Earthquake in Samoan Islands

Earthquake Facts

1. The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on Good Friday, March 28, 1964 UTC.

2. The largest recorded earthquake in the world was a magnitude 9.5 (Mw) in Chile on May 22, 1960.

California

3. The earliest reported earthquake in California was felt in 1769 by the exploring expedition of Gaspar de Portola while the group was camping about 48 kilometers (30 miles) southeast of Los Angeles.

4. Before electronics allowed recordings of large earthquakes, scientists built large spring-pendulum seismometers in an attempt to record the long-period motion produced by such quakes. The largest one weighed about 15 tons. There is a medium-sized one three stories high in Mexico City that is still in operation.

5. The average rate of motion across the San Andreas Fault Zone during the past 3 million years is 56 mm/yr (2 in/yr). This is about the same rate at which your fingernails grow. Assuming this rate continues, scientists project that Los Angeles and San Francisco will be adjacent to one another in approximately 15 million years.

6. The East African Rift System is a 50-60 km (31-37 miles) wide zone of active volcanics and faulting that extends north-south in eastern Africa for more than 3000 km (1864 miles) from Ethiopia in the north to Zambezi in the south. It is a rare example of an active continental rift zone, where a continental plate is attempting to split into two plates which are moving away from one another.

P waves

7. The first "pendulum seismoscope" to measure the shaking of the ground during an earthquake was developed in 1751, and it wasn't until 1855 that faults were recognized as the source of earthquakes.

8. Moonquakes ("earthquakes" on the moon) do occur, but they happen less frequently and have smaller magnitudes than earthquakes on the Earth. It appears they are related to the tidal stresses associated with the varying distance between the Earth and Moon. They also occur at great depth, about halfway between the surface and the center of the moon.

9. Although both are sea waves, a tsunami and a tidal wave are two different unrelated phenomenona. A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth. A tsunami is a sea wave caused by an underwater earthquake or landslide (usually triggered by an earthquake) displacing the ocean water.

10. The hypocenter of an earthquake is the location beneath the earth's surface where the rupture of the fault begins. The epicenter of an earthquake is the location directly above the hypocenter on the surface of the earth.

Pacific Basin

11. The greatest mountain range is the Mid-Ocean Ridge, extending 64,374 km (40,000 mi) from the Arctic Ocean to the Atlantic Ocean, around Africa, Asia, and Australia, and under the Pacific Ocean to the west coast of North America. It has a greatest height of 4207 m (13,800 ft) above the base ocean depth.

12. The world's greatest land mountain range is the Himalaya-Karakoram. It countains 96 of the world's 109 peaks of over 7317 m (24,000 ft). The longest range is the Andes of South America which is 7564 km (4700 mi) in length. Both were created bythe movement of tectonic plates.

13. It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage.

14. It is thought that more damage was done by the resulting fire after the 1906 San Francisco earthquake than by the earthquake itself.

15. A seiche (pronounced SAYSH) is what happens in the swimming pools of Californians during and after an earthquake. It is "an internal wave oscillating in a body of water" or, in other words, it is the sloshing of the water in your swimming pool, or any body of water, caused by the ground shaking in an earthquake. It may continue for a few moments or hours, long after the generating force is gone. A seiche can also be caused by wind or tides.

mid-Atlantic Ridge

16. Each year the southern California area has about 10,000 earthquakes. Most of them are so small that they are not felt. Only several hundred are greater than magnitude 3.0, and only about 15-20 are greater than magnitude 4.0. If there is a large earthquake, however, the aftershock sequence will produce many more earthquakes of all magnitudes for many months.

17. The magnitude of an earthquake is a measured value of the earthquake size. The magnitude is the same no matter where you are, or how strong or weak the shaking was in various locations.
The intensity of an earthquake is a measure of the shaking created by the earthquake, and this value does vary with location.

18. The Wasatch Range, with its outstanding ski areas, runs North-South through Utah, and like all mountain ranges it was produced by a series of earthquakes. The 386 km (240-mile)-long Wasatch Fault is made up of several segments, each capable of producing up to a M7.5 earthquake. During the past 6000 years, there has been a M6.5+ about once every 350 years, and it has been about 350 years since the last powerful earthquake, which was on the Nephi segment.

19. There is no such thing as "earthquake weather". Statistically, there is an equal distribution of earthquakes in cold weather, hot weather, rainy weather, etc. Furthermore, there is no physical way that the weather could affect the forces several miles beneath the surface of the earth. The changes in barometric pressure in the atmosphere are very small compared to the forces in the crust, and the effect of the barometric pressure does not reach beneath the soil.

20. From 1975-1995 there were only four states that did not have any earthquakes. They were: Florida, Iowa, North Dakota, and Wisconsin.

21. The core of the earth was the first internal structural element to be identified. In 1906 R.D. Oldham discovered it from his studies of earthquake records. The inner core is solid, and the outer core is liquid and so does not transmit the shear wave energy released during an earthquake.

S Amer

22. The swimming pool at the University of Arizona in Tucson lost water from sloshing (seiche) caused by the 1985 M8.1 Michoacan, Mexico earthquake 2000 km (1240 miles) away.

