The 1815 Tambora eruption: Its significance to the understanding of large-explosion caldera formations

Volcanic calderas, plentiful on the Earth and the moon, have been of much interest to volcanologists because of their large dimensions and extensive volumes of ejecta. Here, we consider the dynamics of caldera-forming by major explosive eruptions, examining how the breakdown of the earth's surface is caused by violent igneous activity. This leads to the definition of “typical explosion caldera”, which is a prototype of several newly-formed calderas in the historical timescale. There are three examples of such calderas: Tambora (Sumbawa), Krakatau (Sunda Straits), and Novarupta (Alaska). Tam- bora Caldera is the best example of a well-documented, recently formed typical explosion caldera, with no significant subsequent eruptions occurring after its formation. The subsurface structure of Tambora Caldera is discussed and compared to the 1883 eruption of Krakatau, the second largest eruption in historical times. Then, contrasting with the typically basaltic “collapse-type” calderas, a “Tambora-caldera type” is defined as a large “explosion-type” caldera, that may reach up to 10 km in diameter. The Tambora- type caldera concept is useful to qualify and understand the structure and components of other major calderas in the world. Fully developed larger explosion calderas such as Aso and Aira Calderas in Kyushu, Japan are discussed and explained as composite calderas based on geophysical data. Those calderas have repeatedly ejected massive pyroclastic products causing their original structures to grow wider than 10 km.

Beirut Blast 2020: Cries and Bloodshed at the Busiest Hospital

On August 4, 2020, Beirut experienced a large explosion when 2750 tons of ammonium nitrate detonated in the Beirut port resulting in more than 220 deaths, 76 000 injuries, 300 000 people displaced, and 15 billion dollars loss in property damage. Hôtel-Dieu de France (HDF), one of the largest university hospitals in the capital, has an emergency department that typically accommodates 25 patients. On that night, it received the largest number of injuries and had to accommodate more than 700 casualties within a few hours of the blast. This article describes HDF’s preparedness, emergency response, as well as the distribution of admissions to the emergency department, operation rooms, and the general ward. Surge capacity and the triage system are also detailed.

Lebanese Shia will rely on Hezbollah parallel economy

Significance This promptly followed reports of a large explosion at a Hezbollah-linked fuel depot on a smuggling route across the Lebanon-Syria border, possibly targeted by Israeli planes. Impacts Further French diplomatic intervention this month and the advent of US President Joe Biden could resolve the government formation crisis. There is little prospect of a genuinely reformist government that could implement real change and bring in large-scale aid. Once COVID-19 rules are lifted, recent student protests could spread and reinvigorate national demonstrations driven by rising hardship. US re-engagement with Iran could allow the latter to transfer more funds for Hezbollah to build its parallel economy. Lebanese living abroad will play an increasing role in funding key NGO food assistance programmes, as local leaders’ finances run short.

Fusing geophysical signatures of locally recorded surface explosions to improve blast detection

We recorded acoustic, seismic and radio-frequency signatures of 70 solid charge (∼2–12 kg) surface explosions (shots) at local distances (0.1–1.5 km) to determine if such signals could be fused for blast monitoring. We observed that each geophysical signature was sufficiently repeatable between similar shots to be identifiable with multichannel correlation detectors. Using template signals from a large explosion, we then processed heavily contaminated data recording a smaller shot with these detectors, and missed or marginally detected the resultant target signals. By then fusing the p-values of these statistics through Fisher's combined probability test, we clearly identified the same explosion signals at thresholds consistent with the false alarm on noise rates of the correlation detectors. This resulting Fisher test thereby provided high-probability detections, zero false alarms and higher theoretical detection capability.

Study on the Obstruction Effect for a Large Explosion Shock Wave Tube Used the Ideal Nozzle Theory

This paper presents a calculation on the obstruction effects for the given large explosion shock wave tube using the ideal nozzle the theory. The relationship among Mach number, Mach number ratio, dynamic pressure ratio in the nozzle throat and blocking area ratio are established according to the fundamental equations of one-dimensional steady flow, which can be taken as the reference of blocking limit design.

Hypernovae and their nucleosynthesis

We review the characteristics of nucleosynthesis in ‘hypernovae’, i.e., core-collapse supernovae with very large explosion energies (≳ 1052 ergs). The hypernova yields show the following characteristics: (i) the mass ratio between the complete and incomplete Si burning regions is larger in hypernovae than normal supernovae. As a result, higher energy explosions tend to produce larger [(Zn, Co, V)/Fe] and smaller [(Mn, Cr)/Fe], which could explain the trend observed in very metal-poor stars; (ii) because of enhanced α-rich freeze-out, 44Ca, 48Ti, and 64Zn are produced more abundantly than in normal supernovae. The large [(Ti, Zn)/Fe] ratios observed in very metal poor stars strongly suggest a significant contribution of hypernovae; and (iii) oxygen burning takes place in more extended regions in hypernovae to synthesize a larger amount of Si, S, Ar, and Ca (‘Si’), which makes the ‘Si’/O ratio larger. The abundance pattern of the starburst galaxy M 82 may be attributed to hypernova explosions. We thus suggest that hypernovae make important contribution to the early Galactic (and cosmic) chemical evolution.

A seismic refraction and gravity study of the earth's crust in British Columbia

Explosion refraction studies have been carried out in areas adjacent to Vancouver Island, including the Strait of Georgia and Johnstone Strait and along the west coast of the Island. A refraction line has also been observed from a large explosion in Seymour Narrows, eastward through the mountains and for some distance across the plains of Alberta. Although the surficial strata complicate the interpretation, a series of short refraction profiles consistently reveal the presence of an intermediate layer with velocity of about 6.8 km/sec. in the coastal area. The depth to the upper boundary of this layer varies from about 11 km. along the west coast of the Island to less than 5 km. in the Strait of Georgia and along the east side of the Island. The longer range observations parallel to the coast indicate this layer to be more than 40 km. thick. On the profile eastward through the mountains a velocity of 7.8 km/sec. has been found for Pn, from an unreversed profile, with a crustal thickness of approximately 30 km.

THE PRESSURE PULSE PRODUCED BY A LARGE EXPLOSION IN THE ATMOSPHERE. PART II

The pressure pulse produced by a large explosion in the atmosphere is investigated. A realistic model for the vertical temperature is taken, with two temperature ducts and the large temperature gradient in the thermosphere. The first three dominant modes or "free waves" are computed for the low-frequency range. The contribution of these modes to the head of the pressure pulse produced by a large explosion is calculated for a particular range. It is shown that the "high-frequency" phenomena previously observed is a superposition of relatively low-frequency modes. An increase in the altitude of the source produces a corresponding decrease in relative intensity of the higher order modes, so that for an intense explosion at high altitudes, the low-frequency gravity wave mode is dominant.

THE PRESSURE PULSE PRODUCED BY A LARGE EXPLOSION IN THE ATMOSPHERE

The pressure pulse produced by a large explosion in the atmosphere is investigated. The explosion is represented in terms of the excess pressure and normal velocity on a closed surface, outside of which the hydrodynamical equations are linearized. The pulse is represented in terms of a Fourier transform of the associated harmonic frequency problem, for which a ring-source Green's function is obtained in terms of an expansion of the discrete modes. It is shown that the excess pressure may be represented in terms of an integral (containing the Green's function) over the surface surrounding the source. The gravity wave portion of the pressure pulse at the ground is computed for various ranges from the source, which is located at various altitudes, and for three models of the atmosphere. In calculating the head of the pulse a new asymptotic technique is introduced which gives very good results for intermediate and long ranges.