Tuesday, 28 March 2017

geog

  • When two air masses meet, the air within them does not easily mix. That is to say that the air in one air mass will not easily mix with the air from another air mass. Instead, the air stays within its own air mass. Because of this phenomena, a border forms between two clashing air masses as they rub together.  this border is called a front  


  • Fronts that bring warm air are referred to as warm fronts. As this warm air approaches, it is lifted upward above the cooler air. As the air in the warm air mass rises it expands, causing it to cool down. As it cools, water vapor can condense, creating precipitation.
  • This precipitation is generally light and forms gradually. Clouds first form in the sky as the warm air is lifted upward, proceeded by thicker clouds, and ultimately some form of precipitation.

  • A front bringing in a cold air mass is referred to as a cold front. Because cold fronts move along the ground where they encounter friction, they move slower at ground level than they do further up in the atmosphere. For this reason, cold fronts tend to be more sloped than warm fronts. Typically cold fronts move faster than their warmer counterparts. The combination of higher speed and slope push warm air masses upward very quickly. This quick upward air movement causes the warm air being displaced to cool quickly, becoming turbulent. This turbulence often can be the cause of extremely violent weather.
  • Because cold fronts move quickly, the weather associated with them typically also moves quickly and passes over a particular location in a short period of time. The turbulent weather generally stays right in line with the front.


https://www.youtube.com/watch?v=huKYKykjcm0




  jet streams

Jet streams are currents of air high above the Earth. They move eastward at altitudes of about 8 to 15 kilometers (5 to 9 miles). They form where large temperature differences exist in the atmosphere. found along tropopause

Jet streams are super high-speed winds. Each hemisphere’s westerly has two main jet streams. Closer to the poles we find the polar jet stream. At a slightly lower latitude we find the subtropical jet stream.


Into Thin Air
The freezing, powerful winds that whip the top of Mt. Everest, the world's tallest mountain, are actually jet streams. Jet streams can be so cold, and so strong, that climbers cannot leave the shelter of their tents.
Pilots Go With the Flow
Jet streams are so fast and powerful that airplanes have difficulty flying against them. Pilots either fly with the jet stream or above it; they do not attempt to fly against it.

Jet streams are some of the strongest winds in the atmosphere. Their speeds usually range from 129 to 225 kilometers per hour (80 to 140 miles per hour), but they can reach more than 443 kilometers per hour (275 miles per hour). They are faster in winter when the temperature differences between tropical, temperate, and polar air currents are greater.
the westerlies generally blow between 30 ° and 60 ° latitude in both the Northern and Southern hemispheres. The higher one travels into the atmosphere, the more noticeable these westerly winds are.
At the core of the westerly winds lies what scientists call a jet stream. Jet streams are super high-speed winds. Each hemisphere’s westerly has two main jet streams. Closer to the poles we find the polar jet stream. At a slightly lower latitude we find the subtropical jet stream.

ATMOSPHERE 


  • Weather occurs in the troposphere. On average, this layer extends to an altitude of about 10 kilometers (6 miles), ranging from less than 6 kilometers (4 miles) at the poles to about 20 kilometers (12 miles) at the Equator. The top of the troposphere is higher in summer than in winter. Because the troposphere contains most of the atmospheres water vapor, clouds usually form in this layer. Temperature decreases rapidly in the troposphere as altitude increases. 

  • The suns rays pass easily through the troposphere. It is not heated directly by the sun, but by the Earth. The troposphere absorbs heat that is radiated from the Earth into the atmosphere. Various gases in the troposphere, such as carbon dioxide, water vapor, and methane, trap this radiated heat and dont let it escape into space. The warming of the atmosphere through this heat absorption is known as the greenhouse effect which is necessary for life. 

  • The boundary between the turbulent troposphere and the calm, cold stratosphere is called the tropopause. Jet streams travel in the tropopause.

