PIEZOELECTRICITY - Piezoelectricity is the process of using crystals to convert mechanical energy into electrical energy, or vice versa. Regular crystals are defined by their organized and repeating structure of atoms that are held together by bonds - this is called a unit cell. Most crystals, such as iron have a symmetrical unit cell, which makes them useless for piezoelectric purposes. There are other crystals that get lumped together as piezoelectric materials. The structure in these crystals aren’t symmetrical but they still exist in an electrically neutral balance. However, if you apply mechanical pressure to a piezoelectric crystal, the structure deforms, atoms get pushed around, and suddenly you have a crystal that can conduct an electrical current. If you take the same piezoelectric crystal and apply an electric current to it, the crystal will expand and contract, converting electrical energy into mechanical energy.

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Piezoelectricity

Quartz crystal.

How Piezoelectricity Works

Cesca Fleischer

Feel the Squeeze: How Piezoelectricity Works to Make Crystals Conduct Electric Current

Piezo what? It sounds like a lot to take in, but it’s simple to understand.

The word piezoelectric originates from the Greek word piezein, which literally means to squeeze or press.

Instead of squeezing grapes to make wine, we’re squeezing crystals to make an electric current!

Piezoelectricity is found in a ton of everyday electronic devices, from quartz watches to speakers and microphones.

In a nutshell:

Piezoelectricity is the process of using crystals to convert mechanical energy into electrical energy, or vice versa.

Regular crystals are defined by their organized and repeating structure of atoms that are held together by bonds - this is called a unit cell.

Most crystals, such as iron have a symmetrical unit cell, which makes them useless for piezoelectric purposes.

There are other crystals that get lumped together as piezoelectric materials.

The structure in these crystals aren’t symmetrical but they still exist in an electrically neutral balance.

However, if you apply mechanical pressure to a piezoelectric crystal, the structure deforms, atoms get pushed around, and suddenly you have a crystal that can conduct an electrical current.

If you take the same piezoelectric crystal and apply an electric current to it, the crystal will expand and contract, converting electrical energy into mechanical energy.

Types of Piezoelectric Materials

There are a variety of piezoelectric materials that can conduct an electric current, both man-made and natural.

The most well-known, and the first piezoelectric material used in electronic devices is the quartz crystal.

Other naturally occurring piezoelectric materials include cane sugar, Rochelle salt, topaz, tourmaline, and even bone.

As piezoelectric technology started to take off after World War I we began developing man-made materials to rival the performance of quartz.

Man-made piezoelectric materials include:

PZT is made from lead zirconate titanate and can produce more voltage than quartz with the same amount of mechanical pressure.

Barium Titanate is a ceramic piezoelectric material that was discovered during World War II and is known for its long-lasting durability.

Lithium Niobate is a material that combines oxygen, lithium, and nobium together in a ceramic material that performs similar to barium titanate.

How Piezoelectricity Works

We have specific materials that are suited for piezoelectricity applications, but how exactly does the process work? With the Piezoelectric Effect.

The most unique trait of this effect is that it works two ways. You can apply mechanical energy or electrical energy to the same piezoelectric material and get an opposite result.

Applying mechanical energy to a crystal is called a direct piezoelectric effect and works like this:

1.      A piezoelectric crystal is placed between two metal plates. At this point the material is in perfect balance and does not conduct an electric current.

2.      Mechanical pressure is then applied to the material by the metal plates, which forces the electric charges within the crystal out of balance. Excess negative and positive charges appear on opposite sides of the crystal face.

3.      The metal plate collects these charges, which can be used to produce a voltage and send an electrical current through a circuit.

That’s it, a simple application of mechanical pressure, the squeezing of a crystal and suddenly you have an electric current.

You can also do the opposite, applying an electrical signal to a material as an inverse piezoelectric effect. 

It works like this:

1.      In the same situation as the example above, we have a piezoelectric crystal placed between two metal plates. The crystal’s structure is in perfect balance.

2.      Electrical energy is then applied to the crystal, which shrinks and expands the crystal’s structure.

3.      As the crystal’s structure expands and contracts, it converts the received electrical energy and releases mechanical energy in the form of a sound wave.

The inverse piezoelectric effect is used in a variety of applications. Take a speaker for example, which applies a voltage to a piezoelectric ceramic, causing the material to vibrate the air as sound waves.

The Discovery of Piezoelectricity

Piezoelectricity was first discovered in 1880 by two brothers and French scientists, Jacques and Pierre Curie.

