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We present ab initio calculations of the high-temperature axial c/a ratio of hexagonal-close-packed (hcp) iron at Earth's core pressures, in order to help interpret the observed seismic anisotropy of the inner core. The calculations are based on density functional theory, which is known to predict the properties of high-pressure iron with good accuracy. The temperature dependence of c/a is determined by minimising the Helmholtz free energy at fixed volume and temperature, with thermal contributions due to lattice vibrations calculated using harmonic theory. Anharmonic corrections to the harmonic predictions are estimated from calculations of the thermal average stress obtained from ab initio molecular dynamics simulations of hcp iron at the conditions of the inner core. We find a very gradual increase of axial ratio with temperature. This increase is much smaller than found in earlier calculations, but is in reasonable agreement with recent high-pressure, high-temperature diffraction measurements. This result casts doubt on an earlier interpretation of the seismic anisotropy of the inner core.

In this week's bonus segment Ask Tai Why, Tai takes questions from: Penelope Cook, Toronto: Is there such a thing as complete silence? Griff, Yukon: What comes after humans? Finley, Wakefield, Quebec: Does the core of the earth glow?

In this week's bonus segment Ask Tai Why, Tai takes questions from: Penelope Cook, Toronto: Is there such a thing as complete silence? Griff, Yukon: What comes after humans? Finley, Wakefield, Quebec: Does the core of the earth glow?

A scientist invents a giant burrowing machine to explore the centre of the earth and discovers a frightening new world. Starring: Doug McClure, Peter Cushing, Caroline Munro, Cy Grant Distributed by Metro Goldwyn Mayer Classified PG

Geostrophic jets propagating as Alfv\'en waves are shown to arise ina rapidly rotating spherical shell permeated by a magnetic field among the transient motions set up by an impulsive rotation of the inner core. These axially invariant motions evolve on a time-scale which is short compared to the magnetic diffusion time. The numerical study is taken as illustrative of a more general point: on such a fast time-scale the dimensionless number appropriate to compare the rotation and magnetic forces is independent of the magnetic diffusivity in contrast with the often used Elsasser number. Extension of the analysis to non-axisymmetrical motions is supported by published studies of dynamo models and magnetic instabilities.

Dr. Abner Perry (Peter Cushing), a British Victorian scientist, and his US financier David Innes (Doug McClure) make a test run of their Iron Mole drilling machine in a Welsh mountain, but end up in a strange underground labyrinth ruled by a species of giant telepathic flying reptiles, the Mahars, and full of prehistoric beasts and cavemen. They are captured by the Mahars, who keep primitive humans as their slaves through mind control. David falls for the beautiful slave girl Princess Dia (Caroline Munro) but when she is chosen as a sacrificial victim in the Mahar city, David and Perry must rally the surviving human slaves to rebel and not only save her but also win their freedom.

En 1898, grâce à une fabuleuse machine souterraine de leur invention surnommée la Taupe , le professeur Abner Perry et son jeune assistant David Innes sont capables, à bord de leur engin, de creuser des galeries dans la roche. Mais au cours d'une expérience, la machine excavatrice s'emballe et les entraîne à grande vitesse jusqu'au centre de la Terre... Film américano-britannique réalisé par Kevin Connor en 1976.

We're reviewing every movie ever made. Today, At the Earth's Core: 70s Edgar Rice Burroughs shlock, but with Caroline Munroe.

Oldiees Publishing

A measurement of the absorption of neutrinos with energies in excess of 10 TeV when traversing the Earth is capable of revealing its density distribution. Unfortunately, the existence of beams with sufficient luminosity for the task has been ruled out by the AMANDA South Pole neutrino telescope. In this letter we point out that, with the advent of second-generation kilometer-scale neutrino detectors, the idea of studying the internal structure of the Earth may be revived using atmospheric neutrinos instead.

Introduction: Potassium (K) as a large ion lithophile element has dominantly been concentrated in the Earth s crust and the mantle through differentiation, and in the form of K-40 contributes to the planet s heat budget. However, whether or not K also enters core-forming phases, has been debated for over three decades. Arguments favoring entry of K in the core are based on: (1) K-sulfide (with Fe, Ni, Cu, Na, and Cl; djerfisherite) found in highly reduced enstatite chondrites (or aubrites, enstatite achondrites); (2) demonstration that K, owing to an s-d electronic switch at high-pressure, exhibits transition- element like character, (3) solubility of measurable K in Fe-Ni-S liquids at high pressure, temperature conditions, and (4) models of cooling of the core that seem to require, besides convection, some form of radioactivity, and thus lending support to the experimental work. In this contribution, we assess the effect of sequestering K in the core, as it is perhaps an element that is a key to reconciling geochemistry, paleomagnetism, accretion, and thermal evolution models for the planet.