  • Free oxygen may have been added to the atmosphere by primitive organisms, probably bacteria, during photosynthesis. Photosynthesis is the process a plant or other autotroph uses to make food and oxygen from carbon dioxide and water. Later, more complex forms of plant life added more oxygen to the atmosphere. The oxygen in today’s atmosphere probably took millions of years to accumulate. Many were added due to volcanic activity

  • Almost all weather develops in the troposphere because it contains almost all of the atmosphere’s water vapor. Clouds, from low-lying fog to thunderheads to high-altitude cirrus, form in the troposphere. Air masses, areas of high-pressure and low-pressure systems, are moved by winds in the troposphere. These weather systems lead to daily weather changes as well as seasonal weather patterns and climatesystems, such as El Nino.
  • As air in the troposphere thins, temperature decreases. This is why mountaintops are usually much colder than the valleys beneath. Scientists used to think temperature continued to drop as altitude increased beyond the troposphere. But data collected with weather balloons and rockets have showed this is not the case. In the lower stratosphere, temperature stays almost constant. As altitude increases in the stratosphere, temperature actually increases.
  • The stratosphere is crucial to life on Earth because it contains small amounts of ozone, a form of oxygen that prevents harmful UV rays from reaching Earth. The region within the stratosphere where this thin shell of ozone is found is called the ozone layer. The stratosphere’s ozone layer is uneven, and thinner near the poles. The amount of ozone in the Earth’s atmosphere is declining steadily. Scientists have linked use of chemicals such as chlorofluorocarbons (CFCs) to ozone depletion. 
  • Strong horizontal winds blow in the stratosphere, but there is little turbulence. This is ideal for planes that can fly in this part of the atmosphere


Low level ozone (or tropospheric ozone) is an atmospheric pollutant. It is not emitted directly by car engines or by industrial operations, but formed by the reaction of sunlight on air containing hydrocarbons and nitrogen oxides that react to form ozone directly at the source of the pollution or many kilometers down wind.

  • The mesosphere extends from the stratopause (the upper boundary of the stratosphere) to about 85 kilometers (53 miles) above the surface of the Earth. Here, temperatures again begin to fall.

    The mesosphere has the coldest temperatures in the atmosphere, dipping as low as -120 degrees Celsius (-184 degrees Fahrenheit, or 153 kelvin). The mesosphere also has the atmosphere’s highest clouds. In clear weather, you can sometimes see them as silvery wisps immediately after sunset. They are called noctilucent clouds, or night-shining clouds. The mesosphere is so cold that noctilucent clouds are actually frozen water vapor—ice clouds.

    Shooting stars—the fiery burnout of meteors, dust, and rocks from outer space—are visible in the mesosphere. Most shooting stars are the size of a grain of sand and burn up before entering the stratosphere or troposphere. However, some meteors are the size of pebbles or even boulders. Their outer layers burn as they race through the mesosphere, but they are massive enough to fall through the lower atmosphere and crash to Earth as meteorites
  • The ionosphere extends from the top half of the mesosphere all the way to the exosphere. This atmospheric layer conducts electricity. he ionosphere—a layer of free electrons and ions—reflects radio waves. Guglielmo Marconi, the “Father of Wireless,” helped prove this in 1901 when he sent a radio signal from Cornwall, England, to St. John’s, Newfoundland, Canada. Marconi’s experiment demonstrated that radio signals did not travel in a straight line, but bounced off an atmospheric layer—the ionosphere.
  • The ionosphere also reflects particles from solar wind, the stream of highly charged particles ejected by the sun. These electrical displays create auroras (light displays) called the Northern and Southern Lights.
  • The thermosphere extends from the mesopause (the upper boundary of the mesosphere) to 690 kilometers (429 miles) above the surface of the Earth. Here, thinly scattered molecules of gas absorb x-rays and ultraviolet radiation. This absorption process propels the molecules in the thermosphere to great speeds and high temperatures. Temperatures in the thermosphere can rise to 1,500 degrees Celsius (2,732 degrees Fahrenheit, or 1,773 kelvin). 

