Sunday, June 3, 2012
In former times, things used to be very different, and for most of human history the observation of geological phenomena and the acquisition of geological expertise was intimately connected with religious ideas. Earthquakes and volcanoes, towering mountains and conspicuous rock formations, fossils and ore veins were regarded either as due to direct divine action and intervention or as manifestations of the divine itself (Mazadiego et al.; Barbaro). It was God (or Gods), who had created the Earth as ‘home’ for humans, providing the necessary resources (animals and plants, but also water, rocks and metals), or who might be suspected to exert punishment on sinners by means of natural disasters (Kölbl-Ebert 2005; Udias on earthquakes). Although accepting flint and pyrite in prehistoric time, or later copper and other ores, to be gifts of divine providence (Norris) is some sort of explanation for their existence, that assumption was clearly not sufficient to enable adequate strategies for the search for new deposits to be devised. Observational skills and arrangement of observations according to rules and guidelines (involving the formulation of theories) were required, and eventually such knowledge was accumulated and became part of the craft knowledge of miners.
Also, from an intellectual point of view, invoking divine action as a general and all-fitting explanation of phenomena was unsatisfying for an intellectual, and even for the devout theist who would like to know how God ‘did it’. After all, curiosity is a decidedly human trait. For this more theoretical part of ‘geological expertise’, the late Medieval and Renaissance intellectual world turned to the remnants of much older knowledge, that of the antiquity, which apparently had been a golden, better and much more knowledgeable age, judging from the ruins that were still around. Why not trust the explanatory power and authority of ancient texts (including the Bible) that had been produced by these obviously advanced civilizations?
This intimate link between early geo-theory and Christian philosophy proved to be very fruitful for some time, because the Christian tradition of visualizing the history of humans on Earth from the creation, via global revolutions such as the biblical Flood up to historical times (Rudwick 1992; Magruder) and the Judaeo-Christian sense of a finite Earth history (Rudwick; see also Rudwick 2005) prepared the ground for accepting the Earth’s different strata as testimony to the development of our globe through time. It was this religious, theological framework from which the early geology started to evolve, and that provided the tools used in popularization of the new science of the seventeenth century. It is understandable why, for example, geological phenomena such as erratic blocks and other debris covering much of Europe were initially seen as a consequence of events mentioned in the Bible and other ancient texts. However, with increasing observations there was a growing mismatch between what was expected according to ancient authorities (Godard; Luzzini) and the actual data. This was not necessarily a problem, since influential theologians, such as Augustine of Hippo (AD 354– 430) or the medieval theological scholar Thomas Aquinas (1225–1274), knew that biblical texts needed to be interpreted and that adopting a naive literal reading might do more harm than good to the Christian faith:
In discussing questions of this kind two rules are to be observed, as Augustine teaches. The first is, to hold to the truth of Scripture without wavering. The second is that since Holy Scripture can be explained in a multiplicity of senses, one should adhere to a particular explanation only in such measure as to be ready to abandon it if it be proved with certainty to be false,2 lest Holy Scripture be exposed to the ridicule of unbelievers, and obstacles be placed to their believing (Aquinas 1273, 1st part, question 68).
Subsequently, attempts to reconcile the growing timescale of geology with biblical chronology became widespread in the eighteenth and nineteenth centuries. The most popular, apart from more metaphorical interpretations of the biblical creation stories, were possibly the ‘gap theory’ (or ‘chaos/ restitution theory’3), claiming an indefinitely long time span between Genesis 1: 1–2 or 2–3 and the ‘day–age theory’ (or concordance theory), which interpreted the days of biblical creation as seven long eras, which might be equated with different geological formations (see Roberts, on Sedgwick).
Wednesday, May 30, 2012
The Mayan peoples regularly used hallucinogenic drugs (taken from the natural world) in their religious rituals, but they also used them in day to day life as painkillers. Flora such as peyote, the morning glory, certain mushrooms, tobacco, and plants used to make alcoholic substances, were commonly used. In addition, as depicted in Maya pottery and carvings, ritual enemas were used for a more rapid absorption and effect of the substance.
