A lot of people have been mislead by a post that talks about the “lumpy” Earth, and unfortunately it seems that people genuinely believe the Earth is this shape. As one person pointed out, we have images of the Earth from space, and while it would be disingenuous to refer to it as a perfect sphere, it very much is spherical. A rudimentary reverse Google image search tells me that the image in the misleading post is a simulation of the Earth without water… which is just plain wrong.
In fact, the shape you’re seeing is a geoid, which is a simulation of what Earth would look like if you neglected the influence of anything other than rotation and gravity. A geoid is a dynamic equipotential surface, which means that every point on the surface has the same gravitational potential.
Since it was recently NASA’s Astronomy Picture of the Day, this seems like a good opportunity to talk about a geoid that is something more than a context-less gif: the Potsdam Gravity Potato, pictured above. It’s the result of efforts by a group at Helmholtz Centre Potsdam to create a highly detailed map of the Earth’s gravitational field. Like in a heat map, red elevated levels indicate stronger gravitational effects, and depressed blue levels indicate that they’re lower. The potato-like shape occurs due to the Earth’s uneven gravitational field. This is why high places such as the Himalayas coincide with local maxima on the geoid—but of course not all maxima and minima are the result of noticeable physical features; the Earth has inhomogeneous variations in its density, which account for much of the gravitational difference.
A photomicrograph thin section of the aggregate is featured above. Aeolian lava is studied to understand how magma forms at depth and the level of risk of its eruption. This particular glomerocryst is made of two minerals; plagioclase and pyroxene, whose chemical compositions, textures and melt inclusions help decipher just what happens in a magma chamber.
But, if you look closely at its shape, you might learn something more – that even something as hard as a rock has a heart. – Bernardo Cesare
You are likely to see a natural colorful display in the sky if you take a trip to the Arctic Region, in the Northern Hemisphere. Here, the colorful lights are the result of interaction between solar storms from the sun and the earth’s outer atmosphere.
Danish geophysicist Inge Lehmann was born on this day in 1888. Lehmann first proposed the idea that Earth’s core was not a mass of molten metal, but in fact was solid in the middle, subject to such immense pressure that it forced the super-hot iron and nickel back into a denser state.
By observing how seismic waves bounced around within the Earth’s mantle and core, Lehmann was able to sound out the planet’s surprising inner structure. Meg Rosenburg has a great post at her blog True Anomalies telling the story of Lehmann’s work that goes into more detail about the science involved. Essentially, earthquakes create different kinds of seismic waves that each interact in special ways with liquid or solid materials. I love this illustration from Lehmann’s 1936 paper:
Building off Lehmann’s research, modern geophysicists have mapped the internal echoes or earthquakes in much greater detail, giving us images like this:
This was truly pioneering work, both for geophysics and for women in science. Google has marked the occasion with this nifty little doodle:
Be sure to check out my video about why the Earth has layers, posted up top, to learn more about this hot, mostly molten onion that we call home!
Turbidity currents are a gravity-driven, sediment-laden flow, like a landslide or avalanche that occurs underwater. They are extremely turbulent flows with a well-defined leading edge, called a head. Turbidity currents are often triggered by earthquakes, which shake loose sediments previously deposited in underwater mountains and canyons. Once suspended, these sediments make the fluid denser than surrounding water, causing the turbidity current to flow downhill until its energy is expended and its sediment settles to form a turbidite deposit. By sampling cores from the seafloor, scientists studying turbidites can determine when and where magnitude 8+ earthquakes have occurred over the past 12,000+ years! (Video credit: A. Teijen et al.; submitted by Simon H.)
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Estella Atekwana grew up in Cameroon. “My parents very much wanted me to do medicine,” she writes.
“So I got into sciences with that intention. However, I took a course in geology in high school and the teacher indicated that geology was not for girls. I was challenged then to demonstrate that girls could do geology and perform the same as boys or even better. I ended up with the science award that year in chemistry, biology, and geology.”
Image 2:University of Oklahoma seismologist Katie Keranen and Oklahoma State University geophysicist Estella Atekwana install a seismometer following a series of earlier quakes. (Shannon Dulin) via Fracking Spurred Biggest Earthquake Yet
She moved to North America to study the geosciences, earning a bachelor’s and master’s in geology from Howard University and a Ph.D. from Dalhousie University in Canada. “Today, they call me Doctor and that’s fine with my parents.”
