Airborne geophysical study in the pensacola mountains of antarctica

A seismic reflection, gravity, and aeromagnetic reconnaissance was made in the Pensacola Mountains, Antarctica, during the 1965-66 austral summer. Prominent ice streams located between the Neptune and Patuxent Ranges and east of the Forrestal Range overlie channels in the rock surface 2000 meters below sea level which are probably of glacial origin. Seismic reflections show that the Filchner Ice Shelf is 1270 meters thick near its southern margin. Along the boundary between West and East Antarctica, Bouguer anomalies decrease from +60 milligals in West Antarctica to -80 milligals in East Antarctica. An abrupt change in crustal structure across this boundary is required to explainl the 2 milligals per kilometer gradient. This may indicate a fault extending through the crust into the mantle. Aeromagnetic profiles delineate anomalies up to 1800 gamma associated with the basic stratiform intrusion which comprises the Dufek and Forrestal ranges. A probable minimum area of 9500 square kilometers is calculated for the intrusive body on the basis of the magnetic anomalies, making it one of the largest bodies of its type. The extension of this magnetic anominaly across a fault forming the north border of the Pensacola Mountains probably precludes transcurrent movement.     

East pacific rise crest: a near-bottom geophysical profile

A deep-towed magnetometer profile made across the East Pacific Rise crest shows many anomalies with about 1000-gamma amplitudes and 500-meter wavelengths and has larger amplitude changes corresponding to magnetic field reversals. This profile across contacts between normal and reversely magnetized crustal blocks is interpreted to place an upper limit of 4700 years on the time required for field reversals and an upper limit of 280 meters on the width of the intrusion center at the rise crest. This intrusion center may occasionally shift several kilometers laterally with respect to the rise axis. The magnetometer records are compatible with the hypothesis that the magnetic field has undergone many fluctuations of short period and small intensity in the past 2 million years. Sediment accumulation increases from less than 2 meters at the rise crest axis to about 20 meters at the western end and 10 meters at the eastern end of the profile. This increase in accutmiulation appears to be the result of ocean-floor spreading.     

The moon: sources of the crustal magnetic anomalies

Previously unmapped Apollo 16 subsatellite magnetometer data collected at low altitudes over the lunar near side are presented. Medium-amplitude magnetic anomalies exist over the Fra Mauro and Cayley Formations (primary and secondary basin ejecta emplaced 3.8 to 4.0 billion years ago) but are nearly absent over the maria and over the craters Copernicus, Kepler, and Reiner and their encircling ejecta mantles. The largest observed anomaly (radial component approximately 21 gammas at an altitude of 20 kilometers) is exactly correlated with a conspicuous light-colored deposit on western Oceanus Procellarum known as Reiner gamma. Assuming that the Reiner gamma deposit is the source body and estimating its maximum average thickness as 10 meters, a minimum mean magnetization level of 5.2 +/- 2.4 x 10(-2) electromagnetic units per gram, or approximately 500 times the stable magnetization component of the most magnetic returned sample, is calculated. An age for its emplacement of 相似文献   

Lunar magnetic anomalies and surface optical properties

For typical solar wind conditions, lunar magnetic anomalies with dipole moments m > 5 x 10(13) gauss-cubic centimeters will strongly deflect the solar wind, producing local plasma voids at the lunar surface. The correlation of the largest observed anomalies (m approximately 10(16) gauss-cubic centimeters) with unusual, relatively high albedo surface features may therefore imply that solar wind ion bombardment is an important determinant of the optical properties of the lunar surface.     

