Geology

athabasca-basin

Carswell Asteroid Impact Structure

Carswell structure – Interior (pink) = GRANITE; Inner ring (yellow) = DISTURBED ATHABASCA FORMATION; Outer ring (green) = CARSWELL FORMATION (dolomite) – (Sawatzky).   …   The Athabasca basin, a historical shallow tropical sea basin filled with sediments from the Hudsonian mountains. The Athabasca basin was formed during the Statherian or Paleohelikian 1.7 to 1.6 billion years ago….   …   The Carswell crater is the largest known impact crater in Saskatchewan and 4th-largest in Canada.  [It is believed to be roughly 115 million years old.]   …   …   At the contact between the crystalline rocks of the core and upturned sediments, uranium deposits are mined.  [Cluff Lake Mine]   …   …   The Carswell impact structure is therefore older and larger than previously estimated.  … [this] would suggest a crater size in the basement of 118 to 125 km wide.

Out of a Clear Grey Sky    …   THE METEORITE FELL on Carancas (Peru) on September 15th 2007, at 11:40:14 precisely. Unlike most, it did not break up in the atmosphere, but landed with an impact one scientist has equated to 3,000kg of explosives, enough to destroy a city block. It sent up a mushroom of smoke that could be seen five miles away, in Desaguadero, on the border with Bolivia.  ….  As soon as the fireball landed, the skies turned dark with a toxic cloud that killed cattle, put many of the villagers in hospital, and left 600 people, including many of the emergency services, with nausea and headaches. One man told me that the cloud made the village smell “like hell must smell—of sulphur and rotten eggs”. The sky rained down with stones hurled up by the meteorite’s landing. The only glass windows in the hamlet, at the health centre, all shattered.  ….  In this case, the residual heat and impact of the meteorite combusted with the water, which the villagers had been drinking for years. Local health officials now realised the water contained traces of arsenic and that, over the long term, this had caused the liver problems and early mortality in Carancas which had always been put down to the hardship of the villagers’ lives. The meteorite had sent up such a concentrated dose of this arsenic that it finally became apparent; some geologists think that this may have combined with the troilite already present in the meteorite to form a dangerous cocktail.

Araguainha Crater 

Small But Deadly  …   The biggest extinction in history was probably caused by a space rock that changed the climate.

…most people think [the] Araguainha [crater] is too small to be the culprit. It is a mere 40km (25 miles) across. The Chicxulub crater in Mexico, which did for the dinosaurs, is 180km in diameter, and it may have been paired with an even bigger impact in the Indian Ocean. … 

After an extensive geological survey, [Dr. Tohver] and his team discovered that a sizeable amount of this rock is oil shale. Any hydrocarbons in the crater would certainly have been vaporised. More intriguingly, the researchers calculate that the impact would have generated thousands of earthquakes of up to magnitude 9.9 (significantly more powerful than the largest recorded by modern seismologists) for hundreds of kilometres around. In effect, it would have been the biggest fracking operation in history, releasing oil and gas from the shattered rock in prodigious quantities.

 The upshot, Dr Tohver believes, would have been a huge burp of methane into the atmosphere. Since methane is a powerful greenhouse gas, that burp would have resulted in instant global warming, making things too hot for much of the planet’s animal life. Presto! The Permian mass extinction is explained.  

 

World’s Biggest Tsunami
The largest recorded tsunami was a wave 1720 feet (524m) tall in Lituya Bay, Alaska.  July 9, 1958.

Tsunamis in Lake Geneva    A millennium-and-a-half ago, Geneva was destroyed by a giant wave. Recent research suggests it could happen again.
…   The tsunami of 563 started at the opposite end of the lake from Geneva, at the point where it is fed by glacial meltwater carried into it by the Rhône.  …accounts say the wave began with a massive rockfall on what was then called Mount Tauredunum…
…    Dr Kremer thinks that the rocks crashed down onto soft sediments which had accumulated at the river mouth because of the slowing of the river’s flow when it enters the lake. These sediments form an underwater delta that has several canyon-like channels. When the falling rocks hit the delta they destabilised the sediments and caused the canyons to collapse. It was this collapse that created the tsunami.
…    Her discovery is a bed of what is known geologically as turbidite. This is sediment that, because it is laid down by rapid water movements, is not sorted by grain size. The turbidite Dr Kremer found is a mixture of sand and silt roughly 10km (6 miles) long and 5km wide. On average, it is 5 metres deep, and it seems to have formed in a single event. By carbon-dating leaves and other organic material trapped within it, she has shown that it is about the same age as the Tauredunum event.
…    … Dr Kremer’s pinger shows evidence of four layers deeper in the lake bed which also look like turbidite. The formation of these might or might not have triggered tsunamis. But they are a worrying sign.
 
