Stonehenge story     

《Astronomy& Geophysics》2007,48(4):4.43-4.43

The Queen's Birthday Honours list announced on 16 June contained some familiar names from astronomy. Prof. Mark Bailey (1) of Armagh Observatory, currently a Vice-President of the RAS, was awarded an MBE and Dr Heather Couper (2), former President of the British Astronomical Association, a CBE. Prof. Nigel Mason (3) of the Open University and inaugural Director of the Milton Keynes Science Festival received an OBE. Prof. Jocelyn Bell-Burnell (4), President of the RAS from 2002–2004, was awarded a DBE – and an Honorary Doctorate from Harvard University. In addition, Prof. Lord Rees (5), Astronomer Royal, president of the Royal Society and President of the RAS from 1992–1994, was appointed to the Order of Merit.  相似文献   

Shifting of the volcanic fronts during Early to Late Miocene in the Northeast Japan arc     

Jun'ichi  Ohki  Naoki  Watanabe Kenji  Shuto Tetsumaru  Itaya 《Island Arc》1993,2(2):87-93

Abstract Recent advanced chronological studies for the Tertiary volcanic rocks from the Northeast (NE) Japan arc revealed three volcanic fronts which differed in temporal and spatial distribution. These fronts were (i) the Matsumae-Shizukuishi-Shiogama line of 22–25 Ma which is obliquely across the Quaternary volcanic front (QVF); (ii) the Tomari-Shiogama line of 13–16 Ma which exists 30–50 km east of the QVF and (iii) a line of 0–8 Ma which is the same as the QVF. The first shifting of the 22–25 Ma line to the 13–16 Ma one was due to the counterclockwise rotation of the NE Japan arc during 20–12 Ma as proposed by Otofuji et al . (1985), and the second shifting of the 13–16 Ma line to the 0–8 Ma line could have contributed to a decrease in the dip of the slab of the Pacific plate which subducted beneath the NE Japan arc during 13–8 Ma.  相似文献   

The cause of superchrons     

J A Jacobs 《Astronomy& Geophysics》2001,42(6):6.30-6.31

Superchrons – long periods in the geomagnetic record when the Earth's magnetic field did not reverse its polarity – are a challenge to observers and theorists. Jack Jacobs outlines the problems and some possible solutions.
Reversals of polarity are a feature of the geomagnetic record for all the time it has been documented. Although not regular, reversals are sufficiently frequent for their absence to be noticeable. When the Earth's magnetic field retains the same polarity for over 20 million years, a superchron is established. Superchrons demand the attention of geophysicists concerned with the generation of the Earth's field: either they must result from an intrinsic feature of the geodynamo, or they reflect the influence of some external force. Here I discuss internal and external mechanisms for the formation of superchrons, including the role of the inner core, true polar wander, Earth's orbital variations and tides.  相似文献   

A comet in the lab     

Phil A Bland  Anton T Kearsley  P J Wozniakiewicz  M J Burchell  M Gounelle  M E Zolensky  Matt J Genge 《Astronomy& Geophysics》2007,48(6):6.27-6.31

What have Stardust samples told us about the early solar system? Phil A Bland, Anton T Kearsley, P J Wozniakiewicz, M J Burchell, M Gounelle, M E Zolensky and Matt J Genge have some of the answers – and a few more questions.  相似文献   

Fukutoku-oka-no-ba Volcano: A new perspective on the Alkalic Volcano Province in the Izu–Bonin – Mariana arc     

