Solar Variation ( Global Warming )

Variations in solar output, possibly amplified by cloud feedbacks, may have contributed to recent warming. A difference between this mechanism and greenhouse warming is that an increase in solar activity should produce a warming of the stratosphere while greenhouse warming should produce a cooling of the stratosphere. Cooling in the lower stratosphere has been observed since at least 1960, which would not be expected if solar activity were the main contributor to recent warming. (Reduction of stratospheric ozone also has a cooling influence but substantial ozone depletion did not occur until the late 1970s.) Phenomena such as solar variation combined with volcanoes have probably had a warming effect from pre-industrial times to 1950, but a cooling effect since 1950.
A few recent papers have suggested that the Sun's contribution may have been underestimated. Two researchers at Duke University have estimated that the Sun may have contributed about 40–50% of the global surface temperature warming over the period 1900–2000, and about 25–35% between 1980 and 2000. Stott and coauthors suggest that climate models overestimate the relative effect of greenhouse gases compared to solar forcing; they also suggest that the cooling effects of volcanic dust and sulfate aerosols have been underestimated. Nevertheless, they conclude that even with an enhanced climate sensitivity to solar forcing, most of the warming during the latest decades is attributable to the increases in greenhouse gases.
In 2006, a team of scientists from the United States, Germany, and Switzerland found no net increase of solar brightness over the last thousand years. Solar cycles lead to a small increase of 0.07% in brightness over the last 30 years. This effect is far too minute to contribute significantly to global warming. A 2007 paper by Lockwood and Fröhlich further confirms the lack of a correlation between solar output and global warming for the time since 1985.

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Greenhouse gases in the atmosphere ( Global Warming )

The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. It is the process by which absorption and emission of infrared radiation by atmospheric gases warms a planet's atmosphere and surface.
The existence of the greenhouse effect as such is not disputed. Greenhouse gases create a natural greenhouse effect without which mean temperatures on Earth would be an estimated 30 °C (54 °F) lower and Earth would be uninhabitable. Rather, the debate centers on how the strength of the greenhouse effect is changed when human activity increases the atmospheric concentrations of some greenhouse gases.
On Earth, the major natural greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); carbon dioxide (CO2), which causes 9–26%; methane (CH4), which causes 4–9%; and ozone, which causes 3–7%. Some other naturally occurring gases contribute very small fractions of the greenhouse effect; one of these, nitrous oxide (N2O), is increasing in concentration owing to human activity such as agriculture. The atmospheric concentrations of CO2 and CH4 have increased by 31% and 149% respectively above pre-industrial levels since 1750. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that CO2 values this high were last attained 20 million years ago. Fossil fuel burning has produced about three-quarters of the increase in CO2 from human activity over the past 20 years. Most of the rest is due to land-use change, in particular deforestation.
The present atmospheric concentration of CO2 is about 383 parts per million (ppm) by volume. Future CO2 levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, sociological, technological, natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC Special Report on Emissions Scenarios gives a wide range of future CO2 scenarios, ranging from 541 to 970 ppm by the year 2100. Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.
Positive (reinforce) feedback effects such as the expected release of CH4 from the melting of permafrost peat bogs in Siberia (possibly up to 70,000 million tonnes) may lead to significant additional sources of greenhouse gas emissionsnot included in climate models cited by the IPCC.

Feedbacks

The effects of forcing agents on the climate are complicated by various feedback processes.
One of the most pronounced feedback effects relates to the evaporation of water. In the case of warming by the addition of long-lived greenhouse gases such as CO2, the initial warming will cause more water to be evaporated into the atmosphere. Since water vapor itself acts as a greenhouse gas, this causes still more warming; the warming causes more water vapor to be evaporated, and so forth until a new dynamic equilibrium concentration of water vapor is reached with a much larger greenhouse effect than that due to CO2 alone. (Although this feedback process involves an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer.) This feedback effect can only be reversed slowly as CO2 has a long average atmospheric lifetime.
Feedback effects due to clouds are an area of ongoing research. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect. Seen from above, the same clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the type and altitude of the cloud. These details are difficult to represent in climate models, in part because clouds are much smaller than the spacing between points on the computational grids of climate models (about 125 to 500 km for models used in the IPCC Fourth Assessment Report). Nevertheless, cloud feedback is second only to water vapor feedback and is positive in all the models that were used in the IPCC Fourth Assessment Report.
Another important feedback process is ice-albedo feedback. When global temperatures increase, ice near the poles melts at an increasing rate. As the ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice, and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.
Positive feedback due to release of CO2 and CH4 from thawing permafrost is an additional mechanism contributing to warming. Possible positive feedback due to CH4 release from melting seabed ices is a further mechanism to be considered.
The ocean's ability to sequester carbon is expected to decline as it warms, because the resulting low nutrient levels of the mesopelagic zone limits the growth of diatoms in favour of smaller phytoplankton that are poorer biological pumps of carbon.

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Causes ( Global Warming )

Earth's climate changes in response to external forcing, including variations in its orbit around the sun (orbital forcing), volcanic eruptions, and atmospheric greenhouse gas concentrations. The detailed causes of the recent warming remain an active field of research, but the scientific consensus identifies elevated levels of greenhouse gases due to human activity as the main influence. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. In contrast to the scientific consensus that recent warming is mainly attributable to elevated levels of greenhouse gases, other hypotheses have been suggested to explain the observed increase in mean global temperature. One such hypothesis proposes that warming may be the result of increased solar radiation associated with greater numbers of sunspots.
None of the effects of forcing are instantaneous. The thermal inertia of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.

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Global Warming !!!