    Though the temperature is very high, there is not much heat. How is that possible? Heat is created when molecules get excited and transfer energy from one molecule to another. Heat happens in an area of high pressure (think of water boiling in a pot). Since there is very little pressure in the thermosphere, there is little heat transfer.

    The Hubble Space Telescope and the International Space Station (ISS) orbit the Earth in the thermosphere. Even though the thermosphere is the second-highest layer of Earth’s atmosphere, satellites that operate here are in “low-Earth orbit.” REST SATELLITES ARE BEYOND THE ATMOSPHERE.

  • Magnetosphere
    Earth’s magnetosphere is not considered part of the atmosphere. The magnetosphere, formed by the Earth’s magnetic fields, protects the atmosphere by preventing it from being “blown away” by powerful solar wind


UPWELLING

In order to understand the development of El Nio, its important to be familiar with non-El Nio conditions in the Pacific Ocean. Normally, strong trade winds blow west across the tropical Pacific, the region of the Pacific Ocean located between the Tropic of Cancer and the Tropic of Capricorn. These winds push warm surface water towards the west Pacific. The western Pacific Ocean borders Asia and Australia. Due to the warm trade winds, the sea surface is normally about .5 meter (1.5 feet) higher and 45F warmer in Indonesia than Ecuador. The westward movement of warmer waters causes cooler waters to rise up towards the surface on the coasts of Ecuador, Peru, and Chile. This process is known as upwelling. This cold upwelling elevates the thermocline, the level of ocean depth that separates the warmer surface water from the colder water below. 

Upwelling elevates this cold water, rich in nutrients, to the  photic zone, the upper layer of the ocean. Nutrients in the cold water include nitrates and phosphates. Tiny organisms called plankton use them for photosynthesis, the process that creates food from sunlight. Other organisms, such as clams, eat the plankton, while predators like fish or marine mammals prey on the clams.

Upwelling provides food for a wide variety of marine life, including most major fisheries. Fishing is one of the primary industries of Peru, Ecuador, and Chile. Some of the fisheries include anchovy, sardine, mackerel, shrimp, tuna, and hake. 

The upwelling process also influences global climate. It increases rainfall over the western Pacifics warmer waters, such as the islands of Indonesia and New Guinea. The eastern Pacific, along the coast of South America, remains relatively dry.






El Nino, an abnormal warming of surface ocean waters in the eastern tropical Pacific, is one part of what's called the Southern Oscillation. The Southern Oscillation is the see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific; when the surface pressure is high in the eastern tropical Pacific it is low in the western tropical Pacific, and vice-versa. Because the ocean warming and pressure reversals are, for the most part, simultaneous, scientists call this phenomenon the El Nino/Southern Oscillation or ENSO for short. South American fisherman have given this phenomenon the name El Nino, which is Spanish for "The Christ Child," because it comes about the time of the celebration of the birth of the Christ Child-Christmas.
To really understand the effects of an El l9Nino event, compare the normal conditions of the Pacific region and then see what happens during El Nino below.

Normal Conditions (Non El Nino)
El Nino Conditions
Scientists do not really understand how El Nino forms. It is believed that El Nino may have contributed to the 1993 Mississippi and 1995 California floods, drought conditions in South America, Africa and Australia. It is also believed that El Nino contributed to the lack of serious storms such as hurricanes in the North Atlantic which spared states like Florida from serious storm related damage.
Unfortunately not all El Nino's are the same nor does the atmosphere always react in the same way from one El Nino to another. This is why NASA's Earth scientists continue to take part in international efforts to understand El Nino events. Hopefully one day scientists will be able to provide sufficient warning so that we can be better prepared to deal with the damages and changes that El Nino causes in the weather.



  • Orogenic Infants
  • Most fold mountains are very young. In fact, most fold mountains are still growing.
  • Fold mountains are mountain ranges that are formed when two of the tectonic plates that make up the Earth's crustpush together at their border. The extreme pressure forces the edges of the plates upwards into a series of folds. 

  • Fold mountains are created through a process called "orogeny." An orogenic event takes millions of years to create a mountain range because tectonic plates move only centimeters every year. 

