Exercises Countries and nationalities - English - PDF


Philippines Flag Coloring Page

Nigeria Flag Coloring Page

Zimbabwe Flag Coloring Page

Zambia Flag Coloring Page

Singapore Flag Coloring Page

Singapore Flag Colouring Page

Singapore: Flag Printout to Color

Liberia Flag Coloring Page

Hong Kong Flag Coloring Page

Coloring picture of Hong Kong flag

Germany Flag Coloring Page

Germany flag colouring page

Flag of Greenland Coloring page


Flag of Greenland Coloring page.

Flags of North America Coloring Pages

United States Flag Coloring Page
Canadian Flag coloring page
Mexico Flag Colouring Page
Flag of Greenland Coloring page


India Flag Coloring Page

India flag colouring page


South Africa Flag coloring page

South African flag colouring page

South Africa Flag colouring
South Africa Flag color page

District of Columbia (Washington D.C.) Flag Coloring Page

United States Flag Coloring Page

United States Flag Coloring Page

Vermont State Flag Coloring Page

Vermont State Flag Coloring Page

Alaska State Flag Coloring Page

Alaska State Flag Coloring Page

Oregon State Flag Coloring Page

Oregon State Flag Coloring Page

Tennessee State Flag Coloring Page

Tennessee State Flag Coloring Page

South Carolina State Flag Coloring Page

South Carolina State Flag Coloring Page

Minnesota State Flag Coloring Page

Minnesota State Flag Coloring Page

Alabama State Flag Coloring Page

Alabama State Flag Coloring Page

Washington Flag Coloring Page

Washington Flag Coloring Page

Virginia Flag Coloring Page

 Virginia Flag Coloring Page

Michigan Flag Coloring Page

Pennsylvania Flag Coloring Page

 Pennsylvania Flag Coloring Page

Illinois State Flag Coloring Page

Illinois State Flag Coloring Page

California’s State Seal

California’s State Seal - During the constitutional convention,a member named Caleb Lyonpresented a design for a state seal.The seal's design showed thesepictures to tell about ideas that wereimportant to California:
Great Seal of the State of California coloring page for printing.
Goddess Minerva - Minerva (Athenain Greek mythology) in Romanmythology was said to have been bornfrom the head of the god Jupiter intoa full-grown adult. She was includedto show California's quick rise tostatehood without first becoming aterritory like most other states.

Grizzly Bear - California's state animal

Prospector/Miner - The gold rush

Grain - Agriculture

Ships - Economic power and trade

Water - San Francisco Bay

Eureka - written across the top of thepicture and means "I found it". Madepopular during the gold rush becauseprospectors would shout it out whenthey found gold.

Tropic of Cancer? Tropic of Capricorn? Who came up with those names?

These names were thought up about 2,000 years ago. At that time, the Sun was in the direction of the constellation Cancer at the Summer Solstice in June. However, this is no longer true. Earth’s axis wobbles a bit, slowly changing the direction in which it points.
Over 26,000 years, the axis traces out a small cone shape. At this time, the Sun is in Taurus or Gemini (depending on where you draw the boundary between them) at the Summer Solstice. The word "tropic" itself comes from the Greek τροπή (tropi), meaning turn, referring to the fact that the sun appears to "turn back" at the solstices.
In this chart of the zodiac, the Sun is in the constellation Cancer.
When the Tropic of Capricorn was named, the Sun was entering the constellation Capricorn at the Winter Solstice in December. In modern times the Sun appears in the constellation Sagittarius during this time.

Source: Nasa

What is the Coriolis Effect?

A Powerful “Force”

It affects weather patterns, it affects ocean currents, and it even affects air travel. As important as the Coriolis Effect is, many have not heard about it, and even fewer understand it. In simple terms, the Coriolis Effect makes things (like planes or currents of air) traveling long distances around the Earth appear to move at a curve as opposed to a straight line.
The Coriolis Effect is named after French mathematician
and physicist Gaspard-Gustave de Coriolis.
It’s a pretty weird phenomenon, but the cause is simple: Different parts of the Earth move at different speeds.

What Do You Mean Parts of Earth Move at Different Speeds!?

Think about this: It takes the Earth 24 hours to rotate one time. If you are standing a foot to the right of the North or South Pole, that means it would take 24 hours to move in a circle that is about six feet in circumference. That’s about 0.00005 miles per hour.

Hop on down to the equator, though, and things are different. It still takes the Earth the same 24 hours to make a rotation, but this time we are traveling the entire circumference of the planet, which is about 25,000 miles long. That means you are traveling almost 1040 miles per hour just by standing there.
Shorter distance to travel in the same amount
of time means slower speeds closer to the poles.
So even though we are all on Earth, how far we are from the equator determines our forward speed. The farther we are from the equator, the slower we move.

Okay. So How Does That Prevent Things from Traveling in a Straight Line?

Good question! Now think about this: You are on a train traveling at top speed and you are passing a train that is moving a bit slower. You see, for some mysterious reason, that there is a soccer goal on this slower train. Always prepared, you happen to have a soccer ball handy and want to make an impressive trick shot.

You take an incredible shot directly at the goal when you are even with the slower train. Even though your aim is dead-on, the ball travels to the side and misses the net. That’s because the ball is traveling not only in the direction of the goal, but it is also going in the direction (and speed) of your train.
This is what happens with our attempted trick shot.
Let’s pretend these trains are the Earth at different latitudes and add another red train. Think of the two red trains as the northern and southern tropics and the blue train as the equator. The red trains are going slower than the blue train. Remember, the farther you go from the equator, the slower you move.

Now let’s put our trains on an actual Earth-shaped globe:
The trains still move at different speeds, but now
they would appear to travel parallel to each other.
Even though the red trains are going slower than the blue train, since they are traveling a shorter distance, they would appear from a bird’s-eye view to be going at the same speed. That doesn’t mean your trick shot would behave any differently though. From a bird’s-eye view, it would look like this:
A bird's eye view.
And that’s the deflection we are talking about! Anything traveling long distances, like air currents, ocean currents pushed by air, and airplanes, will all be deflected because of the Coriolis Effect! Weird, right?