CHIH-HSIEN  SUN  ROBERT J.  STERN  TAKEYOSHI  YOSHIDA & JUN-ICHI  KIMURA 《Island Arc》1998,7(3):432-442

Pumice samples from Fukutoku-oka-no-ba in the Izu–Bonin – Mariana (IBM) arc were analysed for 40 trace elements and Sr, Nd, and Pb isotopic compositions. These samples are shoshonites (59.4–61.8 wt% SiO₂), characterized by high contents of K₂O (3.74–4.64 wt%), Ba (1274–1540 p.p.m.), Rb (91–105 p.p.m.), and light rare earth elements. The characteristics of alkali-element enrichment are similar to those of other parts of the Alkalic Volcano Province (AVP) in the northern Mariana and southernmost Volcano arcs. Sr (⁸⁷Sr/⁸⁶Sr = 0.7036–0.7038) and Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 19.08–19.11, ²⁰⁷Pb/²⁰⁴Pb = 15.62–15.63, ²⁰⁸Pb/²⁰⁴Pb = 38.85–38.91) of Fukutoku-oka-no-ba pumice are relatively radiogenic, whereas Nd is unradiogenic (¹⁴³Nd/¹⁴⁴Nd = 0.51283–0.51286). Fukutoku-oka-no-ba is isotopically distinct from Iwo Jima and is similar to the Hiyoshi Volcanic Complex, suggesting that Fukutoku-oka-no-ba might have a magma source similar to that of the Hiyoshi volcanic complex. Plots of Pb and Nd isotopes for AVP lavas trend toward the fields of ocean island basalt (OIB) source and pelagic sediments, which are possible sources of AVP enrichments.  相似文献   

Growth history and formation environments of ferromanganese deposits on the Philippine Sea Plate, northwest Pacific Ocean     

Akira  Usui  Ian J.  Graham  Robert G.  Ditchburn  Albert  Zondervan  Hiroshi  Shibasaki  Hajime  Hishida 《Island Arc》2007,16(3):420-430

Abstract   Hydrogenetic ferromanganese crusts are widespread on the floor of the northwestern Pacific Ocean, south and east of the Japanese Islands, despite vigorous tectonic activity, such as subduction and back-arc spreading, since at least the Mid-Paleogene over the Philippine Sea Plate region and nearby. The crusts occur mainly at water depths shallower than 3000 m, but also at greater depths of up to 6000 m. Fine-scale ¹⁰Be/⁹Be dating was undertaken on several 5–10 cm thick hydrogenetic ferromanganese crusts sampled from different geological environments, including inactive submarine volcanoes, tectonic escarpments and abandoned rifts. The results indicate that the crusts have grown at relatively constant rates of 4–7 mm/my without any significant time breaks. These uniform and constant growth rates suggest that the basins have been exposed constantly to oxygenated bottom waters since their formation in the Middle Miocene ( ca 15 Ma) or earlier. Local geological or oceanographic environmental changes might have slowed or increased some of the growth rates resulting in correlation of some internal structures. The Philippine Sea Plate region could have economic potential in areas of thick hydrogenetic ferromanganese crusts over a wide range of water depths.  相似文献   

China heads for Moon     

《Astronomy& Geophysics》2007,48(6):6.05-6.05

The Wide Area Search for Planets – WASP – has found three new exoplanets, in both the northern and southern hemisphere.  相似文献   

The sound of the Sun     

W J Chaplin  I Ballai 《Astronomy& Geophysics》2005,46(4):4.27-4.30

Bill Chaplin and Istvan Ballai review developments in helioseismology – the resonant choir of the Sun – a discipline that now probes the Sun from core to corona.  相似文献   

Using neutrino diffraction to study the Earth's core     

A Dominic Fortes  Ian G Wood  Lothar Oberauer 《Astronomy& Geophysics》2006,47(5):5.31-5.33

A Dominic Fortes, Ian G Wood and Lothar Oberauer think through the possibilities for an entirely new – and currently technologically impossible – means of examining the core of the Earth.  相似文献   

Noble gases in pillow basalt glasses from the northern Mariana Trough back-arc basin     