While experimenting with a variety of crystals, they discovered that applying mechanical pressure to specific crystals like quartz released an electrical charge. They called this the piezoelectric effect.

The next 30 years saw Piezoelectricity reserved largely for laboratory experiments and further refinement.

It wasn’t until World War I when piezoelectricity was used for practical applications in sonar.

Sonar works by connecting a voltage to a piezoelectric transmitter. This is the inverse piezoelectric effect in action, which converts electrical energy into mechanical sound waves.

The sound waves travel through the water until they hit an object. They then return back to a source receiver.

This receiver uses the direct piezoelectric effect to convert sound waves into an electrical voltage, which can then be processed by a signal processing device.

Using the time between when the signal left and when it returned, an object’s distance can easily be calculated underwater.

With sonar a success, piezoelectricity gained the eager eyes of the military. World War II advanced the technology even further as researchers from the United States, Russia, and Japan worked to craft new man-made piezoelectric materials called ferroelectrics.

This research led to two man-made materials that are used alongside natural quartz crystal, barium titanate and lead zirconate titanate.

Piezoelectricity Today

In today’s world of electronics piezoelectricity is used everywhere.

Asking Google for directions to a new restaurant uses piezoelectricity in the microphone.

There’s even a subway in Tokyo that uses the power of human footsteps to power piezoelectric structures in the ground.

You’ll find piezoelectricity being used in these electronic applications:

Actuators

Actuators use piezoelectricity to power devices like knitting and braille machinery, video cameras, and smartphones. In this system, a metal plate and an actuator device sandwiched together a piezoelectric material. Voltage is then applied to the piezoelectric material, which expands and contracts it. This movement causes the actuator to move as well.

Speakers & Buzzers

Speakers use piezoelectricity to power devices like alarm clocks and other small mechanical devices that require high quality audio capabilities. These systems take advantage of the inverse piezoelectric effect by converting an audio voltage signal into mechanical energy as sound waves.

Drivers

Drivers convert a low voltage battery into a higher voltage which can then be used to drive a piezo device. This amplification process begins with an oscillator which outputs smaller sine waves. These sine waves are then amplified with a piezo amplifier.

Sensors

Sensors are used in a variety of applications such as microphones, amplified guitars, and medical imaging equipment. A piezoelectric microphone is used in these devices to detect pressure variations in sound waves, which can then be converted to an electrical signal for processing.

Power

One of the simplest applications for piezoelectricity is the electric cigarette lighter. Pressing the button of the lighter releases a spring-loaded hammer into a piezoelectric crystal. This produces an electrical current that crosses a spark gap to heat and ignite gas. This same piezoelectric power system is used in larger gas burners and oven ranges.

Motors

Piezoelectric crystals are perfect for applications that require precise accuracy, such as the movement of a motor. In these devices, the piezoelectric material receives an electric signal, which is then converted into mechanical energy to force a ceramic plate to move.

Piezoelectricity and the Future

What does the future hold for piezoelectricity? The possibilities abound.

One popular idea that inventors are throwing around is using piezoelectricity for energy harvesting.

Imagine having piezoelectric devices in your smartphone that could be activated from the simple movement of your body to keep them charged.

Thinking a bit bigger, you could also embed a piezoelectric system underneath highway pavement that can be activated by the wheels of traveling cars.

This energy could then be used light stoplights and other nearby devices. Couple that with a road filled with electric cars and you’d find yourself in net positive energy situation.

Want to help move piezoelectricity forward into the future? Autodesk EAGLE has a ton of free piezo libraries ready for use in your next project. Try Autodesk EAGLE for free today!

Cesca is a Stanford University graduate, with a Bachelor of Science in Science, Technology, and Society -- interdepartmental major focusing in Product Design, Technology and Organizational Management.

PCB design made easy

Make anything with EAGLE PCB design software. Professional power for every electronics designer.

https://www.autodesk.com/products/eagle/blog/piezoelectricity/

 

PZT piezo ceramics used in ultrasonic sensors.

Lithium niobate.

Barium Titanate

Pierre Curie with his wife Maria in his lab. 