Global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
Global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the twentieth century. The Intergovernmental Panel on Climate Change (IPCC) concludes, "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations," which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Natural phenomena such as solar variation combined with volcanoes have probably had a small warming effect from pre-industrial times to 1950, but a small cooling effect since 1950. These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. The American Association of Petroleum Geologists is the only scientific society that officially rejects these conclusions. A few individual scientists disagree with some of the main conclusions of the IPCC.
Climate models referenced by the IPCC project that global surface temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100.[1] The range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a millennium even if greenhouse gas levels are stabilized.[1] This reflects the large heat capacity of the oceans.
An increase in global temperatures is expected to cause other changes, including sea level rise, increased intensity of extreme weather events, and changes in the amount and pattern of precipitation. Other effects include changes in agricultural yields, glacier retreat, species extinctions and increases in the ranges of disease vectors.
Remaining scientific uncertainties include the exact degree of climate change expected in the future, and how changes will vary from region to region around the globe. There is ongoing political and public debate on a world scale regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences. Most national governments have signed and ratified the Kyoto Protocol, aimed at reducing greenhouse gas emissions.

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Bionic Hand Unveiled in Britain

July 19, 2007—A new hope has arrived for amputees that would make Luke Skywalker feel right at home: a highly advanced bionic hand controlled by a patient's mind and muscles.
The newly released iLimb is the first prosthetic hand to have fully functional motorized digits that move and bend independently, its makers say. Electrodes taped to the skin transmit signals to tiny motors that power the fingers.
Previous artificial hands had only a thumb and forefinger that worked in a clawlike grasping action. But the new device allows amputees to carry out more delicate movements such as peeling a banana, typing on a computer, or eating with a knife and fork.
The iLimb is also covered by a semitransparent "cosmesis" that is computer modeled to look like human skin.
The hand, manufactured by Touch Bionics of Scotland, went on sale Tuesday in Britain for £8,500 (U.S. $17,454).
Fourteen amputees, including Iraq war veterans, were fitted with the robotic hand during an extensive trial period. One of these patients, Donald McKillop, 61, lost his right hand in an industrial accident nearly 30 years ago.
"They tell you to try and think as if you have two hands," McKillop told the Telegraph newspaper.
"It is a real learning curve, and every day it gets easier. I was amazed how much I could do within the first hour of trying it."

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MOUNT EVEREST

Mount Everest is so famous for being so high that you've probably heard of it before. It has been known the world over since the early 1950s when Sir Edmund Hillary and Tenzig Norgay first climbed to its awesome summit. Hillary surveyed Everest at the time and determined that it was 29,000 ft/8840m high - a figure amazingly close to the current reading of 29,035 ft/8850m, which was confirmed using radar and global positioning satellite (GPS) technology.
Using state-of-the-art technology Professor Brad Washburn of the Boston Museum of Science, the world's foremost mountain cartographer, and his team have calculated that earth's highest elevation is actually 7 feet higher than the previous record. That makes the official height 29,035 ft/8850m. Thanks to some engineering whizzes at the Massachusetts Institute of Technology who developed really light, high-tech gear, the work of Washburn was made easier because he was able to hand carry a radar device to the top of Everest where it could be positioned to measure the actual height of the mountain - underneath all that snow. GPS technology was also deployed near the summit, which uses satellite signal relays to take readings from the top of Everest. After months of crunching numbers Washburn's team arrived at the new, official world-record elevation.
They've also determined that the Himalayan Mountains are still growing higher, at a rate of about 2.4 in/6.1cm per year. That's twice as fast as previously thought. A growth rate of 2.4 in/6.1cm per year doesn't sound like very much. If you think about it, that means in the last 26,000 years the Himalayans have risen almost a mile into the upper reaches of the earth's atmosphere!
When Hillary and Norgay climbed to the top of Everest they wore oxygen tanks. Because Everest is so high it juts into the upper reaches of the earth's atmosphere, where there are much lower concentrations of oxygen than at sea level. What that means to folks trekking up the side of Everest is that their bodies get less oxygen from each breath they breathe while climbing. But their brains and muscles require the same amount of oxygen to perform as they would at sea level. That makes it especially tough to climb Everest.
Try to imagine what it feels like to climb up a mountain with very little oxygen in your body - you get dizzy, your nose, fingers and feet get numb and tingly, your heart thunders in your chest trying furiously to keep up with the muscles' demand for oxygen. You feel sleepy, confused, downright stupid as your brain struggles to function on limited oxygen. Every step you take is extremely slow and plodding, requiring every ounce of will you have. Hillary and Norgay had extra oxygen to help them make the trip, but there have been a few people who have made the trip since who did it without the aid of oxygen - taking one step about every five minutes! About 4,000 climbers have attempted the summit of Everest, but only 660 have made it. One-hundred forty-two people have died trying.

Highest MountainsMount Everest is just one of over 30 peaks in the Himalayas that are over 24,000 ft/7315m high. Himalaya is a Sanskrit word meaning, "abode of snow", which is so true. The snowfields which dominate many of the peaks in the Himalayas are permanent. Yes, they never melt (not even in the summer). That means there are glaciers in the Himalayas - lots of them. Mount Everest is permanently covered in a layer of ice, topped with snow. The "top" of the mountain at which the elevation was measured can vary as much as twenty feet or more, depending on how much snow has fallen on its peak. Scientists believe that the actual tip of the rock lies tens of feet below the ice and snow on its summit. There are current plans to use ground penetrating radar to get a reading of the actual height of the mountain beneath all that snow. Although the Himalayan Range is only 1,550 miles/2480km long, the average height of all the major peaks in the Himalayas easily makes it the highest mountain range on land.

