Exposed guyot from the afar rift, ethiopia

A series of originally submarine volcanoes has been found in the Afar Depression. Some of the volcanic structures are morphologically similar to oceanic guyots. One of them consists of strata of finely fragmented and pulverized basaltic glass. The fragmentation of the lava is probably the result of stream explosions taking place during the submarine eruption. The flat top of this guyot is considered to be a constructional feature; by analogy, it is suggested that not all oceanic guyots are necessarily the result of wave truncation of former volcanic islands.     

Late pliocene faunal turnover in the turkana basin, kenya and ethiopia

Analysis of a large sample of well-dated fossil mammals from localities in the Turkana Basin of Kenya and Ethiopia revealed sampling biases that affect patterns of faunal turnover during the late Pliocene. When these biases were accounted for, results indicated that 58 to 77 percent of the mammal species were replaced between 3.0 and 1.8 million years ago (Ma). Overall diversity increased from 3.0 to 2.0 Ma but then declined. No distinct turnover pulse is seen between 2.8 and 2.5 Ma; instead, the most significant period of faunal change began after 2.5 Ma and continued through 1.8 Ma.     

Submarine thermal sprirngs on the galapagos rift

The submarine hydrothermal activity on and near the Galápagos Rift has been explored with the aid of the deep submersible Alvin. Analyses of water samples from hydrothermal vents reveal that hydrothermal activity provides significant or dominant sources and sinks for several components of seawater; studies of conductive and convective heat transfer suggest that two-thirds of the heat lost from new oceanic lithosphere at the Galápagos Rift in the first million years may be vented from thermal springs, predominantly along the axial ridge within the rift valley. The vent areas are populated by animal communities. They appear to utilize chemosynthesis by sulfur-oxidizing bacteria to derive their entire energy supply from reactions between the seawater and the rocks at high temperatures, rather than photosynthesis.     

Deep magma body beneath the summit and rift zones of kilauea volcano, hawaii

A magnitude 7.2 earthquake in 1975 caused the south flank of Kilauea Volcano, Hawaii, to move seaward in response to slippage along a deep fault. Since then, a large part of the volcano's edifice has been adjusting to this perturbation. The summit of Kilauea extended at a rate of 0.26 meter per year until 1983, the south flank uplifted more than 0.5 meter, and the axes of both the volcano's rift zones extended and subsided; the summit continues to subside. These ground-surface motions have been remarkably steady and much more widespread than those caused by either recurrent inflation and deflation of the summit magma chamber or the episodic propagation of dikes into the rift zones. Kilauea's magmatic system is, therefore, probably deeper and more extensive than previously thought; the summit and both rift zones may be underlain by a thick, near vertical dike-like magma system at a depth of 3 to 9 kilometers.     

Stress control of deep rift intrusion at Mauna Loa volcano, Hawaii

Mauna Loa volcano, Hawaii, deforms by a combination of shallow dike intrusions in the rift zones and earthquakes along the base of the volcano, but it is not known how the spreading is accommodated in the lower part of the volcanic edifice. We present evidence from interferometric synthetic aperture radar data for secular inflation of a dike-like magma body at intermediate depth in the southwest rift zone during 2002 to 2005. Magma accumulation occurred in a section of the rift zone that was unclamped by previous dikes and earthquakes, suggesting that stress transfer plays an important role in controlling subsurface magma accumulation.     

Mechanistic interpretation of rift valley formation

The stress distribution on the lithospheric plate due to excess magma pressure is obtained from an exact solution of the three-dimensional theory of elasticity. The analysis indicates that rift valley formation and associated structural and geophysical characteristics can be suitably explained by dike-like intrusions of magma or igneous mush into the lithospheric plate.     

Explosive deep water basalt in the sumisu backarc rift

Eruption of 1-million-year-old tholeiitic basalt >1800 meters below sea level (>18 megapascals) in a backarc rift behind the Bonin arc produced a scoriaceous breccia similar in some respects to that formed during subaerial eruptions. Explosion of the magma is thought to have produced frothy agglutinate which welded either on the sea floor or in a submarine eruption column. The resulting 135-meter-thick pyroclastic deposit has paleomagnetic inclinations that are random at a scale of <2.5 meters. High magmatic water content, which is about 1.3 percent by weight after vesiculation, contributed to the explosivity.     

成品油罐自然冷却油品最终温度的计算

一些成品油在冬季储存可能会出现凝油现象,最好通过计算求取油品最终温度,以确定是否需要进行保温和加热。通过建立数学模型,获得了最终温度的函数表达式,并采用试算法间接地求取油品的最终温度。     

Growth of bivalves at deep-sea hydrothermal vents along the galapagos rift

Direct measurements of shell growth of an unclassified mussel from active hydrothermal vents along the Galápagos Rift reveal growth rates of approxmately 1 centimeter per year for mature specimens. The largest mussel collected (with shell length of 18.4 centimeters) was estimated to be 19 +/- 7 years old at the time of sampling. Recorded growth rates are among the highest documented for deep-sea species.     

