synthesizing photos on Flickr

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I made this in the early 80's before this guy became so cliched. It was a reaction to the city of Glendale passing a regulation prohibiting neon signs. Auto Tagged By Tagnics

More Scream art can be seen at Eight Recycled Versions of Munch's The Scream"

Calcite (Cave-in-Rock Mining District, Illinois, USA) 1 by James St. John

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Calcite from Illinois, USA. (public display, Geology Department, Wittenberg University, Springfield, Ohio, USA)

A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5400 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The carbonate minerals all contain one or more carbonate (CO3-2) anions.

Calcite is a common mineral. It is calcium carbonate (CaCO3). It has a nonmetallic luster, commonly clearish to whitish to yellowish to grayish in color, is moderately soft (H≡3), moderately light-weight, has hexagonal crystals, and rhombohedral cleavage (three cleavage planes at 75º & 105º angles - cleavage pieces look like lopsided boxes). The easiest way to identify calcite is to drop acid on it - it easily bubbles (effervesces) in acid. The bubbles are carbon dioxide gas. If the acid is dilute hydrochloric acid, the chemical reaction is:

2HCl(aq) + CaCO3(s) -->> CO2(g)↑ + H2O(l) + CaCl2(aq)

The most important & voluminous calcitic rocks in the world are limestone (sedimentary), marble (metamorphic), carbonatite (igneous), and travertine (speleothem, or "cave formations", and many hotspring deposits). Quite a few hydrothermal veins in the world are calcitic or have calcite as a principal component.

This specimen is from a Mississippi Valley-type deposit in southern Illinois. Commonly abbreviated "MVT", Mississippi Valley-type deposits are named for a series of mineral deposits that occur in non-deformed platform sedimentary rocks along the Upper Mississippi River Valley, USA. Many specific minerals occur in MVT deposits, but are dominated by galena, sphalerite, barite, and fluorite. These minerals occur in caves and karst, paleokarst structures, in collapse fabrics, in pull-apart structures, etc. MVT deposits in America are mined as important, large sources of lead ore and zinc ore. The classic areas for MVT deposits are southern Illinois, the tristate area of Oklahoma-Missouri-Kansas, northern Kentucky, southwestern Wisconsin, and southeastern Missouri. The minerals are hydrothermal in origin and were precipitated from basinal brines that were flushed out to the edges of large sedimentary basins (e.g., the Illinois Basin and the Black Warrior Basin). In basin edge areas, the brines came into contact with Mississippian-aged carbonate rocks (limestone and dolostone), which caused mineralization. The brines were 15% to 25% salinity with temperatures of 50 to 200 degrees Celsius (commonly 100 to 150 degrees C). MVT mineralization usually occurs in limestone and dolostone but can also be hosted in shales, siltstones, sandstones, and conglomerates. Gangue minerals include pyrite, marcasite, calcite, aragonite, dolomite, siderite, and quartz. Up to 40 or 50 pulses of brine fluids are recorded in banding of mineral suites in MVT deposits (for example, sphalerite coatings in veins have a stratigraphy - each layer represents a pulse event). Each pulse of water was probably expelled rapidly - overpressurization and friction likely caused the water to heat up. Some bitumen (crystallized organic matter) can occur, which is an indication of the basinal origin of the brines. The presence of asphalt-bitumen indicates some hydrocarbon migration occurred. Some petroleum inclusions are found within fluorite crystals and petroleum scum occurs on fluorite crystals. MVT deposits are associated with oil fields and the temperature of mineral precipitation matches the petroleum window. The brines may simply have accompanied hydrocarbon fluids as they migrated updip.

The high temperatures of these basin periphery deposits wasn't necessarily influenced by igneous hydrothermal activity. Hot fluids can occur in basins that are deep enough for the geothermal gradient to be ~100 to 150 degrees Celsius. If a permeable conduit horizon is present in a succession of interbedded siliciclastic sedimentary rocks, migration of hot, deep basinal brines may be quick enough to get MVT deposit conditions at basin margins.

MVT deposits occur in the Upper Mississippi Valley of America as well as in northern Africa, Scandinavia, northwestern Canada, at scattered sites in Europe, and at some sites in the American Cordillera. Some of these occurrences are in deformed host rocks. MVT deposits have little to no precious metals - maybe a little copper (Cu). Mineralization is usually associated with limestone or dolostone in fracture fillings and vugs. Little host rock alteration has occurred - usually only dolomitization of limestones.

The age of the host rocks in the Mississippi Valley area varies - it ranges from Cambrian to Mississippian. Dating of mineralization has been difficult, but published ages indicate a near-latest Paleozoic to Mesozoic timing.

MVT deposits in the Upper Mississippi River area are often divided into three subtypes based on the dominant mineral: 1) lead-rich (galena dominated); 2) zinc-rich (sphalerite dominated); and 3) fluorite-rich.

