Planet Earth



Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating estimation and other evidence, Earth formed over 4.5 billion years ago.

Earth's gravity interacts with other objects in space, especially the Sun and the Moon, which is Earth's only natural satellite. Earth orbits around the Sun in 365.256 solar days, a period known as an Earth sidereal year. During this time, Earth rotates about its axis 366.256 times, that is, a sidereal year has 366.256 sidereal days.

Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. The gravitational interaction between Earth and the Moon causes tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation. Earth is the densest planet in the Solar System and the largest and most massive of the four rocky planets.




Outer Layer



Earth's outer layer (lithosphere) is divided into several rigid tectonic plates that migrate across the surface over many millions of years. About 29% of Earth's surface is land consisting of continents and islands. The remaining 71% is covered with water, mostly by oceans but also lakes, rivers and other fresh water, which all together constitute the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack.




Internal Structure



Earth's interior remains active with a solid iron inner core, a liquid outer core that generates Earth's magnetic field, and a convecting mantle that drives plate tectonics.


Hunks of oceanic crust are wedged inside Earth's mantle   Live Science - June 9, 2021
Earth's middle layer is chunky, like peanuts in a sea of caramel.


Scientists Detect Signs of a Hidden Structure Inside Earth's Core   Science Alert - March 5, 2021

Now researchers have found more evidence for a whole new chapter deep within Earth's past - Earth's inner core appears to have another even more inner core within it.


Scientists detect unexpected widespread structures near Earth's core   PhysOrg - June 11, 2020
University of Maryland geophysicists analyzed thousands of recordings of seismic waves, sound waves traveling through the Earth, to identify echoes from the boundary between Earth's molten core and the solid mantle layer above it. The echoes revealed more widespread, heterogenous structures -areas of unusually dense, hot rock - at the core-mantle boundary than previously known. Scientists are unsure of the composition of these structures, and previous studies have provided only a limited view of them. Better understanding their shape and extent can help reveal the geologic processes happening deep inside Earth. This knowledge may provide clues to the workings of plate tectonics and the evolution of our planet. The new research provides the first comprehensive view of the core-mantle boundary over a wide area with such detailed resolution.


Superdeep diamonds confirm ancient reservoir deep under Earth's surface   PhysOrg - August 15, 2019
Analyses show that gases found in microscopic inclusions in diamonds come from a stable subterranean reservoir at least as old as the Moon, hidden more than 410 km below sea level in the Earth's mantle.


Ancient crystals offer evidence of the start of Earth's core solidifying   PhysOrg - January 29, 2019
Planetary scientists have found strong evidence that suggests the Earth has an inner and an outer core. The inner core is believed to be solid, while the outer core is made up of molten material. Prior evidence has also indicated that the entire core was once liquid, but as the interior cooled, the innermost part began to crystallize. It is at this point that scientists disagree - some suggest the start of solidification began as far back as 2.5 billion years ago. Others believe it was much more recent - perhaps as recent as just 500 million years ago. In this new effort, the researchers have found evidence that supports the latter theory.


The interior of the Earth, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties, but unlike the other terrestrial planets, it has a distinct outer and inner core. The outer layer of the Earth is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle.

The crust is separated from the mantle by the Mohorovicic discontinuity, and the thickness of the crust varies: averaging 6 km under the oceans and 3050 km on the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, and it is of the lithosphere that the tectonic plates are comprised.

Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at 410 and 660 kilometers below the surface, spanning a transition zone that separates the upper and lower mantle. Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core. The inner core may rotate at a slightly higher angular velocity than the remainder of the planet, advancing by 0.1-0.5° per year.


Researchers confirm Earth's inner core is solid but softer than previously thought   PhysOrg - October 19, 2018


New candidate for 'missing element' in Earth's core   BBC - January 10, 2017
Japanese scientists believe they have established the identity of a "missing element" within the Earth's core. They have been searching for the element for decades, believing it makes up a significant proportion of our planet's centre, after iron and nickel. By recreating the high temperatures and pressures found in the deep interior, experiments suggest the most likely candidate is silicon. The discovery could help us to better understand how our world formed.


Iron 'jet stream' detected in Earth's outer core   BBC - December 19, 2016
Scientists say they have identified a remarkable new feature in Earth's molten outer core. They describe it as a kind of "jet stream" - a fast-flowing river of liquid iron that is surging westwards under Alaska and Siberia. The moving mass of metal has been inferred from measurements made by Europe's Swarm satellites. This trio of spacecraft are currently mapping Earth's magnetic field to try to understand its fundamental workings. The scientists say the jet is the best explanation for the patches of concentrated field strength that the satellites observe in the northern hemisphere.