She is now Sun Chair at Oklahoma State University, where she is a leader in the new field of biogeophysics [Biogeophysics is a subdiscipline of geophysics concerned with how plants, microbial activity and other organisms alter geologic materials and affect geophysical signatures.].
Led by Simone Anzellini, the French research team did their best bet to reproduce the core’s properties in the lab: they took a bunch of iron and crushed it between two pieces of diamond. Then they shot it with a laser. The apparatus produces massive pressures and superheated temperatures. This let them study how the iron behaved under such intense conditions and gave them a window into the conditions found at the planet’s center.
Knowing how hot the Earth’s core is can add to our understanding all sorts of wonders, from the existence of the planetary magnetic field, to the propagation of seismic waves after an earthquake, to the birth of the Earth itself.
This morning I visited the Grand Canyon and along the trail that runs along the south rim there is a segment called “The Trail of Time.”, which showcases several different types of rock taken from the various layers of the Grand Canyon.
The first rock you encounter at the trailhead, also the oldest rock of the collection, called Elves Chasm gneiss (pronounced “nice”) is about 1,840 million years old, or 1.84 billion years old. As you move along the trail you see about 15 other rocks all in descending order of age until you finally come to the last one called Phantom granite, which is a mere 1.66 billion years old.
One of the factors that complicates geophysical flows is that both the atmosphere and the ocean are stratified fluids with many stacked layers of differing densities. These variations in density can generate instabilities, trap rising or sinking fluids, and transmit waves. The animations above show flow over two ridges with dye visualization (top), velocity (middle), and contours of density (bottom). The upstream influence of the left ridge creates a smooth, focused flow that quickly becomes turbulent after the crest. The jet rebounds as a turbulent hydraulic jump before slowing again upstream of the second ridge. Like the first ridge, the second ridge also generates a hydraulic jump on the lee side. Clearly both stratification and the local topography play a big role in how air moves over and between the ridges. If prevailing winds favor these kinds of flows, it can help generate local microclimates. (Image credit and submission: K. Winters, source videos)
A giant lake buried more than two miles beneath the Antarctic ice has been found to contain a “surprising” variety of life.
Analysis of ice cores obtained from the basin of Lake Vostok, the subglacial lake that Russian scientists drilled down to in 2012, have revealed DNA from an estimated 3,507 organisms.
While the majority were found to be bacteria, many of which were new to science, there were also other single celled organisms and multicellular organisms found, including from fungi.
The diversity of life from the lake has surprised scientists as many had thought the lake would be sterile due to the extreme conditions.
Lake Vostok was first covered by ice more than 15 million years ago and is now buried 12,000 feet beneath the surface, creating huge pressures. Few nutrients were expected to be found.
However, samples of ice that had formed as water from the lake froze onto the bottom of the glacial ice sheet above have revealed it is teeming with life.
This will raise hopes that life may be found in other extreme environments on other planets. One of Jupiter’s moons, Europa, for example, is covered with an icy shell that may hide a liqud ocean below where life could exist.
Dr Scott Rogers, a biologist at Bowling Green State University, in Ohio, and led the DNA analysis of biological material found in the ice cores, said:
“We found much more complexity than anyone thought. It really shows the tenacity of life, and how organisms can survive in places where a couple dozen years ago we thought nothing could survive. The bounds on what is habitable and what is not are changing.”
Lake Vostok is around 160 miles long and 30 miles wide, covering an area of more than 6,000 square miles beneath the Antarctic ice sheet.
Among the bacteria found in the samples brought to the surface were those commonly found in the digestive systems of fish, crustaceans and annelid worms, raising the prospect there could be more complex life still living in the lake.
Isolated from the rest of the world for 15 million years, some of the DNA sequences were found to be unique to science and may belong to new species that have evolved in the depths.
Writing in the journal PLOS One, Dr Rogers and his colleagues said:
“The sequences suggest that a complex environment might exist in Lake Vostok. Sequences indicating organisms from aquatic, marine, sediment and icy environments were present in the accretion ice. In addition, another major proportion of the sequences were from organisms that are symbionts of animals and/or plants. Over 35 million years ago, Lake Vostok was open to the atmosphere and was surrounded by a forested ecosystem. At that time, the lake, which might have been a marine bay, probably contained a complex network of organisms. As recently as 15 million years ago, portions of the lake were ice free at least part of the time. During these times, organisms were likely being deposited in the lake. While the current conditions are different than earlier in its history, the lake seems to have maintained a surprisingly diverse community of organisms. These organisms may have slowly adapted to the changing conditions in Lake Vostok during the past 15–35 million years as the lake converted from a terrestrial system to a subglacial system.”