Seismic studies indicate that the Earth's inner core has a complex structure and exhibits a strong elastic anisotropy with a cylindrical symmetry. Among the various models which have been proposed to explain this anisotropy, one class of models considers the effect of the Lorentz force associated with the magnetic field diffused within the inner core. In this paper we extend previous studies and use analytical calculations and numerical simulations to predict the geometry and strength of the flow induced by the poloidal component of the Lorentz force in a neutrally or stably stratified growing inner core, exploring also the effect of different types of boundary conditions at the inner core boundary (ICB). Unlike previous studies, we show that the boundary condition that is most likely to produce a significant deformation and seismic anisotropy is impermeable, with negligible radial flow through the boundary. Exact analytical solutions are found in the case of a negligible effect of buoyancy forces in the inner core (neutral stratification), while numerical simulations are used to investigate the case of stable stratification. In this situation, the flow induced by the Lorentz force is found to be localized in a shear layer below the ICB, which thickness depends on the strength of the stratification, but not on the magnetic field strength. We obtain scaling laws for the thickness of this layer, as well as for the flow velocity and strain rate in this shear layer as a function of the control parameters, which include the magnitude of the magnetic field, the strength of the density stratification, the viscosity of the inner core, and the growth rate of the inner core. We find that the resulting strain rate is probably too small to produce significant texturing unless the inner core viscosity is smaller than about $10^{12}$ Pa.s.

152 p. : 22 cm

This article is from Scientific Reports , volume 3 . Abstract Recent global expansion of seismic data motivated a number of seismological studies of the Earth's inner core that proposed the existence of increasingly complex structure and anisotropy. In the meantime, new hypotheses of dynamic mechanisms have been put forward to interpret seismological results. Here, the nature of hemispherical dichotomy and anisotropy is re-investigated by bridging the observations of PKP(bc-df) differential travel-times with the iron bcc/hcp elastic properties computed from first-principles methods.The Candy Wrapper velocity model introduced here accounts for a dynamic picture of the inner core (i.e., the eastward drift of material), where different iron crystal shapes can be stabilized at the two hemispheres. We show that seismological data are best explained by a rather complicated, mosaic-like, structure of the inner core, where well-separated patches of different iron crystals compose the anisotropic western hemispherical region, and a conglomerate of almost indistinguishable iron phases builds-up the weakly anisotropic eastern side.

The geomagnetic spatial power spectrum R(sub n)(r) is the mean square magnetic induction represented by degree n spherical harmonic coefficients of the internal scalar potential averaged over the geocentric sphere of radius r. McLeod's Rule for the magnetic field generated by Earth's core geodynamo says that the expected core surface power spectrum (R(sub nc)(c)) is inversely proportional to (2n + 1) for 1 less than n less than or equal to N(sub E). McLeod's Rule is verified by locating Earth's core with main field models of Magsat data; the estimated core radius of 3485 kn is close to the seismologic value for c of 3480 km. McLeod's Rule and similar forms are then calibrated with the model values of R(sub n) for 3 less than or = n less than or = 12. Extrapolation to the degree 1 dipole predicts the expectation value of Earth's dipole moment to be about 5.89 x 10(exp 22) Am(exp 2)rms (74.5% of the 1980 value) and the expected geomagnetic intensity to be about 35.6 (mu)T rms at Earth's surface. Archeo- and paleomagnetic field intensity data show these and related predictions to be reasonably accurate. The probability distribution chi(exp 2) with 2n+1 degrees of freedom is assigned to (2n + 1)R(sub nc)/(R(sub nc). Extending this to the dipole implies that an exceptionally weak absolute dipole moment (less than or = 20% of the 1980 value) will exist during 2.5% of geologic time. The mean duration for such major geomagnetic dipole power excursions, one quarter of which feature durable axial dipole reversal, is estimated from the modern dipole power time-scale and the statistical model of excursions. The resulting mean excursion duration of 2767 years forces us to predict an average of 9.04 excursions per million years, 2.26 axial dipole reversals per million years, and a mean reversal duration of 5533 years. Paleomagnetic data show these predictions to be quite accurate. McLeod's Rule led to accurate predictions of Earth's core radius, mean paleomagnetic field intensity, and mean geomagnetic dipole power excursion and axial dipole reversal frequencies. We conclude that McLeod's Rule helps unify geo-paleomagnetism, correctly relates theoretically predictable statistical properties of the core geodynamo to magnetic observation, and provides a priori information required for stochastic inversion of paleo-, archeo-, and/or historical geomagnetic measurements.

We show that a simple, modified version of the Magnetorotational Instability (MRI) can develop in the outer liquid core of the Earth, in the presence of a background shear. It requires either thermal wind, or a primary instability, such as convection, to drive a weak differential rotation within the core. The force balance in the Earth's core is very unlike classical astrophysical applications of the MRI (such as gaseous disks around stars). Here, the weak differential rotation in the Earth core yields an instability by its constructive interaction with the planet's much larger rotation rate. The resulting destabilising mechanism is just strong enough to counteract stabilizing resistive effects, and produce growth on geophysically interesting timescales. We give a simple physical explanation of the instability, and show that it relies on a force balance appropriate to the Earth's core, known as magnetostrophic balance.