YASUO  IKEDA  KEISUKE  NAGAO  ROBERT J.  STERN  MAKOTO  YUASA & SALLY  NEWMAN 《Island Arc》1998,7(3):471-478

Noble gas concentrations and isotopic compositions have been measured in eight samples of pillow basalt glasses collected from seven different localities along 250 km of the Mariana Trough spreading and rifting axis. The samples have uniform and mid-ocean ridge basalt (MORB)-like ³He/⁴He values of 9–12 × 10^–6 (6.4–8.6 times atmospheric) despite large variations in ⁴He. Concentrations of the noble gases Ne, Ar, Kr, and Xe show much smaller variations between samples, but larger variations in isotopic compositions of Ne, Ar, and Xe. Excess radiogenic ²¹Ne is observed in some samples. ⁴⁰Ar/³⁶Ar varies widely (atmospheric to 1880). Kr is atmospheric in composition for all samples. Some samples show a clear excess ¹²⁹Xe, which is a well-known MORB signature. Isotopic compositions of the heavier noble gases (Ar, Kr, and Xe) in some samples, however, show more atmospheric components. These data reflect the interaction of a MORB-like magma with an atmospheric component such as seawater or of a depleted mantle source with a water-rich component that was probably derived from the subducting slab.  相似文献   

Mars as never seen before     

Ernst Hauber  Gerhard Neukum 《Astronomy& Geophysics》2004,45(2):2.21-2.27

Images from the High Resolution Stereo Camera on Mars Express reveal the surface of the Red Planet in unprecedented detail – and should have the whole planet mapped at high resolution in just two years. Over the next six pages, Ernst Hauber and Gerhard Neukum set the scene and reveal some of the spectacular images already captured.
(All images are courtesy of ESA/DLR/FU Berlin/G Neukum unless otherwise credited.)  相似文献   

Whatever happened to Gondwana?     

《Astronomy& Geophysics》2008,49(3):3.06-3.06

The combination of continents into supercontinents, and their subsequent fragmentation and rearrangement is an accepted part of the history of the Earth, but how it happens in detail is not always clear. Did supercontinents split into a few large pieces, or were many small fragments formed in the break-up? Now geophysical measurements have answered this conundrum – which has implications for later continental reconstructions – for the break-up of Gondwana, the supercontinent that existed from about 500–180 million years ago.  相似文献   

The making of Stars 'R' Us!     

Serena Viti  Wendy Brown  Martin McCoustra  Helen Fraser  Nigel Mason  Robert Massey 《Astronomy& Geophysics》2004,45(6):6.22-6.24

The team behind a successful project to broaden the understanding of astrochemistry – Serena Viti, Wendy Brown, Martin McCoustra, Helen Fraser, Nigel Mason and Robert Massey – recount how they went about it and what benefits resulted.  相似文献   

Saturn's icy satellites     

Hazel McAndrews 《Astronomy& Geophysics》2005,46(4):4.22-4.22

Hazel J McAndrews – and colleagues including the CAPS Team – presents initial results from the Cassini Plasma Spectrometer, based on the talk which won her a Rishbeth Prize at the UK MIST meeting in April.  相似文献   

Coronal heating     

Louise Harra FRAS 《Astronomy& Geophysics》2001,42(2):2.18-2.18

Louise Harra presents a summary of a meeting at which a wealth of new sources of data – Yohkoh, SOHO, TRACE, XMM-Newton and Chandra – is bringing new insights to studies of solar and stellar coronal heating.  相似文献   

ASK: Auroral Structure and Kinetics in action     

Mina Ashrafi 《Astronomy& Geophysics》2007,48(4):4.35-4.37

Mina Ashrafi, winner of the Rishbeth Prize at the 2007 NAM, describes the work in her group at Southampton on the questions that a new multi-spectral imager – ASK – can answer about auroral structure and processes.  相似文献   

Enigmatic Eta Carinae     

J M Pittard 《Astronomy& Geophysics》2003,44(1):1.17-1.22

The next stage in the evolution of Eta Carinae – famed for its explosive eruption in the 19th century – should be observed around the world in the summer. Julian Pittard reviews the story so far.  相似文献   

