A summit is a point on a surface, higher in elevation than all points adjacent to it. The topographic terms acme, apex and zenith are synonymous; the term top is used only for a mountain peak, located at some distance from the nearest point of higher elevation. For example, a big massive rock next to the main summit of a mountain is not considered a summit. Summits near a higher peak, with some prominence or isolation, but not reaching a certain cutoff value for the quantities, are considered subsummits of the higher peak, are considered part of the same mountain. A pyramidal peak is an exaggerated form produced by ice erosion of a mountain top. Summit may refer to the highest point along a line, trail, or route; the highest summit in the world is Everest with height of 8844.43 m above sea level. The first official ascent was made by Sir Edmund Hillary, they reached the mountain`s peak in 1953. Whether a highest point is classified as a summit, a sub peak or a separate mountain is subjective; the UIAA definition of a peak is.
Otherwise, it's a subpeak. In many parts of the western United States, the term summit refers to the highest point along a road, highway, or railroad. For example, the highest point along Interstate 80 in California is referred to as Donner Summit and the highest point on Interstate 5 is Siskiyou Mountain Summit. A summit climbing differs from the common mountaineering. Summit expedition requires: 1+ year of training, a good physical shape, a special gear. Although a huge part of climber’s stuff can be left and taken at the base camps or given to porters, there is a long list of personal equipment. In addition to common mountaineers’ gear, Summit climbers need to take Diamox and bottles of oxygen. There are special requirements for crampons, ice axe, rappel device, etc. Geoid Hill – Landform that extends above the surrounding terrain Nadir Summit accordance Peak finder Summit Climbing Gear List
Victoria Peak (Belize)
Victoria Peak within the Maya Mountains is the second highest mountain in Belize. The highest peak in the country, Doyle's Delight at a height of 1,124 metres, is located 57 kilometres southwest of Victoria Peak. Victoria Peak is situated in the Cockscomb Basin Wildlife Sanctuary. Victoria Peak is situated in the Stann Creek District of Belize, in the Cockscomb Basin Wildlife Sanctuary, is home to many flora and fauna common to Belize, it was pronounced a natural monument in 1998, comprising about 4,847 acres bordered by the Sittee River Forest Reserve, Cockscomb Basin Wildlife Sanctuary, Chiquibul National Park. Victoria Peak is situated in a broad-leaved montane elfin forest; the tropical evergreen jungle has been damaged by hurricanes such as Hurricane Hattie in 1961, fires caused by occasional lightning. These environmental factors have caused the ecosystem to become stunted. Along with averages of 100 inches of rainfall per year, Victoria peak is windswept and cloud covered and the soil is poor as the various surrounding vegetation takes up all of the nutrients.
The mountain is found covered with non-calcareous rock, along with the growth of many different plant species. Many of the plants that thrive in this diverse forest are used for medicinal practices, food, or as guides and trail markers ensuring the Maya hunters do not become lost in the forest; the vegetation begins at the base of the mountain with moist, tropical forest, transforming into elfin shrubland, characterized by sphagnum moss and a tree canopy of about 2–3m high. Just ahead of the summit is rich, humid forest, dense with secondary growth among mature tree stands, yet with a clear forest floor; the base of the mountain is compiled of sedge marsh that turns to orange groves as the elevation increases slightly. The many species of trees inhabiting the peak include mahogany, banak, swivelstick, yemeri, santa maria and many more. Frequent species of plants that are characteristic to Victoria Peak and the Cockscomb range are Clusia sp. and Myrica cerifera, two plants species which form thick stands that average about 1-2 m tall.
Shrubs such as these are often accompanied by “beard lichen” growing amongst the branches. Bromeliads and orchids are numerous, such as the orange flowering orchid, Epidendrum ibaguense or the scarlet orchid known as dragon's tongue. Epidendrum ibaguense, or the fiery-coloured orchid, is a rare species of orchid that only grows at higher elevations. One of the other more common plant species seen is the hot lips bush, it is most spotted along the trail edges and is characterized by its ‘pouting’ red flower. AviansAs many as 300 species of birds can be spotted in the Cockscomb Basin itself. There are many native species that reside in the Belizean forests on Victoria Peak, as well as seasonal migrants that average about 18% of the bird population. Of those, there are critically endangered species present such as the ornate hawk-eagle, keel-billed motmot, the scarlet macaw. Other common birds of Victoria Peak and the Cockscomb Basin include: great curassow, crested guan, clay-coloured robins, social flycatchers, collared-seed eaters, crimson-collared tanagers and masked tanagers, bat falcons, Montezuma’s oropendola, as well as white-collared manakins, the slaty-breasted tinamou, chestnut headed oropendolas, parrots and Agami heron to name a few.