  • The Earth has two different types of crust: continental crustand oceanic crust. Orogenic events can occur on both types of crust. The Himalaya Mountains are still growing as the Indian continental plate folds over the Eurasian continental plate. Orogeny can also involve oceanic plates. Beneath themicrocontinent of Zealandia, the Pacific plate is being folded over the Australian plate. The result is New Zealand's Southern Alps. 

  • Most people think of the rugged, soaring heights of the Himalayas, Andes, and Alps when they think of fold mountains. But some of the Earth's smaller mountain ranges were once soaring peaks, too. The Appalachian Mountainsstarted forming 480 million years ago when the North American and Eurasian continental plates collided. The Appalachians were once taller than the Himalayas. The range stretches from Newfoundland in southeastern Canada down through the eastern United States to central Alabama. However, erosion has taken its toll on the Appalachians. Today, some of its higher peaks are less than a third of the height of Everest.

  • Fold mountains are the most common type of mountain on Earth. Other types of mountains are volcanic mountains,erosional mountains, and fault-block mountains. Volcanoes create volcanic mountains. Erosional mountains are created as wind and water wear away soft portions of land and leave rocky hills. Fault-block mountains are created where parts of continental crust are displaced.
 A rift valley forms where the Earth’s crust, or outermost layer, is spreading or splitting apart. This kind of valley is often narrow, with steep sides and a flat floor.

Rift valleys are also called grabens, which means “ditch” in German. While there is no official distinction between a graben and a rift valley, a graben usually describes a small rift valley.

Rift valleys differ from river valleys and glacial valleys because they are created by tectonic activity and not by the process of erosion.

Rift valleys are created by plate tectonics. Tectonic plates are the huge rocky slabs made up of the Earth's crust and upper mantle. They are constantly in motion—shifting against each other, falling beneath one another (a process called subduction), crashing against one another. Tectonic plates also tear apart from each other. Where plates move apart, the Earth’s crust separates, or rifts. Rift valleys can lead to the creation of entirely new continents, or deepen valleys in existing ones.

Many rift valleys have been found underwater, along the large ridges that run throughout the ocean. These mid-ocean ridges are formed as tectonic plates move away from one another. As the plates separate, molten rock from the Earth’s interior may well up and harden as it contacts the sea, forming new oceanic crust at the bottom of the rift valley. 

This occurs along the northern crest of the Mid-Atlantic Ridge, where the North American plate and the Eurasian plate are splitting apart. The Mid-Atlantic Ridge rifts at an average of 2.5 centimeters (1 inch) per year. Over millions of years, the Mid-Atlantic Ridge has formed rift valleys as wide as 15 kilometers (9 miles).
In the Pacific Ocean, the East Pacific Rise has created rift valleys where the Pacific plate is separating from the North American plate, Riviera plate, Cocos plate, Nazca plate, and Antarctic plate. (The Pacific plate is the largest on Earth.) Like many underwater rift valleys, the East Pacific Rise is dotted with hydrothermal vents. The geologic activity beneath the underwater rift valley creates these vents, which spew super-heated water and sometimes-toxic vent fluids into the ocean.

There are only two rift valleys on Earth within continental crust, the Baikal Rift Valley and the East African Rift. Tectonic activity splits continental crust much in the same way it does along mid-ocean ridges. As the sides of a rift valley move farther apart, the floor sinks lower.

The deepest continental rift valley on Earth is the Baikal Rift Valley in the Siberian region of northeastern Russia. Lake Baikal, the deepest and oldest freshwater lake in the world, lies in the Baikal Rift Valley. Here, the Amur plate is slowly tearing itself away from the Eurasian plate, and has been doing so for about 25 million years. The deepest part of Lake Baikal is 1,187 meters (3,893 feet), and getting deeper every year. Beneath this is a layer of soft sediment reaching several kilometers. The actual bottom of the rift extends about 10 kilometers (6.2 miles) deep.
A hot spot is a very hot region deep within the Earth. It is usually responsible for volcanic activity. Volcanic activity happens whenever red-hot material from the Earths thickest layer, the mantle, rises up and leaks through to the Earths surface, the crust. The red-hot material, called magma, sometimes erupts in the form of lava. Lava is the red-orange substance that spills out of a volcano onto the surface.

