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
Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to gravity into the mantle. Regions where this process occurs are known as subduction zones. Rates of subduction are in centimeters per year, with the average rate of convergence being two to eight centimeters per year along most plate boundaries. Plates include continental crust. Stable subduction zones involve the oceanic lithosphere of one plate sliding beneath the continental or oceanic lithosphere of another plate due to the higher density of the oceanic lithosphere; that is, the subducted lithosphere is always oceanic while the overriding lithosphere may or may not be oceanic. Subduction zones are sites that have a high rate of volcanism and earthquakes. Furthermore, subduction zones develop belts of deformation and metamorphism in the subducting crust, whose exhumation is part of orogeny and leads to mountain building in addition to collisional thickening.
Subduction zones are sites of gravitational sinking of Earth's lithosphere. Subduction zones exist at convergent plate boundaries where one plate of oceanic lithosphere converges with another plate; the descending slab, the subducting plate, is over-ridden by the leading edge of the other plate. The slab sinks at an angle of twenty-five to forty-five degrees to Earth's surface; this sinking is driven by the temperature difference between the subducting oceanic lithosphere and the surrounding mantle asthenosphere, as the colder oceanic lithosphere has, on average, a greater density. At a depth of greater than 60 kilometers, the basalt of the oceanic crust is converted to a metamorphic rock called eclogite. At that point, the density of the oceanic crust provides additional negative buoyancy, it is at subduction zones that Earth's lithosphere, oceanic crust and continental crust, sedimentary layers and some trapped water are recycled into the deep mantle. Earth is so far the only planet. Subduction is the driving force behind plate tectonics, without it, plate tectonics could not occur.
Oceanic subduction zones dive down into the mantle beneath 55,000 kilometers of convergent plate margins equal to the cumulative 60,000 kilometers of mid-ocean ridges. Subduction zones burrow but are imperfectly camouflaged, geophysics and geochemistry can be used to study them. Not the shallowest portions of subduction zones are known best. Subduction zones are asymmetric for the first several hundred kilometers of their descent, they start to go down at oceanic trenches. Their descents are marked by inclined zones of earthquakes that dip away from the trench beneath the volcanoes and extend down to the 660-kilometer discontinuity. Subduction zones are defined by the inclined array of earthquakes known as the Wadati–Benioff zone after the two scientists who first identified this distinctive aspect. Subduction zone earthquakes occur at greater depths than elsewhere on Earth; the subducting basalt and sediment are rich in hydrous minerals and clays. Additionally, large quantities of water are introduced into cracks and fractures created as the subducting slab bends downward.
During the transition from basalt to eclogite, these hydrous materials break down, producing copious quantities of water, which at such great pressure and temperature exists as a supercritical fluid. The supercritical water, hot and more buoyant than the surrounding rock, rises into the overlying mantle where it lowers the pressure in the mantle rock to the point of actual melting, generating magma; the magmas, in turn, rise. The mantle-derived magmas can continue to rise to Earth's surface, resulting in a volcanic eruption; the chemical composition of the erupting lava depends upon the degree to which the mantle-derived basalt interacts with Earth's crust and/or undergoes fractional crystallization. Above subduction zones, volcanoes exist in long chains called volcanic arcs. Volcanoes that exist along arcs tend to produce dangerous eruptions because they are rich in water and tend to be explosive. Krakatoa, Nevado del Ruiz, Mount Vesuvius are all examples of arc volcanoes. Arcs are known to be associated with precious metals such as gold and copper believed to be carried by water and concentrated in and around their host volcanoes in rock called "ore".
Although the process of subduction as it occurs today is well understood, its origin remains a matter of discussion and continuing study. Subduction initiation can occur spontaneously if denser oceanic lithosphere is able to founder and sink beneath adjacent oceanic or continental lithosphere. Both models can yield self-sustaining subduction zones, as oceanic crust is metamorphosed at great depth and becomes denser than the surrounding mantle rocks. Results from numerical models favor induced subduction initiation for most modern subduction zones, supported by geologic studies, but other analogue modeling shows the possibility of spontaneous subduction from inherent density differences between two plates at passiv
A stratovolcano known as a composite volcano, is a conical volcano built up by many layers of hardened lava, tephra and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas; the lava flowing from stratovolcanoes cools and hardens before spreading far, due to high viscosity. The magma forming this lava is felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows have travelled as far as 15 km. Stratovolcanoes are sometimes called "composite volcanoes" because of their composite stratified structure built up from sequential outpourings of erupted materials, they are in contrast to the less common shield volcanoes. Two famous examples of stratovolcanoes are Krakatoa, known for its catastrophic eruption in 1883 and Vesuvius, whose eruption in AD79 caused destruction of Pompeii and Herculaneum in 79 AD.