23. Earthquakes occur in the central portion of the United States too! Some very powerful earthquakes occurred along the New Madrid fault in the Mississippi Valley in 1811-1812. Because of the crustal structure in the Central US which efficiently propagates seismic energy, shaking from earthquakes in this part of the country are felt at a much greater distance from the epicenters than similar size quakes in the Western US.

24. Most earthquakes occur at depths of less than 80 km (50 miles) from the Earth's surface.

25. The San Andreas fault is NOT a single, continuous fault, but rather is actually a fault zone made up of many segments. Movement may occur along any of the many fault segments along the zone at any time. The San Andreas fault system is more that 1300 km (800 miles) long, and in some spots is as much as 16 km (10 miles) deep.

26. The world's deadliest recorded earthquake occurred in 1556 in central China. It struck a region where most people lived in caves carved from soft rock. These dwellings collapsed during the earthquake, killing an estimated 830,000 people. In 1976 another deadly earthquake struck in Tangshan, China, where more than 250,000 people were killed.

27. Florida and North Dakota have the smallest number of earthquakes in the United States.

ocean-cont collision

28. The deepest earthquakes typically occur at plate boundaries where the Earth's crust is being subducted into the Earth's mantle. These occur as deep as 750 km (400 miles) below the surface.

29. Alaska is the most earthquake-prone state and one of the most seismically active regions in the world. Alaska experiences a magnitude 7 earthquake almost every year, and a magnitude 8 or greater earthquake on average every 14 years.

30. The majority of the earthquakes and volcanic eruptions occur along plate boundaries such as the boundary between the Pacific Plate and the North American plate. One of the most active plate boundaries where earthquakes and eruptions are frequent, for example, is around the massive Pacific Plate commonly referred to as the Pacific Ring of Fire.

31. The earliest recorded evidence of an earthquake has been traced back to 1831 BC in the Shandong province of China, but there is a fairly complete record starting in 780 BC during the Zhou Dynasty in China.

32. It was recognized as early as 350 BC by the Greek scientist Aristotle that soft ground shakes more than hard rock in an earthquake.

33. The cause of earthquakes was stated correctly in 1760 by British engineer John Michell, one of the first fathers of seismology, in a memoir where he wrote that earthquakes and the waves of energy that they make are caused by "shifting masses of rock miles below the surface".

34. In 1663 the European settlers experienced their first earthquake in America.

35. Human beings can detect sounds in the frequency range 20-10,000 Hertz. If a P wave refracts out of the rock surface into the air, and it has a frequency in the audible range, it will be heard as a rumble. Most earthquake waves have a frequency of less than 20 Hz, so the waves themselves are usually not heard. Most of the rumbling noise heard during an earthquake is the building and its contents moving.

36. When the Chilean earthquake occurred in 1960, seismographs recorded seismic waves that traveled all around the Earth. These seismic waves shook the entire earth for many days! This phenomenon is called the free oscillation of the Earth.

37. The origin of the name of the San Andreas Fault is often cited as the San Andreas Lake. However, based on some 1895 and 1908 reports by geologist A.C. Lawson, who named the fault, the name was actually taken from the San Andreas Valley. He likely did not realize at the time that the fault ran almost the entire length of California!

38. The interior of Antarctica has icequakes which, although they are much smaller, are perhaps more frequent than earthquakes in Antarctica. The icequakes are similar to earthquakes, but occur within the ice sheet itself instead of the land underneath the ice. Some of our polar observers have told us they can hear the icequakes and see them on the South Pole seismograph station, but they are much too small to be seen on enough stations to obtain a location.

How Plate Tectonics Works

Way back in 1912 a scientist by the name of Alfred Wegener came up with a crazy idea. He noticed that all of the continents seemed to fit together like the pieces of a giant puzzle. He thought, "Maybe they were once all joined together in a single, giant landmass that broke up and drifted apart over time?". He decided to give this supercontinent a name and called it Pangea, meaning, "all lands". At the time he presented his idea to the scientific community it came to be known as continental drift theory. Wegener was unable to find solid evidence to support his theory, so the other scientists laughed him off as a crackpot. One of his suggestions for the cause of continental drift was that centrifugal force from the rotation of the earth caused the continents to slide into each other and move around on the surface. They all calculated that there wasn't enough force generated by the earth's rotation to cause shifting of the crust and nobody took him seriously. They were all convinced the earth was rock-solid and immovable.

But then in 1929, along came a scientist named Arthur Holmes who didn't think that Wegener's theory of continental drift was too farfetched. "Now wait just a minute. Maybe he's got something here", he told them. He mentioned one of Wegener's other theories about the source of continental drift; the idea that the molten mantle beneath the earth's crust experiences thermal convection and that the movement of these convection currents in the mantle could cause an upwelling beneath the crust, forcing it to break apart and move. Now, that sounded like a semi-reasonable explanation for the movement of the earth's crust. As a matter of fact, if you looked closely at this idea it explained a lot of things, not just the continental puzzle idea. It also explained how mountain ranges were formed - by continents crashing into each other and 'rumpling up rock'. Still, the other scientists just nodded and said, 'Yeah. Fine. Whatever'. And the theory was neatly tucked away and ignored.