Golubac Fortress was the last military outpost located on the Danube River and the final line of defense between Hungary and the Ottoman Empire. For this reason, the fort witnessed dozens of large scale military conflicts, both cold steel and firearm based. The fortification was a key advantage in the world of conquest and warfare. It regularly shifted hands between the Turks, Hungarians, Serbs, and Austrians until 1867, when it was turned over to the Serbian Knez, Mihailo Obrenović III.
Golubac Fortress is split into three compounds and shows signs of heavy reinforcements over the centuries. It has ten towers, two portcullises, and a collection of military outposts. Each tower had a specific purpose, including a citadel, chapel, dungeon, and weapon storage facilities. The fortress used a large moat, which trapped water from the Danube and made it difficult to reach the land. From 1964-72, a dam was built inside the Iron Gate gorge which elevated the river’s water and flooded sections of the fort. Today, Golubac Fortress has become a popular tourist destination. It is one of the most important sightseeing points on Danube boat tours.
Golubac consists of three main compounds guarded by 10 towers and 2 portcullises, all connected by fortress walls 2–3 meters thick. In front of the fortress, the forward wall (I) doubled as the outer wall of the moat, which connected to the Danube and was likely filled with water. A settlement for common people was situated in front of the wall.
As is the case with many fortresses, Golubac's structure was modified over time. For years, there were only five towers. Later, four more were added. The towers were all built as squares, a sign of the fortress' age, showing that battles were still fought with cold steel. Once firearms came into use, the Turks fortified the western towers with cannon ports and polygonal or cylindrical reinforcements up to two meters thick. After the Hungarian raid in 1481, they added the final tower, complete with cannon embrasures and galleries.
The upper compound (A) is the oldest part of the fortress. It includes the citadel (tower 1) and the Serbian Orthodox chapel (tower 4). Although it remains uncertain, the chapel has led many to believe that this section was built by a Serbian noble.
Later, during either Serbian or Hungarian rule, the fortress was expanded to include the rear and forward compounds.
The rear compound (D) is separated from the upper compound by both a wall connecting towers 2 and 4, and a steep rock 3–4 meters high. Next to tower 5 is a building (VII) which was probably used as a military barracks and for ammunition storage.
The forward compound was split into lower (C) and upper (B) parts by a wall linking towers 4 and 7. The entrance (II) is in the lower part, guarded by towers 8 and 9. Tower 8 has, in turn, been fortified with a cannon port. Opposing the entrance was a second portcullis that led to the rear compound. Along the path was a ditch 0.5 meters wide and 0.75 meters deep which then became a steep decline. At the outer end of the lower part, and connected to the 9th tower with a low wall, is tower 10, which the Turks added to act as a lower artillery tower. It controlled passage along the Danube and guarded the entrance to the harbor, which was probably situated between towers 5 and 10. There are remains connected to tower 8 which probably formed a larger whole with it, but the lower part did not otherwise contain buildings.
In the wall that separated the upper and lower parts was a gate that led to the upper part. The upper part did not have buildings, but there remains a pathway to the stairs up to gate IV, which is 2 meters off the ground, right next to tower 3.
The first nine towers are 20–25 meters high. In all ten towers, the floors and stairs inside were made of wood, while external stairs were made of stone. Half of the towers (1, 2, 4, 5, 10) have all four sides and are completely made of stone, while the other half (3, 6, 7, 8, 9) lack the side facing the interior of the fort.
Tower 1, nicknamed "Hat Tower" (Šešir-kula), is one of the oldest towers, and doubles as citadel and dungeon tower. It has an eight-sided base with a circular spire rising from it and a square interior. The next tower to the west, tower 2, is completely circular in shape. The third tower has a square base, with the open side facing the dungeon tower to the north. On the top floor is a terrace that overlooks the Danube and the entrance to the Iron Gate gorge. Down the slope from tower 3 is tower 4, which also has a square base. The ground floor has a Serbian Orthodox chapel that was built into the tower, rather than being added later. The last tower along this wall, tower 5, is the only tower to remain completely square.
