hydrogen in its atmosphere than it does today and nitrogen was present at double or triple today's concentrations, Earth's average surface temperature would have been 10 to 15°C higher.

This research has implications for other planetary bodies, as they too may be experiencing similar warming effects. If these worlds have a lot of hydrogen within their atmosphere, they may be worth further observing as a potentially habitable world if they are within a habitable zone.

Saturn’s largest moon, Titan, has liquid on its surface despite being so far from the Sun. Its atmosphere has high concentrations of hydrogen and nitrogen; these gases are under so much pressure that their molecules constantly collide. These collisions cause a chemical reaction that traps the energy of the Sun.

This new model does not explain fossilized raindrop imprints on Earth that date back to 2.7 billion years ago. The size of these imprints suggests that the raindrops fell quickly to Earth through a thin atmosphere similar to that of the present day, rather than an atmosphere thick with greenhouse gases. Hydrogen is a light gas, so the raindrops would have passed through it more quickly than through an atmosphere rich with CO2 or methane. The concentrations of hydrogen and nitrogen needed by this new model would have slowed the raindrops too much to make them consistent with the imprints.

Wordsworth does admit that there is little geological evidence that hydrogen and nitrogen levels were as high as suggested by this new model, but believes there are other factors that could have created such an atmosphere. It is possible that Earth’s volcanoes of 2 billion years ago emitted more hydrogen than today’s volcanoes. The atmosphere at that time would have been able to hold more hydrogen as oxygen levels were lower; hydrogen would have been less likely to combine with this oxygen to form water. Microbes that consume hydrogen may have been rarer than they are today as there were fewer nutrients.

Though the model itself is good, according to Chris McKay of the NASA Ames Research Center in Moffett Field, California, there will need to be strong evidence of nitrogen and hydrogen levels being that high.

-TEL

The image shows Earth vs Titan, courtesy Victoria Jaggard of National Geographic News

http://phys.org/news/2013-01-geologists-theorize-early-earth-hydrogen-nitrogen.html#jCp http://www.newscientist.com/article/dn23043-titan-holds-clue-to-faint-young-sun-paradox.html http://www.newscientist.com/article/mg21328585.200-fossil-raindrops-reveal-earths-early-atmosphere.html Hydrogen-Nitrogen Greenhouse Warming in Earth's Early Atmosphere, Science 4 January 2013: Vol. 339 no. 6115 pp. 64-67 DOI: 10.1126/science.1225759 http://www.sciencemag.org/content/339/6115/64

Banded Iron Formations – an insight into early life on Earth While the earth formed some 4.5 billion years ago in the Hadean Eon, most of the rocks we see nowadays are much younger than that. Looking at changing rocks through time we can see a number of distinct environments and time periods represented, such as the impressive exposures of white chalk from the Cretaceous Period, but relatively few opportunities to study the very oldest rocks on the planet remain. On Earth, through the combined actions of metamorphism, erosion and remelting of rocks, Hadean rocks are in very short supply. More samples exist from Earth’s next Eon, the Archaean, including fascinating examples like these that imply a very different world. Banded iron formations (BIFs for short) are distinct, layered, and often heavily deformed rocks. Typical BIFs show repeating, consecutive, iron-rich and iron-poor layers; bands of a few millimetres to centimetres of black, silver or grey iron oxides such as haematite (Fe2O3) or magnetite (Fe3O4) alternate with layers of sediment lacking in iron, like shale or chert that are often red in colour, producing a beautiful layered effect. These formations are therefore an excellent indicator of the Earth’s early environmental history. About 2.4 billion years ago, oxygen first appeared in Earth's atmosphere, the product of organisms called cyanobacteria which first developed the process of photosynthesis around that time. Prior to this, oxygen generally reacted with dissolved iron or organic matter in the oceans, but once these sources became oversaturated O2 started to fill the atmosphere; this is often referred to as the Great Oxygenation Event, the first accumulation of biologically induced oxygen. Without oxygen in the atmosphere, iron does something we're not familiar with today - it actually dissolves in water and can be held in the oceans like salt. Once oxygen began building up in the atmosphere, suddenly all this iron became insoluble, started precipitating out and sinking to the sea floor. This appears to have been a periodic process; periods of abundant dissolved iron alternated with periods of limited dissolved iron and formation of cherts and shales. Once enough oxygen was present to use up the iron dissolved in the oceans, BIFs could no longer form, so the planet no longer makes them today. Their age usually means that they have been subject to a number of deformation processes, producing beautiful folded effects in specimens. Banded iron formations truly are a unique insight into early planetary history. ZM Further information: Genesis of Banded Iron Formations: http://econgeol.geoscienceworld.org/content/89/6/1384.abstract  Banded Iron Formations: http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Banded_iron_formation.html  Image credit: http://www.flickr.com/photos/jsjgeology/14872616219/  Figure: Folded jaspilite BIF (Hamersely Group, Neoarchean to Paleoproterozoic, ~2.47-2.55 Ga; Hamersley Range, Western Australia)