Scientists are trained to be skeptical. They were all waiting for a preponderance of evidence that backed up this harebrained theory.

Over the next thirty years a lot of new and surprise discoveries were made as new technologies were developed for exploring the ocean floor . The discovery of volcanic activity on the ocean floor in the middle of the Antlantic that turned out to be part of a long, unbroken mountain chain of undersea volcanoes was the most ground-breaking discovery that supported the theory of continental drift. Scientists developed instruments for measuring earthquake activity around the world and began plotting the locations of earthquakes. They all got together and started drawing a new map of the world that showed volcanic and seismic (earthquake) activity was concentrated along certain areas that looked like the margins of huge crustal plates. During the 1960s several scientists published papers that reviewed the preponderance of evidence that had been gathered for the theory of continental drift and it soon came to be known as the theory of plate tectonics. The evidence that supports the theory consists of the following discoveries;

Mid-ocean Ridges
A spreading boundary is where the tectonic plates are separating. Some spreading boundaries are places where the crust is sinking downward as it is stretched thin - like in the East Rift Valley of Africa, where the Dead Sea is located. Many of the spreading boundaries are located deep in the ocean on the sea floor. These are places where volcanic activity is at a premium because the crust is being torn apart. New crust is forming when magma from the mantle deep down is forced upward out of the cracks where the plates are coming apart. Long chains of undersea mounts (the world's longest is the mid-Atlantic Ocean Ridge) and volcanic islands typically characterize these type of plate margins.

Geomagnetic Anomalies
New rock formed from magma records the orientation of Earth's magnetic field at the time the magma cooled. By collecting and measuring samples of rock from various locations along the Mid-Atlantic Ridge, scientists have discovered that the newest, youngest crustal rocks are located in the center of the ridge, while the rocks get older as you move away from the ridge center. This supports the idea that oceanic crust continues to be pulled apart, while new crust is formed along the edges of the plates.

Deep Sea Trenches
At the same time, some of the oldest ocean crust occurs in deep sea trenches, which run parallel to continental mountain ranges. A lot of very large earthquakes have been plotted along deep ocean trenches, suggesting that these are seismically active areas (meaning the crust is moving). Scientists put two and two together, noting that the youngest oceanic crust was along the mid-ocean ridges and the oldest ocean crust was along the very bottoms of deep sea trenches. That neatly defined the edges of the tectonic plates and showed the direction of their movement. Where the deep sea trenches were found came to be called converging boundaries.

A converging boundary is the opposite of a spreading boundary. Typically you will see a converging boundary on a tectonic plate that is on the opposite side of a spreading boundary. As a plate moves in one direction it collides with the adjacent plate on its "front" end in a deep sea trench, while the trailing end of the plate is being pulled and stretched (spreading) from the plate on the other end at a mid-ocean ridge. For example, look at the Pacific plate. The entire plate is moving north and westward as the top edge converges with the North American and European plates. You can see the left side of the Pacific plate is converging with the Indian plate. Then if you look at the bottom and right edges of the plate you can see it's spreading apart from the Antarctic and Nazca plates.

Sometimes you'll see volcanic activity at converging boundaries where plates are crashing into each other. When one plate (usually the lighter continental crust) rides up over the top of the other it's called a subduction zone - because one plate margin is being subducted under the other.

A good example of this type of plate margin is where the Nazca and South American plates are crashing into each other. The lighter continental South American plate is riding up over the heavier oceanic Nazca plate. Deep down where the leading edge of the Nazca plate is diving down under the South American plate it's making contact with the molten magma of the earth's mantle. The long cordillera, or chord-like chain of volcanic mountains known as the Andes, are a result of the rumpling of the South American plate where the Nazca plate crashes into it, and the volcanoes that have formed from the increased seismic activity on the Nazca plate margin deep down.

In other converging boundaries, there is no volcanic activity because the tectonic plates are both continental plates, weighing the same. No subduction happens along these margins, just massive deformation of the edges of the plates. A good example of this is the Himalayan Mountains where the European and Indian plates meet. The two plates have continued ramming into each other, causing the crust to buckle, wrinkle, and uplift into the highest mountain range on earth.

The few transverse boundaries are places where the two plates are just sliding past each other. In many of these boundaries there is a lot of tension and strain where the two plates are sliding and scraping past each other. The resulting strain from the sliding action of the plates causes cracks in the crust called faults. As the larger plates move past each other some chunks of crust and overlying rock are broken into fault blocks. When there is a big enough movement along the cracks or faults in the earth's crust we feel it in the form of earthquakes.

One of the most famous faults is the San Andreas, which runs along the west coast of California. It's famous for generating many of the larger quakes in California, including the world-renowned San Francisco earthquake of 1906. Funny thing is, the 1906 earthquake itself didn't do nearly as much damage as the fires that burned the city afterwards - all the water mains had burst and broken during the 'quake so there was no water to put out the fires!