Aeromagnetic and radio echo ice-sounding measurements show much greater area of the dufek intrusion, antarctica

A combined aeromagnetic and radio echo ice-sounding survey made in 1978 in Antarctica over the Dufek layered mafic intrusion suggests a minimum area of the intrusion of about 50,000 square kilometers, making it comparable in size with the Bushveld Complex of Africa. Comparisons of the magnetic and subglacial topographic profiles illustrate the usefulness of this combination of methods in studying bedrock geology beneath ice-covered areas. Magnetic anomalies range in peak-to-through amplitude from about 50 nanoteslas over the lowermost exposed portion of the section in the Dufek Massif to about 3600 nanoteslas over the uppermost part of the section in the Forrestal Range. Theoretical magnetic anomalies, computed from a model based on the subice topography fitted to the highest amplitude observed magnetic anomalies, required normal and reversed magnetizations ranging from 10(-3) to 10(-2) electromagnetic units per cubic centimeter. This result is interpreted as indicating that the Dufek intrusion cooled through the Curie isotherm during one or more reversals of the earth's magnetic field.     

Deep ocean impact of a Madden-Julian oscillation observed by Argo floats

Using the new Argo array of profiling floats that gives unprecedented space-time coverage of the upper 2000 meters of the global ocean, we present definitive evidence of a deep tropical ocean component of the Madden-Julian Oscillation (MJO). The surface wind stress anomalies associated with the MJO force eastward-propagating oceanic equatorial Kelvin waves that extend downward to 1500 meters. The amplitude of the deep ocean anomalies is up to six times the amplitude of the observed annual cycle. This deep ocean sink of energy input from the wind is potentially important for understanding phenomena such as El Ni?o-Southern Oscillation and for interpreting deep ocean measurements made from ships.     

Protonic diffusion in high-pressure ice VII

Near ambient pressures, molecular diffusion dominates protonic diffusion in ice. Theoretical studies have predicted that protonic diffusion will dominate at high pressures in ice. We measured the protonic diffusion coefficient for the highest temperature molecular phase of ice VII at 400 kelvin over its entire stable pressure region. The values ranged from 10(-17) to 10(-15) square meters per second at pressures of 10 to 63 gigapascals. The diffusion coefficients extrapolated to high temperatures close to the ice VII melting curve were less by a factor of 10(2) to 10(3) than a superionic criterion of approximately 10(-8) square meters per second, at which protons would diffuse freely.     

The hawaii to tahiti shuttle experiment

The Shuttle Experiment conducted between Hawaii and Tahiti from January 1979 to June 1980 was designed to observe the changing equatorial ocean structure and circulation, to study the variations and interactions of the four major equatorial ocean currents, and to develop a scientific basis for their monitoring by simple observations of thermal structure and sea level. Preliminary analyses of the results show that the equatorial thermal structure remains intact during a normal year and that only the positions and intensities of the currents are subject to change. The water transport of the equatorial undercurrent varied from 25 x 10(6) cubic meters per second in January to 51 x 10(6) cubic meters per second in July, but also exhibited strong short-term pulsations. The equatorial surface flow responded strongly to the winds at periods of 1 month and longer. An array of drifter buoys in the equatoral countercurrent was subject to very little dispersion while traveling over 4500 kilometers in 4 months. Low-frequency fluctuations in the North Equatorial Countercurrent can be monitored by means of the difference in sea level between Fanning and Majuro.     

Antarctic ice sheet: preliminary results of first core hole to bedrock

The Antarctic ice sheet at Byrd Station has been core-drilled to bedrock; the vertical thickness of the ice is 2164 meters. Liquid water-indicative of pressure melting-was encountered at the bed. Heat flow through the base of the ice sheet is estimated at 1.8 microcalories per square centimeter per second. The minimum temperature was -28.8 degrees C at 800 meters; maximum ice density, 0.9206 at 1000 meters. Core studies reveal the existence of a chemically pure, structurally stratified sheet comprising bubbly ice to 900 meters that transforms to bubble-free deformed ice, with substantially vertically orientated c-axis structure, below 1200 meters. Below 1800 meters the deformed ice structure gives way to large annealed crystals. Several thin layers of dirt between 1300 and 1700 meters are tentatively identified as volcanic ash, and horizontally banded debris, including fragments of granite, is present in the basal ice.     