Precambrian rift: genesis of strata-bound ore deposits

Study of deep seismic reflections has detected a Precambrian rift valley below flat-lying sediments in southern Alberta. The anomalous magnetic and gravity trends show that the rift is continuous across Alberta and British Columbia (through the Kimberley lead-zinc field) and possibly the Coeur d'Alene mining district of Idaho. There is evidence that these ore bodies were deposited in a Precambrian rift under conditions similar to those prevailing in the hot-brine areas of the modern Red Sea.     

森林主伐量的动态分析计算

本文在考虑现有森林各龄级的蓄积及其连年生长率的两个前提下,对能保证永续利用的最大收获量求算方法作了初步的探讨。虽然解决问题的方法归结为非线性目标规划问题,但在编制电算程序时,由于用的是从高龄级到低龄级的试算循环比较法,因而比非线性目标规划程序简短得多,电算时所占的内存空间和耗费的机时也少得多。     

Isotopic evidence for neogene hominid paleoenvironments in the kenya rift valley

Bipedality, the definitive characteristic of the earliest hominids, has been regarded as an adaptive response to a transition from forested to more-open habitats in East Africa sometime between 12 million and 5 million years ago. Analyses of the stable carbon isotopic composition (delta(13)C) of paleosol carbonate and organic matter from the Tugen Hills succession in Kenya indicate that a heterogeneous environment with a mix of C3 and C4 plants has persisted for the last 15.5 million years. Open grasslands at no time dominated this portion of the rift valley. The observed delta(13)C values offer no evidence for a shift from more-closed C3 environments to C4 grassland habitats. If hominids evolved in East Africa during the Late Miocene, they did so in an ecologically diverse setting.     

Kinematics of the asal rift (djibouti) determined from the deformation of fieale volcano

Because of its subaerial exposure the Asal rift segment provides an exceptional opportunity to quantify the deformation field of an active rift and assess the contribution of tectonics and volcanism to rifting processes. The present topography of the Asal rift results from the tectonic dismemberment during the last 100,000 years of a large central volcanic edifice that formed astride the rift zone 300,000 to 100,000 years ago. Three-dimensional deformation of this volcano has been quantified from the combined analysis of the topography and geology. The analysis indicates that spreading at 17 to 29 millimeters per year in a N40 degrees +/- 5 degrees E direction accounts for most of the separation between Arabia and Somalia. The small topographic subsidence relative to extension suggests that tectonic thinning of the crust has been balanced by injection and underplating of magmatic material of near crustal density. The methodology developed in this study could also be applied to quantify deformation in relatively inaccessible areas where the main available information is topography or bathymetry.     

ABA在小立碗藓极端干旱胁迫中的作用机制

[目的]以模式植物小立碗藓为材料,研究脱落酸(ABA)在小立碗藓极端干旱胁迫中的作用机制.[方法]将培养6d的小立碗藓用50 μmol/L ABA预处理1d后(WA),再脱水处理1 d(WAD),然后复水30min (WAR).另外一组材料是将培养7d的小立碗藓(WT,未经ABA处理)直接脱水处理1 d(WD),然后复水30 min (WR).测定6个样品(WT,WA,WAD,WAR,WD,WR)叶绿素荧光光化学淬灭系数(qP,qL)、非光化学淬灭系数(qN)和光合系统Ⅱ的实际光合效率Y(Ⅱ),分析光合作用相关基因的表达.[结果]经ABA预处理的样品脱水-复水后(WAR)其qP、qL、qN、Y(Ⅱ)值可以恢复,而未经ABA预处理的样品脱水-复水后(WR)其qP、qL、Y(Ⅱ)值均为零.进一步分析光合作用相关基因的表达,结果表明,经ABA预处理的样品脱水-复水后(WAR)的光合作用相关基因psbH、psbN和petN相对于其脱水时的表达量上调,petB和petD下降幅度较小;而未经ABA预处理的样品脱水-复水后(WR)的光合作用相关基因psbH、psbN、petN、petB和petD相对于其脱水时的表达量均下调,而且psbH、petN、petB和petD四个基因下降幅度较大.[结论]在复水过程中,ABA可以促进小立碗藓光合作用的恢复,从而提高小立碗藓的抗旱能力.     

钾对冬小麦后期生长及产量和品质的影响

两年度在不同程度缺钾的土壤条件下，研究了钾对冬小麦生育后期某些生理特性、产量和品质的影响。结果表明，供钾能提高小麦旗叶的叶绿素含量，降低气孔阻力，提高蒸腾强度，减轻膜质过氧化程度，延迟衰老，提高籽粒灌浆速率，增加产量，改善品质。文中还讨论了高产高效的施钾量。