1.
Gulf of Aqaba
–
The Gulf of Aqaba or Gulf of Eilat is a large gulf at the northern tip of the Red Sea, east of the Sinai Peninsula and west of the Arabian mainland. Its coastline is divided between four countries, Egypt, Israel, Jordan, and Saudi Arabia, the gulf is east of the Sinai Peninsula and west of the Arabian Peninsula. With the Gulf of Suez to the west, it extends from the portion of the Red Sea. It reaches a depth of 1,850 m in its central area. The gulf measures 24 kilometres at its widest point and stretches some 160 kilometres north from the Straits of Tiran to where Israel meets Egypt, like the coastal waters of the Red Sea, the gulf is one of the worlds premier sites for diving. At this northern end of the gulf are three important cities, Taba in Egypt, Eilat in Israel, and Aqaba in Jordan and they are strategically important commercial ports and popular resorts for tourists seeking to enjoy the warm climate. Further south, Haql is the largest Saudi Arabian city on the gulf, on Sinai, Sharm el-Sheikh and Dahab are the major centers. The largest population center is Aqaba, with a population of 108,000, followed by Eilat with a population of 48,000. The gulf is one of two created by the Sinai Peninsulas bifurcation of the northern Red Sea, the Gulf of Suez lying to the west of the peninsula. Geologically, the forms the southern end of the Dead Sea Transform. It contains three small pull-apart basins, the Elat Deep, Aragonese Deep and Dakar Deep, formed between four left lateral strike-slip fault segments, movement on one of these faults caused the 1995 Gulf of Aqaba earthquake. Trade across the Red Sea between Thebes port of Elim and Elat at the head of the gulf is documented as early as the Fourth Dynasty of Egypt, egyptian settlements near Timna at the head of the gulf date to the Eighteenth dynasty of Egypt. At the northern edge, the ancient city of Ayla was a hub for the Nabateans. The Romans built the Via Traiana Nova, which joined the Kings Highway at Aqaba and connected Africa to Asia, Aqaba was a major Ottoman port, connected to Damascus and Medina by the Hejaz railway. During World War I, the Battle of Aqaba was the key battle that ended a 500-year Ottoman rule over Greater Syria, the gulf is one of the most popular diving destinations in the world. About 250,000 dives are performed annually in Eilats 11 km coastline, the Landscape of Wadi Rum to the east of the northern edge of the gulf is a popular destination. Other destinations are the ruins of the civilization of Ayla in the city of Aqaba. Whales, orcas, dolphins, dugongs, and whale sharks live in the gulf as well
2.
Red Sea
–
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait, to the north lie the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez. The Red Sea is a Global 200 ecoregion, the sea is underlain by the Red Sea Rift which is part of the Great Rift Valley. The Red Sea has an area of roughly 438,000 km2, is about 2250 km long and. It has a depth of 2211 m in the central median trench. However, there are also extensive shallow shelves, noted for their marine life, the sea is the habitat of over 1,000 invertebrate species, and 200 soft and hard corals. It is the worlds northernmost tropical sea, the International Hydrographic Organization defines the limits of the Red Sea as follows, On the North. The Southern limits of the Gulfs of Suez and Aqaba, a line joining Husn Murad and Ras Siyyan. Red Sea is a translation of the Greek Erythra Thalassa, Latin Mare Rubrum, Arabic, البحر الأحمر. Al-Baḥr Al-Aḥmar, Somali Badda Cas and Tigrinya Qeyyiḥ bāḥrī, the name of the sea may signify the seasonal blooms of the red-coloured Trichodesmium erythraeum near the waters surface. A theory favored by modern scholars is that the name red is referring to the direction south. The basis of this theory is that some Asiatic languages used color words to refer to the cardinal directions, herodotus on one occasion uses Red Sea and Southern Sea interchangeably. Historically, it was known to western geographers as Mare Mecca. Some ancient geographers called the Red Sea the Arabian Gulf or Gulf of Arabia. C, in that version, the Yam Suph is translated as Erythra Thalassa. The Red Sea is one of four seas named in English after common color terms — the others being the Black Sea, the White Sea and the Yellow Sea. The direct rendition of the Greek Erythra thalassa in Latin as Mare Erythraeum refers to the part of the Indian Ocean. The earliest known exploration of the Red Sea was conducted by ancient Egyptians, one such expedition took place around 2500 BC, and another around 1500 BC. Both involved long voyages down the Red Sea, historically, scholars argued whether these trips were possible
3.