跨度对日光温室气温和番茄生长的影响及模拟分析

【目的】研究跨度对日光温室保温性能及番茄生长的影响。【方法】对陕西杨凌地区越冬种植番茄的8,10和12 m 3种跨度西北型日光温室的气温、光照、热流等参数进行监测,以日光温室夜间传热模型为基础,通过夜间气温的变化来分析跨度对日光温室保温性能的影响,同时监测了不同跨度日光温室中番茄幼苗的生长情况。【结果】10 m跨度日光温室1月份平均气温分别较8和12 m跨度日光温室高1.9和2.6 ℃;种植番茄的平均株高分别高0.4和2.2 cm,平均茎粗分别高0.3和0.5 mm;夜间气温的模拟值与预测值吻合度均较高,其中8 m跨度日光温室夜间气温预测模型的平均相对误差为4.40%,10和12 m跨度日光温室分别为2.43%和2.38%。【结论】供试3种跨度日光温室中,以10 m跨度日光温室的保温性能最好,较适宜在杨凌地区推广应用。     

An impactor origin for lunar magnetic anomalies

The Moon possesses strong magnetic anomalies that are enigmatic given the weak magnetism of lunar rocks. We show that the most prominent grouping of anomalies can be explained by highly magnetic extralunar materials from the projectile that formed the largest and oldest impact crater on the Moon: the South Pole-Aitken basin. The distribution of projectile materials from a model oblique impact coincides with the distribution of magnetic anomalies surrounding this basin, and the magnetic properties of these materials can account for the intensity of the observed anomalies if they were magnetized in a core dynamo field. Distal ejecta from this event can explain the origin of isolated magnetic anomalies far from this basin.     

Measurement of fluctuating magnetic gradients originating from oceanic internal waves

Fluctuating magnetic gradients over oceans come from electric currents flowing in seawater arising from its motions across the earth's magnetic field. Gradients of 0.3 to 0.6 picoteslas per meter for each meter of internal wave displacement have been measured at frequencies of 2 to 5 millihertz with a superconductive magnetic gradiometer supported 7 meters above the surface of water 18 meters deep about 1.5 kilometers offshore from San Diego, California.     

Detection of emerging sunspot regions in the solar interior

Sunspots are regions where strong magnetic fields emerge from the solar interior and where major eruptive events occur. These energetic events can cause power outages, interrupt telecommunication and navigation services, and pose hazards to astronauts. We detected subsurface signatures of emerging sunspot regions before they appeared on the solar disc. Strong acoustic travel-time anomalies of an order of 12 to 16 seconds were detected as deep as 65,000 kilometers. These anomalies were associated with magnetic structures that emerged with an average speed of 0.3 to 0.6 kilometer per second and caused high peaks in the photospheric magnetic flux rate 1 to 2 days after the detection of the anomalies. Thus, synoptic imaging of subsurface magnetic activity may allow anticipation of large sunspot regions before they become visible, improving space weather forecast.     

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.     

Ceratoscopelus maderensis: peculiar sound-scattering layer identified with this myctophid fish

A sound-scattering layer, composed of discrete hyperbolic echosequences and apparently restricted to the Slope Water region of the western North Atlantic, has been identified from the Deep Submergence Research Vehicle Alvin with schools of the meyctophid fish Ceratoscopelus maderensis. By diving into the layer and using Alvin's echo-ranging sonar, we approached and visually identified the sound scatterers. The number of echo sequences observed with the surface echo-soutnder (1/23.76 x 10(5) cubic meters of water) checked roughly with the number of sonar targets observed from the submarine (1/7.45 x 105 cubic meters). The fish schools appeared to be 5 to 10 meters thick, 10 to 100 meters in diameter, and on centers 100 to 200 meters apart. Density within schools was estimated at 10 to 15 fish per cubic meter.     