Both eruptions claimed thousands of lives. In modern times, Mount St. Helens and Mount Pinatubo have erupted catastrophically, with lesser losses of lives; the possible existence of stratovolcanoes on other terrestrial bodies of the Solar System has not been conclusively demonstrated. The one feasible exception are the existence of some isolated massifs on Mars, for example the Zephyria Tholus. Stratovolcanoes are common at subduction zones, forming chains and clusters along plate tectonic boundaries where oceanic crust is drawn under continental crust or another oceanic plate; the magma forming stratovolcanoes rises when water trapped both in hydrated minerals and in the porous basalt rock of the upper oceanic crust is released into mantle rock of the asthenosphere above the sinking oceanic slab. The release of water from hydrated minerals is termed "dewatering", occurs at specific pressures and temperatures for each mineral, as the plate descends to greater depths; the water freed from the rock lowers the melting point of the overlying mantle rock, which undergoes partial melting and rises due to its lighter density relative to the surrounding mantle rock, pools temporarily at the base of the lithosphere.
The magma rises through the crust, incorporating silica-rich crustal rock, leading to a final intermediate composition. When the magma nears the top surface, it pools in a magma chamber within the crust below the stratovolcano. There, the low pressure allows water and other volatiles dissolved in the magma to escape from solution, as occurs when a bottle of carbonated water is opened, releasing CO2. Once a critical volume of magma and gas accumulates, the plug of the volcanic vent is broken, leading to a sudden explosive eruption. In recorded history, explosive eruptions at subduction zone volcanoes have posed the greatest hazard to civilizations. Subduction-zone stratovolcanoes, such as Mount St. Helens, Mount Etna and Mount Pinatubo erupt with explosive force: the magma is too stiff to allow easy escape of volcanic gases; as a consequence, the tremendous internal pressures of the trapped volcanic gases remain and intermingle in the pasty magma. Following the breaching of the vent and the opening of the crater, the magma degasses explosively.
The magma and gases blast out with full force. Since 1600 CE, nearly 300,000 people have been killed by volcanic eruptions. Most deaths were caused by pyroclastic flows and lahars, deadly hazards that accompany explosive eruptions of subduction-zone stratovolcanoes. Pyroclastic flows are swift, avalanche-like, ground-sweeping, incandescent mixtures of hot volcanic debris, fine ash, fragmented lava and superheated gases that can travel at speeds in excess of 160 km/h. Around 30,000 people were killed by pyroclastic flows during the 1902 eruption of Mount Pelée on the island of Martinique in the Caribbean. In March to April 1982, three explosive eruptions of El Chichón in the State of Chiapas in southeastern Mexico, caused the worst volcanic disaster in that country's history. Villages within 8 km of the volcano were destroyed by pyroclastic flows, killing more than 2,000 people. Two Decade Volcanoes that erupted in 1991 provide examples of stratovolcano hazards. On June 15, Mount Pinatubo spewed an ash cloud 40 km into the air and produced huge pyroclastic surges and lahar floods that devastated a large area around the volcano.
Pinatubo, located in Central Luzon just 90 km west-northwest from Manila, had been dormant for 6 centuries before the 1991 eruption, which ranks as one of the largest eruptions in the 20th century. In 1991, Japan's Unzen Volcano, located on the island of Kyushu about 40 km east of Nagasaki, awakened from its 200-year slumber to produce a new lava dome at its summit. Beginning in June, repeated collapse of this erupting dome generated ash flows that swept down the mountain's slopes at speeds as high as 200 km/h. Unzen is one of more than 75 active volcanoes in Japan; the eruption of Mount Vesuvius in 79 smothered the nearby ancient cities of Pompeii and Herculaneum with thick deposits of pyroclastic surges and lava flows. Although death toll is estimated between 13,000 and 26,000 remains, the exact number still remains unknown. Vesuvius is recognized as one of the most dangerous volcanoes, due to its
Sierra Madre de Chiapas
The Sierra Madre de Chiapas is a major mountain range in Central America. The Sierra Madre de Chiapas is part of the American Cordillera, a chain of mountain ranges that consists of an continuous sequence of mountain ranges that form the western "backbone" of North America, Central America, South America; the range runs northwest–southeast from the state of Chiapas in Mexico, across western Guatemala, into El Salvador and Honduras. Most of the volcanoes of Guatemala, part of the Central America Volcanic Arc, are within the range. A narrow coastal plain lies south of the range, between the Pacific Ocean. To the north lie a series of highlands and depressions, including the Chiapas Depression, which separates the Sierra Madre from the Chiapas Plateau, the Guatemalan Highlands, Honduras' interior highlands; the range forms the main drainage divide between the Atlantic river systems. On the Pacific side the distance to the sea is short, the streams, while numerous, are small and rapid. A few of the streams of the Pacific slopes rise in the Guatemalan Highlands, force a way through the Sierra Madre at the bottom of deep ravines.