The top tower along the front wall of the forward compound, tower 6, has a square base which was reinforced with a six-sided foundation. Working west, the square base of tower 7 was reinforced with a circular foundation. Tower 8, on the upper side of the front portcullis, has an irregular, but generally square, base. It is also the shortest of the first nine towers. Guarding the other side is tower 9, which has a square base reinforced by an eight-sided foundation.
The last tower is the cannon tower. It has only one floor and is the shortest of all ten towers. It was built with an eight-sided base and cannon ports to help control traffic on the Danube. Tower 10 is almost identical to the three artillery towers added to Smederevo fortress.
Saturday, May 26, 2012
Between c. 7000 and 4000 B.C. the climate in Europe reached its optimal level (the Hypsithermal) in the present interglacial. It was not, however, uniform in its onset. In the British Isles the maximal warmth was about 6000–4500 B.C., whereas in northern Europe 4000–2500 B.C. saw the highest average temperatures. There are of course no instrumental records, but data from fossil pollen and other organic remains, the stratigraphy of lakes and bogs, and from tree rings suggest that temperatures were at least 1 to 2°C (1.8 to 3.6°F) above those of the late twentieth century. This implies of course that the spread of agriculture into much of Europe and the development of all the more complex societies of Celtic Europe and their early medieval successors took place in periods of climatic deterioration (albeit with warmer remissions). The hunter-gatherers had had the best of the weather.
The consequences for the natural environment are obvious to some extent. The forest belts extended northward, so mixed deciduous forest was dominant over much of Europe, save from mid- Scandinavia northward, where conifers and birch predominated, and in mountainous areas. Here there were always more conifers, though not to the extent familiar in the Alps, for example, where there was more beech (Fagus spp.). The steppes of the east retreated in favor of woodland cover. Within the forests, too, species that were adapted to greater warmth flourished. The lime (Tilia spp.) is a good example, along with ivy (Hedera sp.), holly (Ilex), and mistletoe (Viscum). The European pond tortoise (Emys orbicularis), confined to the Mediterranean in the twenty-first century, was found in Denmark and southern Sweden. The presence of insect and molluscan faunas also reflected the warmth, but of greater importance for human communities were the large mammals, such as the red and roe deer, wild ox, wild pig, and beaver. As the optimal period peaked, agriculture became important, and it is clearly critical that such cereals as wheat and barley were able to ripen even in the British Isles and southern Scandinavia.
Another feature of the optimal period was its water relations. In the early part the climate over most of Europe was drier than in the twenty-first century, but as time passed there was a move to wetter conditions, especially in the west. In part this change reflected the increasing influence of the sea as its levels rose. A leading consequence of this continued eustasy was the formation of the Dover Strait and then the submergence of the low-lying terrain between England and the Low Countries to form the North Sea. By c. 7400 B.C. the British Isles were insulated from the rest of Europe, and it took the completion of the Channel Tunnel in the 1990s to make it possible again to walk from Dover, England, to Calais, France. In cultural terms this separation took place in the Mesolithic. The adoption of agriculture in the British Isles necessarily was preceded by a sea passage of some kind of mix of ideas, people, seeds, and young cattle.
Wetter conditions are reflected to some extent in higher lake levels and thus the renewal of lake fringe successions, but they are most apparent in upland areas and the western fringe of Europe. Two processes are notable. The first is the leaching of minerals down the profiles of many types of soils, particularly from those on such acid substrates as sandstone and gritstone. The redeposition of minerals, such as iron and manganese, in solid horizons (“pans”) made the soils prone to becoming waterlogged, and hence their floras moved away from large tree species toward wet- and acid-tolerant species, such as birch, and to dwarf shrubs of the Ericaceae family. On some uplands in Scandinavia and the British Isles great blankets of peat formed on low slopes where the rainfall exceeded about 700 millimeters per year. It is possible that there was some human involvement in the inception of these miry spreads, whose surface often was one of the bog mosses of the genus Sphagnum.