The calcite specimen shown here is from the Illinois-Kentucky Fluorspar District ("fluorspar" is a very old name for fluorite), which is an MVT fluoritic subtype. Fluorite and fluorite-rich rocks are mined for the fluorine, which is principally used by the chemical industry to make HF - hydrofluoric acid. Fluorite mineralization in this district occurred at about 277 Ma, during the Early Permian, according to one published study (Chesley et al., 1994). Another study concluded that fluorite mineralization was much later, during the Late Jurassic (see Symons, 1994).

Locality: unrecorded/undisclosed mine/quarry near the town of Cave-in-Rock, Cave-in-Rock Mining District, southern Illinois, USA

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Photo gallery of calcite:

www.mindat.org/gallery.php?min=859

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Some info. on Mississippi Valley-type deposits was synthesized from:

Chesley et al. (1994) - Direct dating of Mississippi Valley-type mineralization: use of Sm-Nd in fluorite. Economic Geology 89: 1192-1199.

Symons (1994) - Paleomagnetism and the Late Jurassic genesis of the Illinois-Kentucky fluorspar deposits. Economic Geology 89: 438-449.

Rakovan (2006) - Mississippi Valley-type deposits. Rocks & Minerals 81(January/February 2006): 69-71.

Fisher et al. (2013) - Fluorite in Mississippi Valley-type deposits. Rocks & Minerals 88(January/February 2013): 20-47.

San Augustine Church by Merril Yu

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Concealed behind the walled city of Intramuros, built by the Spaniards in 1570, is the church of San Agustin. This church is a significant monument to the Spanish colonization of the Philippines, being the first religious structure built in the island of Luzon, after the Spanish relocated from Cebu in the south.

Built within the administrative center of the Spanish government, San Agustin church enjoyed privileges not commonly dispensed to most colonial churches. It was built by the Spaniard Juan Macias in 1586 and was completed in 1606. Luciano Oliver later renovated it in 1854. The book Great Churches of the Philippines points out that the church was designed “according to the plans approved by the Royal Audencia of Mexico and by a Royal Cedula.”

Jesus Encinas, who wrote San Agustin Manila, states that the design of the church was derived from other churches that were built by the Augustinians in Mexico. Pedro Galende, OSA, in his book San Agustin Noble Stone Shrine, adds that the Augustinians “who came from Spain and those born in Mexico had a great opportunity to observe and study the South American monastic architecture which they later used in the Philippines. They took into consideration the quality of the local stone and the weather conditions which required them to sacrifice aesthetic requirement for durability.”

This practical and banal approach to aesthetics is evident on the church’s facade. It may have been the most sought and copied facade in the colonial period, but its static appearance and dark adobe stone lack grace and charm. Even the Augustinians themselves were not too kind with the church’s displeasing appearance. In another book, Angels in Stone, Galende recalls the Augustinian historian, Agustin Ma. de Castro’s critical comment of the church’s facade: “It was of triangular form, very ugly and of a blackish color; flanked by two towers, one of which has no bells and does not serve for anything. Due to the frequent earthquakes in Manila, they (towers) have only one body, ugly and irregular, without elevation or gracefulness.”

Sedate and direct to the point, the facade follows the style of High Renaissance. The symmetrical composition is prefixed by pairs of Tuscan columns that flank the main door of the two-tiered facade. The vertical movement of the paired columns is adapted at the second level by equally paired Corinthian columns. At the second level, mass and void alternate in a simple rhythm of solid walls and windows. The two levels, emphasized by horizontal cornices, are then capped by a pediment that is accentuated with a simple rose window. The facade’s hard composition is held together by two towers; unfortunately, the missing left belfry further exaggerates the lackluster facade. It was taken down after a destructive earthquake hit the church in 1863 and 1880, splitting the tower in two.

The facade has a touch of Baroque by the ornately carved wooden doors that depict floras and religious images. Baroque is also evident in the carved niches that quietly reside between the paired lower columns. The church is bequeathed with Chinese elements in the form of fu dogs that emphatically guard the courtyard entrances.

Alicia Coseteng, in Spanish Churches of the Philippines, describes the church as having “an inverted vaulting foundation, which reacts to seismic effects in much the same manner as the hull of a ship resists the waves.” Although this is difficult to prove, this may be one of the reasons why, amidst the destructive natural calamities that are prevalent in the country, the church is still standing today. Winand Klassen, in his book Architecture in the Philippines, also notes that the church has an inverted vault-like foundation, and was the first earthquake-proof building in stone. This makes San Agustin as the only surviving 16th century edifice, and the oldest church in the Philippines. Another interesting structural component of the church is the lateral bays that act as interior buttressing. This is completely different from all the colonial churches where the wall buttresses flare out at the exterior side of the church walls. Within each compartmentalized bay is a side chapel that Coseteng refers to as cryptocollateral chapel. Seven side chapels line the entire length of each side of the nave.

San Agustin church is also the only colonial church that has retained its original vaulting, despite the destructive forces that shelled the church during WW II. It was a fortuitous turn because San Agustin church flaunts one of the most artistically decorated interiors among all of the colonial churches in the country.