Source: Nasa

What is a Planet?

Science is a dynamic process of questioning, hypothesizing, discovering, and changing previous ideas based on what is learned. Scientific ideas are developed through reasoning and tested against observations. Scientists assess and question each other's work in a critical process called peer review.
Illustration: Eris (left) and Ceres (lower center) compared to Earth and its moon.
Our understanding about the universe and our place in it has changed over time. New information can cause us to rethink what we know and reevaluate how we classify objects in order to better understand them. New ideas and perspectives can come from questioning a theory or seeing where a classification breaks down.
Now: Scaled views of our solar system.
Defining the term planet is important, because such definitions reflect our understanding of the origins, architecture, and evolution of our solar system. Over historical time, objects categorized as planets have changed. The ancient Greeks counted the Earth's moon and sun as planets along with Mercury,Venus, Mars, Jupiter, and Saturn. Earth was not considered a planet, but rather was thought to be the central object around which all the other celestial objects orbited. The first known model that placed the sun at the center of the known universe with the Earth revolving around it was presented by Aristarchus of Samos in the third century BCE, but it was not generally accepted. It wasn't until the 16th century that the idea was revived by Nicolaus Copernicus. By the 17th century, astronomers (aided by the invention of the telescope) realized that the sun was the celestial object around which all the planets - including Earth - orbit, and that the moon is not a planet, but a satellite (moon) of Earth. Uranus was added as a planet in 1781 and Neptune was discovered in 1846.

Ceres was discovered between Mars and Jupiter in 1801 and originally classified as a planet. But as many more objects were subsequently found in the same region, it was realized that Ceres was the first of a class of similar objects that were eventually termed asteroids (star-like) or minor planets.
Copernicus' theory of a sun-centered solar system was not accepted for decades.
Pluto, discovered in 1930, was identified as the ninth planet. But Pluto is much smaller than Mercury and is even smaller than some of the planetary moons. It is unlike the terrestrial planets (Mercury, Venus, Earth, Mars), or the gas giants (Jupiter, Saturn), or the ice giants (Uranus, Neptune). Charon, its huge satellite, is nearly half the size of Pluto and shares Pluto's orbit. Though Pluto kept its planetary status through the 1980s, things began to change in the 1990s with some new discoveries.

Technical advances in telescopes led to better observations and improved detection of very small, very distant objects. In the early 1990s, astronomers began finding numerous icy worlds orbiting the sun in a doughnut-shaped region called the Kuiper Belt beyond the orbit of Neptune - out in Pluto's realm. With the discovery of the Kuiper Belt and its thousands of icy bodies (known as Kuiper Belt objects, or KBOs; also called transneptunians), it was proposed that it is more useful to think of Pluto as the biggest KBO instead of a planet. Then, in 2005, a team of astronomers announced that they had found a tenth planet - it was a KBO even larger than Pluto. People began to wonder what planethood really means. Just what is a planet, anyway? Suddenly the answer to that question didn't seem so self-evident, and, as it turns out, there are plenty of disagreements about it.

The International Astronomical Union (IAU), a worldwide organization of astronomers, took on the challenge of classifying the newly found KBO (later named Eris). In 2006, the IAU passed a resolution that defined planet and established a new category, dwarf planet. Eris, Ceres, Pluto, and two more recently discovered KBOs named Haumea and Makemake, are the dwarf planets recognized by the IAU (as of July 2013). Pluto, Eris, Haumea, and Makemake are also classified as KBOs, and Ceres retains its asteroid label. There may be another 100 dwarf planets in the solar system and hundreds more in and just outside the Kuiper Belt.

Astronomers and planetary scientists did not unanimously agree with these definitions. To some it appeared that the classification scheme was designed to limit the number of planets; to others it was incomplete and the terms unclear. Some astronomers argued that location (context) is important, especially in understanding the formation and evolution of the solar system.
For thousands of years, people thought Earth was the center of the Universe.
One idea is to simply define a planet as a natural object in space that is massive enough for gravity to make it approximately spherical. But some scientists objected that this simple definition does not take into account what degree of measurable roundness is needed for an object to be considered round. In fact, it is often difficult to accurately determine the shapes of some distant objects. Others argue that where an object is located or what it is made of do matter and there should not be a concern with dynamics; that is, whether or not an object sweeps up or scatters away its immediate neighbors, or holds them in stable orbits. The lively planethood debate continues.

As our knowledge deepens and expands, the more complex and intriguing the universe appears. Researchers have found hundreds of extrasolar planets, or exoplanets, that reside outside our solar system; there may be billions of exoplanets in the Milky Way Galaxy alone, and some may be habitable (have conditions favorable to life). Whether our definitions of planet can be applied to these newly found objects remains to be seen.

Source: Nasa

Chicxulub crater

The Chicxulub crater (/ˈtʃiːkʃʉluːb/; Mayan pronunciation: [tʃʼikʃuluɓ]) is an impact crater buried underneath the Yucatán Peninsulain Mexico. Its center is located near the town of Chicxulub, after which the crater is named. The age of the Chicxulub asteroid impact and the Cretaceous–Paleogene boundary (K–Pg boundary) coincide precisely. The crater is more than 180 kilometres (110 mi) in diameter and 20 km (12 mi) in depth, making the feature one of the largest confirmed impact structures on Earth; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter.
Imaging from NASA's Shuttle Radar Topography Mission STS-99 reveals part of the 180 km
(110 mi)-diameter ring of the crater. The numerous sinkholes clustered around
the trough of the crater suggest a prehistoric oceanic basin in the depression left by the impact.
The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater, and gave up his search. Through contact with Alan Hildebrand, Penfield obtained samples that suggested it was an impact feature. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas.