MammalsCockscomb Wildlife Sanctuary in the Victoria Peak region hosts the world’s densest jaguar population. Panthera onca is the third largest member of the cat family in the world and is considered endangered in the majority of its habitat ranges. Other common mammals of the Victoria Peak region that are thriving in the protected area and Cockscomb Sanctuary are: jaguarundi, puma, peccary, paca, as well as brocket deer, nine-banded armadillo, otter, coatimundi and agouti; some of the animals listed on the IUCN Red List of endangered mammals that inhabit Victoria Peak and area are the ocelot, jaguarundi, puma as well as Baird's tapir, all of which have populations beginning to increase in size. OtherThere are many reptiles and insects that frequent the broad-leaved montane elfin forest. Smilisca cyonostica, a species of frog, along with Gastrophryne elegans, a toad that had not been seen in Belize, has been observed on the peak. A week-long diversity survey recorded 44 species of butterfly in the area.
The forest carpet is covered in leaf-cutter ants that create long travelling routes, while tarantulas remain hidden under leaves at trail edges. Botflies are present, due to the presence of cattle ranchers further north that settle throughout Belize, infect mosquitoes with their eggs to be transferred to a bovine host and to hatch into larvae right underneath the epidermal layer. Victoria was thought to be the highest mountain in Belize at 1,120 m, until recently when Doyle’s Delight was measured at 1,124 m; the first exploration of Victoria Peak occurred in British expeditions of 1888 and 1889, but the explorers scaled a nearby peak that they mistakenly labeled Victoria Peak. Several expeditions followed in 1927-1928; the name “Victoria Peak” was given in honor of Queen Victoria for the highest peak in the Cockscomb Basin Wildlife Sanctuary Range. On May 2, 1998, Victoria Peak was declared a natural monument, adding it to the list of protected areas in Belize. Rowan Garel, a 12-year-old visually impaired boy, climbed to the top of Victoria Peak along with his father in 2011.
His efforts, with assistance from Delta Air Lines and his father, raised money for a summer camp put on by the Belize Council for
Guatemala the Republic of Guatemala, is a country in Central America bordered by Mexico to the north and west and the Caribbean to the northeast, Honduras to the east, El Salvador to the southeast and the Pacific Ocean to the south. With an estimated population of around 16.6 million, it is the most populated country in Central America. Guatemala is a representative democracy; the territory of modern Guatemala once formed the core of the Maya civilization, which extended across Mesoamerica. Most of the country was conquered by the Spanish in the 16th century, becoming part of the viceroyalty of New Spain. Guatemala attained independence in 1821 as part of the Federal Republic of Central America, which dissolved by 1841. From the mid to late 19th century, Guatemala experienced civil strife. Beginning in the early 20th century, it was ruled by a series of dictators backed by the United Fruit Company and the United States government. In 1944, authoritarian leader Jorge Ubico was overthrown by a pro-democratic military coup, initiating a decade-long revolution that led to sweeping social and economic reforms.
A U. S.-backed military coup in 1954 installed a dictatorship. From 1960 to 1996, Guatemala endured a bloody civil war fought between the US-backed government and leftist rebels, including genocidal massacres of the Maya population perpetrated by the military. Since a United Nations-negotiated peace accord, Guatemala has witnessed both economic growth and successful democratic elections, though it continues to struggle with high rates of poverty, drug trade, instability; as of 2014, Guatemala ranks 31st of 33 Latin American and Caribbean countries in terms of the Human Development Index. Guatemala's abundance of biologically significant and unique ecosystems includes a large number of endemic species and contributes to Mesoamerica's designation as a biodiversity hotspot; the name "Guatemala" comes from the Nahuatl word Cuauhtēmallān, or "place of many trees", a derivative of the K'iche' Mayan word for "many trees" or more for the Cuate/Cuatli tree Eysenhardtia. This was the name the Tlaxcaltecan soldiers who accompanied Pedro de Alvarado during the Spanish Conquest gave to this territory.