The splendid trompe l’oeil barrel vault and dome magnify the skills of two Italian decorative painters, Alberoni and Dibella, who were commissioned to paint the church’s interior in 1875. With a barren, plain surface, they managed to sculpt and gave life to the ceiling with their paint brushes. Alberoni and Dibella animated every space with wonderful floral motifs, geometric patterns, classic architectural themes, coffers, and religious images. Significantly, the artists developed a language in the trompe l’oeil vaulting that synthesizes with the spatial geometry of the church. The super-imposed columns which divide each side chapel are echoed above by coffered bands that traverse across the barrel vault. Even the faux coffers are organized along the length of the ceiling to suggest depth, movement, balance, and proportion to the nave below. At the crossing, the concentric trompe l’oeil of the shallow dome is curiously crisscrossed by fluted ribs that rise from each pier and merge at the apex.

The playful effect of chiaroscuro-light and shadows-and perspective, restrained only by the limited palette of a few earthly colors, is a visual spectacle. Perhaps, the grandiosity of the painting is a bit too presumptuous to some critics, but one can assume that the vitality of the interior must have roused the imaginations of Simon Flores, a local artist who later became responsible in decorating the interiors of several other churches, including the sumptuous interior of Betis church in Pampanga.

As a final stroke to the exhilarating visual experience, the church is vested with a heavily guilded pulpit, with the native flora and pineapple as decorative motifs, as well as a very ornate altar.

The church is more than just an architectural icon. A side chapel next to the main altar is dedicated to the Spanish Miguel Lopez de Legaspi, the founder of Manila. His remains were re-buried here by the Augustinians, unidentified and mixed along with others, after they were ruthlessly unearthed by the British who were searching for golden treasures in 1762.

At best, today, one can only quietly contemplate the charged bygone days at the foot of Legaspi’s final resting place.

Adjacent to the church, the monastery was converted in 1973 to become a repository for religious artifacts and art treasures dating back as early as the 16th century. Here, one can spend an entire day to cherish and absorb the remains of a resplendent era in the country’s religious history.

San Agustin church is, indeed, the mother of all Philippine colonial churches.

Scan 16 by Morbius19

Opening scene

It is late in the 22nd Century. United Planet cruiser C57D a year out from Earth base on the way to Altair for a special mission. Commander J.J Adams (Leslie Neilsen) orders the crew to the deceleration booths as the ship drops from light speed to normal space.

Adams orders pilot Jerry Farman (Jack Kelly) to lay in a course for the fourth planet. The captain then briefs the crew that they are at their destination, and that they are to look for survivors from the Bellerophon expedition 20 years earlier.

As they orbit the planet looking for signs of life, the ship is scanned by a radar facility some 20 square miles in area. Morbius (Walter Pigeon) contacts the ship from the planet asking why the ship is here. Morbius goes on to explain he requires nothing, no rescue is required and he can't guarantee the safety of the ship or its crew.

Adams confirms that Morbius was a member of the original crew, but is puzzled at the cryptic warning Morbius realizes the ship is going to land regardless, and gives the pilot coordinates in a desert region of the planet. The ship lands and security details deploy. Within minutes a high speed dust cloud approaches the ship. Adams realizes it is a vehicle, and as it arrives the driver is discovered to be a robot (Robby). Robby welcomes the crew to Altair 4 and invites members of the crew to Morbious residence.

Adams, Farman and Doc Ostrow (Warren Stevens) arrive at the residence and are greeted by Morbius. They sit down to a meal prepared by Robbys food synthesizer and Morbius shows the visitors Robbys other abilities, including his unwavering obedience. Morbius then gives Robby a blaster with orders to shoot Adams. Robby refuses and goes into a mechanical mind lock, disabling him till the order is changed.

Morbius then shows the men the defense system of the house (A series of steel shutters). When questioned, Morbius admits that the Belleraphon crew is dead, Morbius and his wife being the only original survivors. Morbius's wife has also died, but months after the others and from natural causes. Morbius goes on to explain many of the crew were torn limb from limb by a strange creature or force living on the planet. The Belleraphon herself was destroyed when the final three surviving members tried to take off for Earth.

Adams wonders why this force has remained dormant all these years and never attacked Morbius. As discussions continue, a young woman Altaira (Anne Francis) introduces herself as Morbius daughter. Farman takes an immediate interest in Altaira, and begins to flirt with her . Altaira then shows the men her ability to control wild animals by petting a wild tiger. During this display the ship checks in on the safety of the away party. Adams explains he will need to check in with Earth for further orders and begins preparations for sending a signal. Because of the power needed the ship will be disabled for up to 10 days. Morbius is mortified by this extended period and offers Robby's services in building the communication facility

The next day Robby arrives at ship as the crew unloads the engine to power the transmitter. To lighten the tense moment the commander instructs the crane driver to pick up Cookie (Earl Holliman) and move him out of the way. Quinn interrupts the practical joke to report that the assembly is complete and they can transmit in the morning.

Meanwhile Cookie goes looking for Robby and organizes for the robot to synthesize some bourbon. Robby takes a sample and tells Cookie he can have 60 gallons ready the next morning for him.