The Birth of a Mountain

Mountains aren't just big piles of dirt, they're made of solid rock. Believe it or not, the rocks that make up the Himalayan mountains used to be an ancient sea floor. Over millions of years, rivers washed rocks and soil from existing mountains on the Indian subcontinent and nearby Asia into a shallow sea where the sediment was deposited on the floor. Layer upon layer of sediment built up over millions of years until the pressure and weight of the overlying sediment caused the stuff way down deep to turn into rock. Then about 40 million years ago, in a process called "uplifting", the sea floor began to be forced upward forming mountains.

Plate Tectonics in Action

What caused the sea floor to be pushed up toward the sky was the result of the action of plate tectonics. The theory of plate tectonics was developed about thirty years ago by scientists who discovered that the earth's crust is made up of many "plates" which are constantly moving around. They are still moving around, even today, but the speeds at which they move are REALLY SLOW. In human terms the movement can't even be seen, but it can be felt occasionally when we have earthquakes. Earthquakes happen when plate margins (edges) move past, or bump into each other. In the case of the Himalayan mountains, the continent of India is part of a plate that "crashed" into southwest Asia, but it didn't stop when it hit. It continued to push northward, crushing and rumpling the earth's crust, resulting in the mountains we see today. If you go back to the map of the Himalayas, you can see that the mountains look kind of like a rumpled blanket. India is still pushing northward today, raising the Himalayas even higher!

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Amphipods from the Challenger Deep

A series of hadal surveys using the ROV "Kaiko" was conducted by Japan Marine Science and Technology Center (JAMSTEC) to clarify distributional chartacteristics of megabenthos at the Challenger Deep (approx. 10,900m deep) located southwestern edge of the Mariana Trench.
During the survey, over 130 specimens of amphipods, Hirondellea gigas, were collected by baited traps. The total length of the largest specimen was over 45mm. It was first collected in the Kurile-Kamchatka Trench in a plankton tow deeper than 6,000m and then in the Philippine Trench and the Mariana Trench between depths of 7,350m and 10,590m.
This is the deepest record to capture the amphipod which is known as endemic scavenger in some trenches. JAMSTEC has a plan to collect amphipods from the Japan Trench and other trenches, and to study phylogenic relationships applying molecular biological techniques.

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CHALLENGER DEEP

Challenger Deep got its name from the British survey ship Challenger II, which pinpointed the deep water off the Marianas Islands in 1951. Then in 1960, the US Navy sent the Trieste (a submersible - a mini-submarine designed to go really deep) down into the depths of the Marianas trench to see just how far they would go (read the original press release). They touched bottom at 35,838 ft/10,923m. That means, while they were parked on the bottom in the bathyscaphe, there were almost seven miles/11km of water over their heads! If you cut Mount Everest off at sea level and put it on the ocean bottom in the Challenger Deep, there would still be over a mile of water over the top of it!
Hydrostatic Pressure When you get into the ocean (or any body of water) and you start diving down from the surface, the deeper you dive the more water is over the top of you. The more gallons of water you put between you and the surface of the ocean, the greater the pressure is on your body because of the weight of the water over the top of you. This pressure is called hydrostatic pressure.
You can really get a sense of hydrostatic pressure when you go into a swimming pool and dive all the way to the bottom of the deep end. You'll feel the hydrostatic pressure against your ear drums, like they're being squeezed or pushed in. Well, you can imagine how incredible the pressure must be in the Challenger Deep with almost seven miles of water overhead - it's 16,000 pounds per square inch!
The Trieste in 1960. Plate Tectonics and the Subduction Zone
So how come the Challenger Deep is so deep? Well, the earth's crust isn't one solid piece of rock, it's really pretty thin, like the shell of an egg is compared to the size of the egg. In fact, it's made up of huge plates of thin crust that "float" on the molten rock of the earth's mantle. While floating around on the mantle the edges of these plates slide past each other, bump into each other, and sometimes even crash. The oceanic crust is much heavier than the continental crust so when the plates crash into each other, the oceanic plate plunges downward toward the molten mantle, while the lighter, continental plate rides up over the top. The forces driving the two plates together are really intense so the underlying oceanic plate (the subducted plate) creates a trench where it drags the edge of the continental crust down as it descends underneath (check out the picture at left).
This is what's happening on the bottom of the Pacific Ocean off the Marianas islands. The really deep part of the ocean is in the bottom of the trench created by the subducting ocean crust.
So, How Do They Know?
In 1984 the Japanese sent a highly specialized survey vessel out to the Marianas Trench and collected some data using a piece of equipment called a narrow, multi-beam echo sounder.
What an echo sounder does is send high frequency sound waves (outside the range of human hearing) through the water down to the ocean bottom. Sound waves will travel through water, even faster than they travel through the air, and bounce off solid objects, such as the ocean bottom. The echo sounder measures precisely how long it takes for the sound waves to be returned to the surface and determines the depth based on the rate of return. These soundings are plotted on a graph by a computer to make an "echo map" of the ocean bottom.

The deepest measurement of the Challenger Deep currently available was taken by the Japanese and was found to be 35,838 feet.