The first evidence of human habitation in Guatemala dates back to 12,000 BC. Evidence, such as obsidian arrowheads found in various parts of the country, suggests a human presence as early as 18,000 BC. There is archaeological proof. Pollen samples from Petén and the Pacific coast indicate that maize cultivation had developed by 3500 BC. Sites dating back to 6500 BC have been found in the Quiché region in the Highlands, Sipacate and Escuintla on the central Pacific coast. Archaeologists divide the pre-Columbian history of Mesoamerica into the Preclassic period, the Classic period, the Postclassic period; until the Preclassic was regarded as a formative period, with small villages of farmers who lived in huts, few permanent buildings. However, this notion has been challenged by recent discoveries of monumental architecture from that period, such as an altar in La Blanca, San Marcos, from 1000 BC; the Classic period of Mesoamerican civilization corresponds to the height of the Maya civilization, is represented by countless sites throughout Guatemala, although the largest concentration is in Petén.
This period is characterized by urbanisation, the emergence of independent city-states, contact with other Mesoamerican cultures. This lasted until 900 AD, when the Classic Maya civilization collapsed; the Maya abandoned many of the cities of the central lowlands or were killed off by a drought-induced famine. The cause of the collapse is debated, but the drought theory is gaining currency, supported by evidence such as lakebeds, ancient pollen, others. A series of prolonged droughts, among other reasons such as overpopulation, in what is otherwise a seasonal desert is thought to have decimated the Maya, who relied on regular rainfall; the Post-Classic period is represented by regional kingdoms, such as the Itza, Kowoj and Kejache in Petén, the Mam, Ki'che', Chajoma, Tz'utujil, Poqomchi', Q'eqchi' and Ch'orti' in the highlands. Their cities preserved many aspects of Maya culture; the Maya civilization shares many features with other Mesoamerican civilizations due to the high degree of interaction and cultural diffusion that characterized the region.
Advances such as writing and the calendar did not originate with the Maya. Maya influence can be detected from Honduras, Northern El Salvador to as far north as central Mexico, more than 1,000 km from the Maya area. Many outside influences are found in Maya art and architecture, which are thought to be the result of trade and cultural exchange rather than direct external conquest. After they arrived in the New World, the Spanish started several expeditions to Guatemala, beginning in 1519. Before long, Spanish contact resulted in an epidemic. Hernán Cortés, who had led the Spanish conquest of Mexico, granted a permit to Captains Gonzalo de Alvarado and his brother, Pedro de Alvarado, to conquer this land. Alvarado at first allied himself with the Kaqchikel nation to fight against their traditional rivals the K'iche' nation
Ruins are the remains of human-made architecture: structures that were once intact have fallen, as time went by, into a state of partial or total disrepair, due to lack of maintenance or deliberate acts of destruction. Natural disaster and population decline are the most common root causes, with many structures becoming progressively derelict over time due to long-term weathering and scavenging. There are famous ruins all over the world, from ancient sites in China, the Indus valley and Judea to Zimbabwe in Africa, ancient Greek and Roman sites in the Mediterranean basin, Incan and Mayan sites in the Americas. Ruins are of great importance to historians and anthropologists, whether they were once individual fortifications, places of worship, ancient universities and utility buildings, or entire villages and cities. Many ruins have become UNESCO World Heritage Sites in recent years, to identify and preserve them as areas of outstanding value to humanity. Ancient cities were highly militarized and fortified defensive settlements.
In times of war they were the central focus of armed conflict and would be sacked and ruined in defeat. Although less central to modern conflict, vast areas of 20th-century cities such as Warsaw, Coventry, Stalingrad, Königsberg, Berlin were left in ruins following World War II, a number of major cities around the world – such as Beirut, Sarajevo and Baghdad – have been or ruined in recent years as a result of more localised warfare. Entire cities have been ruined, some lost to natural disasters; the ancient city of Pompeii was lost during a volcanic eruption in the 1st century AD, its uncovered ruins now preserved as a World Heritage Site. The city of Lisbon was destroyed in 1755 by a massive earthquake and tsunami, the 1906 San Francisco earthquake left the city in complete ruin. Apart from acts of war, some important historic buildings have fallen victim to deliberate acts of destruction as a consequence of social and economic factors; the spoliation of public monuments in Rome was under way during the fourth century, when it was covered in protective legislation in the Theodosian Code and in new legislation of Majorian. and the dismantling increased once popes were free of imperial restrictions.