The age of the rocks marked by the impact shows that this impact structure dates from roughly 66 million years ago, the end of the Cretaceous period, and the start of the Paleogene period. It coincides with the K-Pg boundary, the geological boundary between the Cretaceous and Paleogene. The impact associated with the crater is thus implicated in the Cretaceous–Paleogene extinction event, including the worldwide extinction of non-avian dinosaurs. This conclusion has been the source of controversy. In March 2010, 41 experts from many countries reviewed the available evidence: 20 years' worth of data spanning a variety of fields. They concluded that the impact at Chicxulub triggered the mass extinctions at the K–Pg boundary.

Discovery
In 1978, geophysicists Antonio Camargo and Glen Penfield were working for the Mexican state-owned oil company Petróleos Mexicanos, or Pemex, as part of an airborne magnetic survey of the Gulf of Mexico north of the Yucatán peninsula. Penfield's job was to use geophysical data to scout possible locations for oil drilling. In the data, Penfield found a huge underwater arc with "extraordinary symmetry" in a ring 70 km (40 mi) across. He then obtained a gravity map of the Yucatán made in the 1960s. A decade earlier, the same map suggested an impact feature to contractor Robert Baltosser, but he was forbidden to publicize his conclusion by Pemex corporate policy of the time. Penfield found another arc on the peninsula itself, the ends of which pointed northward. Comparing the two maps, he found the separate arcs formed a circle, 180 km (111 mi) wide, centered near the Yucatán village Chicxulub; he felt certain the shape had been created by a cataclysmic event in geologic history.
Artist's rendering of the gravity anomaly map of the Chicxulub Crater area.
Different colors represent different gravity measurements,
except the white dots, which are sinkholes called cenotes.
The shaded area is the Yucatán Peninsula
Pemex disallowed release of specific data but let Penfield and company official Antonio Camargo presented their results at the 1981Society of Exploration Geophysicists conference. That year's conference was underattended and their report attracted scant attention. Coincidentally, many experts in impact craters and the K–Pg boundary were attending a separate conference on Earth impacts. Although Penfield had plenty of geophysical data sets, he had no rock cores or other physical evidence of an impact.

He knew Pemex had drilled exploratory wells in the region. In 1951, one bored into what was described as a thick layer of andesite about 1.3 km (4,200 ft) down. This layer could have resulted from the intense heat and pressure of an Earth impact, but at the time of the borings it was dismissed as a lava dome — a feature uncharacteristic of the region's geology. Penfield tried to secure site samples, but was told such samples had been lost or destroyed. When attempts at returning to the drill sites and looking for rocks proved fruitless, Penfield abandoned his search, published his findings and returned to his Pemex work.
Penfield with the sample of shocked quartz found at Well #2, Chicxulub.
At the same time, scientist Luis Walter Alvarez put forth his hypothesis that a large extraterrestrial body had struck Earth and, unaware of Penfield's discovery, in 1981 University of Arizona graduate student Alan R. Hildebrand and faculty adviser William V. Boynton published a draft Earth-impact theory and sought a candidate crater. Their evidence included greenish-brown clay with surplus iridium containing shocked quartz grains and small weathered glass beads that looked to be tektites. Thick, jumbled deposits of coarse rock fragments were also present, thought to have been scoured from one place and deposited elsewhere by a kilometres-high tsunami resulting from an Earth impact. Such deposits occur in many locations but seem concentrated in the Caribbean basin at the K–Pg boundary. So when Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on Haiti, Hildebrand suggested it could be a telltale feature of a nearby impact. Tests on samples retrieved from the K–Pg boundary revealed more tektite glass, formed only in the heat of asteroid impacts and high-yield nuclear detonations.

In 1990, Houston Chronicle reporter Carlos Byars told Hildebrand of Penfield's earlier discovery of a possible impact crater. Hildebrand contacted Penfield in April 1990 and the pair soon secured two drill samples from the Pemex wells, stored in New Orleans. Hildebrand's team tested the samples, which clearly showed shock-metamorphic materials.

A team of California researchers including Kevin Pope, Adriana Ocampo, and Charles Duller, surveying regional satellite images in 1996, found a sinkhole (cenote) ring centered on Chicxulub that matched the one Penfield saw earlier; the sinkholes were thought to be caused by subsidence of the impact crater wall. More recent evidence suggests the actual crater is 300 km (190 mi) wide, and the 180 km ring is in fact an inner wall of it.

Impact specifics
Researchers at the University of Glasgow dated rock and ash samples from the impact to 66,038,000 ± 11,000 years ago.
An animation showing the impact, and subsequent crater formation
 (University of Arizona, Space Imagery Center).
The Chicxulub impactor had an estimated diameter of 10 km (6.2 mi) and delivered an estimated energy equivalent of 100 teratons of TNT (4.2×1023 J). By contrast, the most powerful man-made explosive device ever detonated, the Tsar Bomba, had a yield of only 50 megatons of TNT (2.1×1017 J), making the Chicxulub impact 2 million times more powerful. Even the most energetic known volcanic eruption, which released an estimated energy equivalent of approximately 240 gigatons of TNT (1.0×1021 J) and created the La Garita Caldera, delivered only 0.24% of the energy of the Chicxulub impact.

Effects
The impact would have caused some of the largest megatsunamis in Earth's history. A cloud of super-heated dust, ash and steam would have spread from the crater as the impactor burrowed underground in less than a second. Excavated material along with pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon re-entry, broiling the Earth's surface and possibly igniting wildfires; meanwhile, colossal shock waves would have triggered global earthquakes and volcanic eruptions. The emission of dust and particles could have covered the entire surface of the Earth for several years, possibly a decade, creating a harsh environment for living things. The shock production of carbon dioxide caused by the destruction of carbonate rocks would have led to a sudden greenhouse effect. Over a longer period, sunlight would have been blocked from reaching the surface of the Earth by the dust particles in the atmosphere, cooling the surface dramatically. Photosynthesis by plants would also have been interrupted, affecting the entire food chain. A model of the event developed by Lomax et al. (2001) suggests that net primary productivity (NPP) rates may have increased to higher than pre-impact levels over the long term because of the high carbon dioxide concentrations. A long-term effect of the impact was the creation of the sedimentary basin which "ultimately produced favorable conditions for human settlement in a region where surface water is scarce."