Hot spots dont always create volcanoes that spew rivers of lava. Sometimes, the magma heats up groundwater under the Earths surface, which causes water and steam to erupt like a volcano. These eruptions are called geysers. A famous geyser is Old Faithful in Yellowstone National Park in the U.S. state of Wyoming. When it erupts, the water is 95.6 degrees Celsius (204 degrees Fahrenheit) and can reach more than 55 meters (180 feet) high. 

There are 40 to 50 hot spots around the world, including near the Galapagos Islands and Iceland. Hot spots can create entire chains of islands, like the U.S. state of Hawaii. Hawaii is on the Pacific plate, an enormous section of the Earth in the Pacific Ocean that is constantly moving, but very, very slowly. Although the plate is always moving, the hot spot underneath it stays still. The hot spot spewed magma that eventually became a chain of islands that rose over the surface of the water. These islands were created one right after the other as the plate moved, almost like an island factory.

Scientists use hot spots to track the movement of the Earths plates. The Pacific plate is just one of many tectonic plates that make up the Earth: the North American plate, the Caribbean plate, the South American plate, the Scotia plate (beneath South America), the African plate, the Eurasian plate, the Arabian plate, the Indian plate, the Australian plate, the Filipino plate, the Pacific plate, the Cocos plate (west of South America), the Juan deFuca plate (west of the U.S. state of Washington), and the Antarctic plate.
Block Mountain is an uplifted section of crust with one or more faulted boundaries. They are also known as horsts.
Block Mountains are defined as an area of high relief which is bounded on most sides by faults and which has been either uplifted by earth-movement, or left elevated by the sinking of surrounding areas. Black Forest and Vosges Mountains are the fine examples. The Nilgiris in South India are also Block Mountains.
Block Mountains are generally formed due to tensional forces. But sometimes compression also produces such mountains. They are generally straight in form, and are characterized by the presence of fault scarp.
In their extent, they are very limited. Faulting is the main cause for the formation of Block Mountains that is why they are also known as fault-block Mountains. Some block mountains are associated with rift valleys. Several such mountains are found is East Africa.

Dome Mountains:

Dome Mountains are also called Upwarped Mountains. These mountains are formed when large amounts of molten rock or magma push the earth’s crust from underneath. The magma in this case never reaches the top surface of the earth. So even before it can erupt the source of magma goes away leaving the pushed up Rock as such. This rock then cools and forms a mountain. With time the mountain forms a dome shape, where it gets warped due to erosion. The Black hills of South Dakota in the USA and the Adirondack Mountains in New York are examples for Dome Mountains.9
It's winter in the Northern Hemisphere and we're at our closest point to the Sun. Closest? Yes, you read that right. Closest. For northerners, the winter solstice has just passed. But the truth is, on January 3, 2007, Earth reaches perihelion, its closest point to the Sun in its yearly orbit around our star.
At first glance, it makes no sense. If Earth is closest to the Sun in January, shouldn't it be summer? Maybe, if you live in the Southern Hemisphere. So what does this mean?