Marble was still being burned for agricultural lime in the Roman Campagna into the nineteenth century. In Europe, many religious buildings suffered as a result of the politics of the day. In the 16th century, the English monarch Henry VIII set about confiscating the property of monastic institutions in a campaign which became known as the Dissolution of the Monasteries. Many abbeys and monasteries fell into ruin. In the 20th century, a number of European historic buildings fell into ruin as a result of taxation policies, which required all structures with roofs to pay substantial property tax; the owners of these buildings, like Fetteresso Castle and Slains Castle in Scotland, deliberately destroyed their roofs in protest at, defiance of, the new taxes. Other decrees of government have had a more direct result, such as the case of Beverston Castle, in which the English parliament ordered significant destruction of the castle to prevent it being used by opposition Royalists. Post-colonial Ireland has encouraged the ruin of grand Georgian houses, symbols of British imperialism.
As a rule, towers built of steel are dismantled, when not used any more, because their construction can be either rebuilt on a new site or if the state of construction does not allow a direct reuse, the metal can be recycled economically. However, sometimes tower basements remain. One example of such a basement is the basement of the former radio mast of Deutschlandsender Herzberg/Elster; the basements of large wooden towers such as Transmitter Ismaning may be left behind, because removing them would be difficult. The contemplation of "rust belt" post-industrial ruins is in its infancy. In the Middle Ages Roman ruins were inconvenient impediments to modern life, quarries for pre-shaped blocks for building projects, or marble to be burnt for agricultural lime, subjects for satisfying commentaries on the triumph of Christianity and the general sense of the world's decay, in what was assumed to be its last age, before the Second Coming. With the Renaissance, ruins took on new roles among a cultural elite, as examples for a consciously revived and purified architecture all' antica, for a new aesthetic appreciation of their innate beauty as objects of venerable decay.
The chance discovery of Nero's Domus Aurea at the turn of the sixteenth century, the early excavations at Herculaneum and Pompeii had marked effects on current architectural styles, in Raphael's Rooms at the Vatican and in neoclassical interiors, respectively. The new sense of historicism that accompanied neoclassicism led some artists and designers to conceive of the modern classicising monuments of their own day as they would one day appear as ruins. In the period of Romanticism ruins were frequent object for painters, place of meetings of romantic poets, nationalist students etc.. Ruin value is the concept that a building be designed such that if it collapsed, it would leave behind aesthetically pleasing ruins that would last far longer without any maintenance at all. Joseph Michael Gandy completed for Sir John Soane in 1832 an atmospheric watercolor of the architect's vast Bank of England rotunda as a picturesquely overgrown ruin, tha
Cockscomb Basin Wildlife Sanctuary
The Cockscomb Basin Wildlife Sanctuary is a nature reserve in the Stann Creek District of south-central Belize. It was established to protect the forests and watersheds of an 400 square kilometres area of the eastern slopes of the Maya Mountains; the reserve was established in 1986 as the first protected area for protection of the jaguar. It is regarded as a premier site for jaguar preservation in the world; the name'Cockscomb' derives from the appearance of the Cockscomb Mountain ridge, that resembles a rooster's comb, situated at the northern fringe of the reserve and, visible from the coastal plain of the Caribbean Sea. Habitation by the ancient Mayas occurred in the Cockscomb Basin as early as 10,000 BCE. However, the first modern exploration in the recorded history of the basin did not occur until 1888; the Cockscomb Basin Wildlife Sanctuary is comprised by two adjacent geographic basins. The West Basin is drained by the Swasey Branch, one of the main tributaries to the Monkey River; the East Basin consists of the upper watershed of South Stann Creek.
The West Basin, being more difficult to access given distance from trailheads and higher forest density, is as of the current time still unexplored from the standpoint of species mapping, Mayan ruins and other environmental details. The reserve is lozenge-shaped, spanning an east–west dimension of 36 km and a north–south dimension of 14 km. Elevation extremes are 50 m above sea level in the lower reaches of South Stann Creek to 1,160 m atop Victoria Peak; the West Basin is bounded by the ridge of the Maya Mountains on the west, Cockscomb Mountains on the north, a prominent transverse ridge of the Maya Mountains at the south and a low-lying north–south ridge at the east, which separates the West from East Basin. The Swasey Branch exits through the south transverse range via a deep 300 m gorge; the East Basin is bounded on the north by the namesake Cockscomb ridge, to the west by the low-lying north–south ridge separating the two basins, to the east by Cabbage Haul Ridge and to the south by Stann Creek Ridge.