Details (via TDF): In 1957 the Russians established a remote base in Antarctica – the Vostok station. It soon became a byword for hardship – dependent on an epic annual 1000km tractor journey from the coast for its supplies. The coldest temperature ever found on Earth (-89°C) was recorded here on the 21st July 1983. It’s an unlikely setting for a lake of liquid water. But in the 1970’s a British team used airborne radar to see beneath the ice, mapping the mountainous land buried by the Antarctic ice sheet. Flying near the Vostok base their radar trace suddenly went flat. They guessed that the flat trace could only be from water. It was the first evidence that the ice could be hiding a great secret.
But 20 years passed before their suspicions were confirmed, when satellites finally revealed that there was an enormous lake under the Vostok base. It is one of the largest lakes in the world – at 10,000 square km it’s about the extent of Lake Ontario, but about twice as deep (500m in places). The theory was that it could only exist because the ice acts like a giant insulating blanket, trapping enough of the earth’s heat to melt the very bottom of the ice sheet.
Earth’s solid-metal inner core is a key component of the planet, helping to give rise to the magnetic field that protects us from harmful space radiation, but its remoteness from the planet’s surface means that there is much we don’t know about what goes on down there. But some secrets of the inner core are being revealed by acoustic waves passing through the planet’s heart and iron squeezed to enormous pressures in the lab.
Two new studies, both detailed online May 12 in the journal Nature Geoscience, reveal that Earth’s inner core may actually be softer than previously thought, and that the speed at which it spins can fluctuate over time.
Under the liquid-metal outer layer of the Earth’s core is a solid ball of superhot iron and nickel alloy about 760 miles (1,220 kilometers) in diameter. Scientists recently discovered the inner core is, at 10,800 degrees Fahrenheit (6,000 degrees Celsius), as hot as the surface of the sun.
Churning in the liquid outer core results in the dynamo that generates Earth’s magnetic field. Geoscientists think interactions between the inner and outer cores may help explain the nature of the planet’s dynamo, the details of which remain largely unknown.
“The Earth’s inner core is the most remote part of our planet, and so there is a lot we don’t know about it because we can’t go down and collect samples,” said Arianna Gleason, a geoscientist at Stanford University in California.
The emergence of plate tectonics is arguably Earth’s defining moment, the authors of a new Nature paper write. Out of all the planets we’ve looked at carefully, Earth is the only one that has a hard outer crust with distinct pieces that shift and move. Our home is unique in its continents and quakes.
Some scientists think that plate tectonics are essential for life—so much so that if they could figure out a way to spot tectonic action on exoplanets, they think it would be a good indication that there might be life there, too. Tectonic activity recirculates minerals and recycles carbon. As one plate slides under another (a process called subduction), it pushes carbon down into the mantle with it.
Without plate tectonics, carbon would build up in the atmosphere. Venus, which does not have tectonics, shows the results: an atmosphere that is 96 percent carbon dioxide. It’s toxic. Yet Venus is about the same size and composition as our planet, so why doesn’t it have plate tectonics?
Today, millions of people across the world will open their web browsers and see an animation of the Earth split in two, it’s inner core floating in space just above Google’s search box. It’s thanks to a pioneering scientist named Inge Lehmann — who would have turned 127 today — that scientists know that the inner core exists
Human beings have only been able to drill down a third of the way into Earth’s crust. That’s only about 0.3% of the radius of the Earth. So how we know so much about its internal structure?
In this week’s It’s Okay To Be Smart, you’ll earn why the Earth is organized like an onion filled with sizzling magma and metal as hot as the sun, plus how it got to be that way. You’ll also discover how the leftovers from dying stars and a little bit of density put “life” in Earth’s destiny.
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PS - My t-shirt game is strong in this one, if I do say so myself.
1.) Himmelsfurst Mine, Freiberg District, Saxony, Germany (6 x 5 x 2.5 cm). 2.) Tongbai County, Nanyang Prefecture, Henan Province, China (4.3 x 5 x 1.4 cm). 3.) Himmelsfürst Mine, Freiberg District, Saxony, Germany (8 x 6.4 x 5 cm).