Brief history of petrotectonic research on the Sanbagawa Belt, Japan     

Shohei  Banno 《Island Arc》2004,13(4):475-483

Abstract   Petrological study of the Sanbagawa schists was initiated by B. Koto (1856–1935) and extensive petrographic works were performed by J. Suzuki (1896–1970) and Y. Horikosi (1905–1992), who studied in the Besshi area of central Shikoku. Petrological work based on the mineral facies concept of P. Eskola (1883–1964) was initiated in Japan in the 1950s by A. Miyashiro on the low pressure/temperature (P/T) Abukuma complex, and then by Y. Seki and S. Banno on the high P/T Sanbagawa Metamorphic Belt. A unique inverted thermal structure was established by researchers in the 1970s. Therefore, mainly geological and petrographic features of the Sanbagawa Belt were established by the 1990s, and contemporary researchers are now testing the classical images using the new and quantitative viewpoints of geochronological, structural, tectonic, and thermal modeling.  相似文献   

Late Cretaceous-Cenozoic exhumation of the Yanji area, northeast China: Constraints from fission-track thermochronology     

Xiaoming  Li  Guilun  Gong  Xiaoyong  Yang  Qiaosong  Zeng 《Island Arc》2010,19(1):120-133

The Yanji area, located at the border of China, Russia, and Korea, where the Phanerozoic granitoids have been widely exposed, was considered part of the orogenic collage between the North China Block in the south and the Jiamusi–Khanka Massifs in the northeast. In this study, the cooling and inferred uplift and denudation history since the late Mesozoic are intensively studied by carrying out apatite and zircon fission-track analyses, together with electron microprobe analyses (EMPA) of chemical compositions of apatite from the granitoid samples in the Yanji area. The results show that: (i) zircon and apatite fission-track ages range 91.7–99.6 Ma and 76.5–85.4 Ma, respectively; (ii) all apatite fission-track length distributions are unimodal and yield mean lengths of 12–13.2 µm, and the apatites are attributed to chlorine-bearing fluorapatite as revealed by EMPA results; and (iii) the thermal history modeling results based on apatite fission-track grain ages and length distributions indicate that the time–temperature paths display similar patterns and the cooling has been accelerated for each sample since ca 15 Ma. Thus, we conclude that sequential cooling, involving two rapid (95–80 Ma and ca 15–0 Ma) and one slow (80–15 Ma) cooling, has taken place through the exhumation of the Yanji area since the late Cretaceous. The maximum exhumation is more than 5 km under a steady-state geothermal gradient of 35°C/km. Combined with the tectonic setting, this exhumation is possibly related to the subduction of the Pacific Plate beneath the Eurasian Plate since the late Cretaceous.  相似文献   

Rapid tectonics of the Late Miocene Boso accretionary prism related to the Izu–Bonin arc collision     

Yuzuru  Yamamoto  Shunsuke  Kawakami 《Island Arc》2005,14(2):178-198

Abstract   The structure, paleomagnetism and biostratigraphy of the Nishizaki and Kagamigaura formations on the southern Boso Peninsula, central Japan, were investigated to determine the chronographic constraints on the accretion, post-Late Miocene rotation and regional tectonics in the Izu–Bonin island arc collision zone. The geological structures on the southern Boso Peninsula are characterized by an east–west trending and south-verging fold and thrust belt that curves toward the northwest–southeast in the northwest extent of the Nishizaki Formation. Two stages of tectonic rotation were revealed by paleomagnetic and structural studies. The first is believed to have occurred after the accretion of the Nishizaki Formation and before the deposition of the Kagamigaura Formation, while the second is confidently correlated with the 1 Ma Izu block collision. The northwest extent of the Nishizaki Formation was rotated clockwise by approximately 65–80°, whereas the rotation was only 25–30° in the east, and 11–13° in the overlying Kagamigaura Formation. Radiolarian biostratigraphy suggests a depositional age of 9.9–6.8 Ma (Upper Miocene period) for the Nishizaki Formation and 4.19-3.75 Ma (Pliocene period) for the lower Kagamigaura Formation. These results indicate that the age of accretion and first-stage rotation of the Nishizaki Formation can be constrained to the interval of 6.80–3.75 Ma. This structure most likely represents the northward bending caused by collisions of the Tanzawa and Izu blocks with the Honshu island arc, and suggests rapid processes of accretion, collision, uplift and the formation of new sedimentary basins within a relatively short period of time (2.61–3.05 my).  相似文献