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ANTARCTICA Land of Extremes

You want to talk about world records, Antarctica is the land of extremes. It is the coldest, windiest, and highest continent anywhere on earth. With an average elevation about 7,544ft/2,300 meters above sea level it is the highest continent. Even though it is covered in ice it receives some of the least amount of rainfall, getting just slightly more rainfall than the Sahara Desert, making it the largest desert on earth. Most people have the misconception that a desert is a hot, dry, sandy, lifeless place, but the true definition of a desert is any geographical location that receives very, very little rainfall. Even though there's ice on the ground in Antarctica, that ice has been there for a very long time. Antarctica is the only continent that has never had an indigenous population of humans because it has always been such an extreme environment. Just the boat ride getting to the continent is over the most treacherous seas anywhere in the world. The inaccessibility of the place and the lack of reliable food and means for constructing shelter has kept humans away for thousands of years. But the new technologies developed over the last 200 years made it possible for people to reach these icy shores to explore and study the Antarctic for the first time in human history. Since there are no people who claim Antarctica as their homeland, exploration of the continent has been shared by all nations of the world. Scientists from all over the world - Russia, Japan, the United States, United Kingdom, Australia, New Zealand, South America, and many others - come to this place in an internationally cooperative agreement to study the truly unique qualities of Antarctica. Many scientific stations have been constructed on Antarctica to provide shelter and supplies for scientists doing field work there. Meet a scientist who's been to Antarctica - even went diving under the ice! Some scientists actually live on Antarctica for part of the year to conduct their research. Very few scientists stay there more than six months at a time. The sun rises and sets only once a year at the South Pole, which means there are six months of daylight, followed by six months of darkness. During the winter when there is no sun, the Antarctic becomes an even more hostile place to be - colder than cold, BONE-CHILLING cold, and no daylight. Can you imagine living in darkness 24 hours a day? That would almost be like living out in space! Hey.....

The World's Biggest Laboratory
At first, the scientific value of studying the Antarctic was just for the sake of understanding this strange place. Recently, scientists have theorized that the conditions in the Antarctic are similar to those on Mars. Because of the similarities exploration of the Antarctic has taken on a new meaning for the search for signs of life in the most extreme environments. Antarctica is not only fascinating itself, but serves as an excellent laboratory for studying the effects of space travel, developing new technologies for exploring other planets and finding extraterrestrial (yeah, alien) life.
Many, many fascinating things have been discovered in the Antarctic that have challenged some of our most basic ideas about what life on earth means. Some really cool factoids:
Deepest Earth Depression: The lowest point on earth is located in the basin of the Bentley Subglacial Trench. At -2,555 meters (8,325 feet) below sea level it is the world's lowest elevation not under seawater. It is not accessible because it is buried under the thickest ice yet discovered.
90% of the ice on earth is located in Antarctica. There is so much ice there you could carve up a block of ice the size of the Great Giza pyramid for every human being on the planet! 98% of Antarctica is covered in ice.
Marine Life: Some species of fish that live in the waters around Antarctica are specially adapted to life in near-freezing waters. Most living creatures on this planet have hemoglobin in their blood, which gives it that red color we all know so well. These particular species of fish, however, have extremely low levels of hemoglobin in their blood. So low that their blood isn't even red! They also have natural antifreeze in their bodies to protect them from freezing to death. (Even if you're a fish and the water in all the cells of your body freezes and turns to ice crystals, you die. 'Nuff said). If you were to catch one of these fish and cut it open the blood, gills and all the organs would be WHITE.
Weather: Yes, the Antarctic has the coldest temperatures on the earth, but that shouldn't surprise you. (Coldest reported temperature ever was -89.4°C/-129°F.) What most people don't know is that the South Pole has the clearest, calmest weather anywhere on earth. Most of the wickedly high winds that everyone associates with the cold and the ice of the Antarctic are around the edges of the continent at the shores. These winds are so fast and so fierce they are world-famous and they have a special name, too - katabatic winds - and they can blow with hurricane force up to 304kmh/190 mph!
Believe it or not with all the ice in the Antarctic, there is very little actual snowfall or precipitation. It does snow on the ice during the austral winter, but measured on an annual basis the Antarctic is as dry as the Sahara Desert.

Antarctic Ice - The Ultimate Cool
Many scientists study Antarctic ice because it is more than just ice. It has accumulated over time, layer upon layer, building up over the millennia to create a type of sedimentary rock. Yes, rock. Ice crystals can be considered a type of mineral, and glacial ice is composed of crystals of the "mineral" water. Just like sedimentary rock is created over time by the repeated layering of particles of clay or sand, glacial ice builds up over millions of years by the build up of snow that never melts.
Scientists drill down deep into the ice with a drill that works kind of like a cookie cutter, only it cuts out some really deep cookies of ice. These core samples contain many layers of ice that represent what the earth's atmosphere was like at the time each layer of ice was formed. By studying the layers of ice in the core samples scientists can learn about how the earth's atmosphere has changed over geologic time.
In the winter time the ocean around Antarctica freezes for thousands of miles in all directions. This vast expanse of ice surrounding the already immense Antarctic ice sheet covers over eleven million square kilometers. The annual freezing of the ocean around Antarctica generates deep ocean currents worldwide. Differences in ocean temperature are what cause weather all over the globe. Some scientists fear that if the global climate gets too warm or too cold it could affect the formation of Antarctic ice, changing the climate as we know it all over the world.

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The Amazon - Home of Extremes

The Amazon River is not only the greatest in the world, it is home to many other "Extremes" of the natural world. Have you ever seen a catfish? They're usually found in warm, slow moving waters of lakes and streams, and some people keep them as pets in aquariums. Catfish are pretty creepy looking fish with big flat heads and "whiskers" on either side of their heads (hence the name, catfish). Most catfish that we're familiar with here in the U.S. are anywhere from eight inches long to about five feet, weighing in at up to 60 pounds. But the catfish that live in the world's greatest river have all the room in the world to grow as big as nature will allow - they have been captured weighing over 200 pounds! One of the largest freshwater fish in the world is found living in the waters of the Amazon River. Arapaima, also known locally as Pirarucu, Arapaima gigas are the largest, exclusively fresh water fish in the world. They have been found to reach a length of 15 ft/4m and can weigh up to 440lbs/200kg. And yes, for you smartypants out there, sturgeon are even larger than this, but they are not exclusively freshwater fish. Sturgeon spend most of their lives at sea, or in brackish water, and only swim into freshwater rivers to spawn. (Read about the biggest freshwater fish in the world.)
(Buy this Photographic Print at AllPosters.com) The Amazon is also home to some other extreme creatures, featured here in "Extreme Science"; the Anaconda (biggest snake), and Piranha (most ferocious). Check it out!