Egypt
–
Egypt, officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia by a land bridge formed by the Sinai Peninsula. Egypt is a Mediterranean country bordered by the Gaza Strip and Israel to the northeast, the Gulf of Aqaba to the east, the Red Sea to the east and south, Sudan to the south, and Libya to the west. Across the Gulf of Aqaba lies Jordan, and across from the Sinai Peninsula lies Saudi Arabia, although Jordan and it is the worlds only contiguous Afrasian nation. Egypt has among the longest histories of any country, emerging as one of the worlds first nation states in the tenth millennium BC. Considered a cradle of civilisation, Ancient Egypt experienced some of the earliest developments of writing, agriculture, urbanisation, organised religion and central government. One of the earliest centres of Christianity, Egypt was Islamised in the century and remains a predominantly Muslim country. With over 92 million inhabitants, Egypt is the most populous country in North Africa and the Arab world, the third-most populous in Africa, and the fifteenth-most populous in the world. The great majority of its people live near the banks of the Nile River, an area of about 40,000 square kilometres, the large regions of the Sahara desert, which constitute most of Egypts territory, are sparsely inhabited. About half of Egypts residents live in areas, with most spread across the densely populated centres of greater Cairo, Alexandria. Modern Egypt is considered to be a regional and middle power, with significant cultural, political, and military influence in North Africa, the Middle East and the Muslim world. Egypts economy is one of the largest and most diversified in the Middle East, Egypt is a member of the United Nations, Non-Aligned Movement, Arab League, African Union, and Organisation of Islamic Cooperation. Miṣr is the Classical Quranic Arabic and modern name of Egypt. The name is of Semitic origin, directly cognate with other Semitic words for Egypt such as the Hebrew מִצְרַיִם, the oldest attestation of this name for Egypt is the Akkadian
4.
Suez
–
Suez is a seaport city in north-eastern Egypt, located on the north coast of the Gulf of Suez, near the southern terminus of the Suez Canal, having the same boundaries as Suez governorate. It has three harbors, Adabya, Ain Sukhna and Port Tawfiq, and extensive port facilities, together they form a metropolitan area. Railway lines and highways connect the city with Cairo, Port Said, Suez has a petrochemical plant, and its oil refineries have pipelines carrying the finished product to Cairo. In the 7th century AD a town named Kolzum stood just north of the site of present-day Suez and served as terminus of a canal built by Amr ibn al-As linking the Nile River. Kolzums trade fell following the closure of the canal in 770 by the second Abbasid caliph al-Mansur to prevent his enemies in Arabia from accessing supplies from Egypt, nonetheless, the town benefited from the trade that remained between Egypt and Arabia. By 780 al-Mansurs successor al-Mahdi restored part of the canal, the Qarmatians led by Hasan ibn Ahmad defeated a Fatimid army headed by Gawhar al-Siqilli at Kolzum in 971 and thereby captured the town. Following his defeat in Cairo by al-Siqilli at the end of year, Hasan. Suez was situated nearby and served as a source of drinking water for Kolzum according to Arab traveler al-Muqaddasi who visited in 986, the Ayyubid sultan of Egypt, Saladin, fortified both Kolzum and Suez in to defend Egypts eastern frontier from Crusader raids by Raynald of Chatillon. Between 1183-84, Raynald had ships stationed in the Red Sea to prevent the Ayyubid garrison at Kolzum from accessing water, in response, Saladins brother al-Adil had Husam ad-Din Lulu build a naval fleet which sailed to the southern port of Aidab to end Raynalds venture. By the 13th century it was recorded that Kolzum was in ruins as was Suez which had replaced the former as a population center. According to Muslim historians al-Maqrizi and al-Idrisi, Kolzum had once been a prosperous town, Arab geographer al-Dimashqi noted that Kolzum belonged to the Mamluk province of al-Karak at the time. Following the Ottomans conquest of Egypt at the beginning of the 16th century, the Ottoman fleets at Suez were instrumental in disputing control with the Portuguese over Indian Ocean trade. However, by 1798, during Napoleonic invasion, Suez had devolved into an unimportant town, fighting between the French and the British in 1800 left most of the town in ruins. Its importance as a port increased after the Suez Canal opened in 1869, the city was virtually destroyed during battles in the late 1960s and early 1970s between Egyptian and Israeli forces occupying the Sinai Peninsula. The town was deserted following the Six Day War in 1967, reconstruction of Suez began soon after Egypt reopened the Suez Canal, following the October War with Israel. Suez was the first city to major protests against the government of Hosni Mubarak during the 2011 Egyptian revolution and was the scene of the first fatality of that uprising. On account of this, it has called the Sidi Bouzid of Egypt. The city is divided into five districts, It is most populous district of the city
5.
