TPO-14 Maya Water Problems
TPO-26 Sumer and the First Cities of the Ancient Near East
It is an astonishing fact that human civilization should have emerged into the light of history in two separate places at just about the same time. Between 3500 and 3000 B.C. when Egypt was being united under pharaonic rule other great civilization arose in Mesopotamia the “land between the rivers.” And for close to three thousand years, the two rival centers retained their distinct characters, even though they had contact with each other from their earliest beginnings, and their destinies were interwoven in many ways. The pressure that forced the
inhabitants of both regions to abandon the pattern of Neolithic village life may well have been the same. But the valley of the Tigris and Euphrates rivers, unlike that of the Nile, is not a narrow fertile strip protected by desert on either side. It resembles a wide, shallow trough with few natural defenses, crisscrossed by two great rivers and their tributaries, and is easily encroached upon from any direction.
Thus the facts of geography tended to discourage the idea of uniting the entire Mesopotamian area under a single head. Rulers who had this ambition did not appear, so far as we know, until about one thousand years after the beginning of Mesopotamian civilization, and they succeeded in carrying it out only for brief periods and at the cost of almost continuous warfare. As a consequence, the political history of ancient Mesopotamia has no underlying theme of the sort that divine kingship provides for Egypt. Local rivalries foreign incursions, the sudden upsurge and equally sudden collapse of military power–those are its substance. Against such a disturbed background, the continuity of cultural and artistic traditions seems all the more remarkable. This common heritage is very largely the creation of the founders of Mesopotamian Civilization, whom we call Sumerians after the region of Sumer, which they inhabited, near the confluence of the Tigris and Euphrates.
The origin of the Sumerians remains obscure. Their language is unrelated to any other known tongue. Sometimes before 4,000 B.C. they came to southern Mesopotamia, from Persia, and there, within the next thousand years, they founded a number of city-states and developed their distinctive form of writing in cuneiform (wedge-shaped) characters on clay tablets. nUnfortunately, the tangible remains of Sumerian civilization are extremely scanty compared to those of ancient Egypt. nBuilding stone being unavailable in Mesopotamia, the Sumerians used mud brick and wood, so that almost nothing is left of their architecture except the foundation. nNor did they share the Egyptians' concern with the hereafter, although some richly endowed tombs in the shape of vaulted chambers below ground from the early dynastic period have been found in the city of Ur. nOur knowledge of Sumerian Civilization thus depends very
largely on chance fragments brought to light by excavation, including vast numbers of inscribed clay tablets. Yet we have learned enough to form a general picture of this vigorous, inventive, and disciplined people.
Each Sumerian city-state had its own local god, who was regarded as its king and owner. It also had a human ruler, the steward of the divine sovereign, who led the people in serving the deity. The local god, in return, was expected to plead the cause of his subjects among his fellow deities who controlled the forces of nature such as wind and weather, water, fertility, and the heavenly bodies. Nor was the idea of divine ownership treated as a mere pious fiction. The god was quite literally believed to own not only the territory of the city-state but also the labor power of the population and its products. All these were subject to his commands, transmitted to the people by his human steward. The result was an economic system that has been dubbed “theocratic socialism”, a planned society whose administrative center was the temple. The temple controlled the pooling of labor and resources for communal enterprises, such as the building of dikes or irrigation ditches, and it collected and distributed a considerable part of the harvest. All this required the keeping of detailed written records. Hence, we need not be surprised to find that the texts of early Sumerian inscriptions deal very largely with economic and administrative rather than religious matters, although writing was a priestly privilege.
主要内容：有个人提出造成冰川的三个原因。第一，地球轨道的形状，当地球转到一个时间点，温度很mild的时候，夏天就会有更少的冰川融化。第二，地轴的角度。第三，地球的wobble，他们只会改变平均水平，当冬天和夏天变得温和的时候，冰川就形成了，别人质疑他，因为地球会这样周期变化好久，因此冰川应该按照周期发生，但是冰川的形成实际上没有这么有周期频繁发生。有人觉得是solar radiation减少的原因，错的。有人觉得是火山灰block the sky导致温度降低，但是火山喷发时间跟冰川形成的时间没关系。得出结论应该还有别的因素影响冰川，
OG Test 2 Green Icebergs
TPO-15 Glacier Formation
TPO-19 Discovering the Ice Ages
Glaciers form where the accumulation of snow and ice exceeds ablation. The area in which a glacier forms is called a cirque - a typically armchair-shaped geological feature (such as a depression between mountains enclosed by arêtes) - which collects and compresses through gravity the snow which falls into it. This snow collects and is compacted by the weight of the snow falling above it forming névé. Further crushing of the individual snowflakes and squeezing the air from the snow turns it into 'glacial ice'. This glacial ice will fill the cirque until it 'overflows' through a geological weakness or vacancy, such as the gap between two mountains. When the mass of snow and ice is sufficiently thick, it begins to move due to a combination of surface slope, gravity and pressure. On steeper slopes, this can occur with as little as 15 m (50 ft) of snow-ice.
In temperate glaciers, snow repeatedly freezes and thaws, changing into granular ice called firn. Under the pressure of the layers of ice and snow above it, this granular ice fuses into denser and denser firn. Over a period of years, layers of firn undergo further compaction and become glacial ice. Glacier ice is slightly less dense than ice formed from frozen water because it contains tiny trapped air bubbles.
Glacial ice has a distinctive blue tint because it absorbs some red light due to an overtone of the infrared OH stretching mode of the water molecule. Liquid water is blue for the same reason. The blue of glacier ice is sometimes misattributed to Rayleigh scattering due to bubbles in the ice.
主要内容：科学家提出的是asteroid or comet impact造成的，但是没有证据，直到发现了一个地方，在65亿年前的layer最近发现Ir元素在很多地方都有，这个元素地球没有，但是陨石有。而且那里正好有个是200km的坑。符合了其预估的10km小行星产生撞击。后来又说撞击带来了直接和间接的影响，是温度下降，隔绝阳光。恐龙就灭绝了。但是rodent和其他一些小mammal存活下来了，因为他们住在地底下。恐龙灭绝的那个接下去那句99% of the living were killed, and 75% of the living species on the earth were wiped out。
TPO-8 Extinction of the Dinosaurs
Official Model Exam-Meteorite Impact and Dinosaur Extinction
The asteroid collision theory, which was brought to wide attention in 1980 by Walter Alvarez and colleagues, links the extinction event at the end of the Cretaceous period to a bolide impact approximately 66 million years ago. Alvarez et al. proposed that a sudden increase in iridium levels, recorded around the world in the period's rock stratum, was direct evidence of the impact. The bulk of the evidence now suggests that a bolide 5 to 15 kilometers (3 to 9 mi) wide hit in the vicinity of the Yucatán Peninsula (in southeastern Mexico), creating the approximately 180 km (110 mi) Chicxulub Crater and triggering the mass extinction. Scientists are not certain whether dinosaurs were thriving or declining before the impact event. Some scientists propose that the meteorite caused a long and unnatural drop in Earth's atmospheric temperature, while others claim that it would have instead created an unusual heat wave. The consensus among scientists who support this theory is that the impact caused extinctions both directly (by heat from the meteorite impact) and also indirectly (via a worldwide cooling brought about when matter ejected from the impact crater reflected thermal radiation from the sun). Although the speed of extinction cannot be deduced from the fossil record alone, various models suggest that the extinction was extremely rapid, being down to hours rather than years.