In February 2008, a team of researchers led by Sean Gulick at the University of Texas at Austin's Jackson School of Geosciences used seismic images of the crater to determine that the impactor landed in deeper water than was previously assumed. They argued that this would have resulted in increased sulfate aerosols in the atmosphere. According to the press release, that "could have made the impact deadlier in two ways: by altering climate (sulfate aerosols in the upper atmosphere can have a cooling effect) and by generating acid rain (water vapor can help to flush the lower atmosphere of sulfate aerosols, causing acid rain)."

Geology and morphology
In their 1991 paper, Hildebrand, Penfield, and company described the geology and composition of the impact feature. The rocks above the impact feature are layers of marl and limestone reaching to a depth of almost 1,000 m (3,300 ft). These rocks date back as far as the Paleocene. Below these layers lie more than 500 m (1,600 ft) of andesite glass and breccia. These andesitic igneous rocks were only found within the supposed impact feature, as is shocked quartz. The K–Pg boundary inside the feature is depressed to 600 to 1,100 m (2,000 to 3,600 ft) compared with the normal depth of about 500 m (1,600 ft) measured 5 kilometres (3.1 mi) away from the impact feature. Along the edge of the crater are clusters of cenotes or sinkholes, which suggest that there was a water basin inside the feature during the Neogene period, after the impact. The groundwater of such a basin would have dissolved the limestone and created the caves and cenotes beneath the surface. The paper also noted that the crater seemed to be a good candidate source for the tektites reported at Haiti.
The piece of clay, held by Walter Alvarez, that sparked research into the impact theory.
The greenish-brown band in the center is extremely rich in iridium.

Astronomical origin of asteroid
In September 2007, a report published in Nature proposed an origin for the asteroid that created Chicxulub Crater. The authors, William F. Bottke, David Vokrouhlický, and David Nesvorný, argued that a collision in the asteroid belt 160 million years ago resulted in the Baptistina family of asteroids, the largest surviving member of which is 298 Baptistina. They proposed that the "Chicxulub asteroid" was also a member of this group. The connection between Chicxulub and Baptistina is supported by the large amount of carbonaceous material present in microscopic fragments of the impactor, suggesting the impactor was a member of a rare class of asteroids called carbonaceous chondrites, like Baptistina. According to Bottke, the Chicxulub impactor was a fragment of a much larger parent body about 170 km (110 mi) across, with the other impacting body being around 60 km (40 mi) in diameter. In 2011, new data from the Wide-field Infrared Survey Explorer revised the date of the collision which created the Baptistina family to about 80 million years ago. This makes an asteroid from this family highly improbable to be the asteroid that created the Chicxulub Crater, as typically the process of resonance and collision of an asteroid takes many tens of millions of years. In 2010, another hypothesis was offered which implicated the newly discovered asteroid P/2010 A2, a member of the Flora family of asteroids, as a possible remnant cohort of the K/Pg impactor.

Chicxulub and mass extinction
The Chicxulub Crater lends support to the theory postulated by the late physicist Luis Alvarez and his son, geologist Walter Alvarez, that the extinction of numerous animal and plant groups, including dinosaurs, may have resulted from a bolide impact (the Cretaceous–Paleogene extinction event). Luis and Walter Alvarez, at the time both faculty members at the University of California, Berkeley, postulated that this enormous extinction event, which was roughly contemporaneous with the postulated date of formation for the Chicxulub crater, could have been caused by just such a large impact. This theory is now widely accepted by the scientific community. Some critics, including paleontologist Robert Bakker, argue that such an impact would have killed frogs as well as dinosaurs, yet the frogs survived the extinction event. Gerta Keller of Princeton University argues that recent core samples from Chicxulub prove the impact occurred about 300,000 years before the mass extinction, and thus could not have been the causal factor.

The main evidence of such an impact, besides the crater itself, is contained in a thin layer of clay present in the K–Pg boundary across the world. In the late 1970s, the Alvarezes and colleagues reported that it contained an abnormally high concentration of iridium. Iridium levels in this layer reached 6 parts per billion by weight or more compared to 0.4 for the Earth's crust as a whole; in comparison, meteorites can contain around 470 parts per billion of this element. It was hypothesized that the iridium was spread into the atmosphere when the impactor was vaporized and settled across the Earth's surface amongst other material thrown up by the impact, producing the layer of iridium-enriched clay.

Multiple impact theory
In recent years, several other craters of around the same age as Chicxulub have been discovered, all between latitudes 20°N and 70°N. Examples include the disputed Silverpit crater in the North Sea and the Boltysh crater in Ukraine. Both are much smaller than Chicxulub, but are likely to have been caused by objects many tens of metres across striking the Earth. This has led to the hypothesis that the Chicxulub impact may have been only one of several impacts that happened nearly at the same time. Another possible crater thought to have been formed at the same time is the larger Shiva crater, though the structure's status as a crater is contested.

The collision of Comet Shoemaker–Levy 9 with Jupiter in 1994 demonstrated that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet should collide with a planet. Comets undergo gravitational interactions with the gas giants, and similar disruptions and collisions are very likely to have occurred in the past. This scenario may have occurred on Earth at the end of the Cretaceous, though Shiva and the Chicxulub craters might have been formed 300,000 years apart.

In late 2006, Ken MacLeod, a geology professor from the University of Missouri, completed an analysis of sediment below the ocean's surface, bolstering the single-impact theory. MacLeod conducted his analysis approximately 4,500 km (2,800 mi) from the Chicxulub Crater to control for possible changes in soil composition at the impact site, while still close enough to be affected by the impact. The analysis revealed there was only one layer of impact debris in the sediment, which indicated there was only one impact. Multiple-impact proponents such as Gerta Keller regard the results as "rather hyper-inflated" and do not agree with the conclusion of MacLeod's analysis, arguing that there might only be gaps of hours to days between impacts in a multiple impact scenario (cf. Shoemaker-Levy 9) which would not leave a detectable gap in deposits.