South Stann Creek flows out of the East Basin on the south in a meandering gentle gradient, navigated by the British explorers in the 1880s. The site consists of two distinct adjacent watersheds and is accessible via a low-intensity trail system to accommodate visitors and research environmental scientists; the Maya Mountains and foothills are among the oldest surface rock formations of Central America. The principal uplifted rock formations in the Sanctuary are sandstone. Principal plant communities and habitats are Belizean pine forests, elfin scrub, Petén-Veracruz moist forests, sheltered valley forests, floodplain thickets; the principal forest type is tropical moist broadleaf forest, which covers moderate to steep slopes, in some cases sheltered mountain valleys. While much of this forest is secondary due to Mayan era farming as well as modern logging, some of the steeper reaches exhibit primary forest characteristics. Dominant trees in this forest type are mahogany and cedar, which were prized and hence logged from the early 1900s to late in the 20th century.
Fast flowing clear mountain streams flow to the valley floors of the two basins to yield a more turbid water quality during periods of peak rain. This site is known worldwide as the premier habitat for the jaguar, most found in the vast unexplored West Basin wilderness; the riparian zone forest areas feature lush broadleaf rainforest intruding into the verges of fast flowing steep mountain streams as well as the languid meandering valley drainages. There are interesting assemblages of vegetation along the rocky bedded mountain streams which have frequent rapids and deep pools. Due to the density of vegetation and frequent precipitation events, the forest floor appears fresh and verdant after several rainless days. Throughout much of the foothills of the eastern slopes in southern Belize, there is evidence of Mayan habitation since at least 10,000 BCE; the Pearce Ruin was the first Mayan site to have been catalogued in modern history archives in a report to the British Museum in 1931. At that late date two other Mayan sites were documented: Hun' Tul Mo' and Xa'a Yul Ha'.
The first modern explorations that led to recorded features of the Cockscomb Basin were conducted by the British in expeditions of 1888 and 1889. These adventures began with river excursions up the South Stann Creek and resulted in attainment of what these explorers thought to be Victoria Peak, the highest point in Belize. Further exploration of the Cockscomb Basin did not transpire until 1927, when further British expeditions were launched to assess timber reserves. At about the same time as exploitation of these resources was complete, a nationwide study of the jaguar was initiated; this scientific investigation led by Alan Rabinowitz, a recent recipient of the PhD degree from the University of Tennessee, found that the Cockscomb Basin was a important habita
The Maya civilization was a Mesoamerican civilization developed by the Maya peoples, noted for its logosyllabic script—the most sophisticated and developed writing system in pre-Columbian Americas—as well as for its art, mathematics and astronomical system. The Maya civilization developed in an area that encompasses southeastern Mexico, all of Guatemala and Belize, the western portions of Honduras and El Salvador; this region consists of the northern lowlands encompassing the Yucatán Peninsula, the highlands of the Sierra Madre, running from the Mexican state of Chiapas, across southern Guatemala and onwards into El Salvador, the southern lowlands of the Pacific littoral plain. The Archaic period, prior to 2000 BC, saw the first developments in agriculture and the earliest villages; the Preclassic period saw the establishment of the first complex societies in the Maya region, the cultivation of the staple crops of the Maya diet, including maize, beans and chili peppers. The first Maya cities developed around 750 BC, by 500 BC these cities possessed monumental architecture, including large temples with elaborate stucco façades.
Hieroglyphic writing was being used in the Maya region by the 3rd century BC. In the Late Preclassic a number of large cities developed in the Petén Basin, the city of Kaminaljuyu rose to prominence in the Guatemalan Highlands. Beginning around 250 AD, the Classic period is defined as when the Maya were raising sculpted monuments with Long Count dates; this period saw the Maya civilization develop a large number of city-states linked by a complex trade network. In the Maya Lowlands two great rivals, the cities of Tikal and Calakmul, became powerful; the Classic period saw the intrusive intervention of the central Mexican city of Teotihuacan in Maya dynastic politics. In the 9th century, there was a widespread political collapse in the central Maya region, resulting in internecine warfare, the abandonment of cities, a northward shift of population; the Postclassic period saw the rise of Chichen Itza in the north, the expansion of the aggressive Kʼicheʼ kingdom in the Guatemalan Highlands. In the 16th century, the Spanish Empire colonized the Mesoamerican region, a lengthy series of campaigns saw the fall of Nojpetén, the last Maya city, in 1697.