One of the lessons from the present plethora of research into climatic history is that change is not necessarily gradual. In the case of Europe the transition from the tail end of the ice ages to a much more temperate climate was quite rapid. About 9500 B.C. amelioration started to produce warm surface waters (above 14°C [57.2°F]) around the coasts of western Europe, and warming rates may have reached about 1°C (1.8°F) per century in these waters. On land, rates of 3 to 4°C (5.4 to 7.2°F) per 500 years have been postulated for France and even 1.7 to 2.8°C (3.06 to 5.04°F) per century in not yet insular Britain. Overall the climates of Europe may have reached levels similar to those of the twentieth century or even a little warmer by 7000 B.C.
The consequences for the natural world and hence for human habitats were profound. The vegetation belts and their associated fauna shifted northward, so most of Europe was a cool temperate forest zone with dominance by broad-leaved trees. There were montane variants in the Alps, and over much of Scandinavia and eastern Russia the overwhelming dominance of conifers meant that a taiga, or open forest, was the land cover. A taiga biome also penetrated some of the loess lands of the northern European plain, and the Black Sea had a broad penumbra of moist steppe, which was in essence treeless grassland. Within all these biomes, the better conditions encouraged rapid plant growth, so many lakes left in glaciated regions began to fill with organic debris and the area of open water shrank when colonized by marginal vegetation.
A major result of the warming was more free water in the oceans as the polar, mountain, and Laurentide ice sheets melted, producing what are termed “eustatic” rises in sea level. Such increments, however, often were in opposition to isostatic rises in land levels as land surfaces rose when freed from the weight of the ice that had depressed them. The northern part of the Gulf of Bothnia has risen about 850 meters during the Holocene and is still rising at 9 millimeters per year. Northern Britain is still rising, too, though at less than 3 millimeters per year, and the south is sinking at up to 2 millimeters per year. Thus many European coasts during the era of barbarism were the outcomes of competition between eustasy and isostasy, with the latter winning easily to the north. The shorelines and harbors from which the Vikings launched their ships were almost 8 meters above the modern sea level.
The largest-scale physical consequence of sea-level change is found in the Baltic. The region underwent a four-stage evolution in which there was an interaction of ice retreat, eustatic rises of sea level, and isostatic rebound. During the Terminal Pleistocene the Baltic essentially was an ice-dammed freshwater lake, but the retreat of ice in central Sweden led this lake to fall by about 28 meters and become connected to the Atlantic, thus turning brackish. By 7000 B.C. this outlet was closed, and the new but narrow outlet that developed in the region of the Great Belt allowed the Baltic to become a freshwater lake again. After 6500 B.C. more saltwater penetrated, since increased eustasy was accompanied by decreasing isostasy, bringing about the twenty-first-century salinity gradients of the Baltic–Lake Ladoga region.
Saturday, May 12, 2012
Researchers say careful excavations have revealed the first examples of Mayan art on a house interior (Source: Tyrone Turner /National Geographic)
The earliest known Mayan calendar has been found in an ancient house in Guatemala and it offers no hint that the world's end is imminent, say researchers.
Rather, the painted room in the residential complex at Xultun was likely the place where the town scribe kept records, scrawling computations on the walls in an effort to find "harmony between sky events and sacred rituals," says the study in the journal Science.
The hieroglyphs date back to the ninth century, making them hundreds of years older than the calendars in the Maya Codices, which were recorded in bark-paper books from 1300 to 1521.
Some appear to be the 365-day solar calendar, the 584-day cycle of the planet Venus and the 780-day cycle of Mars, says archaeologist William Saturno of Boston University, who led the exploration and excavation.
According to Saturno, the writing looks like someone's attempt to sort out a very long math problem, as if on a blackboard.
"For the first time we get to see what may be actual records kept by a scribe, whose job was to be official record keeper of a Maya community," says Saturno.
Different mid sets"The ancient Maya predicted the world would continue, that 7000 years from now, things would be exactly like this," he adds.