Dr. Abner Perry, a British  Victorian   scientist , and his US financier  David Innes  make a test run of their  Iron Mole  drilling machine in a  Welsh  mountain. While drilling underground, the extreme heat emanating from the magma around the Mole knocks the duo out and makes them temporarily lose control over where the machine is taking them. After it passes through the magma crust and gets closer to the Earth's core, the temperature inside the Mole starts to lower, and the duo regains consciousness. Perry and Innes eventually reach a surface where they can safely get out. The two notice they are in a strange land filled with the flora and fauna of prehistoric times. They are eventually captured by the Sagoths, ape-like creatures, who aim to enslave every human tribe there. The Sagoths are themselves ruled by a species of telepathic flying reptiles, the Mahars ( Pterodactyls  with parrot-like beaks). The Mahars have the power of  mind control . David falls for the enslaved Princess Dia. She is eventually chosen as a sacrificial victim in the Mahar city, while David is put to work in the magma mines and Perry visits the library. Worried about Dia, David incites a riot within the mine and is captured with Ra, another rebellious slave. The two are sent to the arena where a crowd of slaves watch. The Mahars send a giant dinosaur to kill the duo, but with the help of Perry (who shouts about the creature's weak point from the crowd), David and Ra survive. They not only kill the dinosaur but an attacking Mahar as well, earning the respect of the slaves. David and Ra must rally the surviving human slaves to rebel and win their freedom. To achieve this, Innes, Ra and Dia organise the oppressed tribes and help them work together while Perry teaches them how to construct and use bows and arrows. Together, the humans manage to kill the Mahars and subdue their minions. After repairing the Mole, Perry and Innes prepare to go back to the surface with Dia. However, despite how much Dia loves Innes, she believes she will not fit in the surface world, like Innes does not fit in her own world. A hurt Innes accepts her reasoning and decides to return alone with Perry to the United Kingdom. However, a miscalculation results in the Iron Mole resurfacing outside the  White House , much to the shock of two policemen standing guard there.

British-American science fantasy film directed by Kevin Connor, produced by John Dark, Max Rosenberg, and Milton Subotsky for Amicus Productions, and written by Subotsky, based on the 1914 novel of the same name by Edgar Rice Burroughs, the first in his hollow earth series Pellucidar . It stars Peter Cushing and Doug McClure as Victorian scientist Dr. Abner Perry and his American financer David Innes, whose test of their new drilling machine in the Welsh mountains leads them to discover the prehistoric underground world of Pellucidar; a savage land filled with dinosaurs, the ape-men Sagoths, and their telepathic Pterodactyl-like rulers, the Mahars, who aim to rule all the human tribes in the land. Joining forces with the enslaved Princess Dia (Caroline Munro,) they aim to unite the human tribes to overthrow the Mahars and escape back to the surface. It co-stars Cy Grant as Ra, Godfrey James as Ghak the Ugly One, and Robert Gillespie as a photographer. It is part of a loose trilogy of Burroughs adaptations from Amicus, Connor, and Rosenberg, being released between the two parts of the lost world Caprona duology which also starred McClure.

LibriVox recording of At the Earth's Core (version 2) by Edgar Rice Burroughs. Read in English by Mark Nelson David Innes is a mining heir who finances the experimental "iron mole," an excavating vehicle designed by his elderly inventor friend Abner Perry. In a test run, they discover the vehicle cannot be turned, and it burrows 500 miles into the Earth's crust, emerging into the unknown interior world of Pellucidar. In Burroughs' concept, the Earth is a hollow shell with Pellucidar as the internal surface of that shell. Pellucidar is inhabited by prehistoric creatures of all geological eras, and dominated by the Mahars, a species of flying reptile both intelligent and civilized, but which enslaves and preys on the local stone-age humans. Innes and Perry are captured by the Mahars' ape-like Sagoth servants and taken with other human captives to the chief Mahar city of Phutra. Among their fellow captives are the brave Ghak, the Hairy One, from the country of Sari, the shifty Hooja the Sly One and the lovely Dian the Beautiful of Amoz. - Summary by Wikipedia For further information, including links to online text, reader information, RSS feeds, CD cover or other formats (if available), please go to the LibriVox catalog page for this recording. For more free audio books or to become a volunteer reader, visit LibriVox.org . Download M4B (137MB)

S-wave shadow and P-wave detection patterns give us information about the core

There are several hypotheses on the specific processes that might have occurred during the formation of the Earth. One hypothesis that has been proposed is that early in the Earth's formation, there was a magma ocean present, and within this body, siderophile elements separated out of the silicate liquid to form the metal core. This study addresses this hypothesis. P and Mo are moderately siderophile elements that are present in both the mantle and the core. The concentrations of P and Mo in silicate vs. metal can be measured and in turn used to determine the temperatures, pressures, oxygen fugacity and melt composition required to achieve the same concentrations as observed in the mantle. The data here include eight experiments examining the partitioning of P and Mo between metallic liquid and silicate liquid. The purpose of the experiments has been to gain a greater understanding of core-mantle separation during the Earth formation process and examines temperature effect on P and Mo, which has not been systematically studied before.