THE ARCHEAN EON Each geologic eon marks a step in the planet’s history to, well, where we are now. The Archean evolves from the hell of the Hadean at ~ 3.8 billion years in the past, its dawn recorded by the oldest rocks preserved in the geologic record. The end of the Archean, at its boundary with the Proterozoic ~2.5 billion years ago, is marked by one of the greatest catastrophes ever witnessed by the planet – a disaster rooted in early life processes within the Archean and without which there would be no “us” today.  In the beginning of the Archean –  –The sun was still weak, not yet the energy powerhouse of today: the sun is estimated to have been “shining” at about 75% of its present level and strengthened to about 85% by the end of the Archean. –Earth’s heat flow was three times higher than today and cooled to twice by the beginning of the Proterozoic. This would mean that given very little encouragement, anything that might cause a shallow rupture in the incipient crust (perhaps an earthquake, a meteor strike, or convection in underlying magma) could cause yet another volcano to erupt.  –The remnant pieces of Archean lithosphere preserved in the geologic rock record begin to look like primitive versions of today’s. The surface of the ancient earth seemed to have two main kinds of crustal material. One kind was essentially “lava,” hardened at the cold surface of the world. This sort of rock is referred to as “mafic” because it’s rich in magnesium and iron (ferric) and, as this composition implies, it’s a rather heavy rock material. The other sort of crustal material consisted of the lightweight constituents, the “froth” if you will, that collected like scum above the mafic material. Because this is largely composed of feldspars, this is called “felsic.” Felsic scum is the parent of our continental cratons: ~7% of the rocks exposed on the earth today date from the scum of the Archean.  –From a slow start of rock cycle processes in the late Hadean, we can almost recognize plate tectonic activity in earnest within the Archean. There are no properly preserved tectonic plate margins, but there are ancient cratons that seemed to have merged with other cratons. Along the boundaries where these proto-continents welded together are elongate zones of somewhat younger mafic rocks: these are the “greenstone belts.” Greenstone belts, as their name implies, are composed largely of “green” rocks, that is, rocks rich in chlorite and epidote produced during the metamorphic alteration of mafic minerals. The original rock types (before they were “green”) include lavas erupted within seawater, sediments (both rock debris and chemical sediments), and coarser-grained mafic rocks from deeper levels of the ancient “greenstone” crust or mantle. Rock suites that look much like these, given the name “ophiolites,” have been forming ever since the Archean whenever new oceanic lithosphere is created and is preserved through plate collisions onto continental terrains. So, by the end of the Archean, the earliest plate tectonic processes seem to have been functioning.  –The division of the earth’s surface between continental and oceanic terrains in the Archean is speculation. Estimates range from ~5% to 40% continental material (presumably dry land) and the rest oceanic. Today, only ~25% of the earth is continental. The ocean basins of the time were filling with sediments such as greywackes (a sedimentary rock type composed of rock detritus from a close-by source), chemical cherts (cryptocrystalline quartz deposited in the Archean largely by inorganic processes) and some rather strange deposits of “banded iron formations.” At the very least, these sedimentary accumulations attest to the presence of liquid water as a means of erosion on continents and transport of rock detritus: there were rivers as well as oceans.  –Life began to test the waters of the ancient Archean. At first, simple bacteria-like organisms (one-celled organisms lacking cell nuclei such as Archaea and Prokaryotes) used sulfurous and methane-rich sources to obtain metabolic energy. Archean environments in which these anaerobic organisms lived were probably much like those where these creatures are still found today: within and in rocks beneath undersea volcanic vents and in hot springs. These life forms today are labeled “extremophiles” because they enjoy extreme environments.  .  –There may not have been photosynthesis at the beginning of the Archean, but there certainly was by its end. Enter the “cyanobacteria” (blue-green algae), simple organisms capable of using solar energy to thrive; a “waste” product of their metabolism was free oxygen. Fossil cyanobacteria are found in rocks of 3.5 billion years in age, but not until ~2.7 billion years did they really take over the Archean.  –The Archean becomes the Age of the Stromatolites. These almost-creatures are composed of layers of blue-green algae, happily existing off sunlight and carbon dioxide in the Archean seas: as they metabolize carbon dioxide via photosynthesis, layers of calcium carbonate (what limestone is made of) precipitated from their CO2 usage, blocking the sunlight, so they moved a “story” upwards into the light, and started another layer, and another, and another… resulting in football-size spheres of layers of limestone and bacterial gunk. The stromatolites built the first reefs on earth. –Oxygen was poison. The vast majority of life-forms of the early Archean were the extremophiles, happily metabolizing sulfur and methane (to which the addition of oxygen totally blocks the chemical reactions essential to their physiology), and these co-existed quite nicely with the stromatolites throughout most of the Archean. Their savior from free oxygen was …rust. When oxygen entered the Archean seawater, it quite nicely hooked up with iron ions floating about, which then precipitated out of the solution and collected in layers and layers of iron oxide (yes, rust) on the seafloor. These layers formed another famous rock suite of the Archean, the Banded Iron Formations. Banded Iron Formations are still exploited today as iron ore, all due to the activity of the blue-green algae of the Archean.  Towards the end of the Archean, with more and more oxygen being produced by cyanobacteria, more and more iron was precipitated from the oceans until – –There were not enough iron ions in seawater to neutralize oxygen. For the first time an excess of oxygen began to accumulate in the atmosphere. Oh, not much – just up to several percent compared to the ~21% of our modern atmosphere. Never the less, this is termed the Great Oxygenation Event.  Poised on the boundary between the Archean and Proterozoic, the future for all life on earth hinged on the ability of primitive organisms to survive the Great Oxygenation Event. The presence of oxygen caused a massive extinction to the prevailing anaerobic life forms, seemingly a “backfire” in evolution that wiped out all the seeming biologic progress made to that date. But, like a tendril reaching into the future, those blue green algae and a few chemotrophs survived and … well what happens next is a story for the next Eon, the Proterozoic.  The biologic implosion at the end of the Archean is the first, and thought by some to be the greatest, extinction event inflicted on earth’s inhabitants. It was not brought about by meteors or excessive volcanism or global warming – but by oxygen poisoning.  Annie R.  *Expect a summery of the next Eon, the Proterozoic, in about a week’s time. Photo credit: Pilbara Archean Craton (satellite image): http://www.jspacesystems.or.jp/ersdac/ASTERimage/ASTERimage_library_E.html  For the intrepid reader: http://www.facebook.com/photo.php?fbid=426202710774112&set=pb.352857924775258.-2207520000.1353490038&type=3&theater https://www.facebook.com/photo.php?fbid=436673956393654&set=a.352867368107647.80532.352857924775258&type=1&theater http://www.unlockingtheworld.com/resources/public/volcanoes/384-the-early-earth-and-plate-tectonics http://essayweb.net/geology/timeline/archean.shtml http://forces.si.edu/atmosphere/02_02_02.html http://imnh.isu.edu/exhibits/online/geo_time/geo_time_eons.htm http://ammin.geoscienceworld.org/content/90/10/1473.abstract http://www.sciteclibrary.ru/eng/catalog/pages/8684.html http://www.sciencedirect.com/science/article/pii/0012825294900256 http://www.cprm.gov.br/33IGC/1353714.html http://www.noahsarkzoofarm.co.uk/pages/research/07-warm-water/warm-water.php http://www.bbc.co.uk/science/earth/earth_timeline/first_life http://serc.carleton.edu/microbelife/extreme/extremophiles.html