Destruction of Sun-grazing comet C/2011 N3 (SOHO) within the low solar corona

Observations of comets in Sun-grazing orbits that survive solar insolation long enough to penetrate into the Sun's inner corona provide information on the solar atmosphere and magnetic field as well as on the makeup of the comet. On 6 July 2011, the Solar Dynamics Observatory (SDO) observed the demise of comet C/2011 N3 (SOHO) within the low solar corona in five wavelength bands in the extreme ultraviolet (EUV). The comet penetrated to within 0.146 solar radius (~100,000 kilometers) of the solar surface before its EUV signal disappeared. Before that, material released into the coma--at first seen in absorption--formed a variable EUV-bright tail. During the final 10 minutes of observation by SDO's Atmospheric Imaging Assembly, ~6 × 10(8) to 6 × 10(10) grams of total mass was lost (corresponding to an effective nucleus diameter of ~10 to 50 meters), as estimated from the tail's deceleration due to interaction with the surrounding coronal material; the EUV absorption by the comet and the brightness of the tail suggest that the mass was at the high end of this range. These observations provide evidence that the nucleus had broken up into a family of fragments, resulting in accelerated sublimation in the Sun's intense radiation field.     

Spreading of the ocean floor: new evidence

It is suggested that the entire history of the ocean basins, in terms of oceanfloor spreading,is contained frozen in the oceanic crust. Variations in the intensity and polarity of Earth's magnetic field are considered to be recorded in the remanent magnetism of the igneous rocks as they solidified and cooled through the Curie temperature at the crest of an oceanic ridge, and subsequently spread away from it at a steady rate. The hypothesis is supported by the extreme linearity and continuity of oceanic magnetic anomalies and their symmetry about the axes of ridges. If the proposed reversal time scale for the last 4 million years is combined with the model, computed anomaly profiles show remarkably good agreement with those observed, and one can deduce rates of spreading for all active parts of the midoceanic ridge system for which magnetic profilesor surveys are available. The rates obtained are in exact agreement with those needed to account for continental drift. An exceptionally high rate of spreading (approximately 4.5 cm/year) in the South Pacific enables one to deduce by extrapolation considerable details of the reversal time scale back to 11.5 million years ago. Again, this scale can be applied to other parts of the ridge system. Thus one isled to the suggestion that the crest of the East Pacific Rise in the northeast Pacific has been overridden and modified by the westward drift of North America, with the production of the anomalous width and unique features of the American cordillera in the western United States. The oceanicmagnetic anomalies also indicate that there was a change in derection of crustal spreading in this region during Pliocene time from eastwest to southeast-northwest. A profile from the crest to the boundary of the East Pacific Rise, and the difference between axial-zone and flank anomalies over ridges, suggest increase in the frequency of reversal of Earth's magnetic field, together, possibly, with decrease in its intensity, approximately 25 million years ago. Within the framework of ocean-floor spreading, it is suggested that magnetic anomaliesmay indicate the nature of oceanic fracture zones and distinguish the parts of the ridge system that are actively spreading. Thus data derived during the past year lend remarkable support to thehypothesis that magnetic anomalies may reveal the history of the ocean basins.     

Eustatic sea level 120,000 years ago on oahu, hawaii

Extensive dating of the fossil corals associated with the Waimanalo shoreline on Oahu has shown that 120,000 years ago the ocean was approximately 7.6 meters above its present level. Corals grown during that time constitute a major portion of the subaerial reef-derived material on the island, with exposures ranging from about 10 meters to near sea level. This evidence corroborates the notion that 120,000 years before the present was the last time during which the sea stood significantly higher than it does today. The reported benches at 3.7, 1.5, and 0.6 meters, if not of Recent origin, could be features created by brief halts of the sea during rapid regression shortly after the Waimanalo high stand.     

Sherman landslide, alaska

Triggered by the earthquake of 27 March 1964, 3 x 10(7) cubic meters of rock fell 600 meters, then slid at high speed 5 kilometers across the nearly level Sherman glacier near Cordova. The landslide has a number of significant new features in addition to those typical of other large landslides that may have slid on a layer of trapped and compressed air.