Assimilation of surface geomagnetic observations and geodynamo models has advanced very quickly in recent years. However, compared to advanced data assimilation systems in meteorology, geomagnetic data assimilation (GDAS) is still in an early stage. Among many challenges ranging from data to models is the disparity between the short observation records and the long time scales of the core dynamics. To better utilize available observational information, we have made an effort in this study to directly assimilate the Gauss coefficients of both the core field and its secular variation (SV) obtained via global geomagnetic field modeling, aiming at understanding the dynamical responses of the core fluid to these additional observational constraints. Our studies show that the SV assimilation helps significantly to shorten the dynamo model spin-up process. The flow beneath the core-mantle boundary (CMB) responds significantly to the observed field and its SV. The strongest responses occur in the relatively small scale flow (of the degrees L is approx. 30 in spherical harmonic expansions). This part of the flow includes the axisymmetric toroidal flow (of order m = 0) and non-axisymmetric poloidal flow with m (is) greater than 5. These responses can be used to better understand the core flow and, in particular, to improve accuracies of predicting geomagnetic variability in future.

There are several hypotheses on the specific processes that might have occurred during the formation of the Earth. One hypothesis that has been proposed is that early in the Earth's formation, there was a magma ocean present, and within this body, siderophile elements separated out of the silicate liquid to form the metal core. This study addresses this hypothesis. P and Mo are moderately siderophile elements that are present in both the mantle and the core. The concentrations of P and Mo in silicate vs. metal can be measured and in turn used to determine the temperatures, pressures, oxygen fugacity and melt composition required to achieve the same concentrations as observed in the mantle. The data here include eight experiments examining the partitioning of P and Mo between metallic liquid and silicate liquid. The purpose of the experiments has been to gain a greater understanding of core-mantle separation during the Earth formation process and examines temperature effect on P and Mo, which has not been systematically studied before.

Various research studies designed to enhance knowledge about the earth's core are discussed. Areas addressed include: (1) the discovery of the earth's core; (2) experimental approaches used in studying the earth's core (including shock-wave experiments and experiments at high static pressures), the search for the core's light elements, the possible presence of potassium in the core, and use of the diamond cell for investigating the core; (3) seismic explorations of the core; (4) inhomogeneities at the core-mantle boundary; (5) terrestrial magnetism and the outer core; and (6) theories of inner-earth structure from the perspective of solar system history. Studies of the earth's mantle which may provide additional information about the earth's core are also discussed. They include laboratory experiments with mantle materials and modeling of mantle structure at the Carnegie Institution's Department of Terrestrial Magnetism. It is pointed out that although many questions about the earth's core are still unanswered, the promise of new research tools is vast. Favored by advances in computer modeling and in techniques for experiments at very high pressure, today's scientists seem well-positioned to address these questions about the deep earth. (JN)

Free core nutation (FCN) is the main factor that limits the accuracy of the modeling of the motion of Earth's rotational axis in the celestial coordinate system. Several FCN models have been proposed. A comparative analysis is made of the known models including the model proposed by the author. The use of the FCN model is shown to substantially increase the accuracy of the modeling of Earth's rotation. Furthermore, the FCN component extracted from the observed motion of Earth's rotational axis is an important source for the study of the shape and rotation of the Earth's core. A comparison of different FCN models has shown that the proposed model is better than other models if used to extract the geophysical signal (the amplitude and phase of FCN) from observational data.

A general set of methods is presented for calculating chemical potentials in solid and liquid mixtures using {\em ab initio} techniques based on density functional theory (DFT). The methods are designed to give an {\em ab initio} approach to treating chemical equilibrium between coexisting solid and liquid solutions, and particularly the partitioning ratio of solutes between such solutions. For the liquid phase, the methods are based on the general technique of thermodynamic integration, applied to calculate the change of free energy associated with the continuous interconversion of solvent and solute atoms, the required thermal averages being computed by DFT molecular dynamics simulation. For the solid phase, free energies and hence chemical potentials are obtained using DFT calculation of vibrational frequencies of systems containing substitutional solute atoms, with anharmonic contributions calculated, where needed, by thermodynamic integration. The practical use of the methods is illustrated by applying them to study chemical equilibrium between the outer liquid and inner solid parts of the Earth's core, modelled as solutions of S, Si and O in Fe. The calculations place strong constraints on the chemical composition of the core, and allow an estimate of the temperature at the inner-core/outer-core boundary.

Seismic waves sensitive to the outermost part of the Earth's liquid core seem to be affected by a stably stratified layer at the core-mantle boundary. Such a layer could have an observable signature in both long-term and short-term variations of the magnetic field of the Earth, which are used to probe the flow at the top of the core. Indeed, with the recent SWARM mission, it seems reasonable to be able to identify waves propagating in the core with period of several months, which may play an important role in the large-scale dynamics. In this paper, we characterize the influence of a stratified layer at the top of the core on deep quasi-geostrophic (Rossby) waves. We compute numerically the quasi-geostrophic eigenmodes of a rapidly rotating spherical shell, with a stably stratified layer near the outer boundary. Two simple models of stratification are taken into account, which are scaled with commonly adopted values of the Brunt-V{\"a}is{\"a}l{\"a} frequency in the Earth's core. In the absence of magnetic field, we find that both azimuthal wavelength and frequency of the eigenmodes control their penetration into the stratified layer: the higher the phase speed, the higher the permeability of the stratified layer to the wave motion. We also show that the theory developed by Takehiro and Lister [2001] for thermal convection extends to the whole family of Rossby waves in the core. Adding a magnetic field, the penetrative behaviour of the quasi-geostrophic modes (the so-called fast branch) is insensitive to the imposed magnetic field and only weakly sensitive to the precise shape of the stratification. Based on these results, the large-scale and high frequency modes (1 to 2 month periods) may be detectable in the geomagnetic data measured at the Earth's surface, especially in the equatorial area where the modes can be trapped.