"We keep looking for endings. The Maya were looking for a guarantee that nothing would change. It's an entirely different mindset."
Furthermore, there is no sign that the much-hyped myth that the Mayan calendar would end in 2012, and with it the world, has any bearing in reality.
All that ended in 2012 was one of its calendar cycles, says co-author Anthony Aveni, professor of astronomy and anthropology at Colgate University.
"It's like the odometer of a car, with the Maya calendar rolling over from the 120,000s to 130,000," says Aveni.
"The car gets a step closer to the junkyard as the numbers turn over; the Maya just start over," he adds.
"The most exciting point is that we now see that the Maya were making such computations hundreds of years - and in places other than books - before they recorded them in the Codices."
Even though the 31 square kilometre site of Xultun, deep in a rainforest where tens of thousands of people once lived, was first discovered about 100 years ago, the house structure where the calendar is drawn on the walls was spotted in 2010.
Researchers say careful excavations have revealed that the paintings inside - including some of human figures wearing feather head-dresses - show the first examples of Mayan art on a house interior.
"It's weird that the Xultun finds exist at all," says Saturno. "Such writings and artwork on walls don't preserve well in the Maya lowlands, especially in a house buried only a metre below the surface."
Wednesday, May 9, 2012
The evidence comes from changing patterns of salinity in the oceans
greenhouse effect is accelerating the global water cycle almost twice
the rate predicted by climate change models, say researchers.
Oceanographer Dr Susan Wijffels of the CSIRO and colleagues report their findings today in the journal Science.
"The models predict a 4 to 5 per cent amplification of the global water cycle per degree of warming, instead of 8 per cent," says Wijffels.
"It's a significant underestimation. That's a cause for concern."
The transport of water through the atmosphere from the mid-latitudes of Earth to the poles and tropics is called the global water cycle.
How much water evaporates in dry areas and falls as rain in wet areas is vital to society, says Wijffels.
Global climate models predict that as the globe warms, this will heat the lower atmosphere and enable it to hold more moisture, thus speeding up the global water cycle.
"It's like the rich get richer scenario where the wet places will get wetter and the dry places will get a lot drier because the conveyor belt is speeding up between those two places," says Wijffels.
Verification difficultBut attempts to verify the predictions of climate change models have been fraught, with actual measurements of rainfall giving a mixed and confusing picture.
"Rain is most horrible thing to measure because it happens so locally and is so spotty in space and time," says Wijffels.
To make matters worse, measurements have been short-term and are usually taken on land, whereas 71 per cent of the Earth's surface is covered by oceans.
Instead Wijffels and colleagues have looked to the oceans to measure changes in the global water cycle over the past 50 years.
Salinity pattern changesThe more rain that falls in a particular part of the ocean, the more fresh water dilutes out salinity. The more evaporation there is, the higher the ocean's salinity.
Wijffels and colleagues have found that the difference between the saltier and fresher areas have become more marked in the past 50 years, indicating that more water is being pumped through the global cycle.
"We've been able to pick up a very strong and clear fingerprint of the accelerating water cycle in the ocean salinity field," says Wijffels.
She and colleagues have found the same fingerprint across the globe including in the North and South Atlantic, the North and South Pacific and the South Indian ocean basins.
"The fact that we see it independently across the ocean basins gives us some confidence that it's a real phenomenon and we're not just seeing a whole bunch of statistical noise," says Wijffels.
Underestimating modelsAll climate change models show a relationship between the changing salinity patterns and the water cycle speed.
The researchers used this to calculate that the water cycle accelerates by 8 per cent per degree of surface warming.
But, says Wijffels, this rate of acceleration is only reflected in models that include a high degree of warming.
On the whole, the models underestimate the acceleration at 4 to 5 per cent per degree of warming, she says.
Wijffels says the new data will be combined with other observations to help improve global climate change models.
She emphasises that the findings have implications for long-term average rainfall trends, which should not be confused with shorter-term trends that lead to phenomena such as La Niña.
"Variability will always be there but the question is whether, on average, a place will get drier or wetter," says Wijffels.