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How Great is the Amazon River?

The Amazon is the greatest river in the world by so many measures; the volume of water it carries to the sea (approximately 20% of all the freshwater discharge into the oceans), the area of land that drains into it, and its length and width. It is one of the longest rivers in the world and, depending upon who you talk to, is anywhere between 6,259km/3,903mi and 6,712km/4,195mi long.
For the last century the length of the Amazon and the Nile Rivers have been in a tight battle for title of world's longest river. The exact length of the two rivers varies over time and reputable sources disagree as to their actual length. The Nile River in Africa is reported to be anywhere from at 5,499km/3,437mi to 6,690km/4,180mi long. But there is no question as to which of the two great rivers carries the greater volume of water - the Amazon River.

At its widest point the Amazon River can be 11km/6.8 mi wide during the dry season. The area covered by the Amazon River and its tributaries more than triples over the course of a year. In an average dry season 110,000 square km of land are water-covered, while in the wet season the flooded area of the Amazon Basin rises to 350,000 square km. When the flood plains and the Amazon River Basin flood during the rainy season the Amazon River can be up to 40km/24.8 mi wide. Where the Amazon opens at its estuary the river is over 325km/202 mi wide!
Because the Amazon drains the entire Northern half of the South American continent (approx. 40% landmass), including all the torrential tropical rains that deluge the rainforests, it carries an enormous amount of water. The mouth of the Amazon River, where it meets the sea, is so wide and deep that ocean-going ships have navigated its waters and traveled as far inland as two-thirds the way up the entire length of the river.

Amazon River Facts

So, how did the Amazon get to be so big? The first reason has to do with its location - right at the equator. Around the "belt line" of the earth lies a warm, tropical zone where over 400 in/1016cm of rain fall every year. That averages out to more than an inch (3cm) of rain, everyday! A lot of water falls onto the land surrounding the river, what is called the "Amazon River drainage basin". A good way to understand what a drainage basin is to think of the whole northern half of the continent of South America as a shallow dish, or saucer. Whenever rain falls and lands anywhere in the river basin it all runs into the lowest place in the pan, which happens to be the Amazon River. The sheer volume of rain in the Amazon jungle, as well as the slope of the surrounding land, combine to create the enormous river known as the Amazon.

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Krakatoa Volcano: The Son Also Rises

As Americans watch the volcanic activity of Mount St. Helens with awe and unease, on the other side of the world, in Indonesia, tourists flock to the site of one of the most spectacular volcanic explosions ever recorded.
Krakatoa, west of Java, erupted with such fury in 1883 that it reportedly was heard as far away as Bangkok and Australia. It blew the island of Rakata to pieces and killed more than 30,000 people. Some scientists say it was the biggest bang in recorded history.
Anak Krakatau (the "son of Krakatoa") emerged from almost the same spot and is growing every day. At roughly 1,300 feet high, it's a popular tourist destination. Many wonder whether -- or when -- it too might erupt. NPR's Michael Sullivan reports.

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Dodo

Dodo
The Dodo (Raphus cucullatus) was a flightless bird that lived on the islands of Mauritius. Related to pigeons and doves, it stood about a metre tall (three feet), lived on fruit and nested on the ground.
The dodo has been extinct since the mid-to-late 17th century. It is commonly used as the archetype of an extinct species because its extinction occurred during recorded human history, and was directly attributable to human activity. The phrase "as dead as a dodo" means undoubtedly and unquestionably dead.

Etymology

The etymology of the word dodo is not clear. It may be related to dodaars ("plump-arse"), the Dutch name of the Little Grebe. The connection may have been made because of similar feathers of the hind end or because both animals were ungainly. However, the Dutch are also known to have called the Mauritius bird the walghvogel ("loathsome bird" or "nauseating fowl") in reference to its taste. This last name was used for the first time in the journal of vice-admiral Wybrand van Warwijck who visited and named the island Mauritius in 1598. Dodo or Dodaerse is recorded in captain Willem van West-Zanen's journal four years later, but it is unclear whether he was the first one to use this name, because before the Dutch, the Portuguese had already visited the island in 1507, but did not settle permanently.
According to Encarta Dictionary and Chambers Dictionary of Etymology, "dodo" comes from Portuguese doudo (currently doido) meaning "fool" or "crazy". However, the present Portuguese name for the bird, dodô, is of English origin. The Portuguese word doudo or doido may itself be a loanword from Old English (cf. English "dolt").
Yet another possibility is that dodo was an onomatopoeic approximation of the bird's own call, a two-note pigeony sound like 'doo-doo'.

Biology
Systematics and evolution

The dodo is a close relative of modern pigeons and doves. mtDNA cytochrome b and 12S rRNA sequences analysis suggests that the dodo's ancestors diverged from those of its closest known relative, the Rodrigues Solitaire (which is also extinct), around the Paleogene-Neogene boundary. As the Mascarenes are of volcanic origin and less than 10 million years old, both birds' ancestors remained most likely capable of flight for considerable time after their lineages' separation. The same study has been interpreted[6] to show that the Southeast Asian Nicobar Pigeon is the closest living relative of the dodo and the Reunion Solitaire.
However, the proposed phylogeny is rather questionable as regards the relationships of other taxa and must therefore be considered hypothetical pending further research; considering biogeographical data, it is very likely to be erroneous. All that can be presently said with any certainty is that the ancestors of the didine birds were pigeons from Southeast Asia or the Wallacea, which agrees with the origin of most of the Mascarenes' birds. Whether the dodo and Rodrigues Solitaire were actually closest to the Nicobar Pigeon among the living birds, or whether they are closer to other groups of the same radiation such as Ducula, Treron or Goura pigeons is not clear at the moment.
For a long time, the dodo and the Rodrigues Solitaire (collectively termed "didines") were placed in a family of their own, the Raphidae. This was because their relationships to other groups of birds (such as rails) had yet to be resolved. As of recently, it appears more warranted to include the didines as a subfamily Raphinae in the Columbidae.
The supposed "White Dodo" is now thought to be based on misinterpreted reports of the Réunion Sacred Ibis and paintings of apparently albinistic dodos; a higher frequency of albinos is known to occur occasionally in island species (see also Lord Howe Swamphen).