Farman continues to court Altair by teaching her how to kiss, and the health benefits of kissing. Adams interrupts the exercise, and is clearly annoyed with a mix of jealous. He then explains to Altair that the clothes she wears are inappropriate around his crew. Altair tries to argue till Adams looses patience and order Altair to leave the area.

That night, Altair, still furious, explains to her father what occurred. Altair takes Adams advice to heart and orders Robby to run up a less revealing dress. Meanwhile back at the ship two security guards think they hear breathing in the darkness but see nothing.

Inside the ship, one of the crew half asleep sees the inner hatch opened and some material moved around. Next morning the Captain holds court on the events of the night before. Quinn advises the captain that most of the missing and damaged equipment can be replaced except for the Clystron monitor. Angry the Capt and Doc go back to Morbius to confront him about what has occurred.

Morbius is unavailable, so the two men settle in to wait. Outside Adams sees Altair swimming and goes to speak to her. Thinking she is naked, Adams becomes flustered and unsettled till he realizes she wants him to see her new dress. Altair asks why Adams wont kiss her like everyone else has. He gives in and plants one on her. Behind them a tiger emerges from the forest and attacks Altair, Adams reacts by shooting it. Altair is badly troubled by the incident, the tiger had been her friend, but she can't understand why acted as if she was an enemy.

Returning to the house, Doc and Adams accidently open Morbius office. They find a series of strange drawings but no sign of Morbius. He appears through a secret door and is outraged at the intrusion. Adams explains the damage done to the ship the previous night and his concern that Morbius was behind the attack.

Morbius admits it is time for explanations. He goes on to tell them about a race of creatures that lived on the planet called the Krell. In the past they had visited Earth, which explains why there are Earth animals on the planet. Morbius believes the Krell civilization collapsed in a single night, right on the verge of their greatest discovery. Today 2000 centuries later, nothing of their cities exists above ground.

Morbius then takes them on a tour of the Krell underground installation. Morbius first shows them a device for projecting their knowledge; he explains how he began to piece together information. Then an education device that projects images formed in the mind. Finally he explains what the Krell were expected to do, and how much lower human intelligence is in comparison.

Doc tries the intelligence tester but is confused when it does not register as high as Morbius. Morbius then explains it can also boost intelligence, and that the captain of the Belleraphon died using it. Morbius himself was badly injured but when he recovered his IQ had doubled.

Adams questions why all the equipment looks brand new. It is explained that all the machines left on the planet are self repairing and Morbius takes them on a tour of the rest of the installation. First they inspect a giant air vent that leads to the core of the planet. There are 400 other such shafts in the area and 9200 thermal reactors spread through the facilities 8000 cubic miles.

Later that night the crew has completed the security arrangements and tests the force field fence. Cookie asks permission to go outside the fence. He meets Robby who gives him the 60 gallons of bourbon. Outside, something hits the fence and shorts it out. The security team checks the breach but finds nothing. A series of foot like depressions begin forming leading to the ship. Something unseen enters the ship. A scream echos through the compound.

Back at the Morbius residence he argues that only he should be allowed to control the flow of Krell technology back to Earth. In the middle of the discussion, Adams is paged and told that the Chief Quinn has been murdered. Adams breaks of his discussions and heads back to the ship.

Later that night Doc finds the footprints and makes a cast. The foot makes no evolutionary sense. It seems to have elements of a four footed and biped creature; also it seems a predator and herbivore. Adams questions Cookie who was with the robot during the test and decides the robot was not responsible.

The next day at the funeral for Chief Morbius again warns him of impending doom facing the ship and crew. Adams considers this a challenge and spends the day fortifying the position around the ship. After testing the weapons and satisfied all that could be done has, the radar station suddenly reports movement in the distance moving slowly towards the ship.

No one sees anything despite the weapons being under radar fire control. The controller confirms a direct hit, but the object is still moving towards the ship. Suddenly something hits the force field fence, and a huge monster appears outlined in the energy flux. The crew open fire, but seem to do little good. A number of men move forward but a quickly killed.

Morbious wakes hearing the screams of Altair. Shes had a dream mimicking the attack that has just occurred. As Morbious is waking the creature in the force field disappears. Doc theories that the creature is made of some sort of energy, renewing itself second by second.

Adams takes Doc in the tractor to visit Morbius intending to evacuate him from the planet. He leaves orders for the ship to be readied for lift off. If he and Doc dont get back, the ship is to leave without them. They also want to try and break into Morbious office and take the brain booster test.

They are met at the door by Robby, who disarms them. Altair appears and countermands the orders given to Robby by her father. Seeing a chance Doc sneaks into the office. Altair argues with Adams about trying to make Morbius return home, she ultimately declares her love for him.

Robby appears carrying the injured Doc. Struggling to speak and heavy pain, Doc explains that the Krell succeeded in their great experiment. However they forgot about the sub conscious monsters they would release. Monsters from the id.

Morbius sees the dead body of Doc, and makes a series of ugly comments. His daughter reminds him that Doc is dead. Morbius lack of care convinces Altair she is better off going with Adams. Morbius tries to talk Adams out of taking Altair.