Molten 'Jet Stream' Discovered Deep Inside Earth   Live Science - December 19, 2016
A band of molten iron is churning slowly deep inside Earth, much in the same way as a jet stream, a new study finds. Scientists discovered the so-called molten jet stream while analyzing data from a trio of European satellites, called Swarm. The satellites launched in 2013 with the goal of studying Earth's magnetic field. In this case, Swarm's observations helped create a view akin to an X-ray of the planet, the researchers said.




History

Within the first billion years of Earth's history, life appeared in the oceans and began to affect Earth's atmosphere and surface, leading to the proliferation of anaerobic and, later, aerobic organisms. Some geological evidence indicates that life may have arisen as early as 4.1 billion years ago.

Since then, the combination of Earth's distance from the Sun, physical properties and geological history have allowed life to evolve and thrive. In the history of life on Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinctions. Over 99% of all species that ever lived on Earth are extinct. Estimates of the number of species on Earth today vary widely; most species have not been described. Over 7.7 billion humans live on Earth and depend on its biosphere and natural resources for their survival.

Scientists have been able to reconstruct detailed information about the planet's past. The earliest dated Solar System material was formed 4.5672 0.0006 billion years ago, and by 4.54 billion years ago (within an uncertainty of 1%) the Earth and the other planets in the Solar System had formed out of the solar nebula - a disk-shaped mass of dust and gas left over from the formation of the Sun.

This assembly of the Earth through accretion was thus largely completed within 10-20 million years. Initially molten, the outer layer of the planet Earth cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed shortly thereafter, 4.53 billion years ago.

The current consensus model for the formation of the Moon is the giant impact hypothesis, in which the Moon was created when a Mars-sized object (sometimes called Theia) with about 10% of the Earth's mass impacted the Earth in a glancing blow. In this model, some of this object's mass would have merged with the Earth and a portion would have been ejected into space, but enough material would have been sent into orbit to coalesce into the Moon.

Outgassing and volcanic activity produced the primordial atmosphere of the Earth. Condensing water vapor, augmented by ice and liquid water delivered by asteroids and the larger proto-planets, comets, and trans-Neptunian objects produced the oceans. The newly formed Sun was only 70% of its present luminosity, yet evidence shows that the early oceans remained liquid - a contradiction dubbed the faint young Sun paradox.

A combination of greenhouse gases and higher levels of solar activity served to raise the Earth's surface temperature, preventing the oceans from freezing over. By 3.5 billion years ago, the Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind.

Two major models have been proposed for the rate of continental growth: steady growth to the present-day and rapid growth early in Earth history. Current research shows that the second option is most likely, with rapid initial growth of continental crust followed by a long-term steady continental area.

On time scales lasting hundreds of millions of years, the surface continually reshaped as continents formed and broke up. The continents migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago (Ma), one of the earliest known supercontinents, Rodinia, began to break apart. The continents later recombined to form Pannotia, 600540 Ma, then finally Pangaea, which broke apart 180 Ma.




Snowball Earth



The Snowball Earth hypothesis proposes that Earth surface's became entirely or nearly entirely frozen at least once, sometime earlier than 650 Mya (million years ago). Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical palaeolatitudes and other enigmatic features in the geological record. Opponents of the hypothesis contest the implications of the geological evidence for global glaciation and the geophysical feasibility of an ice- or slush-covered ocean and emphasize the difficulty of escaping an all-frozen condition. A number of unanswered questions remain, including whether the Earth was a full snowball, or a "slushball" with a thin equatorial band of open (or seasonally open) water. Read more ...

The snowball-Earth episodes are proposed to have occurred before the sudden radiation of multicellular bioforms, known as the Cambrian explosion. The most recent snowball episode may have triggered the evolution of multicellularity. Another, much earlier and longer snowball episode, the Huronian glaciation, which would have occurred 2400 to 2100 Mya, may have been triggered by the first appearance of oxygen in the atmosphere, the "Great Oxygenation Event".