Morphology and flightlessness

In October 2005, part of the Mare aux Songes, the most important site of dodo remains, was excavated by an international team of researchers. Many remains were found, including bones from birds of various stages of maturity, and several bones obviously belonging to the skeleton of one individual bird and preserved in natural position. These findings were made public in December 2005 in the Naturalis in Leiden. Before this, few associated dodo specimens were known, most of the material consisting of isolated and scattered bones. Dublin's Natural History Museum and the Oxford University Museum of Natural History, among others, have a specimen assembled from these disassociated remains. A Dodo egg is on display at the East London museum in South Africa. Until recently, the most intact remains, currently on display at the Oxford University Museum of Natural History, were one individual's partly skeletal foot and head which contain the only known soft tissue remains of the species.
In June 2007, adventurers exploring a cave in the Indian Ocean discovered the most complete and well-preserved dodo skeleton ever
The remains of the last known stuffed dodo had been kept in Oxford's Ashmolean Museum, but in the mid-18th century, the specimen - save the pieces remaining now - had entirely decayed and was ordered to be discarded by the museum's curator or director in or around 1755. According to the current curator, Malgosia Nowak-Kemp, the commonly-cited story that the remains were merely damaged - implying that more material could or should have been salvaged, and/or that the present remains were serendipitiously saved against the curator's orders - is an urban legend arising from a mistranslation of the Latin museum records.[citation needed] Nevertheless, from artists' renditions we know that the Dodo had greyish plumage, a 23-centimetre (9-inch) bill with a hooked point, very small wings, stout yellow legs, and a tuft of curly feathers high on its rear end. Dodos were very large birds, weighing about 23 kg (50 pounds). The sternum was insufficient to support flight; these ground-bound birds evolved to take advantage of an island ecosystem with no predators.
The traditional image of the dodo is of a fat, clumsy bird, but this view has been challenged in recent times. The general opinion of scientists today is that the old drawings showed overfed captive specimens. As Mauritius has marked dry and wet seasons, the dodo probably fattened itself on ripe fruits at the end of the wet season to live through the dry season where food was scarce; contemporary reports speak of the birds' "greedy" appetite. Thus, in captivity, with food readily available, the birds would become overfed very easily.

Diet

The tambalacoque, also known as the "dodo tree", was hypothesized by Stanley Temple to have been eaten from by Dodos, and only by passing through the digestive tract of the dodo could the seeds germinate; he claimed that the tambalacocque was now nearly extinct due to the dodo's disappearance. He force-fed seventeen tambalacoque fruits to wild turkeys and three germinated. Temple did not try to germinate any seeds from control fruits not fed to turkeys so the effect of feeding fruits to turkeys was unclear. Temple also overlooked reports on tambalacoque seed germination by A. W. Hill in 1941 and H. C. King in 1946, who found the seeds germinated, albeit rarely, without abrading.

Extinction
As with many animals evolving in isolation from significant predators, the dodo was entirely fearless of people, and this, in combination with its flightlessness, made it easy prey. But journals are full of reports regarding the bad taste and tough meat of the dodo, while other local species such as the Red Rail were praised for their taste. It is commonly believed that the Malay sailors held the bird in high regard and killed them only to make head dressings used in religious ceremonies. However, when humans first arrived on Mauritius, they also brought with them other animals that had not existed on the island before, including dogs, pigs, cats, rats, and Crab-eating Macaques, which plundered the dodo nests, while humans destroyed the forests where the birds made their homes; currently, the impact these animals — especially the pigs and macaques — had on the dodo population is considered to have been more severe than that of hunting. The 2005 expedition's finds are apparently of animals killed by a flash flood; such mass mortalities would have further jeopardized an already extinction-prone species.
Although there are scattered reports of mass killings of dodos for provisioning of ships, archaeological investigations have hitherto found scant evidence of human predation on these birds. Some bones of at least two dodos were found in caves at Baie du Cap which were used as shelters by fugitive slaves and convicts in the 17th century, but due to their isolation in high, broken terrain were not easily accessible to dodos naturally. By 1755, Cossigny reports that the number of refugees and settlers which cut down the inland forest was so high that the well-flighted Mauritius Blue Pigeon was rapidly declining all over the island.[citation needed]
There is some controversy surrounding the extinction date of the dodo. Roberts & Solow state that "the extinction of the Dodo is commonly dated to the last confirmed sighting in 1662, reported by shipwrecked mariner Volkert Evertsz" (Evertszoon), but many other sources suggest the more conjectural date 1681. Roberts & Solow point out that because the sighting prior to 1662 was in 1638, the dodo was likely already very rare by the 1660s, and that thus a disputed report from 1674 cannot be dismissed off-hand. Statistical analysis of the hunting records of Issac Johannes Lamotius, carried out by Julian Hume and coworkers,[citation needed] give a new estimated extinction date of 1693, with a 95% confidence interval of 1688 to 1715. Considering more circumstantial evidence such as travellers' reports and the lack of good reports after 1689, it is likely that the dodo became extinct before 1700; thus, the last Dodo died barely more than a century after the species' discovery in 1581.Few took particular notice of the extinct bird. By the early 19th century it seemed altogether too strange a creature, and was believed by many to be a myth. With the discovery of the first batch of dodo bones in the Mare aux Songes and the reports written about them by George Clarke, government schoolmaster at Mahébourg, from 1865 on,[22] interest in the bird was rekindled. In the same year in which Clarke started to publish his reports, the newly-vindicated bird was featured as a character in Lewis Carroll's Alice's Adventures in Wonderland. With the popularity of the book, the dodo became a well-known and easily recognizable icon of extinction.