Called from his home in the African jungle to great adventure, Tarzan of the Apes joins the Jason Gridley expedition to seek the arctic opening in the earth’s surface that leads to the inner world of Pellucidar. Sailing by airship, they glide almost imperceptibly from the world that we know to the strange and terrifying land that lies beneath the earth’s crust.

Called from his home in the African jungle to great adventure, Tarzan of the Apes joins the Jason Gridley expedition to seek the arctic opening in the earth’s surface that leads to the inner world of Pellucidar. Sailing by airship, they glide almost imperceptibly from the world that we know to the strange and terrifying land that lies beneath the earth’s crust.

The long wavelength components of the Earth's gravity field result mainly from density contrasts associated with convection in the mantle. Direct interpretation of the geoid for mantle convection is complicated by the fact that convective flow results in dynamically maintained deformation of the surface of the Earth, the core mantle boundary (CMB), and any interior chemical boundaries which might exist. These boundary deformations effect the geoid opposite in sign and are comparable in magnitude to those of the interior density contrasts driving the flow. The total difference of two relatively large quantities.

Travel times of PcP and P phases from nuclear and high explosive sources are interpreted in terms of variations in the radius of the earth's outer core. This interpretation favors a core which is slightly larger and has less ellipticity than the Taggart-Engdahl reference model. Other interpretations in terms of lateral variation in mantle velocity are possible. Because of the geographic distribution of events and stations, only the northern hemisphere of the core is represented. A modified spherical harmonic analysis method is used to smooth the data and to estimate the shape of the core. The variation of core radius determined from this representation of data truncated at one standard deviation is approximately plus or minus 10 kilometers on the basis of terms to degree and order 5. Variations in geoid height resulting from the inferred variations in core radius do not correlate with, but are of the same order of magnitude as, those determined from satellite observations. PcP amplitude/period shows little variation with ep central distance. The PcP phase is generally shorter in apparent period than the P phase. This relationship is reversed, however, for arrivals from the Novaya Zemlya event of October 27, 1966. Ray tracing techniques are used to estimate the perturbation of the PcP-P time interval and PcP/P amplitude ratio produced by a hypothetical upper mantle low velocity zone of varying thickness.

We employ state-of-the-art ab initio simulations within the dynamical mean-field theory to study three likely phases of iron (hexogonal close-packed, hcp, face centered cubic, fcc, and body centered cubic, bcc) at the Earth's core conditions. We demonstrate that the correction to the electronic free energy due to correlations can be significant for the relative stability of the phases. The strongest effect is observed in bcc Fe, which shows a non-Fermi liquid behaviour, and where a Curie-Weiss behaviour of the uniform susceptbility hints at a local magnetic moment still existing at 5800 K and 300 GPa. We predict that all three structures have sufficiently high magnetic susceptibility to stabilize the geodynamo.

First principles electronic structure calculations based on density functional theory have been used to study the thermodynamic, structural and transport properties of solid solutions and liquid alloys of iron and oxygen at Earth's core conditions. Aims of the work are to determine the oxygen concentration needed to account for the inferred density in the outer core, to probe the stability of the liquid against phase separation, to interpret the bonding in the liquid, and to find out whether the viscosity differs significantly from that of pure liquid iron at the same conditions. It is shown that the required concentration of oxygen is in the region 25-30 mol percent, and evidence is presented for phase stability at these conditions. The Fe-O bonding is partly ionic, but with a strong covalent component. The viscosity is lower than that of pure liquid iron at Earth's core conditions. It is shown that earlier first-principles calculations indicating very large enthalpies of formation of solid solutions may need reinterpretation, since the assumed crystal structures are not the most stable at the oxygen concentration of interest.

First principles electronic structure calculations based on density functional theory have been used to study the thermodynamic, structural and transport properties of solid solutions and liquid alloys of iron and oxygen at Earth's core conditions. Aims of the work are to determine the oxygen concentration needed to account for the inferred density in the outer core, to probe the stability of the liquid against phase separation, to interpret the bonding in the liquid, and to find out whether the viscosity differs significantly from that of pure liquid iron at the same conditions. It is shown that the required concentration of oxygen is in the region 25-30 mol percent, and evidence is presented for phase stability at these conditions. The Fe-O bonding is partly ionic, but with a strong covalent component. The viscosity is lower than that of pure liquid iron at Earth's core conditions. It is shown that earlier first-principles calculations indicating very large enthalpies of formation of solid solutions may need reinterpretation, since the assumed crystal structures are not the most stable at the oxygen concentration of interest.

