1.
Mass wasting
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Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place over timescales from seconds to years. Mass wasting occurs on both terrestrial and submarine slopes, and has observed on Earth, Mars, Venus. When the gravitational force acting on a slope exceeds its resisting force, the slope materials strength and cohesion and the amount of internal friction between material help maintain the slopes stability and are known collectively as the slopes shear strength. The steepest angle that a slope can maintain without losing its stability is known as its angle of repose. When a slope made of loose material possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it. Mass wasting may occur at a slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface. It may also occur at high speed, such as in rockslides or landslides, with disastrous consequences. Factors that change the potential of mass wasting include, change in angle, weakening of material by weathering, increased water content, changes in vegetation cover. Volcano flanks can become over-steep resulting in instability and mass wasting and this is now a recognised part of the growth of all active volcanoes. The failure of the flank of Mount St Helens in 1980 showed how rapidly volcanic flanks can deform. Water can increase or decrease the stability of a slope depending on the amount present, small amounts of water can strengthen soils because the surface tension of water increases soil cohesion. This allows the soil to resist erosion better than if it were dry, if too much water is present the water may act to increase the pore pressure, reducing friction, and accelerating the erosion process and resulting in different types of mass wasting. A good example of this is to think of a sand castle, water must be mixed with sand in order for the castle to keep its shape. If too much water is added the sand away, if not enough water is added the sand falls. Water also increases the mass of the soil, this is important because an increase in mass means that there will be an increase in velocity if mass wasting is triggered. Types of mass movement are distinguished based on how the soil, soil creep is a long term process. The combination of movements of soil or rock in different directions over time are directed by gravity gradually downslope. The steeper the slope, the faster the creep, the creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing
2.
Debris flow
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Debris flows descending steep channels commonly attain speeds that surpass 10 meters per second, although some large flows can reach speeds that are much greater. Debris flows with volumes ranging up to about 100,000 cubic meters occur frequently in mountainous regions worldwide, the largest prehistoric flows have had volumes exceeding 1 billion cubic meters. As a result of their high sediment concentrations and mobility, debris flows can be very destructive, notable debris-flow disasters of the twentieth century involved more than 20,000 fatalities in Armero, Colombia in 1985 and tens of thousands in Vargas State, Venezuela in 1999. Debris flows have volumetric sediment concentrations exceeding about 40 to 50%, by definition, “debris” includes sediment grains with diverse shapes and sizes, commonly ranging from microscopic clay particles to great boulders. Media reports often use the term mudflow to describe debris flows, on Earths land surface, mudflows are far less common than debris flows. However, underwater mudflows are prevalent on submarine continental margins, where they may spawn turbidity currents, Debris flows in forested regions can contain large quantities of woody debris such as logs and tree stumps. Sediment-rich water floods with solid concentrations ranging from about 10 to 40% behave somewhat differently from debris flows and are known as hyperconcentrated floods, normal stream flows contain even lower concentrations of sediment. Debris flows can be triggered by rainfall or snowmelt, by dam-break or glacial outburst floods. Debris flows can be more frequent following forest and brush fires, in Japan a large debris flow or landslide is called yamatsunami, literally mountain tsunami. Debris flows are accelerated downhill by gravity and tend to follow steep mountain channels that debouche onto alluvial fans or floodplains, the front, or head of a debris-flow surge often contains an abundance of coarse material such as boulders and logs that impart a great deal of friction. Trailing behind the high-friction flow head is a lower-friction, mostly liquefied flow body that contains a percentage of sand, silt. These fine sediments help retain high pore-fluid pressures that enhance debris-flow mobility, in some cases the flow body is followed by a more watery tail that transitions into a hyperconcentrated stream flow. Debris flows tend to move in a series of pulses, or discrete surges, wherein each pulse or surge has a head, body. Debris-flow deposits are readily recognizable in the field and they make up significant percentages of many alluvial fans and debris cones along steep mountain fronts. Lateral levees can confine the paths of ensuing debris flows, through dating of trees growing on such deposits, the approximate frequency of destructive debris flows can be estimated. This is important information for development in areas where debris flows are common. Ancient debris-flow deposits that are exposed only in outcrops are more difficult to recognize and this poor sorting of sediment grains distinguishes debris-flow deposits from most water-laid sediments. Other geological flows that can be described as debris flows are typically given more specific names, the word lahar is of Indonesian origin, but is now routinely used by geologists worldwide to describe volcanogenic debris flows
3.