Geoscientists suggest 'snowball Earth' resulted from plate tectonics   PhysOrg - May 7, 2018
About 700 million years ago, the Earth experienced unusual episodes of global cooling that geologists refer to as "Snowball Earth." Several theories have been proposed to explain what triggered this dramatic cool down, which occurred during a geological era called the Neoproterozoic. Now geologists suggest that those major climate changes can be linked to one thing: the advent of plate tectonics. Plate tectonics is a theory formulated in the late 1960s that states the Earth's crust and upper mantle - a layer called the lithosphere - is broken into moving pieces, or plates. These plates move very slowly - about as fast as your fingernails and hair grow - causing earthquakes, mountain ranges and volcanoes.


Ancient soils provide early whiff of oxygen   BBC - September 25, 2013
Oxygen may have been accumulating in Earth's atmosphere hundreds of millions of years earlier than we thought. An international team has made the claim in Nature magazine after studying the oldest soils on Earth. The researchers say elements in the three-billion-year-old material show evidence for oxidative weathering. This is some 700 million years before the Great Oxidation Event when other geological data points to a dramatic rise in free O2 in the atmosphere.


Study debunks theory on end of 'Snowball Earth' ice age   PhysOrg - May 25, 2011
A team of scientists led by researchers from Caltech report in this week's issue of the journal Nature that the rocks on which much of a theory on how the "Snowball Earth" ice age ended was based were formed millions of years after the ice age ended, and were formed at temperatures so high there could have been no living creatures associated with them.


Ice Once Covered the Equator   Live Science - March 5, 2010
Sea ice may have covered the Earth's surface all the way to the equator hundreds of millions of years ago, a new study finds, adding more evidence to the theory that a "snowball Earth" once existed.


Ancient Rocks Show How Young Earth Avoided Becoming Giant Snowball Science Daily - February 6, 2007
A greenhouse gas that has become the bane of modern society may have saved Earth from completely freezing over early in the planet's history, according to the first detailed laboratory analysis of the world's oldest sedimentary rocks.




Great Oxygenation Event


The Great Oxygenation Event (GOE), also called the Oxygen Catastrophe or Oxygen Crisis or Great Oxidation, was the biologically induced appearance of free oxygen (O2) in Earth's atmosphere. Geological, isotopic, and chemical evidence suggest this major environmental change happened around 2.4 billion years ago (2.4 Ga).

Cyanobacteria, which appeared about 200 million years before the GOE, began producing oxygen by photosynthesis. Before the GOE, any free oxygen they produced was chemically captured by dissolved iron or organic matter. The GOE was the point when these oxygen sinks became saturated and could not capture all of the oxygen that was produced by cyanobacterial photosynthesis. After the GOE the excess free oxygen started to accumulate in the atmosphere.

Free oxygen is toxic to obligate anaerobic organisms and the rising concentrations may have wiped out most of the Earth's anaerobic inhabitants at the time. It was a catastrophe for these organisms. Cyanobacteria were therefore responsible for one of the most significant extinction events in Earth's history. Additionally the free oxygen reacted with the atmospheric methane, a greenhouse gas, reducing its concentration and thereby triggering the Huronian glaciation, possibly the longest snowball Earth episode. Free oxygen has been an important constituent of the atmosphere ever since. Read more ...




Evolution of Life

At present, Earth provides the only example of an environment that has given rise to the evolution of life. Highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago and half a billion years later the last common ancestor of all life existed.

The development of photosynthesis allowed the Sun's energy to be harvested directly by life forms; the resultant oxygen accumulated in the atmosphere and formed a layer of ozone (a form of molecular oxygen [O3]) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized the surface of Earth.

Since the 1960s, it has been hypothesized that severe glacial action between 750 and 580 Ma, during the Neoproterozoic, covered much of the planet in a sheet of ice. This hypothesis has been termed "Snowball Earth", and is of particular interest because it preceded the Cambrian explosion, when multicellular life forms began to proliferate.


Humble moss helped to cool Earth and spurred on life   BBC - February 2, 2012
Primitive moss-like plants could have triggered the cooling of the Earth some 470 million years ago, say researchers. A study published in Nature Geoscience may help explain why temperatures gradually began to fall, culminating in a series of "mini ice ages". Until now it had been thought that the process of global cooling began 100 million years later, when larger plants and trees emerged. The simple plants' interactions with rocks are believed to be the cause. The humble moss has created the climate which we enjoy today.