Hot Spots

About 30 years ago a Geophysicist named J. Tuzo Wilson came up with an idea to explain why there was volcanic activity out in the middle of the Pacific Ocean, in the middle of the huge Pacific Plate. At the time, scientists thought that volcanoes only happened at plate boundaries, but nobody could explain why they were happening out in the middle of a tectonic plate. Dr. Wilson said that there are "hot spots", under the earth's crust in some places. These are called hot spots because they are places where a lot of heat is concentrated in a small area. The heat causes the overlying rock to melt. Since the magma is liquid and is lighter than the surrounding rock it "floats" to the surface and forces its way out of fissures in the crust. once magma erupts through the crust it is known as lava. Over time, the continual outpouring of lava can form a sea mount or island volcano if the hot spot is under the ocean floor, as in the case of the Hawaiian Islands. There is just one hot spot that never moves. But the Pacific Plate continually (and slowly) moves north over the hot spot, forming a new volcano on the overlying plate each time.
Doing the Science

Scientists had a lot of questions about why there were volcanic islands way out in the middle of the Pacific plate. It just didn't seem to fit in with their theory of plate tectonics. Dr. Wilson's idea of hot spots helped the island volcanoes to fit into the theory of plate tectonics. If the Pacific plate was moving over a hot spot, then that would explain why a chain of sea mounts and volcanoes had formed as the plate moved. If this was true, then the volcanoes should be of different ages, from oldest to youngest in a single direction.

In order to test his theory, Dr. Wilson took samples of volcanic rock from each of the volcanic islands in the Hawaiian chain and tested them to see how old they were on a geologic time scale. He found that the oldest rocks were from the northernmost island of Kauai, which also had the most weathering of rock. He also found that progressively younger rocks were found on the Hawaiian islands the further south he went (see map). The youngest rocks of all were found on the big island of Hawaii, the southernmost island. In fact, new "rocks" are still forming on the island of Hawaii, making it the youngest volcano in the island chain. There is even more evidence to support his theory because there is a new volcano forming on the sea floor south of Hawaii, called Loihi. Right now it's just a sea mount, but if the lava continues to build up on its slopes, someday it will be a new island.

w Old Is the Earth?

In the very beginning of earth's history, this planet was a giant, red hot, roiling, boiling sea of molten rock - a magma ocean. The heat had been generated by the repeated high speed collisions of much smaller bodies of space rocks that continually clumped together as they collided to form this planet. As the collisions tapered off the earth began to cool, forming a thin crust on its surface. As the cooling continued, water vapor began to escape and condense in the earth's early atmosphere. Clouds formed and storms raged, raining more and more water down on the primitive earth, cooling the surface further until it was flooded with water, forming the seas.

It is theorized that the true age of the earth is about 4.6 billion years old, formed at about the same time as the rest of our solar system. The oldest rocks geologists have been able to find are 3.9 billion years old. Using radiometric dating methods to determine the age of rocks means scientists have to rely on when the rock was initially formed (as in - when its internal minerals first cooled). In the infancy of our home planet the entire earth was molten (melted) rock - a magma ocean.

Since we can only measure as far back in time as we had solid rock on this planet, we are limited in how we can measure the real age of the earth. Due to the forces of plate tectonics, our planet is also a very dynamic one; new mountains forming, old ones wearing down, volcanoes melting and reshaping new crust. The continual changing and reshaping of the earth's surface that involves the melting down and reconstructing of old rock has pretty much eliminated most of the original rocks that came with earth when it was newly formed. So the age is a theoretical age.

When Did Life on Earth Begin?

Scientists are still trying to unravel one of the greatest mysteries of earth: When did "life" first appear and how did it happen? It is estimated that the first life forms on earth were primitive, one-celled creatures that appeared about 3 billion years ago. That's pretty much all there was for about the next two billion years. Then suddenly those single celled organisms began to evolve into multicellular organisms. Then an unprecedented profusion of life in incredibly complex forms began to fill the oceans. Some crawled from the seas and took residence on land, perhaps to escape predators in the ocean. A cascading chain of new and increasingly differentiated forms of life appeared all over the planet, only to be virtually annihilated by an unexplained mass extinction. It would be the first of several mass extinctions in Earth's history.
Where do Gemstones come from?

Scientists have been looking increasingly to space to explain these mass extinctions that have been happening almost like clockwork since the beginning of "living" time. Perhaps we've been getting periodically belted by more space rocks (ie. asteroids), or the collision of neutron stars happening too close for comfort? Each time a mass extinction occurred, life found a way to come back from the brink. Life has tenaciously clung to this small blue planet for the last three billion years. Scientists are finding new cues as to how life first began on earth in some really interesting places - the deep ocean.

Checking the Fossil Record

Geologic History of Earth
What is Plate Tectonics?
Extreme Weather
The Moon
The Sun
Solar System

Scientists have studied rocks using radiometric dating methods to determine the age of earth. Another really cool thing they've found in rocks that tells us more about the story of earth's past are the remains of living creatures that have been embedded in the rocks for all time. We call these fossils. It has been the careful study of earth's fossil record that has revealed the exciting picture about the kinds of creatures that once roamed this planet. Fossilized skeletons of enormous creatures with huge claws and teeth, ancient ancestors of modern day species (such as sharks) that have remained virtually unchanged for millions of years, and prehistoric jungles lush with plant life, all point to a profusion of life and a variety of species that continues to populate the earth, even in the face of periodic mass extinctions.