The Kondyor Massif

While it appears to be a volcano or a meteorite impact crater, the 10km circle on the Siberian surface depicted in the photo is an intrusion of very low silica magma that rose up from the mantle over a billion years ago. It reached a buoyancy point in the Archaean meta-sedimentary rocks of the Siberian craton, stopped, and slowly crystallised (baking the rocks around it into a hard metamorphic rock known as hornfels).

The surrounding ridge is 600 metres high, and the dome is gifted with an uncommon geochemistry that led to one of the world's major platinum placer (alluvial) deposits, located in the snowmelt fed river leading out of the feature. Located between Khabarovsk and Yakutsk in the endless expanse of Russia's far east, the dome was gradually exposed by the forces of erosion, though it took a billion years for the crust above it to be removed.

Those of you who have survived an igneous petrology class will probably have glanced at thin sections of places such as the Bushveld intrusion in South Africa. The complex is mostly made of dunite, a rock made of nearly pure crystalline olivine (aka the gem peridot, seehttp://tinyurl.com/pavuvbq), associated with clinopyroxenite. These intrusions often crystallise simultaneously from the outside inwards in layers, following a complex zoning dance ruled by the laws of physics and chemistry and the complex changing conditions within the magma chamber.

Last year it produced 4 tonnes of the metal, including unique specimens of a very rare alloy of platinum and iron, coated with gold that are found as nuggets in the river. Several rare platinum group (platinum, rhodium, iridium etc) minerals have been named from discoveries here, some unique to this site. Konderite is a mineralogical mishmash of copper, platinum, rhodium, lead, and sulphur, a testimony to its unique geochemistry and crystallisation conditions.

The image was combined from the ASTER instrument on NASA's TERRA Earth observation satellite, by draping a image date onto radar elevation data

Loz

Image credit: NASA http://www.atlasobscura.com/places/kondyor-massif http://earthobservatory.nasa.gov/IOTD/view.php?id=8773 http://russian-platinum.ru/our_business/kondyor_mine_as_amur?setlang=2 http://faena.com/en/content/impressive-kondyor-massif#!/ http://hague6185.wordpress.com/tag/kondyor-massif/ http://conf.uran.ru/12IPS/Kondyor-2_10-03-2014.pdf

Lac Couture The hard metamorphic Archaean (3.8-2.5 billion years old) gneisses of the Precambrian Canadian shield preserve more than their fair statistical share of impact craters, since they are very resistant to erosion. The 8km diameter lake known as Couture lies in the centre of such a crater, being found in Quebec, near Hudson bay. Scientists have dated it by analysing samples of impact melt to the Silurian (around 430 million years ago), just as life was beginning to emerge onto the land. Physical evidence in the form of impact shocked minerals and shatter cones of rock abound in the area. Sited in the slightly bleak looking tundra zone, the area was covered by ice sheets during the ice ages, which planed down toe topography to its currently subdued level. The central peak is submerged under the lake's waters, and the rim has been more or less planed down. The crater was once much larger, but the erosion has only left behind the breccia (shattered rock) that underlay the original impact site.  Our past posts on Canadian impact craters:  Pingualuit: http://tinyurl.com/m3aj4rt Sudbury: http://tinyurl.com/masy7yd Manicouagan: http://tinyurl.com/d4osf4n Loz Image credit: Hearmusicz http://www.passc.net/EarthImpactDatabase/couture.html http://ottawa-rasc.ca/wiki/index.php?title=Odale-Articles-LacCouture