Classic period rule was centred on the concept of the "divine king", who acted as a mediator between mortals and the supernatural realm. Kingship was patrilineal, power would pass to the eldest son. A prospective king was expected to be a successful war leader. Maya politics was dominated by a closed system of patronage, although the exact political make-up of a kingdom varied from city-state to city-state. By the Late Classic, the aristocracy had increased, resulting in the corresponding reduction in the exclusive power of the divine king; the Maya civilization developed sophisticated artforms, the Maya created art using both perishable and non-perishable materials, including wood, obsidian, sculpted stone monuments and finely painted murals. Maya cities tended to expand haphazardly, the city centre would be occupied by ceremonial and administrative complexes, surrounded by an irregular sprawl of residential districts. Different parts of a city would be linked by causeways; the principal architecture of the city consisted of palaces, pyramid-temples, ceremonial ballcourts, structures aligned for astronomical observation.
The Maya elite were literate, developed a complex system of hieroglyphic writing, the most advanced in the pre-Columbian Americas. The Maya recorded their history and ritual knowledge in screenfold books, of which only three uncontested examples remain, the rest having been destroyed by the Spanish. There are a great many examples of Maya text found on stelae and ceramics; the Maya developed a complex series of interlocking ritual calendars, employed mathematics that included one of the earliest instances of the explicit zero in the world. As a part of their religion, the Maya practised human sacrifice; the Maya civilization developed within the Mesoamerican cultural area, which covers a region that spreads from northern Mexico southwards into Central America. Mesoamerica was one of six cradles of civilization worldwide; the Mesoamerican area gave rise to a series of cultural developments that included complex societies, cities, monumental architecture and calendrical systems. The set of traits shared by Mesoamerican cultures included astronomical knowledge and human sacrifice, a cosmovision that viewed the world as divided into four divisions aligned with the cardinal directions, each with different attributes, a three-way division of the world into the celestial realm, the earth, the underworld.
By 6000 BC, the early inhabitants of Mesoamerica were experimenting with the domestication of plants, a process that led to the establishment of sedentary agricultural societies. The diverse climate allowed for wide variation in available crops, but all regions of Mesoamerica cultivated the base crops of maize and squashes. All Mesoamerican cultures used Stone Age technology. Mesoamerica lacked draft animals, did not use the wheel, possessed few domesticated animals. Mesoamericans viewed the world as hostile and governed by unpredictable deities; the ritual Mesoamerican ballgame was played. Mesoamerica is linguistically diverse, with most languages falling within a small number of language families—the major families are Mayan, Mixe–Zoquean and Uto-Aztecan.
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, the longest period of the Phanerozoic Eon; the Cretaceous Period is abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas; these oceans and seas were populated with now-extinct marine reptiles and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared; the Cretaceous ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs and large marine reptiles died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras.
The Cretaceous as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the Paris Basin and named for the extensive beds of chalk, found in the upper Cretaceous of Western Europe. The name Cretaceous was derived from Latin creta; the Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use; as with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system's base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is defined, being placed at an iridium-rich layer found worldwide, believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico.
This layer has been dated at 66.043 Ma. A 140 Ma age for the Jurassic-Cretaceous boundary instead of the accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a "first step" toward formally changing the age in the International Union of Geological Sciences. From youngest to oldest, the subdivisions of the Cretaceous period are: Late Cretaceous Maastrichtian – Campanian – Santonian – Coniacian – Turonian – Cenomanian – Early Cretaceous Albian – Aptian – Barremian – Hauterivian – Valanginian – Berriasian – The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms; the Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type, formed under warm, shallow marine circumstances.
Due to the high sea level, there was extensive space for such sedimentation. Because of the young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide. Chalk is a rock type characteristic for the Cretaceous, it consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas. In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast; the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not consolidated and the Chalk Group still consists of loose sediments in many places; the group has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is a marine system consisting of competent limestone beds or incompetent marls.
Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean. Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half the worlds petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and the Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval; these shales are an important source rock for oil and gas, for example in the subsurface of the North Sea. During th