NOSTRADAMUS: PREDICTIONS OF THINGS PAST - Though widely regarded as a prophet, many who have studied Nostradamus's works find that most of the amazing prophecies attributed to him are merely the result of poor linguistic and historical scholarship - Nostradamus remains famous over four hundred years after his death mostly for a 1555 book he wrote titled "Centuries," a collection of one thousand quatrains (four-line rhyming verses) which are said to foretell the future. Depending on which source you consult, Nostradamus has been credited with accurately predicting the bombing of Hiroshima, Japan, in 1945; the Space Shuttle Challenger accident in 1986; the French Revolution in 1789; the Apollo moon landing in 1969; the death of Princess Diana in 1997; both World Wars, and so on. Nostradamus wrote in Middle French, using vague words, metaphors, and obscure, dated references. There are dozens of different translations of his "Centuries" book, with many variations on different words and phrases. This wide variety of interpretations helps the prophecies come "true," since if one translation doesn't really support the historical evidence, another can often be found that fits better. Often even Nostradamus scholars can't agree on what he was trying to say. Several of the prophecies have been the result of simple ignorance of the language, history, or both.

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Nostradamus: Predictions of Things Past

Though widely regarded as a prophet, many who have studied Nostradamus's works find that most of the amazing prophecies attributed to him are merely the result of poor linguistic and historical scholarship

By Benjamin Radford - Live Science Contributor 

The writer Michel de Nostredame, better known as Nostradamus, is widely known as a French physician, astrologer and prophet.

Nostradamus remains famous over four hundred years after his death mostly for a 1555 book he wrote titled "Centuries," a collection of one thousand quatrains (four-line rhyming verses) which are said to foretell the future. 

Depending on which source you consult, Nostradamus has been credited with accurately predicting the bombing of Hiroshima, Japan, in 1945; the Space Shuttle Challenger accident in 1986; the French Revolution in 1789; the Apollo moon landing in 1969; the death of Princess Diana in 1997; both World Wars, and so on.

In fact you'd be hard pressed to name some significant global event that Nostradamus was not said, by someone, to have foreseen.

Nostradamus and 9/11

Perhaps the most famous assertion made in the past 20 years was that Nostradamus predicted the September 11, 2011, terrorist attacks.

It's a story that circulated widely in late 2001, and is still widely believed. One verse in particular went viral on the Internet: 

"Two steel birds will fall from the sky on the Metropolis, The sky will burn at forty-five degrees latitude Fire approaches the great new city Immediately a huge, scattered flame leaps up Within months, rivers will flow with blood The undead will roam the earth for little time."

Could "steel birds" be interpreted as airplanes? Could New York City be the "Metropolis" that lies at about 40 degrees north latitude?

Many people thought so; however, it was later revealed that this piece is a hybrid of real Nostradamus verse and fiction.

Not only is it not in quatrain form, but the phrase "two steel birds" is particularly revealing, as steel suitable for airplanes wasn't invented until 1854 — nearly 200 years after Nostradamus died.

Another quatrain read: 

"In the city of God there will be a great thunder Two brothers torn apart by Chaos while the fortress endures The great leader will succumb The third big war will begin when the big city is burning” — Nostradamus 1654

Given the fact that Nostradamus died in 1566, eighty-eight years before the quatrain was supposedly written, it would be a remarkable piece indeed.

This was actually published on a Canadian website as part of an essay on how easily important-sounding prophecy can be created using vague imagery.

It is ironic that what began as an essentially skeptical, anti-prophecy piece circulated as the real thing.

Say what? 

In 2007, John Hogue, author of several books about Nostradamus prophecies, stated that the following year a global famine would kill millions of people: "the era of global famine foreseen by Nostradamus will begin in 2008," he wrote.

The prediction of a global famine obviously (and thankfully) was one of many that didn't come true, but the faulty prophecy highlights another aspect of the Nostradamus industry: there's little or no general agreement about what exactly he meant. 

Nostradamus wrote in Middle French, using vague words, metaphors, and obscure, dated references.

There are dozens of different translations of his "Centuries" book, with many variations on different words and phrases.

This wide variety of interpretations helps the prophecies come "true," since if one translation doesn't really support the historical evidence, another can often be found that fits better.

Often even Nostradamus scholars can't agree on what he was trying to say. Several of the prophecies have been the result of simple ignorance of the language, history, or both.

For example, one famous line widely interpreted as referring to Adolf Hitler mentions "The major battle shall be close by the Hister / He shall cause the great one to be dragged in an iron cage, while the Germans shall be looking at the infant Rhine." 

It mentions Germany, and a war, and Hister (which kind of sounds like Hitler to modern ears): amazing prophetic powers?

No; in fact "Hister" (which can also be translated as "Ister" or "Iter") is not the name of Adolf Hitler or anyone else; it is another name for the lower Danube River, a word that Nostradamus also used in his 1554 "Almanac."