Book from Project Gutenberg: At the Earth's Core

As Earth's main magnetic field weakens, our magnetic shield against the onslaught of the solar wind thins. And the field strength needed to fend off battering by solar coronal mass ejections is decreasing, just when the delicate complexity of modem, vulnerable, electro-technological systems is increasing at an unprecedented rate. Recently, a working group of distinguished scientist from across the nation has asked NASA's Solid Earth and Natural Hazards program a key question: What are the dynamics of Earth s magnetic field and its interactions with the Earth system? Paleomagnetic studies of crustal rocks magnetized in the geologic past reveal that polarity reversals have occurred many times during Earth s history. Networked super-computer simulations of core field and flow, including effects of gravitational, pressure, rotational Coriolis, magnetic and viscous forces, suggest how this might happen in detail. And space-based measurements of the real, time-varying magnetic field help constrain estimates of the speed and direction of fluid iron flowing near the top of the core and enable tests of some hypotheses about such flow. Now scientists at NASA s Goddard Space Flight Center have developed and applied methods to test the hypotheses of narrow scale flow and of a dynamically weak magnetic field near the top of Earth s core. Using two completely different methods, C. V. Voorhies has shown these hypotheses lead to specific theoretical forms for the "spectrum" of Earth s main magnetic field and the spectrum of its rate of change. Much as solar physicists use a prism to separate sunlight into its spectrum, from long wavelength red to short wavelength blue light, geophysicists use a digital prism, spherical harmonic analysis, to separate the measured geomagnetic field into its spectrum, from long to short wavelength fields. They do this for the rate of change of the field as well.

The thirteenth Edgar Rice Burroughs Tarzan book. This Ace edition was published in 1963 without a copyright notice. It was first published as a serial in The Blue Book Magazine in 1929.

This version of Alex Raymond's comic strip hero moves Flash to the year 3061, where he battles criminals and evil aliens for the Galaxy Bureau of Investigation. Starring Steve Holland as Flash Gordon, Irene Champlin as Dale Arden, Joseph Nash as Dr. Alexis Zarkov. In this episode, to investigate the source of a series of unexplained earthquakes, Flash and his companions use an atomic boring machine to burrow deep into the Earth, where they find a subterranean race intent on conquering the surface.

SCIENCE FICTION, ENGLISH, EDGAR RICE BURROUGHS

POPULAR SCIENCE, ENGLISH

Pilot (The Green Slime) Here comes Captain Feathersword! (The Crawling Eye) Manos: The Hands of Fate Werewolf The Wiggles Movie Danger!! Death Ray! Earth Vs The Spider Daddy-O Beginning Of The End Eegah The Killer Shrews Last Of The Wild Horses Godzilla Vs Megaton Godzilla Vs The Sea Monster I Accuse My Parents The Wild World Of Batwoman Attack Of The Giant Leeches Robot Holocaust Night Of The Blood Beast Gorgo Quest Of The Delta Knights Santa Claus Conquers The Martians Time Of The Apes The Mad Monster Teenage Crime Wave Fugitive Alien Gamera Star Force: Fugitive Alien 2 Gamera Vs Gaos Gamera Vs Zigra Gamera vs Barugon Gamera vs Guidon Pod People Master Ninja Master Ninja 2 Castle Of Fu Manchu The Amazing Colossal Man War of the Colossal Beast Mighty Jack Red Zone Cuba Fire Maidens From Outer Space Hercules And The Captive Women Rocketship X-M Operation Double 007 The Indestructible Man The Atomic Brain Invasion Of The Neptune Men SST Death Flight Legend of the Dinosaurs Superdome Cosmic Princess Humanoid Woman Lost Continent The Last Chase Moon Zero Two The Millon Eyes Of Subaru Revenge of The Mysterious From Mars Invaders From The Deep Women Of The Prehistoric Planet The Magic Voyage Of Sinbad Hercules (1953) The Unearthly Hercules Against The Moon Men The Human Duplicators Tormented Angel's Revenge The Beatniks The Incredibly Strange Creatures Who Stopped Living And Became Mixed Up Zombies This Island Earth Racket Girls Bride Of The Monster Hercules Unchained Santa Claus (Mexican) The Robot Vs The Aztec Mummy The Saga Of The Viking Women And Their Voyage To The Waters Of The Sea Serpent The Corpse Vanishes The Amazing Transparent Man Swamp Diamonds The Crawling Hand Manhunt In Space Crash Of The Moons Monster A Go Go Cave Dwellers The Brute Man The Sword And The Dragon Untamed Youth It Conquered The World The Painted Hills The Black Scorpion The Day The Earth Froze The Magic Sword Secret Agent Super Dragon The Beast Of Yucca Flats Invasion USA The Girl In Lover's Lane City Limits The Rebel Set Bloodlust Girls Town Gunslinger Being From Another Planet Warrior Of The Lost World Zombie Nightmare Deathstalker And The Warriors Of Hell Teenage Strangler Space Travelers The Dead Talk Back The Creeping Terror Stranded In Space The Screaming Skull Rocket Attack USA The Slime People Reptilicus San Fransico International Alien From L.A. Colossus And The Headhunters Wild Rebels Cry Wilderness Starcrash The Time Travelers The Loves Of Hercules Wizards Of The Lost Kingdom Wizards Of The Lost Kingdom 2 Yongary, Monster From The Deep The Christmas That Almost Wasn't At The Earth's Core The Beast Of Hollow Mountain Little Red Riding Hood (Mexican) Avalanche Carnival Magic Invasion Of The Animal People Code Name Diamond Head The Land That Time Forgot The Skydivers The Violent Years Eliminators The Starfighters The Hellcats The Sidehackers Horrors Of Spider Island Kitten With A Whip Ring Of Terror High School Big Shot Track Of The Moon Beast Projected Man The Incredible Melting Man Escape 2000 Phantom Planet Hobgoblins Project Moonbase The Sinster Urge Robot Monster I Was A Teenage Werewolf Merlin's Shop Of Mystical Wonders It Lives By Night Outlaw Of Gor Boggy Creek II: The Legend Continues The Girl In The Gold Boots Blood Waters Of Dr.Z The Final Sacrifice Parts: The Clonus Horror Future War Hamlet (German Black And White) Devil Fish Touch Of Satan The Space Children Agent For H.A.R.M Final Justice Village Of The Giants Samson Vs The Vampire Woman Laserblast Revenge Of The Creature The Leech Woman The Thing That Wouldn't Die Mac And Me Atlantic Rim The Day Time Ended Killer Fish Lords Of The Deep Ator Gamera VS Viras Gamera VS Jiger Gamera Super Monster Argoman Deathstalker 2 The Brain World Without End No Retreat No Surrender Circus Of Horrors