Though the basin in which Lake Geneva sits is ancient, the modern lake is a product of the end of the last Ice Age. Exactly when it formed is unclear. The whole area was still buried under ice 19,000 years ago. By 13,000 years ago the glaciers had retreated at least as far east as Lausanne. But the age of the current delta is still unknown. That five layers of turbidite may have formed in this time gives a rough sense of how frequently tsunamis might happen. The details will remain obscure, though, until the older beds are examined closely, and core samples taken from them.
…    Dr Kremer’s work also raises the question of whether other lakes are at risk of generating tsunamis. Some might be. In 1806, for example, a landslide into Lake Lauerz, farther east in Switzerland, triggered a tsunami 20 metres high.

Ultra-thin fault caused gravity-distorting Japan quake   …   The results … revealed a significant presence of smectite, a slippery clay largely responsible for many major landslides in Europe….  Temperature measurements confirmed the fault had a coefficient of friction of only 0.1, making it very likely to shift. Most rocks slip at about 0.5 or 0.6….   …the fault zone was found to be less than 5 metres thick, tens of times thinner than at other subduction zones.    … It seems that subduction zones with particularly thin fault zones and a lot of smectite can produce slips of more than 50 metres….

The Tohoku slip was so big that the infrasound waves generated by the quake propagated more than 200 kilometres through the atmosphere. That disturbed the orbit of the European Space Agency’s GOCE satellite….

Coefficient of Friction    …   Essentially, the coefficient of friction tell us how much sideways force is required to move a given object across a surface.  So, if a 100 kilogram object can be moved by 40 kilograms of force, the coefficient of friction would be 40/100.  This ratio converts to .40/1.00, and is usually written as a simple decimal number .40, or just .4.

Coefficient of Friction (Table of Materials)   …   Teflon has a coefficient of friction of .04, which is only 2.5x more slippery than smectite.

Slippery Floors versus Smectite    …   “Polishes and other floor maintenance coatings having a static coefficient of friction of not less than 0.5 … have been recognized as providing nonhazardous walkways.”   …   Smectite is about 5x more slippery than the accepted safety standard for floors.

Smectite Clay Products Teaching Materials (Audrey C. Rule)   …   Sodium Bentonite is a form of Smectite.  Bentonite is commonly used as a drilling “mud.”  It is also used for cat litter boxes.  [Note to Self:  Do NOT use clay cat litter on icy sidewalks, or under car tires when stuck in snow.]

Canadian Minerals Yearbook:  Clays    …   The most important commercial clays mined in Saskatchewan include kaolinite, montmorillorite (i.e., bentonite), and illite clays   …   Canadian Clay Products Inc. quarries sodium bentonite near Truax, 60 km southwest of Regina….

Smectite in the treatment of acute diarrhea   …   Geology for the average (human).

Canadian Geoscience Education Network

Colours of time smeared in mountain-sized tectonic rip   …  Piqiang Fault, China. 

Earthquakes in Canada

Flint and Chert    Flint and chert are dense, cryptocrystalline varieties of quartz, slightly translucent to almost opaque. Firestone, Hornstone, and Silex are other names for flint and chert….    …Flint freshly removed from chalk contains a few percent of water. After a couple of years they have mostly dried out and get more brittle. Flint will crack in fire because of the water in it, sometimes so badly that small flint chips fly around.  [Flint that has been heated to about 300 degrees Celsius is easier to knap.]    …Flint is easy to spot in a gravel pit: often it is covered by a thin white layer, and – in contrast to the other pebbles – it has an irregular shape.    …We know from findings in the Olduvai Gorge in Kenia (where the remains of “Lucy”, a female Australopithecus, have been discovered) and many other classic locations of anthropology, that flint, along with obsidian and crystalline quartz has been used as a raw material for tools as early as 1.5 million years ago.   