In his book "The Complete Prophecies of Nostradamus," Henry S. Roberts offers the following translation of Century VIII (2): 

"Condon and Aux, and about Mirande I see a fire from heaven that surrounds them. Sol, Mars, in conjunction with the lion, and then Marmande. Lightning, great war, wall falls into the Garonne." 

What in the world does this mean? Sol and Mars may refer to the Sun and Mars (or not). Condon and the other proper nouns are place names (probably).

And a fire from the heaven could be anything from a comet to an exploding sun. What do you think Roberts made of it? 

If you guessed alien contact, you're right; according to Roberts's learned interpretation "Fire from heaven suggests extraterrestrial spacecraft landing amid a great war on Earth."

Since no date is given it may yet happen of course — or maybe it was referring to Halley's Comet, which is seen about every 75 years and certainly has appeared in times of strife — or any number of other things.

Though widely regarded as a prophet, many who have studied Nostradamus's works find that most of the amazing prophecies attributed to him are merely the result of poor linguistic and historical scholarship.

In his book "Nostradamus, Bibliomancer: The Man, the Myth, the Truth," Peter Lemesurier, a former Cambridge linguist and author of nearly a dozen books on the French seer, concludes that Nostradamus was neither a doctor nor an astrologer, nor even (by his own admission) a prophet.

He merely believed that history repeats itself, and thus projected known past events into the future. 

Lemesurier laments that "Most of those who make such [predictions] — including the English-speaking authors of many popular books on the subject — know next to nothing either about Nostradamus, the texts, or even the sixteenth-century French in which they are written.

Few of them have ever seen an original text, or even know sufficient French....

As a result [such predictions] are the result of not reading what the texts actually say, but of shamelessly twisting half-understood words retrospectively to fit the proposed event, or in some cases even twisting the event itself to fit the words." 

Nostradamus couched his quatrains in such vague terms that people read whatever they want into them.

Nostradamus did not in fact make predictions (statements that are read and known about before they happen); instead he made post-dictions (statements that appear to come true only after the events already happened).

If Nostradamus had truly predicted the September 11 attacks, World War II, or the Challenger shuttle accident, for example, the world should have known about them decades (indeed centuries) before they occurred.

Predictions that only make sense after the event they foretell are no predictions at all.

Accurate or not, for a man who hasn't written anything in well over 400 years, Nostradamus's works and biographies show no signs of slowing down. 

Benjamin Radford

Live Science Contributor

Benjamin Radford is the Bad Science columnist for Live Science. He covers pseudoscience, psychology, urban legends and the science behind "unexplained" or mysterious phenomenon. Ben has a master's degree in education and a bachelor's degree in psychology. He is deputy editor of Skeptical Inquirer science magazine and has written, edited or contributed to more than 20 books, including "Scientific Paranormal Investigation: How to Solve Unexplained Mysteries," "Tracking the Chupacabra: The Vampire Beast in Fact, Fiction, and Folklore" and “Investigating Ghosts: The Scientific Search for Spirits,” out in fall 2017. His website is www.BenjaminRadford.com.

https://www.livescience.com/24213-nostradamus.html

AIRPLANES FLYING UPSIDE DOWN - Airplanes, or anything that sails through the air for that matter, such as birds, kites, a boomerang or even a folded paper plane, have a physical force working in their favor that allows them to continue their flight: lift. Lift, deserves its name, as it is the force that lifts things into the air. It is closely linked to Newton’s Third Law of Motion: “To every action, there is an equal and opposite reaction.” The lift generated by an airplane depends on its wings; although their shape matters, that’s not the primary contributor to the lift that an airplane experiences. The ‘angle of attack’ of the wings is what makes an airplane cruise. The ‘angle of attack’ is the angle that an imaginary reference line on the airplane makes with the oncoming air. The higher the angle of attack, the more lift is generated beneath the airplane.

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Airplanes Flying Upside Down

How Do Fighter Jets Fly Upside Down?

Ashish  

Wings are the most important part of an airplane when it comes to flying, because they’re shaped in a way that maximizes the buoyant force offered by air.

However, if the shape of the wings is the sole reason behind the capacity of an airplane to fly, then how do stunt planes and fighter jets manage to fly upside down?

Doesn’t the orientation of the wings with respect to the airplane body get messed up when airplanes fly upside down?

In other words, when the plane’s wings face the opposite direction of their aerodynamic design, why don’t they crash?