Lahar
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A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley, lahars are extremely destructive, they can flow tens of metres per second, be 140 metres deep, and destroy any structures in their path. Notable lahars include those at Mount Pinatubo and Nevado del Ruiz, the word lahar is the Javanese term for flowing lava. A lahar is a volcanic mudflow or debris flow, lahars have the consistency, viscosity and approximate density of wet concrete, fluid when moving, solid at rest. Lahars can be huge.3 cubic kilometres, a lahar of sufficient size and intensity can erase virtually any structure in its path, and is capable of carving its own pathway, making the prediction of its course difficult. Conversely, a lahar quickly loses force when it leaves the channel of its flow, even frail huts may remain standing, a lahars viscosity decreases with time, and can be further thinned by rain, but it nevertheless solidifies quickly when coming to a stop. Lahars vary in size and speed, small lahars less than a few metres wide and several centimetres deep may flow a few metres per second. Large lahars hundreds of metres wide and tens of metres deep can flow tens of metres per second. With the potential to flow at speeds up to 100 kilometres per hour, and flow distances of more than 300 kilometres, a lahar can cause catastrophic destruction in its path. Lahars from the 1985 Nevado del Ruiz eruption in Colombia caused the Armero tragedy, which killed an estimated 23,000 people, a lahar caused New Zealands Tangiwai disaster, where 151 people died after a Christmas Eve express train fell into the Whangaehu River in 1953. Lahars have been responsible for 17% of volcano-related deaths between 1783 and 1997, a lahar can cause fatalities years after its precipitating eruption. For example, the Cabalantian tragedy occurred four years subsequent to the 1991 eruption of Mount Pinatubo, the word lahar is of Indonesian origin. Lahars have several causes, Snow and glaciers can be melted by lava or pyroclastic flows during an eruption. Lava flows out of vents and can mix with wet soil and mud on the slope of the volcano making a very viscous. A flood caused by a glacier, lake breakout, or heavy rainfall can release a lahar, also called glacier run or jökulhlaup Water from a crater lake, heavy rainfall on unconsolidated pyroclastic deposits. Snow and glaciers can melt during periods of mild weather Earthquakes underneath or close to the volcano can shake material loose and cause it to collapse triggering a lahar avalanche. Rainfall can cause the still-hanging slabs of solidified mud to come rushing down the slopes at a speed of more than 30 kilometres per hour, causing devastating results. Several towns in the Puyallup River valley in Washington state, including Orting, are built on top of lahar deposits that are only about 500 years old
4.
Pyroclastic rock
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Pyroclastic rocks or pyroclastics are clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, pyroclastic rocks may be a range of clast sizes, from the largest agglomerates, to very fine ashes and tuffs. Pyroclasts of different sizes are classified as bombs, lapilli. Ash is considered to be pyroclastic because it is a fine dust made up of volcanic rock, one of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event. Three modes of transport can be distinguished, pyroclastic flow, pyroclastic surge, during Plinian eruptions, pumice and ash are formed when silicic magma is fragmented in the volcanic conduit, because of decompression and the growth of bubbles. Pyroclasts are then entrained in a buoyant eruption plume which can rise several kilometers into the air, particles falling from the eruption clouds form layers on the ground. Pyroclastic density currents, which are referred to as flows or surges depending on particle concentration, the deposits of pumice-rich pyroclastic flows can be called ignimbrites. A pyroclastic eruption entails spitting or fountaining lava, where the lava will be thrown into the air along with ash, pyroclastic materials, hawaiian eruptions such as those at Kīlauea can eject clots of magma suspended into gas, this is called a fire fountain. The magma clots, if hot enough may coalesce upon landing to form a lava flow, pyroclastic deposits consist of pyroclasts which are not cemented together. Pyroclastic rocks are pyroclastic deposits which have been lithified
5.
Tibes
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Tibes is one of the 31 barrios in the municipality of Ponce, Puerto Rico. Together with Magueyes, Portugues, Montes Llanos, Maragüez, Machuelo Arriba, Sabanetas, Tibes attracted attention recently when, in 1975, what was to become the discovery of the oldest cemetery in the West Indies came about as a result of rains. The name of this barrio is of native Indian origin, Tibes is a mountainous rural barrio located in the central section of the municipality, north of the city of Ponce. Tibes is located on the foothills of the Cordillera Central, Tibes has 7.01 square miles of land area and no water area. In 2000, the population of Tibes was 866 persons, Tibes is the second least populated barrio in Ponce, after San Patricio. Major roads serving Barrio Tibes are PR-10 and PR-503, the highest point in Barrio Tibes is Cerro del Diablo which stands at 2,234 feet. Another notable land feature is Cerro La Mesa which stands at 1,742 feet, the Portugues Dam currently under construction and scheduled for completion in 2013, is also located in Barrio Tibes
6.