Adams demands an explanation of the id. Morbius realizes he is the source of the creature killing everyone. The machine the Krell built was able to release his inner beast, the sub conscious monster dwelling deep inside his ancestral mind.

Robby interrupts the debate to report something approaching the house. Morbius triggers the defensive shields of the house, which the creature begins to destroy. Morbius then orders Robby to destroy the creature, however Robby short circuits. Adams explained that it was useless; Robby knew it was Morbius self.

Adams, Altair and Morbius retreat to the Krell lab and sealed themselves in by sealing a special indestructible door. Adams convinces Morbius that he is really the monster, and that Morbius can not actually control his subconscious desires.

The group watch as the creature beings the slow process of burning through the door. Panicked Morbius implores Altair to say it is not so. Suddenly the full realization comes, and he understands that he could endanger or even kill Altair.

As the creature breaks through Morbius rushes forward and denies its existence. Suddenly the creature disappears but Morbius is mortally wounded. With his dying breath he instructs Adams to trigger a self destruct mechanism linked to the reactors of the great machine. The ship and crew have 24 hours to get as far away from the planet as possible

The next day we see the ship deep in space. Robby and Altair are onboard watching as the planet brightens and is destroyed. Adams assures Altair that her fathers memory will shine like a beacon.

Pocillopora palmata coralstone (Cockburn Town Member, Grotto Beach Formation, Upper Pleistocene, 114-127 ka; Cockburn Town Fossil Reef, San Salvador Island, Bahamas) 16 by James St. John

Pocillopora palmata - in-situ fossil cauliflower coral colony in the reef facies of the Cockburn Town Member, upper Grotto Beach Formation at the Cockburn Town Fossil Reef, western margin of San Salvador Island.

The Cockburn Town Fossil Reef is a well-preserved, well-exposed Pleistocene fossil reef. It consists of non-bedded to poorly-bedded, poorly-sorted, very coarse-grained, aragonitic fossiliferous limestones (grainstones and rubblestones), representing shallow marine deposition in reef and peri-reef facies. Cockburn Town Member reef facies rocks date to the MIS 5e sea level highstand event (early Late Pleistocene). Dated corals in the Cockburn Town Fossil Reef range in age from 114 to 127 ka.

Pocillopora is the only coral genus that went extinct in the Caribbean at the end-Pleistocene.

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The surface bedrock geology of San Salvador consists entirely of Pleistocene and Holocene limestones. Thick and relatively unforgiving vegetation covers most of the island’s interior (apart from inland lakes). Because of this, the most easily-accessible rock outcrops are along the island’s shorelines.

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Stratigraphic Succession in the Bahamas:

Rice Bay Formation (Holocene, <10 ka), subdivided into two members (Hanna Bay Member over North Point Member)

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Grotto Beach Formation (lower Upper Pleistocene, 119-131 ka), subdivided into two members (Cockburn Town Member over French Bay Member)

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Owl's Hole Formation (Middle Pleistocene, ~215-220 ka & ~327-333 ka & ~398-410 ka & older)

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San Salvador’s surface bedrock can be divided into two broad lithologic categories:

1) LIMESTONES

2) PALEOSOLS

The limestones were deposited during sea level highstands (actually, only during the highest of the highstands). During such highstands (for example, right now), the San Salvador carbonate platform is partly flooded by ocean water. At such times, the “carbonate factory” is on, and abundant carbonate sediment grains are generated by shallow-water organisms living on the platform. The abundance of carbonate sediment means there will be abundant carbonate sedimentary rock formed after burial and cementation (diagenesis). These sea level highstands correspond with the climatically warm interglacials during the Pleistocene Ice Age.

Based on geochronologic dating on various Bahamas islands, and based on a modern understanding of the history of Pleistocene-Holocene global sea level changes, surficial limestones in the Bahamas are known to have been deposited at the following times (expressed in terms of marine isotope stages, “MIS” - these are the glacial-interglacial climatic cycles determined from δ18O analysis):

1) MIS 1 - the Holocene, <10 k.y. This is the current sea level highstand.

2) MIS 5e - during the Sangamonian Interglacial, in the early Late Pleistocene, from 119 to 131 k.y. (sea level peaked at ~125 k.y.)

3) MIS 7 - ~215 to 220 k.y. - late Middle Pleistocene

4) MIS 9 - ~327-333 k.y. - late Middle Pleistocene

5) MIS 11 - ~398-410 k.y. - late Middle Pleistocene

Bahamian limestones deposited during MIS 1 are called the Rice Bay Formation. Limestones deposited during MIS 5e are called the Grotto Beach Formation. Limestones deposited during MIS 7, 9, 11, and perhaps as old as MIS 13 and 15, are called the Owl’s Hole Formation. These stratigraphic units were first established on San Salvador Island (the type sections are there), but geologic work elsewhere has shown that the same stratigraphic succession also applies to the rest of the Bahamas.