Although it’s true that the shape of an airplane’s wings plays a significant role in its ability to fly, that’s not actually the primary reason why an airplane is able to soar through the air.

If it were, then fighter jets and other aircraft would never be able to fly upside down and perform such breathtaking maneuvers while airborne, because the shape of the wings would change with respect to the direction of the airplane’s motion. 

There is clearly another important factor at play….

1.      Lift

2.      Airplanes, or anything that sails through the air for that matter, such as birds, kites, a boomerang or even a folded paper plane, have a physical force working in their favor that allows them to continue their flight: lift.

3.      Put in simple terms, ‘lift’ deserves its name, as it is the force that lifts things into the air.

4.      More specifically, it directly opposes the weight of an object moving through a fluid (air, in this case).

5.      It is closely linked to Newton’s Third Law of Motion: “To every action, there is an equal and opposite reaction.”

6.      For an airplane moving through air, the force acting downwards on its body is its ‘Weight’ (slightly different from the ‘mass’ of the airplane, by the way).

7.      To counteract this force, lift is applied perpendicular to the plane, but in the upward direction.

8.      To better understand the forces acting on an airplane in flight, take a look at this image:

Angle of attack

The lift generated by an airplane depends on its wings; although their shape matters, that’s not the primary contributor to the lift that an airplane experiences.

Rather, the ‘angle of attack’ of the wings is what makes an airplane cruise.

The ‘angle of attack’ is the angle that an imaginary reference line on the airplane makes with the oncoming air.

The picture below will help you visualize this better:

 

The higher the angle of attack, the more lift is generated beneath the airplane.

That’s why airplane wings are tilted with the leading edge pointed up relative to the oncoming wind. This forces wind to ‘pile up’ beneath the wings.

The velocity of wind moving above the wings is greater than the velocity of the wind beneath them. Therefore, there is greater pressure beneath the wings due to Bernoulli’s principle.

You can say that the airplane (more specifically, the wing) is riding atop a ‘dense cloud of air’, which provides sufficient lift.

The same is true for airplanes flying upside down. Note that not every airplane is meant to fly upside down; you wouldn’t expect a commercial plane flying in this fashion, except in Hollywood flicks (like Flight).

However, airplanes that consistently have to fly upside down (like stunt planes or fighter aircraft), have symmetrical wings.

Therefore, they can’t rely on the shape of the wings; they only manage to fly upside down by tilting their wings in the right direction to generate sufficient lift.

All in all, it’s true that the shape of the wings does play a significant role in making an airplane fly.

However, it’s essentially the angle of attack of the wings that facilitates all those arduous and breathtaking maneuvers that stunt airplanes and fighter jets pull off so impeccably.

Ashish is a Science graduate (Bachelor of Science) from Punjabi University (India). He spends a lot of time watching movies, and an awful lot more time discussing them. He likes Harry Potter and the Avengers, and obsesses over how thoroughly Science dictates every aspect of life… in this universe, at least.

https://www.scienceabc.com/eyeopeners/how-airplane-jets-stunt-planes-fly-upside-down-lift-shape-of-wings-angle-of-attack.html

ABRASIVE MINERALS - Sanding was originally done with sand -- fine-grained quartz. Quartz sand is hard enough for woodworking (Mohs hardness 7), but it's not very tough or sharp. The virtue of sand sandpaper is its cheapness. Fine woodworkers do occasionally use flint sandpaper or glass paper. Corundum is the workhorse abrasive of sandpaper. Extremely hard (Mohs 9) and sharp, corundum is also usefully brittle, breaking into sharp fragments that keep on cutting. It's great for wood, metal, paint, and plastic. All sanding products today use artificial corundum -- aluminum oxide.

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Abrasive Minerals

by Andrew Alden 

Abrasives today are largely precision-manufactured substances, but natural mineral abrasives are often still used.

A good abrasive mineral is not just hard, but also tough and sharp. It must be plentiful -- or at least widespread -- and pure.

Not many minerals share all these attributes, so the list of abrasive minerals is short but interesting. 

Sanding Abrasives 

Sanding was originally done with (surprise!) sand -- fine-grained quartz.

Quartz sand is hard enough for woodworking (Mohs hardness 7), but it's not very tough or sharp.

The virtue of sand sandpaper is its cheapness.

Fine woodworkers do occasionally use flint sandpaper or glass paper. 

Flint, a form of chert, is a rock made of microcrystalline quartz. It's no harder than quartz but it's tougher so its sharp edges last longer. 