In fact, Earth's elliptical orbit has nothing to do with seasons. The reason for seasons was explained in last month's column, and it has to do with the tilt of Earth's axis. But our non-circular orbit does have an observable effect. It produces, in concert with our tilted axis, the analemma.
comets asteroids and meteor 
Sunspot populations quickly rise and more slowly fall on an irregular cycle of 11 years, although significant variations in the number of sunspots attending the 11-year period are known over longer spans of time.  Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature. They usually appear as pairs, with each sunspot having the opposite magnetic pole than the other.
Fjords are found in locations where current or past glaciation extended below current sea level. A fjord is formed when a glacier retreats, after carving its typical U-shaped valley, and the sea fills the resulting valley floor. This forms a narrow, steep sided inlet (sometimes deeper than 1300 metres) connected to the sea. The terminal moraine pushed down the valley by the glacier is left underwater at the fjord's entrance, causing the water at the neck of the fjord to be shallower than the main body of the fjord behind it.
 A ria is an example of a submergent coastal landform. Rias are caused by a rise in sea-levels, a fall in coastal levels (due to the action of plate tectonics) or a combination of the two. The feature occurs when an area of land previously above sea level becomes permanently flooded. The old hilltops stick up above the surface of the water and the old rivers' valleys become deep bays

  • intraplate or hotspot
  • SUBDUCTION ZONE VOLCANISM
  • SPREADING CENTER VOLCANISM

  • A cirque (from a French word for "arena"), can be a corrie (from Scottish Gaelic coire meaning a pot or cauldron) or cwm (Welsh for "valley") which have an amphitheatre-like valley head, formed at the head of a valley glacier by erosion.



  •  
    A U-shaped valley or glacial trough is formed by the process of glaciation. It has a characteristic U shape, with steep, straight sides and a flat bottom. Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice.
    Examples of U-valleys are found in mountainous region like the Alps, Himalaya, Rocky mountains, Scottish Highlands, Scandinavia and Canada. A classic glacial trough in Glacier National Park in Montana, USA in which the St. Mary River runs.

    As a glacier moves downhill through a valley, the shape of the valley is transformed. A V-shaped valley is transformed into a U-shaped valley through the glacial erosion processes of plucking and abrasion. This results in large rocky material (glacial till) being carried in the glacier. A material called boulder clay is deposited on the floor of the valley. As the ice melts and retreats, the valley is left with very steep sides and a wide, flat floor. A riveror stream may flow through the valley due to melt-water from the glacier.

    when the u shaped valleys are filled by ocean water they come to be called as fjords




The main processes of fluvial erosion occur throughout the course of the river. These are outlined below.
The river itself, however, will try to erode in different directions, depending on how far down the course you are. Very basically, rivers are trying to erode down to their base level. In most cases this is sea level, but it can also be the level of a lake that the river might be flowing into.
At the top of the river, near its source, the river has a huge amount of material to get through to reach base level, so it primarily cuts downwards, creating a steep-sided v-shaped valley.
Abrasion - Glaciers carry a large amount of material with them. Some of these sharp boulders are embedded in the bottom of the glacier and act as erosive agents for the glacier. These rocks mean that the glacier acts like sandpaper, scouring along the valley floor. The effects of abrasion are that the rock surface of the valley will be polished and may have deep grooves cut in them. These grooves are called striations.
Plucking - This is the main erosive process of a glacier. As the glacier moves along the valley the ice melts slightly around large boulders, before re-freezing around them. As it then moves on the boulders are literally ripped out of the ground and will often become agents of abrasion.
Arêtes - Where two corries formed back to back they both eroded backwards until they created a narrow knife-edge ridge between them This is called an Arête. Also see pyramid peaks.
Corries - Also known as cirques, they are the starting point of a glacier.
At the beginning of the last age snow began to accumulate in hollows on hillsides, slowly accumulating enough to turn into ice. This ice slowly gouged out a steep back wall through the processes of freeze-thaw and plucking. Large crevasses on the top of the ice, called bergschrund's allowed water to flow into the ice, where it froze to create more ice.
The bottom of the corrie was eroded by abrasion as the ice moved forward in a rotational way. Where the rate of erosion was less, at the front of the ice, a rock lip was left. As more and more ice accumulated it flowed over the lip and into the valley below, creating a glacier.
Once the ice melted the corrie was often filled by melt water to form a lake. The rock lip and moraine acted as a natural dam. These lakes are known in Britain as Tarns.



coral reefs often are referred to as the "rainforests of the oceans."