By studying the fossil record scientists have determined that the earth has experienced very different climates in the past. In fact, general climactic conditions, as well as existing species, are used to define distinct geologic time periods in earth's history. For example, periodic warming of the earth - during the Jurassic and Cretaceous periods - created a profusion of plant and animal life that left behind generous organic materials from their decay. These layers of organic material built up over millions of years undisturbed. They were eventually covered by younger, overlying sediment and compressed, giving us fossil fuels such as coal, petroleum and natural gas.

Alternately, the earth's climate has also experienced periods of extremely cold weather for such prolonged periods that much of the surface was covered in thick sheets of ice. These periods of geologic time are called ice ages and the earth has had several in its history. Entire species of warmer-climate species died out during these time periods, giving rise to entirely new species of living things which could tolerate and survive in the extremely cold climate. Believe it or not, humans were around during the last ice age - the Holocene (about 11,500 years ago) - and we managed to survive. Creatures like the Woolly Mammoth - a distant relative of modern-day elephants - did not.

Read about a really exciting recent find of a perfectly-preserved, frozen Woolly Mammoth! This was a particularly exciting find because it wasn't a fossil that scientists found, but actual tissue, which still has its DNA record intact.

Also, read more about the Ice Man - another frozen tissue sample of a human being who was frozen into the high mountains of France. He was just recently discovered as thousands of years of ice pack have finally melted from around his body.



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.


Meet Dr. Zeb Hogan here on Extreme Science...
The Amazon - Home of Extremes
The Amazon River is not only the greatest in the world, it is home to many other "Extremes" Arapaima is one of the largest freshwater fish in the worldof 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. (Read about the biggest freshwater fish in the world.)




Amazon River, Brazil (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!

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.



A Really "Cool" Place to Be a Scientist

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.
Antarctic Snowscape, Antarctica Buy this Antarctica Print at AllPosters.com

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.



Why is it Called the Dead Sea?
Satellite image of Dead Sea
Satellite view of the Dead Sea. NASA.

Sounds kinda creepy, doesn't it? The name 'Dead Sea' is actually a kinder, gentler translation from the Hebrew name 'Yam ha Maved', which means, 'Killer Sea'. It is some of the saltiest water anywhere in the world, almost six times as salty as the ocean! The Dead Sea is completely landlocked and it gets saltier with increasing depth. The surface, fed by the River Jordan, is the least saline. Down to about 130 feet (40 meters), the seawater comprises about 300 grams of salt per kilogram of seawater. That's about ten times the salinity of the oceans. Below 300 feet, though, the sea has 332 grams of salt per kilogram of seawater and is saturated. Salt precipitates out and piles up on the bottom of the sea.

There are no fish or any kind of swimming, squirming creatures living in or near the water. There are, however, several types of bacteria and one type of algea that have adapted to harsh life in the waters of the Dead Sea. What you'll see on the shores of the Sea is white, crystals of salt covering EVERYTHING. And this is no ordinary table salt, either. The salts found in the Dead Sea are mineral salts, just like you find in the oceans of the world, only in extreme concentrations. The water in the Dead Sea is deadly to living things. Fish accidentally swimming into the waters from one of the several freshwater streams that feed the Sea are killed instantly, their bodies quickly coated with a preserving layer of salt crystals and then tossed onto shore by the wind and waves. Brutal!

Floating in the Dead SeaThe guy to the left is actually floating in the Dead Sea. "But, hey, I thought you said the Dead Sea was DEADLY!" Not to us. Humans are remarkably adaptable. We can swim in the Dead Sea, just like we can swim in the ocean. Well, people don't really "swim" in the Dead Sea - they just "hang out". That's what's so cool about the Dead Sea. Because of the extremely high concentration of dissolved mineral salts in the water its density is way more than that of plain old fresh water. What this means is our bodies are more buoyant in the Dead Sea - so you bob like a cork. In fact, people are so buoyant in this water, it makes it kinda tough to actually swim. Most people like to just kick back in the water and read. It almost looks as though this guy is sitting on an air mattress that has sunk below the surface, but he's not. He's really just floating, without having to hold is feet in that position! If you think this is easy, try floating like this in a freshwater swimming pool.

What Caused the Dead Sea to Form?

This lesson takes us back to the subject of plate tectonics. In this part of the world there is a rift forming where two crustal plates are spreading apart. The East Rift Valley runs through most of Africa, but it starts north of the Dead Sea and runs south along the eastern side of the continent. The Sea is located right along the Rift Valley where the earth's crust is being stretched thin. To get an idea of how this "crustal spreading" thing works, take a bar of taffy, or taffy-like candy and try to pull it apart. You'll see where the candy starts to come apart it gets really thin just before it breaks. That's what is happening to the earth's crust in the Rift Valley. Where the earth's crust gets thin that part of the surface sinks downward. Look at the picture at left to see how the rift forms, sinking downward where the crust is stretched thin. You know what? The Dead Sea is still sinking lower, even today. Scientists figure that the Dead Sea lowers by as much as 13 inches per year. On a geologic time scale that's incredibly fast!
Why is the Dead Sea so Salty?