Puerto Rico
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Puerto Rico, officially the Commonwealth of Puerto Rico and briefly called Porto Rico, is an unincorporated territory of the United States located in the northeast Caribbean Sea. It is an archipelago that includes the island of Puerto Rico and a number of smaller ones such as Mona, Culebra. The capital and most populous city is San Juan and its official languages are Spanish and English, though Spanish predominates. The islands population is approximately 3.4 million, Puerto Ricos rich history, tropical climate, diverse natural scenery, renowned traditional cuisine, and attractive tax incentives make it a popular destination for travelers from around the world. Four centuries of Spanish colonial government transformed the ethnic, cultural and physical landscapes primarily with waves of African captives, and Canarian. In the Spanish imperial imagination, Puerto Rico played a secondary, in 1898, following the Spanish–American War, the United States appropriated Puerto Rico together with most former Spanish colonies under the terms of the Treaty of Paris. Puerto Ricans are natural-born citizens of the United States, however, Puerto Rico does not have a vote in the United States Congress, which governs the territory with full jurisdiction under the Puerto Rico Federal Relations Act of 1950. As a U. S. territory, American citizens residing on the island are disenfranchised at the level and may not vote for president. However, Congress approved a constitution, allowing U. S. citizens on the territory to elect a governor. A fifth referendum will be held in June 2017, with only Statehood, in early 2017, the Puerto Rican government-debt crisis posed serious problems for the government. The outstanding bond debt that had climbed to $70 billion or $12,000 per capita at a time with 12. 4% unemployment, the debt had been increasing during a decade long recession. Puerto Ricans often call the island Borinquen – a derivation of Borikén, its indigenous Taíno name, the terms boricua and borincano derive from Borikén and Borinquen respectively, and are commonly used to identify someone of Puerto Rican heritage. The island is also known in Spanish as la isla del encanto. Columbus named the island San Juan Bautista, in honor of Saint John the Baptist, eventually traders and other maritime visitors came to refer to the entire island as Puerto Rico, while San Juan became the name used for the main trading/shipping port and the capital city. The islands name was changed to Porto Rico by the United States after the Treaty of Paris of 1898, the anglicized name was used by the US government and private enterprises. The name was changed back to Puerto Rico by a joint resolution in Congress introduced by Félix Córdova Dávila in 1931, the ancient history of the archipelago known today as Puerto Rico is not well known. The scarce archaeological findings and early Spanish scholarly accounts from the colonial era constitute the basis of knowledge about them. The first comprehensive book on the history of Puerto Rico was written by Fray Íñigo Abbad y Lasierra in 1786, the first settlers were the Ortoiroid people, an Archaic Period culture of Amerindian hunters and fishermen who migrated from the South American mainland
7.
Snow
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Snowstorms organize and develop by feeding on sources of atmospheric moisture and cold air. Snowflakes nucleate around particles in the atmosphere by attracting supercooled water droplets, snowflakes take on a variety of shapes, basic among these are platelets, needles, columns and rime. As snow accumulates into a snowpack, it may blow into drifts, over time, accumulated snow metamorphoses, by sintering, sublimation and freeze-thaw. Where the climate is cold enough for year-to-year accumulation, a glacier may form, otherwise, snow typically melts seasonally, causing runoff into streams and rivers and recharging groundwater. Major snow-prone areas include the regions, the upper half of the Northern Hemisphere and mountainous regions worldwide with sufficient moisture. In the Southern Hemisphere, snow is confined primarily to mountainous areas, Snow affects ecosystems, as well, by providing an insulating layer during winter under which plants and animals are able to survive the cold. Snow develops in clouds that themselves are part of a weather system. The physics of snow crystal development in clouds results from a set of variables that include moisture content. The resulting shapes of the falling and fallen crystals can be classified into a number of shapes and combinations. Occasionally, some plate-like, dendritic and stellar-shaped snowflakes can form under clear sky with a cold temperature inversion present. Two additional and locally productive sources of snow are lake-effect storms and elevation effects, miid-latitude cyclones are low pressure areas which are capable of producing anything from cloudiness and mild snow storms to heavy blizzards. During a hemispheres fall, winter, and spring, the atmosphere over continents can be cold enough through the depth of the troposphere to cause snowfall, in the Northern Hemisphere, the northern side of the low pressure area produces the most snow. For the southern mid-latitudes, the side of a cyclone that produces the most snow is the southern side, a cold front, the leading edge of a cooler mass of air, can produce frontal snowsqualls—an intense frontal convective line, when temperature is near freezing at the surface. The strong convection that develops has enough moisture to produce whiteout conditions at places which line passes over as the wind causes intense blowing snow. This type of snowsquall generally lasts less than 30 minutes at any point along its path, in cases where there is a large amount of vertical growth and mixing the squall may develop embedded cumulonimbus clouds resulting in lightning and thunder which is dubbed thundersnow. A warm front can produce snow for a period, as warm, moist air overrides below-freezing air, often, snow transitions to rain in the warm sector behind the front. The same effect occurs over bodies of salt water, when it is termed ocean-effect or bay-effect snow. The effect is enhanced when the air mass is uplifted by the orographic influence of higher elevations on the downwind shores