During times of lowstands (= times of climatically cold glacial intervals of the Pleistocene Ice Age), weathering and pedogenesis results in the development of soils. With burial and diagenesis, these soils become paleosols. The most common paleosol type in the Bahamas is calcrete (a.k.a. caliche; a.k.a. terra rosa). Calcrete horizons cap all Pleistocene-aged stratigraphic units in the Bahamas, except where erosion has removed them. Calcretes separate all major stratigraphic units. Sometimes, calcrete-looking horizons are encountered in the field that are not true paleosols.

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Subsurface Stratigraphy of San Salvador Island:

The island’s stratigraphy below the Owl’s Hole Formation was revealed by a core drilled down ~168 meters (~550-feet) below the surface (for details, see Supko, 1977). The well site was at 3 meters above sea level near Graham’s Harbour beach, between Line Hole Settlement and Singer Bar Point (northern margin of San Salvador Island). The first 37 meters were limestones. Below that, dolostones dominate, alternating with some mixed dolostone-limestone intervals. Reddish-brown calcretes separate major units. Supko (1977) infers that the lowest rocks in the core are Upper Miocene to Lower Pliocene, based on known Bahamas Platform subsidence rates.

In light of the successful island-to-island correlations of Middle Pleistocene, Upper Pleistocene, and Holocene units throughout the Bahamas (see the Bahamas geologic literature list below), it seems reasonable to conclude that San Salvador’s subsurface dolostones may correlate well with sub-Pleistocene dolostone units exposed in the far-southeastern portions of the Bahamas Platform.

Recent field work on Mayaguana Island has resulted in the identification of Miocene, Pliocene, and Lower Pleistocene surface outcrops (see: www2.newark.ohio-state.edu/facultystaff/personal/jstjohn/...). On Mayaguana, the worked-out stratigraphy is:

- Rice Bay Formation (Holocene)

- Grotto Beach Formation (Upper Pleistocene)

- Owl’s Hole Formation (Middle Pleistocene)

- Misery Point Formation (Lower Pleistocene)

- Timber Bay Formation (Pliocene)

- Little Bay Formation (Upper Miocene)

- Mayaguana Formation (Lower Miocene)

The Timber Bay Fm. and Little Bay Fm. are completely dolomitized. The Mayaguana Fm. is ~5% dolomitized. The Misery Point Fm. is nondolomitized, but the original aragonite mineralogy is absent.

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The stratigraphic information presented here is synthesized from the Bahamian geologic literature.

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Supko, P.R. 1977. Subsurface dolomites, San Salvador, Bahamas. Journal of Sedimentary Petrology 47: 1063-1077.

Bowman, P.A. & J.W. Teeter. 1982. The distribution of living and fossil Foraminifera and their use in the interpretation of the post-Pleistocene history of Little Lake, San Salvador, Bahamas. San Salvador Field Station Occasional Papers 1982(2). 21 pp.

Sanger, D.B. & J.W. Teeter. 1982. The distribution of living and fossil Ostracoda and their use in the interpretation of the post-Pleistocene history of Little Lake, San Salvador Island, Bahamas. San Salvador Field Station Occasional Papers 1982(1). 26 pp.

Gerace, D.T., R.W. Adams, J.E. Mylroie, R. Titus, E.E. Hinman, H.A. Curran & J.L. Carew. 1983. Field Guide to the Geology of San Salvador (Third Edition). 172 pp.

Curran, H.A. 1984. Ichnology of Pleistocene carbonates on San Salvador, Bahamas. Journal of Paleontology 58: 312-321.

Anderson, C.B. & M.R. Boardman. 1987. Sedimentary gradients in a high-energy carbonate lagoon, Snow Bay, San Salvador, Bahamas. CCFL Bahamian Field Station Occasional Paper 1987(2). (31) pp.

1988. Bahamas Project. pp. 21-48 in First Keck Research Symposium in Geology (Abstracts Volume), Beloit College, Beloit, Wisconsin, 14-17 April 1988.

1989. Proceedings of the Fourth Symposium on the Geology of the Bahamas, June 17-22, 1988. 381 pp.

1989. Pleistocene and Holocene carbonate systems, Bahamas. pp. 18-51 in Second Keck Research Symposium in Geology (Abstracts Volume), Colorado College, Colorado Springs, Colorado, 14-16 April 1989.

Curran, H.A., J.L. Carew, J.E. Mylroie, B. White, R.J. Bain & J.W. Teeter. 1989. Pleistocene and Holocene carbonate environments on San Salvador Island, Bahamas. 28th International Geological Congress Field Trip Guidebook T175. 46 pp.

1990. The 5th Symposium on the Geology of the Bahamas, June 15-19, 1990, Abstracts and Programs. 29 pp.

1991. Proceedings of the Fifth Symposium on the Geology of the Bahamas. 247 pp.

1992. The 6th Symposium on the Geology of the Bahamas, June 11-15, 1992, Abstracts and Program. 26 pp.

1992. Proceedings of the 4th Symposium on the Natural History of the Bahamas, June 7-11, 1991. 123 pp.

Boardman, M.R., C. Carney, B. White, H.A. Curran & D.T. Gerace. 1992. The geology of Columbus' landfall: a field guide to the Holcoene geology of San Salvador, Bahamas, Field trip 3 for the annual meeting of the Geological Society of America, Cincinnati, Ohio, October 26-29, 1992. Ohio Division of Geological Survey Miscellaneous Report 2. 49 pp.