Source: Wikipedia

Armero tragedy

The Armero tragedy (Spanish: Tragedia de Armero [tɾaˈxeðja ðe arˈmeɾo]) was one of the major consequences of the eruption of the Nevado del Ruiz stratovolcano in Tolima, Colombia, on November 13, 1985. After 69 years of dormancy, the volcano's eruption caught nearby towns unaware, even though the government had received warnings from multiple volcanological organizations to evacuate the area when volcanic activity had been detected in September 1985.
Lahars covered the town of Armero. More than 20,000 people died.
As pyroclastic flows erupted from the volcano's crater, they melted the mountain's glaciers, sending four enormous lahars(volcanically induced mudslides, landslides, and debris flows) down its slopes at 50 kilometers per hour (30 miles per hour). The lahars picked up speed in gullies and coursed into the six major rivers at the base of the volcano; they engulfed the town of Armero, killing more than 20,000 of its almost 29,000 inhabitants. Casualties in other towns, particularly Chinchiná, brought the overall death toll to 23,000. Footage and photographs of Omayra Sánchez, a young victim of the tragedy, were published around the world. Other photographs of the lahars and the impact of the disaster captured attention worldwide and led to controversy over the degree to which the Colombian government was responsible for the disaster. A banner at a mass funeral in Ibagué read, "The volcano didn't kill 22,000 people. The government killed them."

The relief efforts were hindered by the composition of the mud, which made it nearly impossible to move through without becoming stuck. By the time relief workers reached Armero twelve hours after the eruption, many of the victims with serious injuries were dead. The relief workers were horrified by the landscape of fallen trees, disfigured human bodies, and piles of debris from entire houses. This was the second-deadliest volcanic disaster of the 20th century, surpassed only by the 1902 eruption of Mount Pelée, and is the fourth-deadliest volcanic event recorded since 1500 AD. The event was a foreseeable catastrophe exacerbated by the populace's unawareness of the volcano's destructive history; geologists and other experts had warned authorities and media outlets about the danger over the weeks and days leading up to the eruption. Hazard maps for the vicinity were prepared, but poorly distributed. On the day of the eruption, several evacuation attempts were made, but a severe storm restricted communications. Many victims stayed in their houses as they had been instructed, believing that the eruption had ended. The noise from the storm may have prevented many from hearing the sounds from Ruiz until it was too late.

Nevado del Ruiz has erupted several times since the disaster, and continues to threaten up to 500,000 people living along the Combeima, Chinchina, Coello-Toche, and Guali river valleys. A lahar (or group of lahars) similar in size to the 1985 event could potentially travel as far as 100 kilometers (60 mi) from the volcano, and could be triggered by a small eruption. To counter this threat, the Colombian government established a specialized office which promotes awareness of natural threats. The United States Geological Survey also created the Volcano Disaster Assistance Program and the Volcano Crisis Assistance Team, which evacuated roughly 75,000 people from the area around Mount Pinatubo before its 1991 eruption. In 1988, three years after the eruption, Dr. Stanley Williams of Louisiana State University stated that, "With the possible exception of Mount St. Helens in the state of Washington, no other volcano in the Western Hemisphere is being watched so elaborately" as Nevado del Ruiz. Additionally, many of Colombia's cities have programs to raise awareness of natural disaster planning programs which have helped save lives in natural disasters. Near Nevado del Ruiz in particular, locals have become wary of volcanic activity: when the volcano erupted in 1989, more than 2,300 people living around it were evacuated.

Background
Armero, located 48 kilometers (30 mi) from the Nevado del Ruiz volcano and 169 kilometers (105 mi) from Colombia's capital of Bogotá, was the third largest town in Tolima Department, after Ibagué and Espinal. A prominent farming town before the eruption, it was responsible for roughly one-fifth of Colombia's rice production, and for a large share of the cotton, sorghum, and coffee crops. Much of this success can be attributed to Nevado del Ruiz, as the fertile volcanic soil had stimulated agricultural growth.  Built on top of an alluvial fan  that had been host to historic lahars, the town was previously destroyed by a volcanic eruption in 1595 and by mudflows in 1845. In the 1595 eruption, three distinct Plinian eruptions produced lahars that claimed the lives of 636 people. During the 1845 event, 1,000 people were killed by earthquake-generated mudflows near the Magdalena River.

Nevado del Ruiz has undergone three distinct eruptive periods, the first beginning 1.8 million years ago. During the present period (beginning 11,000 years ago), it has erupted at least twelve times, producing ashfalls, pyroclastic flows, and lahars. The historically recorded eruptions have primarily involved a central vent eruption (in the caldera) followed by an explosive eruption, then the formation of lahars. Ruiz's earliest identified Holocene eruption was in about 6660 BC, and further eruptions occurred around 1245, 850, 200 BC and in about 350, 675, in 1350, 1541 (perhaps), 1570, 1595, 1623, 1805, 1826, 1828 (perhaps), 1829, 1831, 1833 (perhaps), 1845, 1916, December 1984 through March 1985, 1987 through July 1991, and possibly in April 1994. Many of these eruptions involved a central vent eruption, a flank vent eruption, and a phreatic (steam) explosion.Ruiz is the second-most active volcano in Colombia after Galeras.

One week before the eruption, the Palace of Justice siege took place. The assailants (M-19 a Marxist, Terrorist Insurgency group) planned to hold a trial involving Colombian President Belisario Betancur. He refused to participate and sent the national army into the building. The attackers were holding several hundred hostages, including the 24 Supreme Court justices and 20 other judges. In the ensuing battle between the two forces, more than 75 hostages died (including 11 judges). This disaster, coupled with the Armero tragedy, spurred the Colombian government to predict and prepare for a broad range of threats.

1985 activity
In late 1984, geologists noticed that seismic activity in the area had begun to increase. Increased fumarole activity, deposition of sulfur on the summit of the volcano, and phreatic eruptions also alerted geologists to the possibility of an eruption. Phreatic events, when rising magma encounters water, continued well into September 1985 (one major event took place on September 11, 1985), shooting steam high into the air. Activity began to decline in October, probably because the new magma had finished ascending into Nevado del Ruiz's volcanic edifice.
An Italian volcanological mission analyzed gas samples from fumaroles along the Arenas crater floor and found them to be a mixture of carbon dioxide and sulfur dioxide, indicating a direct release of magma into the surface environment. Publishing a report for officials on October 22, 1985, the scientists determined that the risk of lahars was unusually high. To prepare for the eruption, the report gave several simple preparedness techniques to local authorities. Another team gave the local officials seismographs, but no instructions on how to operate them.