Life may have survived 'Snowball Earth' in ocean pockets   BBC - December 14, 2010
Life may have survived a cataclysmic global freeze some 700 million years ago in pockets of open ocean. Researchers claim to have found evidence in Australia that turbulent seas still raged during the period, where microorganisms may have clung on for life. Conditions on what is dubbed "Snowball Earth" were so harsh that most life is thought to have perished. Following the Cambrian explosion, about 535 Ma, there have been five major mass extinctions. The most recent such event was 65 Ma, when an asteroid impact triggered the extinction of the (non-avian) dinosaurs and other large reptiles, but spared some small animals such as mammals, which then resembled shrews.




Future of the Earth

The future of the planet is closely tied to that of the Sun. As a result of the steady accumulation of helium at the Sun's core, the star's total luminosity will slowly increase. The luminosity of the Sun will grow by 10% over the next 1.1 Gyr (1.1 billion years) and by 40% over the next 3.5 Gyr. Climate models indicate that the rise in radiation reaching the Earth is likely to have dire consequences, including the loss of the planet's oceans.

The Earth's increasing surface temperature will accelerate the inorganic CO2 cycle, reducing its concentration to levels lethally low for plants (10 ppm for C4 photosynthesis) in approximately 500 million to 900 million years. The lack of vegetation will result in the loss of oxygen in the atmosphere, so animal life will become extinct within several million more years. After another billion years all surface water will have disappeared and the mean global temperature will reach 70 °C (158 F).

The Earth is expected to be effectively habitable for about another 500 million years from that point, although this may be extended up to 2.3 billion years if the nitrogen is removed from the atmosphere. Even if the Sun were eternal and stable, the continued internal cooling of the Earth would result in a loss of much of its CO2 due to reduced volcanism, and 35% of the water in the oceans would descend to the mantle due to reduced steam venting from mid-ocean ridges.

The Sun, as part of its evolution, will become a red giant in about 5 Gyr. Models predict that the Sun will expand out to about 250 times its present radius, roughly 1 AU (150,000,000 km). Earth's fate is less clear. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, the Earth will move to an orbit 1.7 AU (250,000,000 km) from the Sun when the star reaches it maximum radius.

The planet was therefore initially expected to escape envelopment by the expanded Sun's sparse outer atmosphere, though most, if not all, remaining life would have been destroyed by the Sun's increased luminosity (peaking at about 5000 times its present level). However, a 2008 simulation indicates that Earth's orbit will decay due to tidal effects and drag, causing it to enter the red giant Sun's atmosphere and be vaporized.




Other News ...





Hunks of oceanic crust are wedged inside Earth's mantle   Live Science - June 9, 2021
Earth's middle layer is chunky, like peanuts in a sea of caramel.




Earth's oldest minerals date onset of plate tectonics to 3.6 billion years ago   PhysOrg - May 15, 2021
Earth is the only planet known to host complex life and that ability is partly predicated on another feature that makes the planet unique: plate tectonics. No other planetary bodies known to science have Earth's dynamic crust, which is split into continental plates that move, fracture and collide with each other over eons. Plate tectonics afford a connection between the chemical reactor of Earth's interior and its surface that has engineered the habitable planet people enjoy today, from the oxygen in the atmosphere to the concentrations of climate-regulating carbon dioxide. But when and how plate tectonics got started has remained mysterious, buried beneath billions of years of geologic time.




Gazing Into a Diamond's Flaws Has Revealed Hidden Clues About How Our Planet Formed   Science Alert - May 15, 2021
More than mere beautiful, coveted stones, diamonds hold another sort of wealth: fragments of Earth's deep history. From flaws within the mineral's near-perfect lattice, scientists have just worked out how to extract long-hidden records of our planet's past.




Rare 'Alien' Isotopes in Earth's Crust Point to Recent Brush With a Cataclysmic Event   Science Alert - May 15, 2021
Far down in the periodic table you'll find a list of heavy elements born in chaos. The kind of chaos you might find in an exploding star perhaps, or a collision between two neutron stars.




Extraterrestrial Plutonium Atoms Turn Up on Ocean Bottom - The rare form of the element found on the Pacific seabed points to its violent birth in colliding stars   Live Science - May 13, 2021
The plutonium-244 hints at how heavy metals form in stars. A rare version of the radioactive element plutonium embedded in Earth's crust below the deep sea is providing new clues as to how heavy metals form in the stars. The new research finds that the isotope, called plutonium-244, may arrive on Earth in tandem with iron-60, a lighter metal known to form in supernovas, explosions that occur during the death throes of many types of stars. This finding suggests that supernovas may create both heavy metals - although it's possible that other events, such as the mergers of neutron stars, are responsible for at least some of the plutonium-244. Understanding how heavy elements formed is one of the top three most burning questions in physics. Half of elements heavier than iron are built in the hearts of stars through a fairly well-understood process of fusion. The other half, though, requires a high density of free neutrons to form. This means they must form in a more explosive environment than a typical star core - supernovas, perhaps, or massive events such as a neutron-star merger or a collision of a black hole and a neutron star.




Climate has shifted the axis of the Earth   PhysOrg - April 23, 2021
Glacial melting due to global warming is likely the cause of a shift in the movement of the poles that occurred in the 1990s.




For The First Time, A 'Space Hurricane' Has Been Detected Over The North Pole   Science Alert - March 5, 2021
For the first time, a hurricane has been detected in Earth's upper atmosphere. In 2014, satellites recorded a huge flowing swirl of plasma extending high into the magnetosphere that lasted for hours before dispersing. Although we've never seen anything like this before, its detection suggests that space hurricanes, as they are known, could be a common planetary phenomenon.




The Gulf Stream is slowing to a 'tipping point' and could disappear   Live Science - March 5, 2021
The current could slow down to a point of no return, altering the climate on both sides of the Atlantic.




A Long-Ago Lake Amid the Dunes   Earth Observatory - March 3, 2021
Long-sustained westerly winds shaped the dunes surrounding the Saudi Arabian oasis of Jubbah in this photograph shot by an astronaut from the International Space Station (ISS). Jubbah sits in the protective wind shadow of Jabel Umm Sinman, which roughly translates from Arabic as two camel-hump mountain. The hard, black rock of the mountain disrupts wind flow and blocks dunes from forming on its lee side. The area around Jabel Umm Sinman has been at the center of significant climatic and anthropological shifts during the Holocene, a geologic term for the past 10,000 years.




Earth Was Spinning Faster Last Year Than at Any Other Time in The Past 50 Years   Science Alert - January 8, 2021
The 28 fastest days on record (since 1960) all occurred in 2020, with Earth completing its revolutions around its axis milliseconds quicker than average.




Scientists discover distant 'mirror image' of the Earth and the sun   Science Tech Daily - June 7, 2020

The star Kepler-160 and its companion KOI-456.04 are more reminiscent of the Sun-Earth system than any previously known exoplanet-star pair. Among the more than 4,000 known exoplanets, KOI-456.04 is something special: less than twice the size of Earth, it orbits a Sun-like star. And it does so with a star-planet distance that could permit planetary surface temperatures conducive to life.




Diamond samples in Canada reveal size of lost continent   BBC - March 21, 2020
Canadian scientists have discovered a fragment of an ancient continent, suggesting that it was 10% larger than previously thought. They were studying diamond samples from Baffin Island, a glacier-covered land mass near Greenland, when they noticed a remnant of North Atlantic Craton. Cratons are ancient, stable parts of the Earth's continental crust. The North American Craton stretched from present-day Scotland to North America and broke apart 150m years ago. Scientists chanced on the latest evidence as they examined exploration samples of kimberlite, a rock that often contains diamonds, from Baffin Island.




Geologists find lost fragment of ancient continent in Canada's North   PhysOrg - March 20, 2020

Sifting through diamond exploration samples from Baffin Island, Canadian scientists have identified a new remnant of the North Atlantic craton - an ancient part of Earth's continental crust. A chance discovery by geologists poring over diamond exploration samples has led to a major scientific payoff. Kimberlite rock samples are a mainstay of diamond exploration. Formed millions of years ago at depths of 150 to 400 kilometers, kimberlites are brought to the surface by geological and chemical forces. Sometimes, the igneous rocks carry diamonds embedded within them. The newly identified fragment covers the diamond bearing Chidliak kimberlite province in southern Baffin Island. It adds roughly 10 percent to the known expanse of the North Atlantic craton.




Off the Coast of Portugal, the Earth's Crust Might Be Peeling in Two   Live Science - May 7, 2019
In 1969, a giant earthquake off the coast of Portugal kicked up a tsunami that killed over a dozen people. Some 200 years prior, an even larger earthquake hit the same area, killing around 100,000 people and destroying the city of Lisbon.Two earthquakes in the same spot over a couple hundred years is not cause for alarm. But what puzzled seismologists about these tremors was that they began in relatively flat beds of the ocean - away from any faults or cracks in the Earth's crust where tectonic plates slip past each other, releasing energy and causing earthquakes.




Earth's atmosphere stretches out to the moon - and beyond   PhysOrg - February 20, 2019
The gaseous layer that wraps around Earth reaches up to 630,000 kilometers away, or 50 times the diameter of our planet Where our atmosphere merges into outer space, there is a cloud of hydrogen atoms called the geocorona. One of the spacecraft instruments, SWAN, used its sensitive sensors to trace the hydrogen signature and precisely detect how far the very outskirts of the geocorona are. These observations could be done only at certain times of the year, when the Earth and its geocorona came into view for SWAN. For planets with hydrogen in their exospheres, water vapor is often seen closer to their surface. That is the case for Earth, Mars and Venus.




Earth's lucky escape 565 million years ago: Study finds our planet's magnetic field was 'on the verge of collapse'   Daily Mail - January 29, 2019
Earth narrowly avoided a catastrophic collapse of the magnetic field that protects our planet 565 million years ago, it has been revealed. Researchers say that it is had collapsed, life on Earth would have faced severe challenges as the solar wind would have stripped the planet of its atmosphere and bombarded the surface with harmful radiation. Researchers found that, luckily, our planet's core solidified 'right in the nick of time', recharging Earth's magnetic field when it was at its weakest point.




Secrets of Earth's sunken 'lost continent' revealed: Drilling of Zealandia suggests it was closer to land level than thought, and acted as a bridge for animals 80 million years ago   Daily Mail - September 27, 2017
An international team of scientists found fossilized remains and evidence of large-scale tectonic plate shifts as part of one of the first extensive surveys of the region. The discovery of microscopic shells of organisms that lived in warm shallow seas, and spores and pollen from land plants, reveal that the geography and climate of Zealandia was dramatically different in the past.




Zealandia: Is there an eighth continent under New Zealand?   BBC - February 18, 2017
You think you know your seven continents? Think again, as there's a new contender hoping to join that club. Say hello to Zealandia, a huge landmass almost entirely submerged in the southwest Pacific. It's not a complete stranger, you might have heard of its highest mountains, the only bits showing above water: New Zealand. Scientists say it qualifies as a continent and have now made a renewed push for it to be recognized as such. In a paper published in the Geological Society of America's Journal, researchers explain that Zealandia measures five million sq km (1.9m sq miles) which is about two thirds of neighboring Australia.




Analysis of titanium in ancient rocks creates upheaval in history of early Earth   PhysOrg - September 22, 2017
The Earth's history is written in its elements, but as the tectonic plates slip and slide over and under each other over time, they muddy that evidence - and with it the secrets of why Earth can sustain life.




Breakup of supercontinent Pangea cooled mantle and thinned crust   PhysOrg - December 13, 2016
The oceanic crust produced by the Earth today is significantly thinner than crust made 170 million years ago during the time of the supercontinent Pangea. The thinning is related to the cooling of Earth's interior prompted by the splitting of the supercontinent Pangaea, which broke up into the continents that we have today. The mantle is the very hot, but mostly solid, layer of rock between the Earth's crust and core. Magma from the mantle forms oceanic crust when it rises from the mantle to the surface at spreading centers and cools into the rock that forms the very bottom of the seafloor. Since about 2.5 billion years ago, the mantle has been cooling - a phenomenon that doesn't influence the climate on the surface of the Earth and has nothing to do with the issue of short-term man-made climate change.




All hail the humble moss, bringer of oxygen and life to Earth   The Guardian - August 15, 2016
Scientists have identified the creature that gave the Earth its first breath of fresh, clean air and made life possible for everything ranging from ardvaarks to Olympic athletes and zebra finches. It was a moss. The drama unfolded more than 400 million years ago and there are no surviving witnesses. The episode had to be reconstructed in computer models from the testimony of rocks, the fossils in the sea and the few spores preserved in ancient sediments.




Where Did Earth's Water Come From?   Live Science - July 7, 2016
Look at Earth compared to other rocky planets in the neighborhood, and the first thing that would likely jump out is that there's A LOT of water. So how did 70 percent of our planet's surface become covered in this essential life ingredient? That question is the subject of lively scientific debate, it turns out. There are two prevailing theories: One is that the Earth held onto some water when it formed, as there would have been ice in the nebula of gas and dust (called the proto-solar nebula) that eventually formed the sun and the planets about 4.5 billion years ago. Some of that water has remained with the Earth, and might be recycled through the planet's mantle layer, according to one theory. The second theory holds that the Earth, Venus, Mars and Mercury would have been close enough to that proto-solar nebula that most of their water would have been vaporized by heat; these planets would have formed with little water in their rocks. In Earth's case, even more water would have been vaporized when the collision that formed the moon happened. In this scenario, instead of being home-grown, the oceans would have been delivered by ice-rich asteroids, called carbonaceous chondrites.




Massive 'Lava Lamp' Blobs Deep Inside Earth Have Scientists Puzzled   Live Science - July 5, 2016
Two continent-size blobs of hot - and possibly molten - rock can be found deep underground, about halfway to the center of the Earth, according to a new study. These curious structures - each of which is so large that it would be 100 times taller than Mount Everest - could be made up of materials that may shed light on how the Earth formed, the researchers said. One of the blobs is located beneath the Pacific Ocean, and the other can be found beneath the Atlantic. These underground structures start where the Earth's mantle meets the core, but they send "plumes" up through the rock like a Lava Lamp, the researchers said. Scientists now think these masses differ from the surrounding rock in more than just temperature. They're also "compositionally distinct," meaning they could contain materials not typically found in the rest of the Earth's mantle. Yet even some of the most basic information about the blobs is still a mystery.




Researchers shed new light on the origins of Earth's water   PhysOrg - November 12, 2015
Water covers more than two-thirds of Earth's surface, but its exact origins are still something of a mystery. Scientists have long been uncertain whether water was present at the formation of the planet, or if it arrived later, perhaps carried by comets and meteorites. Now researchers from the University of Hawaii at Manoa, using advanced ion-microprobe instrumentation, have found that rocks from Baffin Island in Canada contain evidence that Earth's water was a part of our planet from the beginning.




Ancient recording of Earth core's birth   BBC - October 8, 2015
A reassessment of ancient rocks has led scientists to estimate that Earth's inner core started to form earlier than was previously thought, around 1.3 billion years ago. As it started to freeze, the core began generating a bigger magnetic field, which continues to today. Earth's active core contrasts sharply with that of our neighbor Mars, whose strong early magnetic field died around four billion years ago. Our planet's magnetic field is generated deep in the planet by the turbulent motion of the electrically conducting molten iron of the outer core. We may have to revise our ideas about the core yet again. It aligns compass needles north-south, but also protects Earth from the solar storms that the Sun throws out relentlessly.




How magnetism manifests in the universe   PhysOrg - June 30, 2015
My main interest is in "cosmic magnetism" - magnets in outer space. Incredibly, magnetism is everywhere in the cosmos: planets, stars, gaseous nebulae, entire galaxies and the overall universe are all magnetic. What does it mean to say that a heavenly body is magnetic? For a solid body like the Earth, the idea is reasonably simple: the Earth's core is a giant bar magnet, with north and south poles. But farther afield, things get weird. Our entire Milky Way galaxy is also a magnet. Just like for the Earth, the Milky Way's magnetism is produced by electrical currents. But while the Earth has a molten core to carry these currents, our galaxy's magnetism is powered by uncounted numbers of electrons, slowly drifting in formation through space. The result is a magnet like nothing you've ever seen.




Earth's 6-Year Twitch Changes Day Length   Live Science - July 10, 2013
Periodic wobbles in Earth's core change the length of a day every 5.9 years. Teasing out this subtle cycle, which subtracts and adds mere milliseconds to each day, also revealed a match between abrupt changes in the length of day and Earth's magnetic field. During these short-lived lurches in the magnetic field intensity, events called geomagnetic jerks, Earth's day also shifts by 0.1 millisecond, the researchers report. Since 1969, scientists have detected 10 geomagnetic jerks lasting less than a year. Seemingly negligible, these fleeting variations are mighty to those who study the planet and its core. All of a sudden, a planet changes its spin like a figure skater open or closing her arms. The rotational effect helps scientists understand what's happening inside the Earth's core. Shifts in the magnetic field also provide clues to the inaccessible iron core. But their source remains a mystery.





ASTRONOMY INDEX


EARTH'S MOON


EARTH CHANGES


EARTH'S MAGNETIC FIELD


PLATE TECTONICS


EARTHQUAKES


POLE SHIFTS


CRUSTAL DISPLACEMENT


CONTINENTAL DRIFT


GEOLOGY


PACIFIC RING OF FIRE


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