On the eastern side a number of the rivers of the Atlantic slopes attain a considerable volume and size. It is known near Guatemala city as the Sierra de las Nubes, enters Mexico as the Sierra de Istatan, its summit is not a well-defined crest, but is rounded or flattened into a table-land. The direction of the great volcanic cones, which rise in an irregular line above it, is not identical with the main axis of the Sierra itself, except near the Mexican frontier, but has a more southerly trend towards El Salvador; the base of many of the volcanic igneous peaks rests among the southern foothills in the southern region of the range. It is, impossible to subdivide the Sierra Madre into a northern and a volcanic chain. Viewed from the coast, the volcanic cones seem to rise directly from the central heights of the Sierra Madre, above which they tower. East of Volcán Tacana which marks the Mexican frontier, the principal volcanoes are Tajumulco. East of the Guatemalan border, the range forms the boundary between El Honduras.
In El Salvador, the volcanoes form a line well south of the range, where over twenty volcanoes form five clusters. Between the Sierra Madre and the Volcanic line lies a central plateau. Geography of Mesoamerica Sierra Madre de Chiapas topics Chisholm, Hugh, ed.. "Chiapas". Encyclopædia Britannica. 6. Cambridge University Press. P. 117
A pyroclastic flow is a fast-moving current of hot gas and volcanic matter that moves away from a volcano about 100 km/h on average but is capable of reaching speeds up to 700 km/h. The gases can reach temperatures of about 1,000 °C. Pyroclastic flows are a devastating result of certain explosive eruptions, their speed depends upon the density of the current, the volcanic output rate, the gradient of the slope. The word pyroclast is derived from the Greek πῦρ, meaning "fire", κλαστός, meaning "broken in pieces". A name for pyroclastic flows which glow red in the dark is nuée ardente. Pyroclastic flows that contain a much higher proportion of gas to rock are known as "fully dilute pyroclastic density currents" or pyroclastic surges; the lower density sometimes allows them to flow over higher topographic features or water such as ridges, hills and seas. They may contain steam and rock at less than 250 °C. Cold pyroclastic surges can occur when the eruption is from a vent under the sea. Fronts of some pyroclastic density currents are dilute.
A pyroclastic flow is a type of gravity current. There are several mechanisms that can produce a pyroclastic flow: Fountain collapse of an eruption column from a Plinian eruption. In such an eruption, the material forcefully ejected from the vent heats the surrounding air and the turbulent mixture rises, through convection, for many kilometers. If the erupted jet is unable to heat the surrounding air sufficiently, convection currents will not be strong enough to carry the plume upwards and it falls, flowing down the flanks of the volcano. Fountain collapse of an eruption column associated with a Vulcanian eruption; the gas and projectiles create a cloud, denser than the surrounding air and becomes a pyroclastic flow. Frothing at the mouth of the vent during degassing of the erupted lava; this can lead to the production of a rock called ignimbrite. This occurred during the eruption of Novarupta in 1912. Gravitational collapse of a lava dome or spine, with subsequent avalanches and flows down a steep slope.
The directional blast when part of a volcano explodes. As distance from the volcano increases, this transforms into a gravity-driven current; the volumes range from a few hundred cubic meters to more than 1,000 cubic kilometres. The larger ones can travel for hundreds of kilometres, although none on that scale have occurred for several hundred thousand years. Most pyroclastic flows are around travel for several kilometres. Flows consist of two parts: the basal flow hugs the ground and contains larger, coarse boulders and rock fragments, while an hot ash plume lofts above it because of the turbulence between the flow and the overlying air and heating cold atmospheric air causing expansion and convection; the kinetic energy of the moving cloud will flatten buildings in its path. The hot gases and high speed make them lethal, as they will incinerate living organisms instantaneously: The cities of Pompeii and Herculaneum, for example, were engulfed by pyroclastic surges on August 24, 79 AD with many lives lost.