Sinai Peninsula
–
The Sinai Peninsula or simply Sinai is a peninsula in Egypt, situated between the Mediterranean Sea to the north and the Red Sea to the south, serving as a land bridge between Asia and Africa. It is the part of Egyptian territory located in Asia. Sinai has an area of about 60,000 km2. The bulk of the peninsula is divided administratively into two of Egypts 27 governorates, the Sinai Peninsula has been a part of Egypt from the First Dynasty of ancient Egypt. In periods of occupation, the Sinai was, like the rest of Egypt, also occupied and controlled by foreign empires, in more recent history the Ottoman Empire. Israel invaded and occupied Sinai during the Suez Crisis of 1956, on 6 October 1973, Egypt launched the Yom Kippur War to retake the peninsula, which was the site of fierce fighting between Egyptian and Israeli forces. Today, Sinai has become a tourist destination due to its setting, rich coral reefs. Mount Sinai is one of the most religiously significant places in Abrahamic faiths, in addition to its formal name, Egyptians also refer to it as Arḍ ul-Fairūz. The ancient Egyptians called it Ta Mefkat, or land of turquoise, Sinai is triangular in shape, with northern shore lying on the southern Mediterranean Sea, and southwest and southeast shores on Gulf of Suez and Gulf of Aqaba of the Red Sea. It is linked to the African continent by the Isthmus of Suez,125 kilometres wide strip of land, the eastern isthmus, linking it to the Asian mainland, is around 200 kilometres wide. The peninsulas eastern shore separates the Arabian plate from the African plate, the southernmost tip is the Ras Muhammad National Park. Most of the Sinai Peninsula is divided among the two governorates of Egypt, South Sinai and North Sinai, together, they comprise around 60,000 square kilometres and have a population of 597,000. Three more governates span the Suez Canal, crossing into African Egypt, Suez is on the end of the Suez Canal, Ismailia in the centre. The largest city of Sinai is Arish, capital of the North Sinai, other larger settlements include Sharm el-Sheikh and El-Tor, on the southern coast. Inland Sinai is arid, mountainous and sparsely populated, the largest settlements being Saint Catherine, Sinai is one of the coldest provinces in Egypt because of its high altitudes and mountainous topographies. Winter temperatures in some of Sinais cities and towns reach −16 °C, the mines were worked intermittently and on a seasonal basis for thousands of years. Modern attempts to exploit the deposits have been unprofitable and these may be the first historically attested mines. According to the Hebrew Bible, the peninsula was crossed by the Israelites during the Exodus from Egypt and this included numerous halts over a 40-year period of travel sometime towards the end of the Bronze Age
6.
Africa
–
Africa is the worlds second-largest and second-most-populous continent. At about 30.3 million km² including adjacent islands, it covers 6% of Earths total surface area and 20.4 % of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the human population. The continent includes Madagascar and various archipelagos and it contains 54 fully recognized sovereign states, nine territories and two de facto independent states with limited or no recognition. Africas population is the youngest amongst all the continents, the age in 2012 was 19.7. Algeria is Africas largest country by area, and Nigeria by population, afarensis, Homo erectus, H. habilis and H. ergaster – with the earliest Homo sapiens found in Ethiopia being dated to circa 200,000 years ago. Africa straddles the equator and encompasses numerous climate areas, it is the continent to stretch from the northern temperate to southern temperate zones. Africa hosts a diversity of ethnicities, cultures and languages. In the late 19th century European countries colonized most of Africa, Africa also varies greatly with regard to environments, economics, historical ties and government systems. However, most present states in Africa originate from a process of decolonization in the 20th century, afri was a Latin name used to refer to the inhabitants of Africa, which in its widest sense referred to all lands south of the Mediterranean. This name seems to have referred to a native Libyan tribe. The name is connected with Hebrew or Phoenician ʿafar dust. The same word may be found in the name of the Banu Ifran from Algeria and Tripolitania, under Roman rule, Carthage became the capital of the province of Africa Proconsularis, which also included the coastal part of modern Libya. The Latin suffix -ica can sometimes be used to denote a land, the later Muslim kingdom of Ifriqiya, modern-day Tunisia, also preserved a form of the name. According to the Romans, Africa lay to the west of Egypt, while Asia was used to refer to Anatolia, as Europeans came to understand the real extent of the continent, the idea of Africa expanded with their knowledge. 25,4, whose descendants, he claimed, had invaded Libya, isidore of Seville in Etymologiae XIV.5.2. Suggests Africa comes from the Latin aprica, meaning sunny, massey, in 1881, stated that Africa is derived from the Egyptian af-rui-ka, meaning to turn toward the opening of the Ka. The Ka is the double of every person and the opening of the Ka refers to a womb or birthplace
7.
Asia
–
Asia covers an area of 44,579,000 square kilometres, about 30% of Earths total land area and 8. 7% of the Earths total surface area. The continent, which has long been home to the majority of the population, was the site of many of the first civilizations. Asia is notable for not only its large size and population. In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, the western boundary with Europe is a historical and cultural construct, as there is no clear physical and geographical separation between them. The most commonly accepted boundaries place Asia to the east of the Suez Canal, the Ural River, and the Ural Mountains, and south of the Caucasus Mountains, China and India alternated in being the largest economies in the world from 1 to 1800 A. D. The accidental discovery of America by Columbus in search for India demonstrates this deep fascination, the Silk Road became the main East-West trading route in the Asian hitherland while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism as well as robust population growth during the 20th century, given its size and diversity, the concept of Asia—a name dating back to classical antiquity—may actually have more to do with human geography than physical geography. Asia varies greatly across and within its regions with regard to ethnic groups, cultures, environments, economics, historical ties, the boundary between Asia and Africa is the Red Sea, the Gulf of Suez, and the Suez Canal. This makes Egypt a transcontinental country, with the Sinai peninsula in Asia, the border between Asia and Europe was historically defined by European academics. In Sweden, five years after Peters death, in 1730 Philip Johan von Strahlenberg published a new atlas proposing the Urals as the border of Asia, the Russians were enthusiastic about the concept, which allowed them to keep their European identity in geography. Tatishchev announced that he had proposed the idea to von Strahlenberg, the latter had suggested the Emba River as the lower boundary. Over the next century various proposals were made until the Ural River prevailed in the mid-19th century, the border had been moved perforce from the Black Sea to the Caspian Sea into which the Ural River projects. The border between the Black Sea and the Caspian is usually placed along the crest of the Caucasus Mountains, the border between Asia and the loosely defined region of Oceania is usually placed somewhere in the Malay Archipelago. The terms Southeast Asia and Oceania, devised in the 19th century, have had several different geographic meanings since their inception. The chief factor in determining which islands of the Malay Archipelago are Asian has been the location of the possessions of the various empires there. Lewis and Wigen assert, The narrowing of Southeast Asia to its present boundaries was thus a gradual process, Asia is larger and more culturally diverse than Europe. It does not exactly correspond to the borders of its various types of constituents. From the time of Herodotus a minority of geographers have rejected the three-continent system on the grounds there is no or is no substantial physical separation between them
8.
Limestone
–
Limestone is a sedimentary rock, composed mainly of skeletal fragments of marine organisms such as coral, forams and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate, about 10% of sedimentary rocks are limestones. The solubility of limestone in water and weak acid solutions leads to karst landscapes, most cave systems are through limestone bedrock. The first geologist to distinguish limestone from dolomite was Belsazar Hacquet in 1778, like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of organisms such as coral or foraminifera. Other carbonate grains comprising limestones are ooids, peloids, intraclasts and these organisms secrete shells made of aragonite or calcite, and leave these shells behind when they die. Limestone often contains variable amounts of silica in the form of chert or siliceous skeletal fragment, some limestones do not consist of grains at all, and are formed completely by the chemical precipitation of calcite or aragonite, i. e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters and this produces speleothems, such as stalagmites and stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance, the primary source of the calcite in limestone is most commonly marine organisms. Some of these organisms can construct mounds of rock known as reefs, below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone typically does not form in deeper waters. Limestones may also form in lacustrine and evaporite depositional environments, calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, and dissolved ion concentrations. Calcite exhibits a characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors, especially with weathered surfaces, Limestone may be crystalline, clastic, granular, or massive, depending on the method of formation. Crystals of calcite, quartz, dolomite or barite may line small cavities in the rock, when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams, particularly there are waterfalls. Calcium carbonate is deposited where evaporation of the leaves a solution supersaturated with the chemical constituents of calcite. Tufa, a porous or cellular variety of travertine, is found near waterfalls, coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the building process, limestone recrystallizes into marble
9.
Paleozoic
–
The Paleozoic Era is the earliest of three geologic eras of the Phanerozoic Eon, from 541 to 252.17 million years ago. It is the longest of the Phanerozoic eras, and is subdivided into six periods, the Cambrian, Ordovician, Silurian, Devonian, Carboniferous. The Paleozoic comes after the Neoproterozoic era of the Proterozoic and is followed by the Mesozoic, the Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earths history, known as the Cambrian explosion, fish, arthropods, amphibians, anapsids, synapsids, euryapsids and diapsids all evolved during the Paleozoic. Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, Great forests of primitive plants covered the continents, many of which formed the coal beds of Europe and eastern North America. Towards the end of the era, large, sophisticated diapsids and synapsids were dominant, the Paleozoic Era ended with the largest extinction event in the history of Earth, the Permian–Triassic extinction event. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover, recovery of life in the sea may have been much faster. The Paleozoic era began and ended with supercontinents and in between were the rise of mountains along the margins, and flooding and draining of shallow seas between. At its start, the supercontinent Pannotia broke up, paleoclimatic studies and evidence of glaciers indicate that central Africa was most likely in the polar regions during the early Paleozoic. During the early Paleozoic, the huge continent Gondwana formed or was forming, by mid-Paleozoic, the collision of North America and Europe produced the Acadian-Caledonian uplifts, and a subduction plate uplifted eastern Australia. There are six periods in the Paleozoic Era, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, the Cambrian spans from 541 million years to 485 million years and is the first period of the Paleozoic era of the Phanerozoic. The Cambrian marked a boom in evolution in an event known as the Cambrian explosion in which the largest number of creatures evolved in any period of the history of the Earth. Creatures like algae evolved, but the most ubiquitous of that period were the armored arthropods, almost all marine phyla evolved in this period. During this time, the supercontinent Pannotia begins to break up, the Ordovician spanned from 485 million years to 443 million years ago. The Ordovician is a time in Earths history in many of the biological classes still prevalent today evolved, such as primitive fish, cephalopods. The most common forms of life, however, were trilobites, snails, more importantly, the first arthropods went ashore to colonize the empty continent of Gondwana. By the end of the Ordovican, Gondwana was at the pole, early North America had collided with Europe. Glaciation of Africa resulted in a drop in sea level
10.
Oligocene
–
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present. As with other geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start. The name Oligocene comes from the Ancient Greek ὀλίγος and καινός, the Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period, the Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included an expansion of grasslands. By contrast, the Oligocene–Miocene boundary is not set at an easily identified worldwide event, Oligocene faunal stages from youngest to oldest are, The Paleogene Period general temperature decline is interrupted by an Oligocene 7-million-year stepwise climate change. A deeper 8.2 °C,400, 000-year temperature depression leads the 2 °C, the stepwise climate change began 32.5 Ma and lasted through to 25.5 Ma, as depicted in the PaleoTemps chart. The Oligocene climate change was a increase in ice volume. The 7-million-year depression abruptly terminated within 1–2 million years of the La Garita Caldera eruption at 28–26 Ma, a deep 400, 000-year glaciated Oligocene Miocene boundary event is recorded at McMurdo Sound and King George Island. During this epoch, the continued to drift toward their present positions. Antarctica became more isolated and finally developed an ice cap, a brief marine incursion marks the early Oligocene in Europe. Marine fossils from the Oligocene are rare in North America, there appears to have been a land bridge in the early Oligocene between North America and Europe, since the faunas of the two regions are very similar. Sometime during the Oligocene, South America was finally detached from Antarctica and it also allowed the Antarctic Circumpolar Current to flow, rapidly cooling the Antarctic continent. Angiosperms continued their expansion throughout the world as tropical and sub-tropical forests were replaced by deciduous forests. Open plains and deserts became more common and grasses expanded from their habitat in the Eocene moving out into open tracts. However, even at the end of the period, grass was not quite enough for modern savannas. In North America, subtropical species dominated with cashews and lychee trees present, and temperate trees such as roses, beeches, the legumes spread, while sedges, bulrushes, and ferns continued their ascent. Even more open landscapes allowed animals to grow to larger sizes than they had earlier in the Paleocene epoch 30 million years earlier, marine faunas became fairly modern, as did terrestrial vertebrate fauna on the northern continents
11.
Clastic rock
–
Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus, chunks and smaller grains of rock broken off other rocks by physical weathering. Geologists use the term clastic with reference to sedimentary rocks as well as to particles in sediment transport whether in suspension or as bed load, clastic sedimentary rocks are rocks composed predominantly of broken pieces or clasts of older weathered and eroded rocks. Clastic sediments or sedimentary rocks are classified based on size, clast and cementing material composition. The classification factors are often useful in determining a samples environment of deposition, an example clastic environment would be a river system in which the full range of grains being transported by the moving water consist of pieces eroded from solid rock upstream. Grain size varies from clay in shales and claystones, through silt in siltstones, sand in sandstones, the Krumbein phi scale numerically orders these terms in a logarithmic size scale. Siliciclastic rocks are clastic rocks that are composed almost exclusively of silicon. The composition of sedimentary rocks includes the chemical and mineralogical components of the framework as well as the cementing material that make up these rocks. Boggs divides them into four categories, major minerals, accessory minerals, rock fragments, major minerals can be categorized into subdivisions based on their resistance to chemical decomposition. Those that possess a great resistance to decomposition are categorized as stable, while those that do not are considered less stable, the most common stable mineral in siliciclastic sedimentary rocks is quartz. Quartz makes up approximately 65 percent of framework grains present in sandstones, less stable minerals present in this type of rocks are feldspars, including both potassium and plagioclase feldspars. Feldspars comprise a considerably lesser portion of framework grains and minerals and they only make up about 15 percent of framework grains in sandstones and 5% of minerals in shales. Clay mineral groups are present in mudrocks but can be found in other siliciclastic sedimentary rocks at considerably lower levels. Accessory minerals are associated with those whose presence in the rock are not directly important to the classification of the specimen and these generally occur in smaller amounts in comparison to the quartz, and feldspars. Furthermore, those that do occur are generally heavy minerals or coarse grained micas, rock fragments also occur in the composition of siliciclastic sedimentary rocks and are responsible for about 10 -15 percent of the composition of sandstone. They generally make up most of the gravel size particles in conglomerates, though they sometimes are, rock fragments are not always sedimentary in origin. They can also be metamorphic or igneous, chemical cements vary in abundance but are predominantly found in sandstones. The two major types, are based and carbonate based
12.
Miocene
–
The Miocene is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago. The Miocene was named by Sir Charles Lyell and its name comes from the Greek words μείων and καινός and means less recent because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene Epoch and is followed by the Pliocene Epoch, the earth went from the Oligocene through the Miocene and into the Pliocene, with the climate slowly cooling towards a series of ice ages. The Miocene boundaries are not marked by a single distinct global event, the apes arose and diversified during the Miocene, becoming widespread in the Old World. By the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path, as in the Oligocene before it, grasslands continued to expand and forests to dwindle in extent. In the Miocene seas, kelp forests made their first appearance, the plants and animals of the Miocene were fairly modern. The Miocene faunal stages from youngest to oldest are typically named according to the International Commission on Stratigraphy, Two subdivisions each form the lower, middle, continents continued to drift toward their present positions. Mountain building took place in western North America, Europe, both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the North American Great Plains, India continued to collide with Asia, creating dramatic new mountain ranges. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish–Arabian region between 19 and 12 Ma. The subsequent uplift of mountains in the western Mediterranean region and a fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea near the end of the Miocene. The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture, climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued. Although a long-term cooling trend was well underway, there is evidence of a period during the Miocene when the global climate rivalled that of the Oligocene. The Miocene warming began 21 million years ago and continued until 14 million years ago, by 8 million years ago, temperatures dropped sharply once again, and the Antarctic ice sheet was already approaching its present-day size and thickness. Greenland may have begun to have large glaciers as early as 7 to 8 million years ago, life during the Miocene Epoch was mostly supported by the two newly formed biomes, kelp forests and grasslands. This allows for more grazers, such as horses, rhinoceroses, ninety five percent of modern plants existed by the end of this epoch. The higher organic content and water retention of the deeper and richer grassland soils, with long term burial of carbon in sediments, produced a carbon and this, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to a cooler, drier climate. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO2
