|
Edaga Arbi Glacials
The Edaga Arbi Glacials are a Palaeozoic geological formation in Tigray (northern Ethiopia) and in Eritrea. The matrix is composed of grey, black and purple clays (locally silt), that contains rock fragments up to 6 metres across. Pollen dating yields a Late Carboniferous (~323 million years or Ma) to Early Permian (~295 Ma) age. Name and definition The name was coined by geologist D.B.Dow and colleagues They referred to the wide outcrops surrounding the town of Idaga Arbi. So far the nomenclature has not been proposed for recognition to the International Commission on Stratigraphy. Stratigraphic context The Edaga Arbi Glacials fill the bottom of north-south oriented valleys, that were carved by glaciers, into the Precambrian basement and in Early Palaeozoic sediments. These valleys were often several kilometres wide and tens of meters deep. Indeed, northern Ethiopia was glaciated in the Early Palaeozoic (Late Ordovician; ~445 Ma), and in the Late Palaeozoic (Carboniferous-Permi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethiopia
Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east and northeast, Kenya to the south, South Sudan to the west, and Sudan to the northwest. Ethiopia has a total area of . As of 2022, it is home to around 113.5 million inhabitants, making it the 13th-most populous country in the world and the 2nd-most populous in Africa after Nigeria. The national capital and largest city, Addis Ababa, lies several kilometres west of the East African Rift that splits the country into the African and Somali tectonic plates. Anatomically modern humans emerged from modern-day Ethiopia and set out to the Near East and elsewhere in the Middle Paleolithic period. Southwestern Ethiopia has been proposed as a possible homeland of the Afroasiatic langua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dropstone
Dropstones are isolated fragments of rock found within finer-grained water-deposited sedimentary rocks or pyroclastic beds. They range in size from small pebbles to boulders. The critical distinguishing feature is that there is evidence that they were not transported by normal water currents, but rather dropped in vertically through the air or water column. Such deposition can occur i.e. during a volcanic eruption. Background When deposited into fine layered mud, such evidence includes an impact depression beneath the dropstone, and indication that the mud has been squeezed up around the edges of the falling rock. Subsequent deposits of mud drape over the dropstone and its crater. Glacial dropstones, involving rocks falling out of icebergs, are one of the most common types of dropstone preserved in the geological record, particularly when deposited in low-energy deep sea or lake environments. Dropstones differ from erratics found in glacial till in that they are deposited in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mudstones
Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, W. H. Freeman, 2nd ed, 529 pp. The term ''mudstone'' is also used to describe carbonate rocks (limestone or dolomite) that are composed predominantly of carbonate mud. However, in most contexts, the term refers to siliciclastic mudstone, composed mostly of silicate minerals. The NASA Curiosity rover has found deposits of mudstone on Mars that contain organic substances such as propane, benzene and toluene. Definition There is not a single definition of mudstone that has gained general acceptance,Boggs 2006, p.143 though there is wide agreement that mudstones are fine-grained sedimentary rocks, composed mostly of silicate grains with a grain size less than . Individual grains this size are too small to be distingui ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moraines
A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sheet. It may consist of partly rounded particles ranging in size from boulders (in which case it is often referred to as boulder clay) down to gravel and sand, in a groundmass of finely-divided clayey material sometimes called glacial flour. Lateral moraines are those formed at the side of the ice flow, and terminal moraines were formed at the foot, marking the maximum advance of the glacier. Other types of moraine include ground moraines (till-covered areas forming sheets on flat or irregular topography) and medial moraines (moraines formed where two glaciers meet). Etymology The word ''moraine'' is borrowed from French , which in turn is derived from the Savoyard Italian ("mound of earth"). ''Morena'' in this case was derived from Proven ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as ''physical'' or ''mechanical'' erosion; this contrasts with ''chemical'' erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and waves; glacial plucking, abrasion, and scour; areal flooding; wind abrasion; groundwater processes; and mass movement processes in steep landscapes like landslides and debris flows. The rates at which such processes act control how fast a surface is eroded. Typically, physical erosion procee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ethiopian Highlands
The Ethiopian Highlands is a rugged mass of mountains in Ethiopia in Northeast Africa. It forms the largest continuous area of its elevation in the continent, with little of its surface falling below , while the summits reach heights of up to . It is sometimes called the Roof of Africa due to its height and large area. Most of the Ethiopian Highlands are part of central and northern Ethiopia, and its northernmost portion reaches into Eritrea. History In the southern parts of the Ethiopian Highlands once was located the Kingdom of Kaffa, a medieval early modern state, whence the coffee plant was exported to the Arabian Peninsula. The land of the former kingdom is mountainous with stretches of forest. The land is very fertile, capable of three harvests a year. The term ''coffee'' derives from the ar, قهوة, italic=no ()''Oxford English Dictionary'', 1st ed. "coffee, ''n.''" Oxford University Press (Oxford), 1891. and is traced to Kaffa. Physical geography The Highl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia. The Permian witnessed the diversification of the two groups of amniotes, the synapsids and the sauropsids ( reptiles). The world at the time was dominated by the supercontinent Pangaea, which had formed due to the collision of Euramerica and Gondwana during the Carboniferous. Pangaea was surrounded by the superocean Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, which could better cope with these drier conditions, rose to dominance in place of their am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous'' means "coal-bearing", from the Latin '' carbō'' ("coal") and '' ferō'' ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern 'system' names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession. The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial animal life was well established by the Carboniferous Period. Tetrapods (four limbed vertebrates), which had originated from lobe-finned fish during the preceding Devonian, became pentadactylous in and diversified during the Carboniferous, including early amphibian line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Palaeozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ''zōḗ'' (), "life", meaning "ancient life" ). It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): # Cambrian # Ordovician # Silurian # Devonian # Carboniferous # Permian The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era. The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared. Arthropods, molluscs, fish, amphibians, reptiles, and synapsids all evolved during the Paleozoic. Life began in the oce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Ordovician
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian Pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glaciation
A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate between glacial periods. The Last Glacial Period ended about 15,000 years ago. The Holocene is the current interglacial. A time with no glaciers on Earth is considered a greenhouse climate state. Quaternary Period Within the Quaternary, which started about 2.6 million years before present, there have been a number of glacials and interglacials. At least eight glacial cycles have occurred in the last 740,000 years alone. Penultimate Glacial Period The Penultimate Glacial Period (PGP) is the glacial period that occurred before the Last Glacial Period. It began about 194,000 years ago and ended 135,000 years ago, with the beginning of the Eemian interglacial. Last Glacial Period The last glacial period was the most recent glacial period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.JPG "Click for more on -> Moraines")
.jpg "Click for more on -> Ethiopian Highlands")