Corals themselves are tiny animals which belong to the group cnidaria (the "c" is silent). Other cnidarians include hydras, jellyfish, and sea anemones. Corals are sessileanimals, meaning they are not mobile but stay fixed in one place. They feed by reaching out with tentacles to catch prey such as small fish and planktonic animals. Corals live in colonies consisting of many individuals, each of which is called polyp. They secrete a hard calcium carbonate skeleton, which serves as a uniform base or substrate for the colony. The skeleton also provides protection, as the polyps can contract into the structure if predators approach. It is these hard skeletal structures that build up coral reefs over time. The calcium carbonate is secreted at the base of the polyps, so the living coral colony occurs at the surface of the skeletal structure, completely covering it. Calcium carbonate is continuously deposited by the living colony, adding to the size of the structure. Growth of these structures varies greatly, depending on the species of coral and environmental conditions-- ranging from 0.3 to 10 centimeters per year. Different species of coral build structures of various sizes and shapes ("brain corals," "fan corals," etc.), creating amazing diversity and complexity in the coral reef ecosystem. Various coral species tend to be segregated into characteristic zones on a reef, separated out by competition with other species and by environmental conditions.

Virtually all reef-dwelling corals have a symbiotic (mutually beneficial) relationship with algae called zooxanthellae. The plant-like algae live inside the coral polyps and perform photosynthesis, producing food which is shared with the coral. In exchange the coral provides the algae with protection and access to light, which is necessary for photosynthesis. The zooxanthellae also lend their color to their coral symbionts. Coral bleaching occurs when corals lose their zooxanthellae, exposing the white calcium carbonate skeletons of the coral colony. There are a number of stresses or environmental changes that may cause bleaching including disease, excess shade, increased levels of ultraviolet radiation, sedimentation, pollution, salinity changes, and increased temperatures.

Because the zooxanthellae depend on light for photosynthesis, reef building corals are found in shallow, clear water where light can penetrate down to the coral polyps. Reef building coral communities also require tropical or sub-tropical temperatures, and exist globally in a band 30 degrees north to 30 degrees south of the equator. Reefs are generally classified in three types. Fringing reefs, the most common type, project seaward directly from the shores of islands or continents. Barrier reefs are platforms separated from the adjacent land by a bay or lagoon. The longest barrier reefs occur off the coasts of Australia and Belize 
waves

Destructive waves

The effects of a high wave
The effects of a high wave
  • Destructive waves are created in storm conditions.
  • They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
  • They occur when wave energy is high and the wave has travelled over a long fetch.
  • They tend to erode the coast.
  • They have a stronger backwash than swash.
  • They have a short wave length and are high and steep.

Constructive waves

The effects of a low wave
The effects of a low wave
  • They are created in calm weather and are less powerful than destructive waves.
  • They break on the shore and deposit material, building up beaches.
  • They have a swash that is stronger than the backwash.
  • They have a long wavelength, and are low in height

the distance a wave has travelled is called a fetch
 Deposition is likely to occur when:
waves enter an area of shallow water.
waves enter a sheltered area.
there is longshore drift.
where there are constructive waves.
all of the above.


One of the most common features of a coastline is a cliff. Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions.
Soft rock, eg sand and clay, erodes easily to create gently sloping cliffs. Hard rock, eg chalk, is more resistant and erodes slowly to create steep cliffs.


The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland. The areas where the soft rock has eroded away, next to the headland, are called bays.

geology is the study of the types of rocks that make up the Earth's crust. Coastlines where the geology alternates between strata (or bands) of hard rock and soft rock are called discordant coastlines. A concordant coastline has the same type of rock along its length. Concordant coastlines tend to have fewer bays and headlands.
 

Rainforest water cycle

The roots of plants take up water from the ground and the rain is intercepted as it falls - much of it at the canopy level. As the rainforest heats up, the water evaporates into the atmosphere and forms clouds to make the next day's rain. This is convectional rainfall.