Flint Genesis      The exact mode of formation of flint is not yet clear but it is thought that it occurs as a result of chemical changes in compressed sedimentary rock formations, during the process of diagenesis. One hypothesis is that a gelatinous material fills cavities in the sediment, such as holes bored by crustaceans or molluscs and that this becomes silicified. This theory certainly explains the complex shapes of flint nodules that are found. The source of dissolved silica in the porous media could arise from the spicules of silicious sponges. Certain types of flint, such as that from the south coast of England, contain trapped fossilised marine flora. Pieces of coral and vegetation have been found preserved like amber inside the flint. Thin slices of the stone often reveal this effect.       

Fort Qu’Appelle Geolog Tour   …   The geology of Saskatchewan, in simple terms.  One of several parts.  

Geologic Time Scale 

How Rocks Evolve

Ice-sheet collapse and sea-level rise at the Bølling warming 14,600 years ago  

International Commission on Stratigraphy

Manufacturing metals:  A tantalising prospect    ALUMINIUM was once more costly than gold. Napoleon III, emperor of France, reserved cutlery made from it for his most favoured guests, and the Washington monument, in America’s capital, was capped with it not because the builders were cheapskates but because they wanted to show off. How times change. And in aluminium’s case they changed because, in the late 1880s, Charles Hall and Paul Héroult worked out how to separate the stuff from its oxide using electricity rather than chemical reducing agents. Now, the founders of Metalysis, a small British firm, hope to do much the same with tantalum, titanium and a host of other recherché and expensive metallic elements including neodymium, tungsten and vanadium.

The effect could be profound. Tantalum is an ingredient of the best electronic capacitors. At the moment it is so expensive ($500-2,000 a kilogram) that it is worth using only in things where size and weight matter a lot, such as mobile phones….
…    The company’s first product is tantalum. Its factory is not much bigger than a house, but has enough capacity to supply 3-4% of the 2,500 tonnes of this metal that are used around the world each year….
 

Measure of Global Warming  …  AT NOON on May 4th the carbon-dioxide concentration in the atmosphere around the Mauna Loa Observatory in Hawaii hit 400 parts per million (ppm). The average for the day was 399.73 and researchers at the observatory expect this figure, too, to exceed 400 in the next few days. The last time such values prevailed on Earth was in the Pliocene epoch, 4m years ago, when jungles covered northern Canada.    

Triassic extinction tied to massive lava spills

 

Sunstone, Iceland Spar, or Calcite
Navigation:  Crystal gazing
THIS may look like a nondescript lump of rock, but it is, in fact, a sunstone. That, at least, is the opinion of Guy Ropars of Rennes University, in France, and his colleagues. Sunstones are legendary items supposed to have been used by Viking sailors in the days before magnetic compasses. Looking at the sky through one, it is said, would reveal the sun’s direction even on a cloudy day or when that fiery orb was below the horizon.

Dr Ropars thinks sunstones were real, and were actually crystals of Iceland spar, a form of calcite that polarises light (and therefore reacts to polarised light). Light from the sky is polarised and, as he discovered in 2011, looking through a piece of Iceland spar reveals the direction of polarisation, and thus the direction of the sun, to within 5°   …    He also did further experiments….  He and his colleagues found they could locate the direction of the sun even more accurately than before: to within 1°.

Rocks and Minerals Magazine  …  For Everyone Interested in Minerals, Rocks & Fossils

Great Diamond Hoax of 1872   …   How a Kentucky grifter and his partner pulled off one of the era’s most spectacular scams….

 

pedothem

When rainwater filters through the ground in arid regions, it dissolves calcium from soils, which can react with carbon dioxide to form the mineral calcite. This calcite precipitates on rocks ranging in size from pebbles to boulders, coating them with white growth-ring-like layers called pedothems.  [These provide evidence of climate changes.]

Advertisements

%d bloggers like this: