Planet Earth

Earth (or the Earth) is the third planet from the Sun and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the World, the Blue Planet, or by its Latin name, Terra.

Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas giant like Jupiter. It is the largest of the four solar terrestrial planets in size and mass. Of these four planets, Earth also has the highest density, the highest surface gravity, the strongest magnetic field, and fastest rotation. It also is the only terrestrial planet with active plate tectonics.

Home to millions of species including humans, Earth is currently the only astronomical body where life is known to exist. The planet formed 4.54 billion years ago, and life appeared on its surface within a billion years.

Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful solar radiation, permitting life on land.

The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist during this period. The planet is expected to continue supporting life for at least another 500 million years.

Earth's outer surface is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt water oceans, the remainder consisting of continents and islands which together have many lakes and other sources of water contributing to the hydrosphere.

Liquid water, necessary for all known life, is not known to exist in equilibrium on any other planet's surface. Earth's poles are mostly covered with solid ice (Antarctic ice sheet) or sea ice (Arctic ice cap). The planet's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.

Earth interacts with other objects in space, especially the Sun and the Moon. At present, Earth orbits the Sun once every 366.26 times it rotates about its own axis, which is equal to 365.26 solar days, or one sidereal year. The Earth's axis of rotation is tilted 23.4 away from the perpendicular of its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days).

Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. Between approximately 3.8 billion and 4.1 billion years ago, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment.

Both the mineral resources of the planet, as well as the products of the biosphere, contribute resources that are used to support a global human population. These inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade, and military action. Human cultures have developed many views of the planet, including personification as a deity, a belief in a flat Earth or in the Earth as the center of the universe, and a modern perspective of the world as an integrated environment that requires stewardship.

Epic view of moon transiting Earth

Full Moon, Full Earth   NASA - August 7, 2015

The Moon was new on July 16. Its familiar nearside facing the surface of planet Earth was in shadow. But on that date a million miles away, the Deep Space Climate Observatory (DSCOVR) spacecraft's Earth Polychromatic Imaging Camera (EPIC) captured this view of an apparently Full Moon crossing in front of a Full Earth. In fact, seen from the spacecraft's position beyond the Moon's orbit and between Earth and Sun, the fully illuminated lunar hemisphere is the less familiar farside. Only known since the dawn of the space age, the farside is mostly devoid of dark lunar maria that sprawl across the Moon's perpetual Earth-facing hemisphere. Only the small dark spot of the farside's Mare Moscoviense (Sea of Moscow) is clear, at the upper left. Planet Earth's north pole is near 11 o'clock, with the North America visited by Hurricane Dolores near center. Slight color shifts are visible around the lunar edge, an artifact of the Moon's motion through the field caused by combining the camera's separate exposures taken in quick succession through different color filters. While monitoring the Earth and solar wind for space weather forcasts, about twice a year DSCOVR can capture similar images of Moon and Earth together as its crosses the orbital plane of the Moon.

  From a Million Miles Away, NASA Camera Shows Moon Crossing Face of Earth   NASA - August 6, 2015
These images were taken between 3:50 p.m. and 8:45 p.m. EDT on July 16, showing the moon moving over the Pacific Ocean near North America. The North Pole is in the upper left corner of the image, reflecting the orbital tilt of Earth from the vantage point of the spacecraft. This animation features actual satellite images of the far side of the moon, illuminated by the sun, as it crosses between the DSCOVR spacecraft's Earth Polychromatic Imaging Camera (EPIC) and telescope, and the Earth - one million miles away. EPIC maintains a constant view of the fully illuminated Earth as it rotates, providing scientific observations of ozone, vegetation, cloud height and aerosols in the atmosphere. Once EPIC begins regular observations next month, the camera will provide a series of Earth images allowing study of daily variations over the entire globe. About twice a year the camera will capture the moon and Earth together as the orbit of DSCOVR crosses the orbital plane of the moon.


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 1020 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.

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 ...

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.

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.

The mystery of how Earth's primordial soup came to life   NBC - February 20, 2012
Just as species are believed to have evolved over time, the individual molecules that form the basis of life also likely developed in response to natural selection, scientists say. Life on Earth first bloomed around 3.7 billion years ago, when chemical compounds in a "primordial soup " somehow sparked into life, scientists suspect. But what turned sterile molecules into living, changing organisms? That's the ultimate mystery. By studying the evolution of not just life, but life's building blocks as well, researchers hope to come closer to the answer.

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.

Snowball Earth: Deep Freeze May Have Spawned Complex Life   Live Science - October 27, 2010
The "Snowball Earth" idea that the planet was coated in ice for millions of years might help explain the emergence of complex animals, some scientists say. The Snowball Earth hypothesis suggests the planet was covered from pole to pole with a thick sheet of ice, perhaps more than once, for millions of years at a time. Supporters of this proposal suggest the glaciations, which would have been the most severe in Earth history, occurred between roughly 750 million and 635 million years ago.

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. Over the past 65 million years, mammalian life has diversified, and several million years ago an African ape-like animal such as Orrorin tugenensis gained the ability to stand upright. This enabled tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which allowed the evolution of the human race. The development of agriculture, and then civilization, allowed humans to influence the Earth in a short time span as no other life form had, affecting both the nature and quantity of other life forms. The present pattern of ice ages began about 40 Ma and then intensified during the Pleistocene about 3 Ma. High-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating every 40100,000 years. The last continental glaciation ended 10,000 years ago.

Internal Structure

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.

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. Now 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.

Earth's Core, Magnetic Field Changing Fast, Study Says National Geographic - July 1, 2008

Rapid changes in the churning movement of Earth's liquid outer core are weakening the magnetic field in some regions of the planet's surface.

Researchers confirm discovery of Earth's inner, innermost core Science Daily - March 11, 2008

3D illustration of the Earth's inner core structure and the texturing of its iron crystals. The transparent outer surface is the inner core boundary (at radius 1220 km). The opaque inner sphere is the inner inner core (slightly less than half of the inner core radius) found in this study. The sticks represent the alignments of iron crystals in the outer part of the inner core. The longer the stick is, the higher the degree of alignment is and the stronger the seismic anisotropy is. The fast direction is parallel to the spin axis. Geologists have confirmed the discovery of Earth's inner, innermost core, and have created a three-dimensional model that describes the seismic anisotropy and texturing of iron crystals within the inner core.

Snowball Earth

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

"Snowball Earth" Confirmed: Ice Covered Equator   National Geographic - March 5, 2010
But volcanoes would've made Earth more mud ball than snowball, scientists say.
Earth's now steamy Equator was covered with ice 716 million years ago.

Violent Planet: The Forces that Shape Earth   Live Science - March 5, 2010

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.

Snowball Earth

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.

In the News ...

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.

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.

Earth's center is out of sync   PhysOrg - May 13, 2013

We all know that the Earth rotates beneath our feet, but new research has revealed that the center of the Earth is out of sync with the rest of the planet, frequently speeding up and slowing down. The use of earthquake doublets to measure the rotation speed of Earth's inner core over the last 50 years showed that not only did the inner core rotate at a different rate to the mantle - the layer between the core and the crust that makes up most of the planet's interior - but its rotation speed was variable.

Infant, Magma-Ball Earth Glimpsed Via Newfound Rocks   National Geographic - August 12, 2010

Canada's Baffin Island, home to perhaps the world's oldest rocks.

Arctic rocks may contain oldest remnants of Earth   BBC - August 11, 2010

Scientists have found Arctic rocks that may preserve the earliest remnants of Earth. Over billions of years, much of the material that made up the early Earth was modified by processes such as melting and mixing. But the Arctic rocks seem to contain chemical signatures that date from just after the Earth's violent origin.

Silver tells a volatile story of Earth's origin: Water was present during its birth   PhysOrg - May 13, 2010

Tiny variations in the isotopic composition of silver in meteorites and Earth rocks are helping scientists put together a timetable of how our planet was assembled beginning 4.568 billion years ago. The new study indicates that water and other key volatiles may have been present in at least some of Earth's original building blocks, rather than acquired later from comets, as some scientists have suggested.

Quantum mechanics reveals new details of deep earth   PhysOrg - May 11, 2010
Scientists have used quantum mechanics to reveal that the most common mineral on Earth, silica, is relatively uncommon deep within the planet.

'Goldilocks Zone' may go colder than previously thought   PhysOrg - April 20, 2010
The survival of life on Earth is possible only within a relatively narrow temperature range known as the "Goldilocks Zone," which ranges from around 0 to 100C. In many ecosystems .... Goldilocks Planet   Wikipedia
  Goldilocks Planet   Google Videos

Chile Earthquake Altered Earth Axis, Shortened Day   National Geographic - March 2, 2010
Chilean Quake May Have Shortened Earth Days   NASA - March 2, 2010

The Earth has its own set of rules   PhysOrg - March 3, 2010
Early in our history it didn't make any difference how we viewed our environment. We could change it, and if we didn't like what we did to it, we could move and natural processes would soon obliterate whatever we had done. Over the years, models of our relationship to the environment have been based on religious views, with the world provided for us to dominate and subdue as described in Genesis, and philosophical views, seeing wisdom and virtue in nature as described by Thoreau.

How Earth Survived Its Birth: New Simulation Reveals Planet Migration Prevents Plunge Into Sun   Science Daily - January 8, 2010
How Earth avoided falling into the sun   MSNBC - January 7, 2010
In short, temperature differences in the space around the sun, 4.6 billion years ago, caused Earth to migrate outward as much as gravity was trying to pull it inward, and so the fledgling world found equilibrium in what we now know to be a very habitable orbit.

Comet Dust Older Than the Sun Found in Earth's Atmosphere   National Geographic - April 28, 2009
Meteorites on the ground or icy comets millions of miles away are usually the only sources of ancient matter from the early days of the solar system. But in a high-flying experiment, researchers have used a sort of chemical flypaper to scoop up comet dust from Earth's atmosphere - and it appears to be some of the oldest matter in our cosmic neighborhood.

Earth's crust melts easier than previously thought   PhysOrg - March 18, 2009
In the study, researchers measured how well rocks conduct heat at different temperatures and found that as rocks get hotter in the Earth's crust, they become better insulators and poorer conductors. This finding provides insight into how magmas are formed and will lead to better models of continental collision and the formation of mountain belts.

Quebec: Oldest Rocks on Earth Found   Live Science - September 25, 2008
Scientists have found the oldest known rocks on Earth. They are 4.28 billion years old, making them 250 million years more ancient than any previously discovered rocks. Earth formed about 4.6 billion years ago from a disk of gas and dust circling the sun. Remnants of crust from Earth's infancy are hard to come by because most of that material has been recycled into Earth's interior several times by the plate tectonics that continue to shape our planet's surface.

Diamonds hint at 'earliest life' on Earth   BBC - July 2, 2008
Tiny slivers of diamond forged on an infant Earth may contain the earliest traces of life, a study has shown. Analysis of the crystals showed they

History of Ancient Supercontinent's Breakup Detailed   Live Science - April 29, 2008
The breakup of the supercontinent Gondwana eventually formed the continents in the Southern Hemisphere. Exactly how this happened has been debated by geologists for years. Most theories say Gondwana broke into many different pieces, but new research suggests the large land mass simply split in two.

New Discovery Of 'Old Growth' Crystals Provides New Record Of Planetary Evolution   Science Daily - March 5, 2008

Three-billion year-old zircon microcrystals found in northern Ontario are proving to be a new record of the processes that form continents and their natural resources, including gold and diamonds. Measuring no more than the width of a human hair, the 200-million-year growth span of these ancient microcrystals is longer than any previously discovered.

The Expanding Earth Debate - Part One - February 21, 2008
The Expanding Earth Debate - Part Two - February 22, 2008
The Expanding Earth Debate - Part Three - February 26, 2008

Early Earth Was Purple, Study Suggests   Live Science - April 11, 2007

The earliest life on Earth might have been just as purple as it is green today, a scientist claims. Ancient microbes might have used a molecule other than chlorophyll to harness the Sun's rays, one that gave the organisms a violet hue. Chlorophyll, the main photosynthetic pigment of plants, absorbs mainly blue and red wavelengths from the Sun and reflects green ones, and it is this reflected light that gives plants their leafy color. This fact puzzles some biologists because the sun transmits most of its energy in the green part of the visible spectrum.

Sea floor records ancient Earth   BBC - March 26, 2007

A sliver of four-billion-year-old sea floor has offered a glimpse into the inner workings of an adolescent Earth. The baked and twisted rocks, now part of Greenland, show the earliest evidence of plate tectonics, colossal movements of the planet's outer shell. Until now, researchers were unable to say when the process, which explains how oceans and continents form, began. Plate tectonics is a geological theory used to explain the observed large-scale motions of the Earth's surface.

Scientists probe 'hole in Earth' in the mid-Atlantic   BBC - March 1, 2007
The hole in the crust is midway between the Cape Verde Islands and the Caribbean, on the Mid-Atlantic Ridge. Usually the plates are pulled apart and to fill the gap the mantle underneath has to rise up. As it comes up it starts to melt. That forms the magma. That's the normal process. Here it has gone awry for some reason. The crust does not seem to be repairing itself.

Mission to Study Earth's Gaping 'Open Wound'   Live Science - March 1, 2007
A team of scientists will embark on a voyage next week to study an 'open wound' on the Atlantic seafloor where the Earth's deep interior lies exposed without any crust covering. There are two popular hypotheses about how these holes in the Earth's crust form.