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Tyrannosaurus Rex (T-REX)

Tyrannosaurus is a genus of theropod dinosaur. The species Tyrannosaurus rex, commonly abbreviated to T. rex, is one of the dinosaurs most often featured in popular culture around the world. It hails from what is now western North America. Some scientists consider Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus, while others maintain Tarbosaurus as a separate genus.
Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and retained only two digits. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring over 13 metres (43 feet) in length and up to 6.8 metric tons (7.5 short tons) in weight.
Fossils of T. rex have been found in North American rock formations dating to the last three million years of the Cretaceous Period at the end of the Maastrichtian stage, approximately 68.5 to 65.5 million years ago; it was among the last dinosaurs to exist prior to the Cretaceous-Tertiary extinction event. More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons. Some researchers claim to have discovered soft tissue as well. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of T. rex are a few of the topics which remain controversial.

Description

Tyrannosaurus rex was one of the largest land carnivores of all time, measuring 12 to 13 meters (40 to 43.3 feet) long, and 4.5-5 m (14-16.6 ft) tall, when fully-grown. Mass estimates have varied widely over the years, from more than 7,200 kilograms (8 tons), to less than 4,500 kg (5 tons), with most modern estimates ranging between 5,400 and 6,800 kg (between 6 and 7.5 tons).The largest known T. rex skulls measure up to 1.5 m (5 ft) in length. Compared to other theropods, the skull was heavily modified. The skull was extremely wide posteriorly, with a narrow snout, allowing some degree of binocular vision. Some of the bones, such as the nasals, were fused, preventing movement between them. Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment. The bones themselves were massive, as were the serrated teeth which, rather than being bladelike, were oval in cross-section. Like other tyrannosaurids, T. rex displayed marked heterodonty, with the premaxillary teeth at the front of the upper jaw closely-packed and D-shaped in cross-section. Large bite marks found on bones of other dinosaurs indicate that these teeth could penetrate solid bone. T. rex had the greatest bite force of any dinosaur and one of the strongest bite forces of any animal. Worn or broken teeth are often found, but unlike those of mammals, tyrannosaurid teeth were continually replaced throughout the life of the animal.The neck of T. rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The two-fingered forelimbs were very small relative to the size of the body, but heavily built. In contrast, the hindlimbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow. This reduced the weight of the skeleton while maintaining much of the strength of the bones.

Classification

Tyrannosaurus is the type genus of the superfamily Tyrannosauroidea, the family Tyrannosauridae, and the subfamily Tyrannosaurinae. Other members of the tyrannosaurine subfamily include the North American Daspletosaurus and the Asian Tarbosaurus, both of which have occasionally been synonymized with Tyrannosaurus. Tyrannosaurids were once commonly thought to be descendants of earlier large theropods such as megalosaurs and carnosaurs, although more recently they were reclassified with the generally smaller coelurosaurs.
In 1955, Soviet paleontologist Evgeny Maleev named a new species, Tyrannosaurus bataar, from Mongolia. By 1965, this species had been renamed Tarbosaurus bataar. Despite the renaming, many phylogenetic analyses have found Tarbosaurus bataar to be the sister taxon of Tyrannosaurus rex, and it has often been considered an Asian species of Tyrannosaurus. A recent redescription of the skull of Tarbosaurus bataar has shown that it was much narrower than that of Tyrannosaurus rex and that during a bite, the distribution of stress in the skull would have been very different, closer to that of Alioramus, another Asian tyrannosaur. A related cladistic analysis found that Alioramus, not Tyrannosaurus, was the sister taxon of Tarbosaurus, which, if true, would suggest that Tarbosaurus and Tyrannosaurus should remain separate.
Other tyrannosaurid fossils found in the same formations as T. rex were originally classified as separate taxa, including Aublysodon and Albertosaurus megagracilis, the latter being named Dinotyrannus megagracilis in 1995. However, these fossils are now universally considered to belong to juvenile T. rex. A small but nearly complete skull from Montana, 60 cm (2 ft) long, may be an exception. This skull was originally classified as a species of Gorgosaurus (G. lancensis) by Charles W. Gilmore in 1946, but was later referred to a new genus, Nanotyrannus. Opinions remain divided on the validity of N. lancensis. Many paleontologists consider the skull to belong to a juvenile T. rex. There are minor differences between the two species, including the higher number of teeth in N. lancensis, which lead some scientists to recommend keeping the two genera separate until further research or discoveries clarify the situation.

Manospondylus controversy

The first fossil specimen which can be attributed to Tyrannosaurus rex consists of two partial vertebrae (one of which has been lost) found by Edward Drinker Cope in 1892 and described as Manospondylus gigas. Osborn recognized the similarity between M. gigas and T. rex as early as 1917 but, due to the fragmentary nature of the Manospondylus vertebrae, he could not synonymize them conclusively.
Controversy erupted in June 2000 after the Black Hills Institute located the type locality of M. gigas in South Dakota and unearthed more tyrannosaur bones there. These were judged to represent further remains of the same individual, and to be identical to those of T. rex. According to the rules of the International Code of Zoological Nomenclature (ICZN), the system that governs the scientific naming of animals, Manospondylus gigas should therefore have priority over Tyrannosaurus rex, because it was named first. However, the Fourth Edition of the ICZN, which took effect on January 1, 2000, states that "the prevailing usage must be maintained" when "the senior synonym or homonym has not been used as a valid name after 1899" and "the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years..." Tyrannosaurus rex easily qualifies as the valid name under these conditions and would most likely be considered a nomen protectum ("protected name") under the ICZN if it was ever challenged, which it has not yet been. Manospondylus gigas would then be deemed a nomen oblitum ("forgotten name").