We talked about how the surface of the Sea got down so low in elevation, but why is it so salty? All roads lead to the Sea when it comes to the rivers in the area. The Dead Sea is continually fed water from the rivers and streams coming down off the mountains that surround it. But the kicker is this....no rivers drain out of the Dead Sea. The only way water gets out of the Sea is through evaporation. And boy does it evaporate! This part of the world get plenty hot. When thewater evaporates, it leaves behind all the dissolved minerals in the Sea, just making it saltier. In fact, it's through the dual action of; 1) continuing evaporation and 2) minerals salts carried into the Sea from the local rivers, that makes the Sea so salty. The fact that the water doesn't escape the Sea just traps the salts within its shores. There's nothing living in the Dead Sea because it got so salty, so quickly, that evolution has not had a chance to produce any creatures that could adapt to such brutal conditions.



How Hot is Hot?
There are many places on earth that are plenty hot - record-breaking hot. In fact, there's a good chance on the day this record-breaking temperature was recorded by a meteorological station in El Azizia in 1922 there were other places hundreds of miles away that were even hotter. In all likelihood, this record temperature has been exceeded since then in many places on earth, but we have no official records of the temperatures. It is important to note that when atmospheric temperatures are recorded it is not the surface temperature, where it can sometimes reach 150° F/ 66° C, but rather the air temperature at about 5 feet (1.6 m) above the surface in an enclosed shelter. Of course, it's important that the temperature sensor is not exposed to direct sunlight - the shelter is louvered to permit air flow across the sensor. Most humans don't 'hang out' where some of the hottest tempertatures on earth are regularly experienced so there aren't a lot of meterological stations in these places to reliably record extreme temperatures.

Desert Lands

As big as the earth is, over two thirds of its surface is covered in water from the oceans. The remaining one-third of the earth's surface is exposed as dry land for us to live on, but a third of that dry land is really dry. In fact, it's inhospitable desert. Much of the deserts in the world are clustered between 5 to 30 degrees north and south of the equator, in what are called subtropical zones. Scientists have theorized that these desert belts are due to two things:
1) Heat (read more about the Sun)
2) Lack of moisture
Duh? Anybody who's ever been outside on a hot summer day, all day, knows that. Just about every continent on earth that is inhabited by humans experiences seasonal weather changes, with a distinct winter and summer. Just because there's hot, dry weather during the summer, doesn't mean that where you live is going to turn into a desert. What makes the desert so hot and dry is the climactic conditions that are sustained almost continually, year round. Any part of the world that's hot and dry for long enough periods throughout the year won't be able to support much plant or animal life. Living things need water to survive.

Why is it so Dry All the Time?

First, the air in the earth's atmosphere is warmest around the equator (because the sun reaches the earth at a direct 90° angle) so that warmer air rises and flows north and south of the equator. As the air "piles" up in the northern and southern latitudes, these zones of "piled-high" warm air become permanent high pressure zones. As the air at the "bottom of the pile" descends toward the earth it gets warmed up even more. Because this descending warm air has no clouds (i.e., condensing water vapor), that allows the burning sun to go right through the air and heat the land mass below even more. Hence, extreme heat.

Where's the coldest place on earth?

Warm air can hold a lot more moisture (water vapor) than colder air. Unless this really warm air contacts some much cooler air (or cooler land mass), there's nothing to coax the moisture out of the air in the form of precipitation (rain, fog). Hence, lack of moisture.
What Goes Around, Comes Around

This hot air moves northward and southward of the equator, almost continuously in the form of reliable winds called the Trade Winds. As these warm winds circulate back around towards the equator they rise into the upper atmosphere again, cooling. The water vapor in the cooling air mass condenses and rains, and rains and rains all over the equator in the Tropical zones. All this rain makes the land mass around the equator the lushest, wettest, most densely forested in the world (plants love water!). It's ironic that the wettest and hottest places in the world occur within just a few thousand miles of each other.

Though the hottest place in the world, El Azizia, is a desert, not all deserts are hot. Antarctica, for example, is the driest continent on earth, getting less than 4 in/10cm of precipitation a year. What characterizes or defines a desert is the lack of precipitation - less than 10 in/25.4cm per year. In the Antarctic, there is very little precipitation in the form of rain or snow. Even though there's water, water everywhere it's locked up in the form of ice.