Carew, J.L., J.E. Mylroie, N.E. Sealey, M. Boardman, C. Carney, B. White, H.A. Curran & D.T. Gerace. 1992. The 6th Symposium on the Geology of the Bahamas, June 11-15, 1992, Field Trip Guidebook. 56 pp.

1993. Proceedings of the 6th Symposium on the Geology of the Bahamas, June 11-15, 1992. 222 pp.

Lawson, B.M. 1993. Shelling San Sal, an Illustrated Guide to Common Shells of San Salvador Island, Bahamas. San Salvador, Bahamas. Bahamian Field Station. 63 pp.

1994. The 7th Symposium on the Geology of the Bahamas, June 16-20, 1994, Abstracts and Program. 26 pp.

1994. Proceedings of the 5th Symposium on the Natural History of the Bahamas, June 11-14, 1993. 107 pp.

Carew, J.L. & J.E. Mylroie. 1994. Geology and Karst of San Salvador Island, Bahamas: a Field Trip Guidebook. 32 pp.

Godfrey, P.J., R.L. Davis, R.R. Smtih & J.A. Wells. 1994. Natural History of Northeastern San Salvador Island: a "New World" Where the New World Began, Bahamian Field Station Trail Guide. 28 pp.

Hinman, G. 1994. A Teacher's Guide to the Depositional Environments on San Salvador Island, Bahamas. 64 pp.

Mylroie, J.E. & J.L. Carew. 1994. A Field Trip Guide Book of Lighthouse Cave, San Salvador Island, Bahamas. 10 pp.

1995. Proceedings of the Seventh Symposium on the Geology of the Bahamas, June 16-20, 1994. 134 pp.

1995. Terrestrial and shallow marine geology of the Bahamas and Bermuda. Geological Society of America Special Paper 300.

1996. The 8th Symposium on the Geology of the Bahamas, May 30-June 3, 1996, Abstracts and Program. 21 pp.

1996. Proceedings of the 6th Symposium on the Natural History of the Bahamas, June 9-13, 1995. 165 pp.

1997. Proceedings of the 8th Symposium on the Geology of the Bahamas and Other Carbonate Regions, May 30-June 3, 1996. 213 pp.

Curran, H.A., B. White & M.A. Wilson. 1997. Guide to Bahamian Ichnology: Pleistocene, Holocene, and Modern Environments. San Salvador, Bahamas. Bahamian Field Station. 61 pp.

1998. The 9th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 4-June 8, 1998, Abstracts and Program. 25 pp.

Wilson, M.A., H.A. Curran & B. White. 1998. Paleontological evidence of a brief global sea-level event during the last interglacial. Lethaia 31: 241-250.

1999. Proceedings of the 9th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 4-8, 1998. 142 pp.

2000. The 10th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 8-June 12, 2000, Abstracts and Program. 29+(1) pp.

2001. Proceedings of the 10th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 8-12, 2000. 200 pp.

Bishop, D. & B.J. Greenstein. 2001. The effects of Hurricane Floyd on the fidelity of coral life and death assemblages in San Salvador, Bahamas: does a hurricane leave a signature in the fossil record? Geological Society of America Abstracts with Programs 33(4): 51.

Gamble, V.C., S.J. Carpenter & L.A. Gonzalez. 2001. Using carbon and oxygen isotopic values from acroporid corals to interpret temperature fluctuations around an unconformable surface on San Salvador Island, Bahamas. Geological Society of America Abstracts with Programs 33(4): 52.

Gardiner, L. 2001. Stability of Late Pleistocene reef mollusks from San Salvador Island, Bahamas. Palaios 16: 372-386.

Ogarek, S.A., C.K. Carney & M.R. Boardman. 2001. Paleoenvironmental analysis of the Holocene sediments of Pigeon Creek, San Salvador, Bahamas. Geological Society of America Abstracts with Programs 33(4): 17.

Schmidt, D.A., C.K. Carney & M.R. Boardman. 2001. Pleistocene reef facies diagenesis within two shallowing-upward sequences at Cockburntown, San Salvador, Bahamas. Geological Society of America Abstracts with Programs 33(4): 42.

2002. The 11th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 6th-June 10, 2002, Abstracts and Program. 29 pp.

2004. The 12th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 3-June 7, 2004, Abstracts and Program. 33 pp.

2004. Proceedings of the 11th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 6-10, 2002. 240 pp.

Martin, A.J. 2006. Trace Fossils of San Salvador. 80 pp.

2006. Proceedings of the 12th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 3-7, 2004. 249 pp.

2006. The 13th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 8-June 12, 2006, Abstracts and Program. 27 pp.

Mylroie, J.E. & J.L. Carew. 2008. Field Guide to the Geology and Karst Geomorphology of San Salvador Island. 88 pp.