Volcanic activity increased again in November 1985 as magma neared the surface. Increasing quantities of gases rich in sulfur dioxide and elemental sulfur began to appear in the volcano. The water content of the fumaroles' gases decreased, and water springs in the vicinity of Nevado del Ruiz became enriched with magnesium, calcium and potassium, leached from the magma. The thermodynamic equilibration temperatures, corresponding to the chemical composition of the discharged gases, ranged from 200 to 600 °C (400 to 1,100 °F); this is a measure of the temperature at which the gases equilibrated within the volcano. The extensive degassing of the magma caused pressure to build up inside the volcano in the space above the magma, which eventually resulted in the explosive eruption.

Preparation and attempted evacuation
In September 1985, as earthquakes and phreatic eruptions rocked the area, local officials began planning for an evacuation. In October, a hazard map was finalized for the area around Nevado del Ruiz. This map highlighted the danger from falling material—including ash and rock—near Murillo, Santa Isabel, and Libano, as well as the threat of lahars in Mariquita, Guayabal, Chinchiná and Armero. Unfortunately, the map was poorly distributed to the people at high risk from Ruiz: many survivors had never heard of it, even though several of the country's major newspapers featured versions of the map. Henry Villegas of INGEOMINAS (Colombian Institute of Mining and Geology[es]) stated that the hazard maps clearly demonstrated that Armero would be affected by the lahars, but that the map "met with strong opposition from economic interests." He added that because the map was not prepared long before the eruption, mass production and distribution of it in time was difficult.
A recent hazard map prepared for Nevado del Ruiz and vicinity,
showing all of the major disaster zones affected by the eruption
At least one of the hazard maps published in the prominent El Espectador newspaper in Bogotá included glaring errors. Without proper graphic scaling, it was unclear how big the map's hazard zones really were. The lahars on the map did not have a distinct ending point, and the main threat seemed to be from pyroclastic flows, not from mudflows. Though the map was colored blue, green, red, and yellow, there was no key to indicate what each color represented, and Armero was located in the green zone (believed to indicate the safest area). Another map published by the El Tiempo newspaper featured illustrations which "gave a perception of topography to the public unfamiliar with maps, allowing them to relate hazard zones to the landscape." In spite of this presentation that was keyed to the audience, the map ended up a more artistic representation of the risk than a purely scientific one.

The day of the eruption, black ash columns erupted from the volcano at approximately 3:00 pm local time. The local Civil Defense director was promptly alerted to the situation. He contacted INGEOMINAS, which ruled that the area should be evacuated; he was then told to contact the Civil Defense directors in Bogotá and Tolima. Between 5:00 and 7:00 pm, the ash stopped falling, and local officials instructed people to "stay calm" and go inside. Around 5:00 pm an emergency committee meeting was called, and when it ended at 7:00 pm, several members contacted the regional Red Cross over the intended evacuation efforts at Armero, Mariquita, and Honda. The Ibagué Red Cross contacted Armero's officials and ordered an evacuation, which was not carried out because of electrical problems caused by a storm. The storm's heavy rain and constant thunder may have overpowered the noise of the volcano, and with no systematic warning efforts, the residents of Armero were completely unaware of the continuing activity at Ruiz. At 9:45 pm, after the volcano had erupted, Civil Defense officials from Ibagué and Murillo tried to warn Armero's officials, but could not make contact. Later they overheard conversations between individual officials of Armero and others; famously, a few heard the Mayor of Armero speaking on a ham radio, saying "that he did not think there was much danger", when he was overtaken by the lahar.

Eruption
At 9:09 pm, on November 13, 1985, Nevado del Ruiz ejected dacitic tephra more than 30 kilometers (20 mi) into the atmosphere. The total mass of the erupted material (including magma) was 35 million metric tons – only three percent of the amount that erupted from Mount St. Helens in 1980. The eruption reached 3 on the Volcanic Explosivity Index. The mass of the ejected sulfur dioxide was about 700,000 metric tons, or about two percent of the mass of the erupted solid material, making the eruption unusually sulfur rich.
Armero, the aftermath
The eruption produced pyroclastic flows that melted summit glaciers and snow, generating four thick lahars that raced down river valleys on the volcano's flanks, destroying a small lake that was observed in Arenas' crater several months before the eruption. Water in such volcanic lakes tends to be extremely salty, and may contain dissolved volcanic gases. The lake's hot, acidic water significantly accelerated the melting of the ice, an effect confirmed by the large amounts of sulfates and chlorides found in the lahar flow.

The lahars, formed of water, ice, pumice, and other rocks, incorporated clay from eroding soil as they traveled down the volcano's flanks. They ran down the volcano's sides at an average speed of 60 kilometers (40 mi) per hour, dislodging rock and destroying vegetation. After descending thousands of meters down the side of the volcano, the lahars followed the six river valleys leading from the volcano, where they grew to almost four times their original volume. In the Gualí River, a lahar reached a maximum width of 50 meters (160 ft).

Survivors in Armero described the night as "quiet". Volcanic ash had been falling throughout the day, but residents were informed it was nothing to worry about. Later in the afternoon, ash began falling again after a long period of quiet. Local radio stations reported that residents should remain calm and ignore the material. One survivor reported going to the fire department to be informed that the ash was "nothing".

During the night, the electrical power suddenly turned off and the radios went silent. Just before 11:30 pm, a huge stream of water swept through Armero; it was powerful enough to flip cars and pick up people. A loud roar could be heard from the mountain, but the residents were panicked over what they believed to be a flood.