The 1902 eruption of Mount Pelée destroyed the Martinique town of St. Pierre. Despite signs of impending eruption, the government deemed St. Pierre safe due to hills and valleys between it and the volcano, but the pyroclastic flow charred the entirety of the city, killing all but two of its 30,000 residents. A pyroclastic surge killed volcanologists Harry Glicken and Katia and Maurice Krafft and 40 other people on Mount Unzen, in Japan, on June 3, 1991; the surge started as a pyroclastic flow and the more energised surge climbed a spur on which the Kraffts and the others were standing. On 25 June, 1997 a pyroclastic flow travelled down Mosquito Ghaut on the Caribbean island of Montserrat. A large energized pyroclastic surge developed; this flow could not be restrained by the Ghaut and spilled out of it, killing 19 people who were in the Streatham village area. Several others in the area suffered severe burns. Testimonial evidence from the 1883 eruption of Krakatoa, supported by experimental evidence, shows that pyroclastic flows can cross significant bodies of water.
However, that might be a pyroclastic surge, not flow, because the density of a gravity current means it cannot move across the surface of water. One flow reached the Sumatran coast as much as 48 km away. A 2006 BBC documentary film, Ten Things You Didn't Know About Volcanoes, demonstrated tests by a research team at Kiel University, Germany, of pyroclastic flows moving over water; when the reconstructed pyroclastic flow hit the water, two things happened
A phreatic eruption called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground or surface water. The extreme temperature of the magma causes near-instantaneous evaporation to steam, resulting in an explosion of steam, ash and volcanic bombs. At Mount St. Helens, hundreds of steam explosions preceded a 1980 plinian eruption of the volcano. A less intense geothermal event may result in a mud volcano. Phreatic eruptions include steam and rock fragments; the temperature of the fragments can range from cold to incandescent. If molten magma is included, it is classified as a phreatomagmatic eruption; these eruptions create broad, low-relief craters called maars. Phreatic explosions can be accompanied by carbon hydrogen sulfide gas emissions; the former can asphyxiate at sufficient concentration. A 1979 phreatic eruption on the island of Java killed 140 people, most of whom were overcome by poisonous gases. Phreatic eruptions are classed as volcanic eruptions because a phreatic eruption could bring juvenile material to the surface.
It is believed that the 1883 eruption of Krakatoa, which obliterated most of the volcanic island and created the loudest sound in recorded history, was a phreatic event. Kilauea, in Hawaii, has a long record of phreatic explosions. Additional examples are the 1963–65 eruption of Surtsey, the 1965 eruption of Taal Volcano, the 1982 Mount Tarumae eruption, the 2014 eruption of Mount Ontake and on May 7, 2013, at 8 a.m. Mayon Volcano produced a surprise phreatic eruption lasting 73 seconds. Types of volcanic eruptions – Basic mechanisms of eruption and variations Phreatic Hydrothermal explosion – Explosion of superheated ground water converting to steam Steam cannon
A dissected plateau is a plateau area, eroded so that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, extensive faulting, or magmatic activity that accompanies orogeny; the Allegheny Plateau, the Cumberland Plateau, the Ozark Plateau, the Catskill Mountains in the United States and the Blue Mountains in Australia and the Deccan Plateau in India are examples of dissected plateaus formed after regional uplift. These older uplifts have been eroded by creeks and rivers to develop steep relief not distinguishable from mountains. Many areas of the Allegheny Plateau and the Cumberland Plateau, which are at the western edge of the Appalachian Mountains of eastern North America, are called "mountains" but are dissected plateaus. One can stand on the top of one of these high "mountains" and note that all the other tops are nearly the same height, which represents the original elevation profile of the plain before uplift, thereafter the subsequent weather erosion.
A dissected plateau may be formed, or created on a comparatively small scale, by the levelling of terrain by planing and deposition beneath an ice sheet or an ice cap. Subsequently, during the same or a glacial, the margins of the glacial till plain are removed by glaciers, leaving the plateau into which erosion by water incises valleys; such a plateau may be level or sloping but may be distinguished by the till caps on its hills. Glacial till is still known in Britain by the older name of boulder clay. Dissected volcanic plateaus include the Pajarito Plateau in New Mexico, on the skirt of the enormous Valles Caldera. Isolated portions of this plateau are known as mesas, long, connected portions are known as potreros. Summit accordance Syrt, denudational uplands or dissected plateaus in Turkic toponymy of Russia and Central Asia