Pilot (The Green Slime) Here comes Captain Feathersword! (The Crawling Eye) Manos: The Hands of Fate Werewolf The Wiggles Movie Danger!! Death Ray! Earth Vs The Spider Daddy-O Beginning Of The End Eegah The Killer Shrews Last Of The Wild Horses Godzilla Vs Megaton Godzilla Vs The Sea Monster I Accuse My Parents The Wild World Of Batwoman Attack Of The Giant Leeches Robot Holocaust Night Of The Blood Beast Gorgo Quest Of The Delta Knights Santa Claus Conquers The Martians Time Of The Apes The Mad Monster Teenage Crime Wave Fugitive Alien Gamera Star Force: Fugitive Alien 2 Gamera Vs Gaos Gamera Vs Zigra Gamera vs Barugon Gamera vs Guidon Pod People Master Ninja Master Ninja 2 Castle Of Fu Manchu The Amazing Colossal Man War of the Colossal Beast Mighty Jack Red Zone Cuba Fire Maidens From Outer Space Hercules And The Captive Women Rocketship X-M Operation Double 007 The Indestructible Man The Atomic Brain Invasion Of The Neptune Men SST Death Flight Legend of the Dinosaurs Superdome Cosmic Princess Humanoid Woman Lost Continent The Last Chase Moon Zero Two The Millon Eyes Of Subaru Revenge of The Mysterious From Mars Invaders From The Deep Women Of The Prehistoric Planet The Magic Voyage Of Sinbad Hercules (1953) The Unearthly Hercules Against The Moon Men The Human Duplicators Tormented Angel's Revenge The Beatniks The Incredibly Strange Creatures Who Stopped Living And Became Mixed Up Zombies This Island Earth Racket Girls Bride Of The Monster Hercules Unchained Santa Claus (Mexican) The Robot Vs The Aztec Mummy The Saga Of The Viking Women And Their Voyage To The Waters Of The Sea Serpent The Corpse Vanishes The Amazing Transparent Man Swamp Diamonds The Crawling Hand Manhunt In Space Crash Of The Moons Monster A Go Go Cave Dwellers The Brute Man The Sword And The Dragon Untamed Youth It Conquered The World The Painted Hills The Black Scorpion The Day The Earth Froze The Magic Sword Secret Agent Super Dragon The Beast Of Yucca Flats Invasion USA The Girl In Lover's Lane City Limits The Rebel Set Bloodlust Girls Town Gunslinger Being From Another Planet Warrior Of The Lost World Zombie Nightmare Deathstalker And The Warriors Of Hell Teenage Strangler Space Travelers The Dead Talk Back The Creeping Terror Stranded In Space The Screaming Skull Rocket Attack USA The Slime People Reptilicus San Fransico International Alien From L.A. Colossus And The Headhunters Wild Rebels Cry Wilderness Starcrash The Time Travelers The Loves Of Hercules Wizards Of The Lost Kingdom Wizards Of The Lost Kingdom 2 Yongary, Monster From The Deep The Christmas That Almost Wasn't At The Earth's Core The Beast Of Hollow Mountain Little Red Riding Hood (Mexican) Avalanche Carnival Magic Invasion Of The Animal People Code Name Diamond Head The Land That Time Forgot The Skydivers The Violent Years Eliminators The Starfighters The Hellcats The Sidehackers Horrors Of Spider Island Kitten With A Whip Ring Of Terror High School Big Shot Track Of The Moon Beast Projected Man The Incredible Melting Man Escape 2000 Phantom Planet Hobgoblins Project Moonbase The Sinster Urge Robot Monster I Was A Teenage Werewolf Merlin's Shop Of Mystical Wonders It Lives By Night Outlaw Of Gor Boggy Creek II: The Legend Continues The Girl In The Gold Boots Blood Waters Of Dr.Z The Final Sacrifice Parts: The Clonus Horror Future War Hamlet (German Black And White) Devil Fish Touch Of Satan The Space Children Agent For H.A.R.M Final Justice Village Of The Giants Samson Vs The Vampire Woman Laserblast Revenge Of The Creature The Leech Woman The Thing That Wouldn't Die Mac And Me Atlantic Rim The Day Time Ended Killer Fish Lords Of The Deep Ator Gamera VS Viras Gamera VS Jiger Gamera Super Monster Argoman Deathstalker 2 The Brain World Without End No Retreat No Surrender Circus Of Horrors