At 11:30 pm, the first lahar hit, followed shortly by the others. One of the lahars virtually erased Armero; three-quarters of its 28,700 inhabitants were killed. Proceeding in three major waves, this lahar was 30 meters (100 ft) deep, moved at 12 meters per second (39 ft/s), and lasted ten to twenty minutes. Traveling at about 6 meters (20 ft) per second, the second lahar lasted thirty minutes and was followed by smaller pulses. A third major pulse brought the lahar's duration to roughly two hours; by that point, 85 percent of Armero was enveloped in mud. Survivors described people holding on to debris from their homes in attempts to stay above the mud. Buildings collapsed, crushing people and raining down debris. The front of the lahar contained boulders and cobbles which would have crushed anyone in their path, while the slower parts were dotted by fine, sharp stones which caused lacerations. Mud moved into open wounds and other open body parts – the eyes, ears, and mouth – and placed pressure capable of inducing traumatic asphyxia in one or two minutes upon people buried in it. Martí and Ernst state in their work Volcanoes and the Environment that they believe that many who survived the lahars succumbed to their injuries as they were trapped, or contracted hypothermia – though the latter is unlikely, given that survivors described the water as warm.

Another lahar, which descended through the valley of the Chinchina River, killed about 1,800 people and destroyed 400 homes in Chinchina. In total, more than 23,000 people were killed, approximately 5,000 were injured, and 5,000 homes throughout thirteen villages were destroyed. Some 230,000 people were affected, 27,000 acres (110 km2) were disrupted, and there were nearly 20,000 survivor-refugees. The Armero tragedy, as the event came to be known, was the second-deadliest volcanic disaster of the 20th century, surpassed only by the 1902 eruption of Mount Pelée, and is the fourth-deadliest volcanic eruption recorded since 1500 AD. It is also the deadliest lahar, and Colombia's worst natural disaster.

Impact
The loss of life was exacerbated by the lack of an accurate timeframe for the eruption and the unwillingness of local authorities to take costly preventative measures without clear signs of imminent danger. Because its last substantial eruption had occurred 140 years earlier, in 1845, it was difficult for many to accept the danger presented by the volcano; locals even called it the "Sleeping Lion."Hazard maps showing that Armero would be completely flooded after an eruption were distributed more than a month before the eruption, but the Colombian Congress criticized the scientific and civil defense agencies for scaremongering. The eruption occurred at the height of guerrilla warfare in Bogotá, Colombia's capital, and so the government and army were occupied at the time of the eruption.
The day after the eruption, relief workers were appalled at its impact. The lahars had left behind a gray mass which covered the entire town. Armero was dotted with broken trees and horribly disfigured human bodies. Debris from huts and homes protruded from beneath the gray mud. A few bags filled with crops were discovered in the mud. Workers described an acrid smell of "rotting bodies, [...] wood smoke and decaying vegetables." To the horror of these workers, who were scrambling to begin relief efforts, survivors let out moans of pain and agony. The damages were assessed at one billion dollars, an amount approximately one-fifth of Colombia's 1985 Gross National Product.

As news of the catastrophe spread around the world, the ongoing presidential election stopped, and the guerrilla fighters stopped their campaign "in view of the painful tragedy that has befallen our [the Colombian fighters] nation." Tickets for Colombian national championship soccer games added a surcharge of five cents to go to relief efforts.

Scientists who later analyzed the seismograph data noticed that several long-period earthquakes (which begin strongly and then slowly die out) had occurred in the final hours before the eruption. Volcanologist Bernard Chouet said that, "the volcano was screaming 'I'm about to explode'", but the scientists who were studying the volcano at the time of the eruption were not able to read the signal.

Relief efforts
The eruption occurred at the same time as the 1985 Mexico City earthquake, limiting the amount of supplies that could be sent to each of the disasters. Efforts were organized in Ibagué and Bogotá for Armero and in Cali for Chinchina, where medical teams gathered. Makeshift triage stations were established in Lerida, Guayabal, and Mariquita, and soon were overwhelmed with the sheer number of victims. The remaining victims were directed to Ibagué's hospitals, as local institutions had already been destroyed or were at risk from further lahars.

The US government spent over $1 million in aid, and US Ambassador to Colombia Charles S. Gillespie, Jr. donated an initial $25,000 to Colombian disaster assistance institutions. The Office of Foreign Disaster Assistance of the US Agency for International Development (AID) sent one member of the United States Geological Survey (USGS), along with an AID disaster-relief expert and 12 helicopters with support and medical personnel from Panama. The US subsequently sent additional aircraft and supplies, including 500 tents, 2,250 blankets, and several tent repair kits. Twenty-four other nations contributed to the rescue and assistance of survivors. Ecuador supplied a mobile hospital, and Iceland's Red Cross sent $4,650. The French government sent their own medical supplies with 1,300 tents. Japan sent $1.25 million, along with eight doctors, nurses, and engineers, plus $50,000 to the United Nations for relief efforts. Another $50,000 was donated by the Lions Clubs International Foundation.

Rescue efforts were hindered by the soft mud that was up to 4.6 meters (15 ft) deep in some places, making it virtually impossible for anyone to traverse it without sinking in. To make the situation worse, the highway connected to Armero and several bridges to it had been demolished by the lahars. It took twelve hours for the first survivors to be rescued, so those with serious but treatable injuries probably died before the rescuers arrived. Because Armero's hospital was destroyed in the eruption, helicopters moved survivors to nearby hospitals. Six local towns set up makeshift emergency relief clinics, consisting of treatment areas and shelters for the homeless. To help with the treatment, physicians and rescue teams came from all over the country. Of the 1244 patients spread over the clinics, 150 died from infection or associated complications. Had antibiotics been readily available and all of their lacerations been thoroughly cleaned, many of these people could have been saved.

On November 20, 1985, one week later, rescue efforts began to cease. Nearly 4,000 relief workers and rescue team members were still searching for survivors, with little hope of finding any. By then, the official death toll was registered at 22,540 people; additional counts showed that 3,300 were missing, 20,000 homeless, and 4,000 injured. Looters raided the ruins and survivors faced concerns of typhus and yellow fever. For most of the relief workers, their job was over.