2008. Proceedings of the 13th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 8-12, 2006. 223 pp.

2008. The 14th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 12-June 16, 2006, Abstracts and Program. 26 pp.

2010. Proceedings of the 14th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 12-16, 2008. 249 pp.

2010. The 15th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 17-June 21, 2010, Abstracts and Program. 36 pp.

2012. Proceedings of the 15th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 17-21, 2010. 183 pp.

2012. The 16th Symposium on the Geology of the Bahamas and Other Carbonate Regions, June 14-June 18, 2012, Abstracts with Program. 45 pp.

Geodes and agate-filled nodules (Las Choyas Geode Deposit, near-latest Eocene, ~35 Ma; Chihuahua, Mexico) by James St. John

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Geodes and agate-filled nodules mined from the Eocene of Mexico. (public exhibit photo by Jeff Smith; shot taken in the field on 29 October 2004)

This is Mexico's famous Las Choyas Geode Deposit. At this locality, geodes occur in structurally-folded, rhyolitic volcanic tuffs (ash flow tuffs) of Middle to Late Eocene age (~35 to 44 Ma). The geodes were originally cavities in the rhyolitic rock. These cavities (lithophysae) formed before the rock completely lithified. The original ash flow deposit had some subspherical structures known as spherulites, composed of glassy to cryptocrystalline material (many felsic extrusive igneous rocks have these). Expanding gases in the spherulites destroyed the material, resulting in empty spaces. In the near-latest Eocene (~35 Ma), regional rhyolite dome intrusions resulted in hot groundwater percolating through the rocks, leaching out silica and precipitating quartz in the lithophysae/cavities.

About eighty percent of the geodes mined at this site are solid agate/quartz nodules.

Locality: Las Choyas Geode Deposit, northern Aldama County, north-central Chihuahua State, northern Mexico

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Info. synthesized from:

Keller (1977) - Quartz geodes from near the Sierra Gallego area, Chihuahua, Mexico. Mineralogical Record 10: 207-212.

Smith (2010) - The Las Choyas Geode Deposit, Chihuahua, Mexico. Rocks & Minerals 85: 112-122.

Western Arabia Terra - Mars Express by Aster Cowart

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Western Arabia Terra imaged by the Mars Express HRSC instrument. This image captures the transition from the rugged equatorial highland terrain of Arabia Terra as it transitions into the relatively featureless northern lowland region of Acidalia Planitia. Although this region is among the oldest locations on the Martian surface, the geology is unspectacular, consisting of generally unmodified craters, few tectonic features, and relatively few channels carved by water. In the absence of attention from geologists, very few of the craters in this region have been named.

This image was captured in the middle of Martian summer, when Mars is near its furthest from the Sun. During this period, the Martian atmosphere cools substantially, allowing daytime water ice clouds to form at equatorial latitudes across the entire planet for a few months. This phenomenon, called the Aphelion Cloud Belt, was active in this photo, although the clouds associated with it were beginning to thin for the season when this image was taken.

This image was created using two limb-scan images taken through Mars Express' blue and green filters. These sequences are designed to study Martian atmospheric layers. These sequences require a complex geometric correction to resemble what a human eye might see. In addition, a red channel has been synthesized by subtracting blue channel data from the green channel data.

This image was taken during Mars Express' 15481st orbit of the red planet, March 19, 2016.

Image Credit: ESA/DLR/FU Berlin/J. Cowart, CC BY-SA 3.0 IGO

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This graphic shows how green hydrogen is made and its applications. On left are three types of renewable energy — hydroelectric, solar and wind — used in the electrolysis process. On right are three applications: chemical industry, transportation and aerospace. In center, we see the process of separating the water molecule into hydrogen and oxygen.

Green hydrogen is produced using energy from renewable sources — such as hydroelectric, solar or wind power. Through a process known as electrolysis, this clean electricity separates water into its two constituent elements: oxygen and hydrogen. The hydrogen is then stored and transported. It can be used directly in industrial processes; be combined with other elements to create synthetic fuels; or be mixed with oxygen to generate electricity again, as is the case with hydrogen fuel-cell cars.

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The rise of green hydrogen in Latin America

In anticipation of future demand, several projects are underway in the region to produce this clean energy source

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América Latina abre la puerta al hidrógeno verde

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Hydrogen Production and Its Applications to Mobility, Annual Review of Chemical and Biomolecular Engineering

The transportation sector is a major contributor to carbon dioxide emissions. Although there are major challenges, green hydrogen is an attractive alternative to achieve a complete transformation.

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Pisolites in basket structure under calcrete paleosol capping the Grotto Beach Formation (Upper Pleistocene; Watling's Quarry, San Salvador Island, Bahamas) 2 by James St. John

Pisolites in a basket structure under a calcrete paleosol that caps the Grotto Beach Formation (lower Upper Pleistocene) at Watling's Quarry, southwestern San Salvador Island, eastern Bahamas.

Pisolites are moderately large versions of oolites - they’re >2 mm-sized, subspherical to ellipsoidal, concentrically to irregularly concentrically laminated structures, commonly composed of calcium carbonate (as these are). They are often perceived to be biogenic in origin. Pisolites are not uncommon below calcrete/caliche paleosol horizons.