Life history

The identification of several specimens as juvenile Tyrannosaurus rex has allowed scientists to document ontogenetic changes in the species, estimate the lifespan, and determine how quickly the animals would have grown. The smallest known individual (LACM 28471, the "Jordan theropod") is estimated to have weighed only 29.9 kg (66 lb), while the largest, such as FMNH PR2081 ("Sue") most likely weighed over 5400 kg (6 short tons). Histologic analysis of T. rex bones showed LACM 28471 had aged only 2 years when it died, while "Sue" was 28 years old, an age which may have been close to the maximum for the species.
Histology has also allowed the age of other specimens to be determined. Growth curves can be developed when the ages of different specimens are plotted on a graph along with their mass. A T. rex growth curve is S-shaped, with juveniles remaining under 1800 kg (2 short tons) until approximately 14 years of age, when body size began to increase dramatically. During this rapid growth phase, a young T. rex would gain an average of 600 kg (1600 lb) a year for the next four years. At 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only 600 kg (1,300 lb) separated the 28-year-old "Sue" from a 22-year-old Canadian specimen (RTMP 81.12.1). Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age. This sudden change growth rate may indicate physical maturity, a hypothesis which is supported by the discovery of medullary tissue in the femur of a 16 to 20-year-old T. rex from Montana (MOR 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age. Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.
Over half of the known T. rex specimens appear to have died within six years of reaching sexual maturity, a pattern which is also seen in other tyrannosaurs and in some large, long-lived birds and mammals today. These species are characterized by high infant mortality rates, followed by relatively low mortality among juveniles. Mortality increases again following sexual maturity, partly due to the stresses of reproduction. One study suggests that the rarity of juvenile T. rex fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and so were not often fossilized. However, this rarity may also be due to the incompleteness of the fossil record or to the bias of fossil collectors towards larger, more spectacular specimens.

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Mammoth

A mammoth is any of a number of an extinct genus of proboscidean (of which the elephant remains), often with long curved tusks and, in northern species, a covering of long hair. They lived from the Pliocene epoch from 4.8 million years ago to around 4,000 years ago. The word mammoth comes from the Russian мамонт mamont, probably in turn from the Khanty

Evolutionary history

Mammoth remains have been found in Europe, Africa, Asia, and North America. They are believed to have originally evolved in North Africa about 4.8 million years ago, during the Pliocene, where bones of Mammuthus africanavus have been found in Chad, Libya, Morocco and Tunisia. Mammuthus subplanifrons, found in South Africa and Kenya, is also believed to be one of the oldest species (about 4 million years ago).
Despite their African ancestry, they are in fact more closely related to the modern Asian Elephant than either of the two African elephants (as both Mammuthus and Elephas also originated in Africa). The common ancestor of both mammoths and Asian elephants split from the line of African elephants about 6 - 7.3 million years ago. The Asian elephants and mammoths diverged about half a million years later (5.5 - 6.3 million years ago).
In due course the African mammoth migrated north to Europe and gave rise to a new species, the southern mammoth (Mammuthus meridionalis). This eventually spread across Europe and Asia and crossed the now-submerged Bering Land Bridge into North America.
Around 700,000 years ago, the warm climate of the time deteriorated markedly and the savannah plains of Europe, Asia and North America gave way to colder and less fertile steppes. The southern mammoth consequently declined, being replaced across most of its territory by the cold-adapted steppe mammoth (Mammuthus trogontherii). This in turn gave rise to the woolly mammoth, Mammuthus primigenius) around 300,000 years ago. Woolly mammoths were better able to cope with the extreme cold of the Ice Ages.
The woollies were a spectacularly successful species; they ranged from Spain to North America and are thought to have existed in huge numbers. The Russian researcher Sergei Zimov estimates that during the last Ice Age, parts of Siberia may have had an average population density of sixty animals per hundred square kilometres - equivalent to African elephants today.

Extinction

Most mammoths died out at the end of the last Ice Age. A definitive explanation for their mass extinction is yet to be agreed upon. A small population survived on St. Paul Island, Alaska, up until 6000 BC , and the small mammoths of Wrangel Island became extinct only around 1700 to 1500 BC.
Whether the general mammoth population died out for climatic reasons or due to overhunting by humans is controversial. Another theory suggests that mammoths may have fallen victim to an infectious disease. A combination of climate change and hunting by humans is probably the most likely explanation for their extinction.
New data derived from studies done on living elephants and reported by the American Institute of Biological Sciences (BioScience, April 2006, Vol. 56 No. 4, pp. 292-298) suggests that though human hunting may not have been the primary cause toward the mammoth's final extinction, human hunting was likely a strong contributing factor. Homo erectus is known to have consumed mammoth meat as early as 1.8 million years ago (BioScience, April 2006, Vol. 56 No. 4, p. 295).
However, the American Institute of Biological Sciences also notes that bones of dead elephants, left on the ground and subsequently trampled by other elephants, tend to bear marks resembling butchery marks, which have previously been misinterpreted as such by archaeologists.
The survival of the dwarf mammoths on Russia's Wrangel Island was due to the fact that the island was very remote, and uninhabited in the early Holocene period. The actual island was not discovered by modern civilization until the 1820s by American whalers. A similar dwarfing occurred with Mammoths on the outer Channel Islands of California, but at an earlier period. Those animals were very likely killed by early Paleo-Native Americans, and habitat loss caused by a rising sea level that split the Santa Rosae into the outer Channel Islands.

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