Serpentine Falls The Serpentine Falls are located within Serpentine National Park, which is approximately 50km South-East of Perth, Western Australia. Part of the Serpentine River, and located on the Darling Scarp, the falls and the surrounding bush were designated a National Park in 1957. The falls are seasonal, and if visiting from December to March it is unlikely that there will be a lot, if any water flowing over the falls.  The River Serpentine and the falls cut through a series of Archean Gneisses and Granites. The rocks can be viewed on all of the walking trails within the park, and there are some spectacular outcrops and fresh exposures.  The Darling Scarp (Or the Darling Ranges as they are sometimes known) are the Perth surface expression of the Darling Fault, which runs for over 1000km's, from Shark Bay in the North to Albany in the South. It is believed that originally the Scarp followed the exact path of the Darling fault, but erosion has pushed it to the East by around 15km. To find out more about Serpentine National Park head to the links below. -LL Links; http://www.sjshire.wa.gov.au/ http://www.serpentinevalley.com.au/ http://www.skwirk.com.au/p-c_s-75_u-394_t-1370_c-5277/the-darling-range/vic/humanities/discovering-australia/rivers-mountains-and-reefs http://www.dec.wa.gov.au/pdf/nature/management/serpentine.pdf http://anpsa.org.au/APOL22/jun01-4.html Image; Mandurah and Peel

OMG we might be right! When the Apollo program returned samples from the Moon, the rocks clearly differed from rocks on Earth. Different minerals, different abundances of minerals, clearly different histories and chemistries, but there were also surprising links between the two bodies. Oxygen is the most abundant atom in the Earth, making up nearly half of the planet’s mass. Oxygen has 3 isotopes with masses 16, 17, and 18. Modern instruments can measure the ratios of these 3 isotopes in rocks and one key observation is that almost every object in the solar system has a different mixture. Mars is different from the Earth, the Earth is different from meteorites, meteorites from one asteroid differ every other asteroid. But there was one exception; to within error, the Earth and the Moon matched.  This match was a big deal at the time and still is today. Since oxygen is so abundant it’s impossible to get a match by random chance: it’s like mixing 8 different types of pop at a soda fountain and coming out with the same exact mixture 2 times in a row.  Out of this data was born the idea that the Moon was formed by a giant impact into Earth. Late in Earth’s history ~50 million years after the planet started forming, an object at least the size of Mars, if not bigger, slammed into the Earth, spraying debris into orbit around the planet. That debris came together under gravity to form the Moon. That model could explain the Moon’s chemistry; identical to Earth in its oxygen isotopes but slightly different in its chemistry since it formed in a different way. The model fits many other parameters, like where the Moon formed, the ages of the Moon rocks, and why the Earth spins at the rate it does, so it is a very good model. But there was a problem. To understand how a giant impact could occur, scientists used advanced computer simulations to model how the energy and mass moved around during the impact (described here:https://www.facebook.com/TheEarthStory/posts/556021494458899). While doing this, they noticed something odd; the Moon kept being formed mostly out of material from the impactor.  There was a lot of exchange of mass between the two bodies since most of the mass of the moon was literally vaporized by the impact, but some parts of the impactor, known as Theia, should have been big contributors to the Moon. If this is the case, then how in the world could the Moon’s oxygen isotopes match the Earth so perfectly? Well, today we have the answer. Over time, we’ve been able to measure oxygen isotopes more precisely as better instruments are developed, and better measurements can detect smaller differences. New research just published in the journal Science by a team from Georg-August-University ät Göttingen measured rocks from the Moon and Earth at the best resolution ever done and found the tiniest of differences! This is about as exciting of a measurement of an incredibly tiny difference as we can get. This measurement fits with exactly what the people who developed the Giant Impact model for the Moon’s formation have been predicting and have been unable to explain for years. There should be tiny differences between the Moon and Earth if the Moon was splashed off of the Earth in a giant impact, and scientists finally just found one! Maybe, just maybe, we’re actually right! How cool is that! -JBB Image credit: http://www.nasa.gov/multimedia/imagegallery/image_feature_1454.html Original paper: http://www.sciencemag.org/content/344/6188/1146 Commentary: http://www.nature.com/news/lunar-rock-chemistry-supports-big-smash-theory-1.15356#/b1