Even the Driest Place on Earth has Water

The Atacama desert is found along the coast of Chile, South America - right next to the Pacific Ocean - the biggest body of water in the world. Much of the desert extends up into the Andes mountains and is very high in elevation. Unlike more familiar deserts, like the Sahara desert in Africa and the Mojave in California, the Atacama is actually a pretty cold place, with average daily temperatures ranging between 0°C and 25°C. The annual rainfall (or lack of it) defines a desert, but that doesn't mean that it never rains in Atacama. Every so often a warming effect over the Pacific Ocean around the equator changes the weather the world over and even places like the driest desert in the world can become doused with drenching storms. Even though Atacama gets almost no rainfall, there is water in this arid place and you'll find it in the following places:
Salt Lakes

During years of heavy rainfall in the distant past, enough water accumulated in basins found throughout the Andes to create lakes. Some of the lakes got their water from melting glaciers at the end of the last ice age. But in some lakes in the Andes mountains, such as Atacama, more water is lost through evaporation than is replaced by rainfall so the lakes are drying up. As the water evaporates, the mineral salts in the water become more concentrated, creating very salty water.
Snow

In the higher elevations when precipitation comes to Atacama snow falls instead of rain. There are small patches of unmelted snow in the mountain tops where in never gets warm enough to melt the snow.
Underground

Anywhere you go in the world, regardless of how much or little it rains, there is always water underground. After it rains, some of the rainwater evaporates back into the air, but much of it trickles down into the ground and stays there - even in the desert. How much water and where depends on a number of things; soil composition, air and soil surface temperature, amount and frequency of rainfall/precipitation, and drainage. Since the Andes is a volcanically active mountain range, the magma beneath the ground will heat the groundwater in certain places causing geysers to erupt.

Fog and Dew
mummy
This mummy of a girl is from the Atacama Desert. Her remains are estimated to be about 800 years old. Find out more about mummies.

Most of the precipitation that comes to the Atacama is in the form of fog that blows in the from the Pacific. Fog is essentially very low clouds, consisting of water vapor cooling and beginning to condense. If you've ever been in fog you know that it can leave you a little moist. When the air temperature reaches dew point the water vapor in the air condenses to leave little droplets of water behind. The few things that are able to survive in the Atacama live on the combined moisture from fog and dew.

Where's the wettest place on earth?

Does Anything Live There?

Many people have the view that deserts are places forsaken by Mother Nature and that no living thing would possibly want to set up camp in a place so dry. Although it is tough to find anything living in the Atacama there are isolated pockets and small patches of plants, which support life for animals and insects. Some plant species have adapted well to this dry environment by developing tap roots that run very deep into the ground gathering water from below. There are flocks of flamingos that live in and around the salt lakes feeding on red algae that grows in the waters. There are even people living in the Atacama.

There is a town called Calama in the desert which is complete with motels, restaurants and shops, but it is definitely not the norm. For the most part, Atacama is a pretty lonely place. Humans have lived in the Atacama for many thousands of years, based on the cultural relics and artifacts that archaeologists have found. The South American Indians who have set up housekeeping in the desert over the millennia have left relics from their culture and even themselves. Because the Atacama is so bone-dry the bodies of the buried indians have dried perfectly preserved turning them into mummies. Some of the oldest mummies found anywhere on earth have come from the Atacama Desert and have been dated to be 9,000 years old!

What Causes Deserts?

One reason is that the high atmospheric pressure in this region over the Andes can cause dry, cold air from the upper altitudes to compress and come down to earth. This dry air has almost no water vapor so it can be easily heated by the sun, causing high ground temperatures with very low humidity.rainshadow effect

Another reason that the Atacama doesn't get enough rainfall is because of a phenomenon called rainshadow. The warm, moist tropical air that blows on the tradewinds from the east, which douse the South American rainforest, get hung-up on the east side of the Andes. The mountains are so high in altitude that the air cools, condenses and rains (or snows) on the mountains. As the air descends the other side of the mountain range it warms, holding in its moisture preventing rain from falling on to the ground below.

This is one of the reasons why the Amazon basin and river are the largest anywhere in the world. The mountains that cause the Amazon to be the largest river from collecting all the rainfall are also responsible for preventing the Atacama from ever receiving any rainfall. The driest and one of the wettest places in the world are right next to each other!



World Famous Extremes

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! Approximately 6,000 climbers have attempted the summit of Everest, but only 2,249 have made it. Over 200 people have died trying and of those, at least 120 bodies are still missing on the mountain.
Highest Mountains

Mount 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 name of the mountain in Nepal is Sagarmatha, which means "goddess of the sky". 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 look at a 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!
Convergent boundary
The Himalayan Mountains are forming where two tectonic plates are crashing into each other, known as a convergent boundary.

Need more earth science information? Read about the geologic history of earth.
How Do They Know?

Scientists know this because they've been measuring the increasing height of the mountains. There have also been a lot of earthquakes recorded down deep in the mountains, which indicates continuing movement. The Himalayas are growing, but only about 2 inches a year. That's not very much in human terms, but imagine how much that would be over millions of years! You may be thinking, "That would have been kinda cool to be here on earth 40 million years ago to be able to watch the Himalayas forming". You would have been really bored, though. The movement that took many millions of years to form the mountain range is still taking place today, and I doubt you would stake out a camp at the foot of the mountains just to watch them grow. You'd be waiting a LONG TIME.