Rainforest nutrient cycle

The rainforest nutrient cycling is rapid. The hot, damp conditions on the forest floor allow for the rapid decomposition of dead plant material. This provides plentiful nutrients that are easily absorbed by plant roots. However, as these nutrients are in high demand from the rainforest's many fast-growing plants, they do not remain in the soil for long and stay close to the surface of the soil. If vegetation is removed, the soils quickly become infertile and vulnerable to erosion.
If the rainforest is cleared for agriculture it will not make very good farmland, as the soil will not be rich in nutrients.

Soils in deciduous woodland

The soil type is brown earth. This is a fertile soil. In the autumn the leaves fall from the trees. The leaves decompose and help to give the soil its nutrients. Earthworms in the soil help to mix the nutrients, and blend the layers within the soil.
Rich Soil and Humus
The tree roots are deep and so help to break up the rock below. This helps to give the soil more minerals. The trees take up the nutrients in the soil as they grow. However, more nutrients are put back in the soil when the autumn comes.

Buttress roots (stilt roots or prop roots) are large roots on all sides of a shallowly rooted tree. Typically, they are found in nutrient-poor rainforest soils and do not penetrate to deeper layers. Almost all types of mangroves have these type of roots. They prevent the tree from falling over (hence the name buttress) while also gathering more nutrients. Buttresses are tension elements, being larger on the side away from the stress of asymmetrical canopies.

 Saffir-Simpson Hurricane for cyclonic activity...
 
In geography, a cape is a headland or promontory of large size extending into a body of water, usually the sea.[1] A cape usually represents a marked change in trend of the coastline. Their proximity to the coastline makes them prone to natural forms of erosion, mainly tidal actions. This results in capes having a relatively short geologic lifespan. Capes can be formed by glaciers, volcanoes, and changes in sea level. Erosion plays a large role in each of these methods of formation.
An epiphyte is a plant that grows upon another plant (such as a tree) non-parasitically or sometimes upon some other object (such as a building or a telegraph wire), derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it. Epiphytes are usually found in the temperate zone (e.g., many mosses, liverworts, lichens and algae) or in the tropics (e.g., many ferns, cacti, orchids, and bromeliads)
The color of an object changes depending on the colors contained in the light source; for example, red paint, viewed under blue light, looks black. Isaac Newton demonstrated with a prism that the white light of the sun contains all colors of the visible spectrum, so all colors are possible in sunlight.
In school, most of us learned that a banana appears yellow because it reflects yellow light and absorbs all other wavelengths. This is not accurate. A banana scatters as much orange and red as it does yellow, and scatters all of the colors of the visible range to some degree or other [source: Bohren]. The real reason it looks yellow relates to how our eyes sense light. Before we get into that, however, let's look at what color the sky actually is.
Like bananas, atoms, molecules and particles in the atmosphere absorb and scatter light. If they didn't, or if the Earth had no atmosphere, we would perceive the sun as a very bright star among others in a sky of perpetual night. Not all wavelengths in the visible light spectrum scatter equally, however. Shorter, more energetic wavelengths, toward the violet end of the spectrum, scatter better than those toward the longer, less energetic, red end. This tendency is due in part to their higher energy, which allows them to ping-pong around more, and in part to the geometry of the particles that they interact with in the atmosphere.



Smog is a chemical cocktail of low-level ozone (molecules of three oxygen atoms bound together), particulates (such as dust, soot and smoke), and other pollutants, such as carbon monoxide, nitrogen dioxide, sulfur dioxide and lead [source: Rea]. When pollutants in the atmosphere are absorbed through your skin, your whole body can suffer the consequences [source: Goldsmith].

You hear a lot about the ozone layer these days, and for good reason. The ozone layer in the stratosphere, or upper atmosphere, protects you by blocking harmful ultraviolet radiation from the sun, but ozone in the troposphere, or ground level, is a major component in smog [source: EPA]. When the sun's rays hit the smog, it breaks down into free radicals. If they enter the body, the free radicals bounce all over the place within the cells and chip away the cells' walls. Several diseases, including cancer, Alzheimer's and Parkinson's, have been linked to free radical damage [source: LiveScience].



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