Called from his home in the African jungle to great adventure, Tarzan of the Apes summons his Waziri spearmen and joins the Jason Gridley expedition to seek the artic opening in the earthâs surface that leads to the inner world of Pellucidar. Sailing by airship, they glide almost imperceptibly from the world that we know to the strange and terrifying land that lies beneath the earthâs crust. There, where time does not exist, where neither Tarzanâs jungle lore nor the charts of scientists are of any use as guides they face the problem of rescuing an American adventurer who is held captive by the blood-thirsty Korsars. Here, on land and sea and even in the air, lurk unknown perils. Tarzan is carried off in the talons of a ferocious bat-like creature to its mountain eyrie. Slashing his way through trackless forests and the dangerous swamps, outwitting his cruel human captors, Tarzan faces the most terrific encounters of his adventure-crammed life when, rescuing the beautiful Jana, known as The Red Flower, he falls into the hands of the reptile-men who, astride gigantic lizards, move with lightning speed and relentless ferocity to spread terror throughout the land. Long available only with censored text, this is the original First Edition book version of this novel in the Tarzan Series.

Bande-annonce de At the Earth's Core , film américano-britannique réalisé par Kevin Connor en 1976. En 1898, grâce à une fabuleuse machine souterraine de leur invention surnommée la Taupe , le professeur Abner Perry et son jeune assistant David Innes sont capables, à bord de leur engin, de creuser des galeries dans la roche. Mais au cours d'une expérience, la machine excavatrice s'emballe et les entraîne à grande vitesse jusqu'au centre de la Terre.

Bande-annonce de At the Earth's Core , film américano-britannique réalisé par Kevin Connor en 1976. En 1898, grâce à une fabuleuse machine souterraine de leur invention surnommée la Taupe , le professeur Abner Perry et son jeune assistant David Innes sont capables, à bord de leur engin, de creuser des galeries dans la roche. Mais au cours d'une expérience, la machine excavatrice s'emballe et les entraîne à grande vitesse jusqu'au centre de la Terre.

LibriVox recording of At the Earth's Core, by Edgar Rice Burroughs. This is the first book in the Pellucidar series. Pellucidar is a fictional Hollow Earth milieu invented by Edgar Rice Burroughs for a series of action adventure stories. The stories initially involve the adventures of mining heir David Innes and his inventor friend Abner Perry after they use an "iron mole" to burrow 500 miles into the earth's crust. (adapted from Wikipedia) For further information, including links to online text, reader information, RSS feeds, CD cover or other formats (if available), please go to the LibriVox catalog page for this recording. For more free audio books or to become a volunteer reader, visit LibriVox.org . Download M4B (97MB)

While cleaning out an old dusty trunk in your Grandfather's attic, you discover a diary written by a man named Wendorf MacMillan. The entry dated April 3, 1857 tells where a small gold mine is located in the Rocky Mountains. In the entries that follow, Wendorf tells about a series of underground caves he discovered while digging in his mine. Vividly, he describes his Journey to the Earth's Core. The path is laden with danger and with great riches, including fistfuls of diamonds at the Earth's Core. After carefully weighing all the risks, you decide to make the Journey to the Earth's Core. You will start your journey at a small store in the Rocky Mountains. You have $1,000 to spend on supplies. The store carries a variety of items, such as ropes, weapons, and tools. You should buy what you think you will need to complete the entire journey. When you leave the store, you will find yourself at the bottom of the tall mountain described in Wendorf's diary. Your first objective will be to find the entrance to Wendorf's Gold Mine.

A spherical harmonic representation of the geomagnetic field and its secular variation for epoch 1980, designated GSFC(9/84), is derived and evaluated. At three epochs (1977.5, 1980.0, 1982.5) this model incorporates conservation of magnetic flux through five selected patches of area on the core/mantle boundary bounded by the zero contours of vertical magnetic field. These fifteen nonlinear constraints are included like data in an iterative least squares parameter estimation procedure that starts with the recently derived unconstrained field model GSFC (12/83). Convergence is approached within three iterations. The constrained model is evaluated by comparing its predictive capability outside the time span of its data, in terms of residuals at magnetic observatories, with that for the unconstrained model.

A spherical harmonic representation of the geomagnetic field and its secular variation for epoch 1980, designated GSFC(9/84), is derived and evaluated. At three epochs (1977.5, 1980.0, 1982.5) this model incorporates conservation of magnetic flux through five selected patches of area on the core/mantle boundary bounded by the zero contours of vertical magnetic field. These fifteen nonlinear constraints are included like data in an iterative least squares parameter estimation procedure that starts with the recently derived unconstrained field model GSFC (12/83). Convergence is approached within three iterations. The constrained model is evaluated by comparing its predictive capability outside the time span of its data, in terms of residuals at magnetic observatories, with that for the unconstrained model.