The eruption was used as an example for psychiatric recuperation after natural disasters by Robert Desjarlais and Leon Eisenberg in their work World Mental Health: Problems and Priorities in Low-Income Countries. The authors were concerned that only initial treatment for the survivors' trauma was conducted. One study showed that the victims of the eruption suffered from anxiety and depression, which can lead to alcohol abuse, marital problems and other social issues. Rafael Ruiz, an Army Major who briefly served as Armero's provisional mayor after the disaster, stated that there were survivors who, due to the trauma of the event, were "jittery", experienced "nightmares", and suffered from "emotional problems." He added that the progress made by Christmas of 1985 was considerable, but that there was "still a long way to go."

Aftermath
A lack of preparation for the disaster contributed to the high death toll. Armero had been built on an alluvial fan that had been overrun by historic mudflows; authorities had ignored a hazard-zone map that showed the potential damage to the town from lahars. Residents stayed inside their dwellings to avoid the falling ash, as local officials had instructed them to do, not thinking that they might be buried by the mudflows.

The disaster gained international notoriety due in part to a photograph taken by photographer Frank Fournier of a young girl named Omayra Sánchez, who was trapped beneath rubble for three days before she died. Following the eruption, relief workers gathered around the girl, speaking with her and listening to her responses. She attracted the attention of the reporters at the site because of her sense of dignity and courage, and caused controversy when people wondered why the media workers had not saved her (which was impossible without equipment). An appeal to the government for a pump to lower the water around her was left unanswered, and she succumbed to gangrene and hypothermia after 60 hours of being trapped. Her death epitomized the tragic nature of the Armero disaster – she could have been saved had the government responded promptly and addressed the concerns over the volcano's potency. The photograph earned the World Press Photo of the Year for "capturing the event of greatest journalistic importance".

Two photographers from the Miami Herald won a Pulitzer Prize for photographing the effects of the lahar. Dr. Stanley Williams of Louisiana State University said that following the eruption, "With the possible exception of Mount St. Helens in the state of Washington, no other volcano in the Western Hemisphere is being watched so elaborately." In response to the eruption, the USGS Volcano Crisis Assistance Team was formed in 1986, and the Volcano Disaster Assistance Program. The volcano erupted several more times between 1985 and 1994.

Controversy
Concerns over the alleged negligence of local officials to alert locals of the volcano's threat led to controversy. The mayor of Armero (Ramon Rodriguez) and other local officials had tried to bring the volcano's potential to the attention of the Colombian government, but to no avail. For months, Rodriguez appealed to various officials, including congressmen and the Governor of Tolima Department. Rodriguez once referred to the volcano as a "time bomb" and told reporters that he believed an eruption would disrupt the natural dam above Armero, resulting in floods. Despite his persistence, only one congressman managed to inquire about the reality of the situation. Reports from the Colombian Minister of Mines, Minister of Defence, and Minister of Public Works "all asserted that the government was aware of the risk from the volcano and was acting to protect the population". The lack of responsibility for the disaster prompted lawmakers to campaign for Tolima's governor (Eduardo Alzate Garcia) to resign. In the media, similar thoughts and questions were hotly debated. One of the most aggressive campaigns came from a mass funeral in Ibagué for the victims, claiming that "The volcano didn't kill 22,000 people. The government killed them."

Legacy
The volcano continues to pose a serious threat to nearby towns and villages. Of the threats, the one with the most potential for danger is that of small-volume eruptions, which can destabilize glaciers and trigger lahars. Although much of the volcano's glacier mass has retreated, a significant volume of ice still sits atop Nevado del Ruiz and other volcanoes in the Ruiz–Tolima massif. Melting just 10 percent of the ice would produce lahars with a volume of up to 200 million cubic meters – similar to the lahar that destroyed Armero in 1985. In just hours, these lahars can travel up to 100 km along river valleys. Estimates show that up to 500,000 people living in the Combeima, Chinchina, Coello-Toche, and Guali valleys are at risk, with 100,000 individuals being considered to be at high risk. Lahars pose a threat to the nearby towns of Honda, Mariquita, Ambalema, Chinchina, Herveo, Villa Hermosa, Salgar and La Dorada. Although small eruptions are more likely, the two-million-year eruptive history of the Ruiz–Tolima massif includes numerous large eruptions, indicating that the threat of a large eruption cannot be ignored. A large eruption would have more widespread effects, including the potential closure of Bogotá's airport due to ashfall.

As the Armero tragedy was exacerbated by the lack of early warnings, unwise land use, and the unpreparedness of nearby communities, the government of Colombia created a special program, the Oficina Nacional para la Atención de Desastres (National Office for Disaster Preparedness), now known as the Dirección de Prevención y Atención de Desastres (Directorate for Disaster Prevention and Preparedness) – to prevent such incidents in the future. All Colombian cities were directed to promote prevention planning to mitigate the consequences of natural disasters, and evacuations due to volcanic hazards have been carried out. About 2,300 people living along five nearby rivers were evacuated when Nevado del Ruiz erupted again in 1989. When another Colombian volcano, Nevado del Huila, erupted in April 2008, thousands of people were evacuated because volcanologists worried that the eruption could be another "Nevado del Ruiz".

The lessons from the Armero tragedy have inspired a lahar warning system for Mt. Rainier, which has a similar potential for lahars.

Armero was never rebuilt after the tragedy. Instead, the survivors were relocated to the towns of Guayabal and Lérida, rendering Armero a ghost town.

Commemorations
A little less than one year later, Pope John Paul II flew over Armero and then visited Lérida's refugee camps with Colombian President Belisario Betancur. He spoke about the disaster and declared the site of Armero "holy land". Although many victims of the disaster were commemorated, Omayra Sanchez in particular was immortalized by poems, novels, and music pieces. One work (Adios, Omayra) by Eduardo Santa illustrated the girl's last days of life and her symbolism of the catastrophe. Survivors were also recognized in Germán Santa María Barragán's dramatized television special titled "No Morirás" (You Will Not Die). Much of the cast was composed of victims of the tragedy who appeared at the cast calls to be extras.

Source: Wikipedia