A Land of Contrasts

It's ironic that the wettest place in the world manages to thirst for water each winter when no rain falls at all for months at a time. The type of weather phenomenon that brings so much rain to this part of the world is called the monsoons. Monsoons are seasonal winds that blow from one direction for approximately six months, bringing torrential rains, and then blow from the opposite direction for the remaining six months, during which little rain falls. During the wet season moist air is cooled as it blows over rising land, letting abundant rain fall on the windward side of mountain ranges. But because of widespread destruction of conifer forests that protected the soil, the ground does not absorb the rain that falls so heavily during the monsoon season. The city of Cherrapunji is 1290 meters above sea level and much of the torrential rains run off the mountains into the valley below. The irrigation system for the town of Cherrapunji is insufficient to provide adequate amounts of clean, potable water from below during the dry season. People who live there frequently have to travel on foot for several kilometers to bathe and get drinking water.
What Causes so much Rainfall?

The oceans are the chief source of rain, but lakes and rivers also contribute to it. The sun's heat evaporates the water. It remains in the atmosphere as an invisible vapor until it condenses, first into clouds and then into raindrops. Condensation happens when the air is cooled. For raindrops to form there must be particulate matter in the air, such as dust or salt, at temperatures above freezing. These particles are called condensation nuclei. When the nuclei are cooled to temperatures below the freezing point, water condenses around them in layers. The particles become so heavy they resist updrafts and fall through the clouds as rain.

In Cherrapunji it rains so much for two reasons:

Elevation: because of the elevation of Cherrapunji, air that blows over the plains below is cooled as it rises to the higher elevation. This cooling of the air causes the moisture trapped in the air to condense, forming clouds, which then release rain.

Monsoons: the prevailing winds in that part of the world are very heavily laden with moisture. The constant supply of moist air for six months straight results in almost continual rainfall.



A Land of Contrasts

It's ironic that the wettest place in the world manages to thirst for water each winter when no rain falls at all for months at a time. The type of weather phenomenon that brings so much rain to this part of the world is called the monsoons. Monsoons are seasonal winds that blow from one direction for approximately six months, bringing torrential rains, and then blow from the opposite direction for the remaining six months, during which little rain falls. During the wet season moist air is cooled as it blows over rising land, letting abundant rain fall on the windward side of mountain ranges. But because of widespread destruction of conifer forests that protected the soil, the ground does not absorb the rain that falls so heavily during the monsoon season. The city of Cherrapunji is 1290 meters above sea level and much of the torrential rains run off the mountains into the valley below. The irrigation system for the town of Cherrapunji is insufficient to provide adequate amounts of clean, potable water from below during the dry season. People who live there frequently have to travel on foot for several kilometers to bathe and get drinking water.
What Causes so much Rainfall?

The oceans are the chief source of rain, but lakes and rivers also contribute to it. The sun's heat evaporates the water. It remains in the atmosphere as an invisible vapor until it condenses, first into clouds and then into raindrops. Condensation happens when the air is cooled. For raindrops to form there must be particulate matter in the air, such as dust or salt, at temperatures above freezing. These particles are called condensation nuclei. When the nuclei are cooled to temperatures below the freezing point, water condenses around them in layers. The particles become so heavy they resist updrafts and fall through the clouds as rain.

In Cherrapunji it rains so much for two reasons:

Elevation: because of the elevation of Cherrapunji, air that blows over the plains below is cooled as it rises to the higher elevation. This cooling of the air causes the moisture trapped in the air to condense, forming clouds, which then release rain.

Monsoons: the prevailing winds in that part of the world are very heavily laden with moisture. The constant supply of moist air for six months straight results in almost continual rainfall.



A Land of Contrasts

It's ironic that the wettest place in the world manages to thirst for water each winter when no rain falls at all for months at a time. The type of weather phenomenon that brings so much rain to this part of the world is called the monsoons. Monsoons are seasonal winds that blow from one direction for approximately six months, bringing torrential rains, and then blow from the opposite direction for the remaining six months, during which little rain falls. During the wet season moist air is cooled as it blows over rising land, letting abundant rain fall on the windward side of mountain ranges. But because of widespread destruction of conifer forests that protected the soil, the ground does not absorb the rain that falls so heavily during the monsoon season. The city of Cherrapunji is 1290 meters above sea level and much of the torrential rains run off the mountains into the valley below. The irrigation system for the town of Cherrapunji is insufficient to provide adequate amounts of clean, potable water from below during the dry season. People who live there frequently have to travel on foot for several kilometers to bathe and get drinking water.
What Causes so much Rainfall?

The oceans are the chief sour

my God! what a very long comment..

That's quite a massive earthquake. It's great to hear that no damage has been reported. Safety is a number one priority. Hopefully they're doing everything they can to preserve it.

Thats a massive article and massive earthquake hahah. However, glad to see for the most part that people were safe and sound from that hard hitting earthquake!

Wow, Zareen71--that is undoubtedly the longest comment--ever!

that is the longest comment ever! lol- you could have written an article instead however it was real informative!

wow that is big

wow, what a comment lol

Wow

It is good that there is no damage caused by this tsunami. Hopefully, none ever

I hope there is minimal damage and that it calms down before reaching shore. I am sure it is terrifying to be on any of those Islands right now.

hope that there will be no casualties, thank god that most of them, are safe

I got dizzy readin' all that info.

I only hope that there were no casualties, this kind of earthquake is really scary and very alarming...