Hallelujah, it’s rainin’ chert! This layer is one of the most common rock types found in sediments from the ancient ocean; chert. Chert is made of fine-grained silica, and in rocks from the Precambrian, layers of it are found all over the place. They formed over hundreds of millions of years, on different continents, in different settings, and even mixed with other common rock types like banded iron formations and carbon-rich sediments possibly left over from early organisms. Despite these cherts being so common in the Precambrian, Earth doesn’t commonly make them today. That could make some sense because of evolution; some organisms have figured out how to make shells out of silica, which removes it from ocean waters. But…that leaves the question about how the ancient ocean made layers like this. There are some ideas. Some scientists have proposed that chert could form as groundwater flowed through sediments after burial; any silica dissolved in the water could precipitate new minerals like chert. Others suggested chert might at the bottom of the ocean as tiny grains pile up and water was squeezed out. Based on photos like the one you’re looking at, a group of Stanford scientists led by Elizabeth Stefurak have found strong evidence for a different mechanism. They looked at cherts from all over the world, formed hundreds of millions of years apart and they kept finding a strange texture. See how there are “grains” in this chert layer? None of the known ways to form chert can produce that texture. They found granules in rocks formed from both deep and shallow waters, so however the Earth was making these; the planet transported them all over. Although they can be compacted, they formed as nearly spherical grains. The scientists hypothesized that maybe they were commonly formed in shallow waters and carried farther out to sea by waves or submarine landslides. Imagine a landslide millimeter-sized balls of chert pouring down a slope or even raining down on the floor of the ocean; that’s very different from anything happening today, but something like that happened billions of years ago to make this rock. The geologic record is full of interesting changes we are still trying to understand. You’re looking at a rock found all over, over hundreds of millions of years, and yet because the oceans today are so different, it takes detailed study to understand the story of how those rocks formed. -JBB Image credit: Elizabeth Stefurak Original paper: http://geology.geoscienceworld.org/content/early/2014/02/07/G35187.1.abstract

The Pilbara Region. The Pilbara, located in the North Of Western Australia is a vast but remote area of land. The area has an arid and tropical climate, with periods of no rain and temperature of above 45 degrees Celsius, and tropical Summer cyclones. Cyclones hit the Pilbara with a frequency of around 7 per 10 years, but due to the area being very thinly populated these cyclones rarely have a devastating effect. The name Pilbara is said to derive from the aboriginal word "bilybara" meaning dry, however an opposing view has said that the name is derived from the aboriginal word "pilbarra" meaning mullet (a type of fish) and is reference to the Pilbarra Creek a tributary of the Yule River which runs through the Pilbara region, and discharges in the Indian Ocean. The Pilbara covers a region of 507,896 square km and has a population of just 48,610. The economy of the Pilbara region is supported by the vast amounts of Iron Ore mined mainly from around the Newman and Tom Price areas. Geology. The Pilbara craton is a very old, stable piece of continental lithosphere made up of archean rocks and is around 3.5Ga. The Pilbara is one of only two pristine areas of archean crust found in the world (the other is the Kaapval Craton in South Africa). The oldest rock types that make up the Pilbara are granitoid Greenstone belts overlaid by felsic volcanic rocks. Other rocks which make up the Pilbara region are mafic to ultramafic volcanics, felsic volcanics, cherts interbedded with basalt. large amounts of banded iron are found, pyroclastics, rhyloites and agglomerates. The structure of the area is defined by crustal thickening, accretion of island arcs, strike-slip faulting, diaprism, vertical tectonics and core complex formation. This Link; http://www.wa.gsa.org.au/publications/guidebook4.pdf Is a PDF guidebook to the geology of the region, and contains detailed maps, descriptions and references. Well worth a Look! -LL Links For more information about the Pilbara: http://www.ga.gov.au/minerals/projects/concluded-projects/north-pilbara-project/introduction.html http://www.westernaustralia.com/Experience_Extraordinary/Pages/Karijini_Discovery.aspx?CID=dgm%3Asem%3Aaud1112%3AWA+Extraordinary+Experiences+Karijini+Discovery%3AThe+Pilbara&gclid=CJGU8-vbjbECFeuTpgodqi62Qg Types of Volcanic Rock; http://www.rocksandminerals4u.com/example_of_igneous_rocks.html Image Hosted By; http://www.phvc.com.au/port-hedland/camping-and-caravans