Garnet paper is still widely available. The garnet mineral almandine is harder than quartz (Mohs 7.5), but its real virtue is its sharpness, giving it cutting power without scratching wood too deeply.

Corundum is the workhorse abrasive of sandpaper. 

Extremely hard (Mohs 9) and sharp, corundum is also usefully brittle, breaking into sharp fragments that keep on cutting. It's great for wood, metal, paint, and plastic.

All sanding products today use artificial corundum -- aluminum oxide.

If you find an old stash of emery cloth or paper, it probably uses the real mineral. Emery is a natural mix of fine-grained corundum and magnetite.

Polishing Abrasives 

Three natural abrasives are commonly used for polishing and cleaning metal: enamel finishes, plastic, and tile. 

Pumice is a stone, not a mineral, a volcanic product with a very fine grain. Its hardest mineral is quartz, so it has a gentler action than sanding abrasives.

Softer still is feldspar (Mohs 6), which is most famously used in the Bon Ami brand household cleaner.

For the most delicate polishing and cleaning work, such as with jewelry and fine crafts, the gold standard is tripoli, also called rottenstone.

Tripoli is microscopic, microcrystalline quartz mined from beds of decomposed limestone.

Sandblasting and Waterjet Cutting

Applications of these industrial processes range from scrubbing rust off of steel girders to inscribing gravestones, and a wide range of blasting abrasives is in use today.

Sand is one, of course, but airborne dust from crystalline silica is a health hazard.

Safer alternatives include garnet, olivine (Mohs 6.5) and staurolite (Mohs 7.5).

Which to choose depends on many factors other than mineralogical considerations, including cost, availability, the material being worked, and the experience of the worker.

Many artificial abrasives are in use in these applications, too, as well as in exotic things like ground walnut shells and solid carbon dioxide.

Diamond Grit

The hardest mineral of all is diamond (Mohs 10), and diamond abrasive is a large part of the world diamond market.

Diamond paste is available in many grades for sharpening hand tools, and you can even buy nail files impregnated with diamond grit for the ultimate grooming aid.

Diamond is best suited for cutting and grinding tools, however, and the drilling industry uses lots of diamond for drill bits.

The material used is worthless as jewelry, being black or included - full of inclusions - or too fine-grained. This grade of diamond is called bort.

Diatomaceous Earth

The powdery substance composed of the microscopic shells of diatoms is known as diatomaceous earth or DE.

Diatoms are a kind of algae that form exquisite skeletons of amorphous silica. 

DE is not abrasive to humans, metals, or anything else in our everyday world, but at the microscopic scale, it's very damaging to insects.

The broken edges of crushed diatom shells scratch holes in their hard outer skins, causing their internal fluids to dry out.

It's safe enough to strew in the garden or to mix with food, such as stored grain, to prevent infestations.

When they aren't calling it diatomite, geologists have another name for DE, borrowed from German: kieselguhr.

Andrew Alden

Professional geologist, writer, photographer, and geological tour guide

Thirty-seven years of experience writing about geological subjects

Six years as a research guide with U.S. Geological Survey (USGS)

Member of Geological Society of America (GSA), and American Geophysical Union (AGU)

Experience

Andrew Alden is a former writer for ThoughtCo who contributed hundreds of articles for more than 17 years. Andrew works as a geologist, writer, editor, and photographer. He has written on geological subjects since 1981 and participates actively in his field. For example, Andrew spent six years as a research guide with the U.S. Geological Survey, leading excursions on both land land and at sea. And since 1992, he has hosted the earthquakes conference for the online discussion platform, The Well, which began as a dialogue between the writers and readers of the Whole Earth Review. 

In addition, Andrew is a longtime member of the member of the Geological Society of America — an international society that serves members in academia, government, and industry; and the American Geophysical Union — a community of earth and space scientists that advances the power of science to ensure a sustainable future.

Andrew lives in Oakland, California; and though he writes about the whole planet and beyond, Andrew finds his own city full of interest too and blogs about its geology. 

Education

Andrew Alden holds a bachelor's (B.A.) degree in Earth Science from the University of New Hampshire, College of Engineering and Physical Sciences, in Durham, N.H.

Awards and Publications

Andrew Alden on Earthquakes ​(The Well Group, Inc., 2011)

Assessment of River — Floodplain Aquifer Interactions (Environmental and Engineering Geoscience, 1997)

Andrew Alden on Hosting (The Well Group, Inc., 1995)

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/what-are-abrasive-minerals-1439101