Nature Vol. 287 30 October 1980 779 We are left with the problem that too imagine a temporary hot oxidising atmos­ function of particle size these events are many spherules are found to be produced phere at the collision site due to the placed in the asteroid belt. by meteorite or fireball parent body abundance of hydrated minerals thus pro­ Adherents to the first 'meteoritic spalation alone. Indeed, according to ducing the requisite wtistite. But are ablation' theory are still not convinced. Parkin et al. X-ray microprobe chemical asteroid collisions frequent enought to U-2 aeroplanes flying in the stratosphere at analysis and examination with a scanning produce 5,000 tonnes of spherules per altitudes of 20 km collect many particles electron microscope indicate considerable year? with meteoritic, extraterrestrial differences between spherules and Many people think that the asteroids compositions. Brownlee, Blanchard, meteorite fusion crusts. To them the sphe­ have been around since the dawn of the Cunningham, Beauchamp and Fruland (J. rules seem to have survived the passage solar system and that this permanence Geophys. Res. 80, 4917; 1975) find that through the atmosphere relatively un­ relies to a considerable extent on a collision about 10 per cent of them are spherules. To scathed. Where did they come from? rate which is decreasing with time. them X-ray diffraction, mineralogy and. The authors point to the asteroid belt and Individual collisions may produce swarms texture all point to a very strong similarity suggest that spherules are quenched sparks of spherules followed by long time periods between spherules and meteorite fusion formed by colliding asteroids. They even when the production rate is much smaller. crusts. It is possible that both theories are went so far as to collect rounded, quenched The beauty of core analysis is that, right and spherules can be formed either grindwheel sparks from a wheel being used assuming a constant sedimentation rate, from ablation droplets or from quenched to grind a steel bar and to claim that there you have a perfect means of measuring the asteroid sparks. Indeed, still further were distinct similarities to the deep sea spherule influx rate as a function of time. sources are not ruled out - maybe comets spherules. Microdebris from asteroid In a note added in proof the authors claim contain spherules and maybe planetary collision would take about 106 y to spiral in to be able to see evidence for individual cratering events produce spherules in the to the Earth's orbit under the influence of collision events. By considering the way in ejector. We have plenty of possibilities the Poynting-Robertson effect, ample time which spherule size varies as a function of available. What is needed are more _to adsorb solar wind. It is even possible to core depth and the spiraling time varies as a scientific investigators. D Did the Santorini eruption destroy the Minoan world? from J()rg Keller THE recent report in Nature1 of the discovery Recent research in the Aegean area, both end of the Minoan civilization on Crete. of volcanic ash from Santorini on the island on land and in the deep sea has produced a Various ideas have been presented to 7 of Rhodes raises once again the possibility distribution map for the Minoan ashfall •8, account for the difference in the timing of that Minoan Crete was destroyed by the which shows an easterly dispersion away the two events. Multistage volcanic effects of a volcanic eruption. from the volcano towards Western activity, the possibility that the pottery Marinatos2 was the first to postulate a Anatolia. Substantial fall-out must have might have been more old-fashioned in direct connection between two of the most affected the Eastern Aegean Sea and provincial Akrotiri, the destruction of dramatic events in the early history of the Western Anatolia (for example 30cm of Akrotiri by precursor earthquakes, or Aegean area - the tremendously powerful tephra have been found on the Island of evacuation of the settlement some 30 years eruption of the volcano of Santorini Kos 8), but it is inferred that Crete received before the fatal eruption, have all been (Thera) early in the 15th century BC and the only a few centimeters of ash, too thin to considered as explanations. sudden and enigmatic decline of the account for the desertion of the Late Only when Dorothy and Charles flourishing Minoan civilization on Crete. Bronze age settlements. Vitaliano9, 10 found microscopic traces of Seismic tidal waves, volcanic earth­ The findings on Santorini also suggest Santorini tephra in archeological sites on quakes and ash-fall were the physical that the volcanic destruction of the city of Crete and Melos, and within strata believed effects considered most likely to have Akrotiri occured one stage earlier on the to be uncontaminated Late Minoan IA did seriously damaged Minoan settlements all pottery-based time-scale of the archeo­ the possibility emerge that the climax of the over Crete. A blanket of ash, thick enough logists than the devastation of Minoan Santorini eruption actually preceeded the to suffocate the agricultural economy on cities and palaces on Crete. The Bronze age end of the Minoan civilization by about 30 Crete, was widely thought to have fallen pottery style "Late Minoan IA" is fully years. since deep-sea sediment cores drilled north developed in Akrotiri and the pottery This interpretation seems now to be fully and south of Crete had proved that the record ends with this stage. In contrast, all supported by the new findings on Rhodes. tephra had reached the island3• over Crete LM IA is followed by pottery of The future investigations which Doumas Since 1967, the settlement of Akrotiri Late Minoan IB, with its highly and Papazoglou have announced will has been excavated from underneath a characteristic decoration showing marine hopefully yield a complete pottery thick pumice cover on the island of Thera subjects. It is thought that the time inventory from both below and above the (Santorini). An unexpectedly wealthy, difference between the two substages is tephra layer. They should characterize a cosmopolitan Minoan community has about 30-50 years. This suggests a date of possible LM 1B destruction level. But come to light. Countless examples of fine 1500-1480 BC for the end of Akrotiri on already their conclusions appear to be pottery, both of local manufacture and Santorini and 1450 BC for the sudden inevitable: life continued without any significant break after the ash fall . The imported from Crete, and frescoes of I. Doumas, C. & Pa r azogolou, L Nature 287,322 (1980). incomparable beauty were found in three­ 2. Marinates, S. A ntiquity 13,425 (1939). later destruction of Minoan Crete is once 3. Ninkovich, D. & Heezen. B. C. Colston P apers 17, 413 4 • The more an enigma. The influence of other storied houses and mansions (1965). catastrophic dimensions of the Santorini 4. Marinates, S. Excavations at Thera I-Vil (1 967-73 ). civilizations especially neighbouring eruption are very obvious. With increasing 5. Marina! os, S . (ed .) Acta Int. Scient. Cong. Volcano of Mycenae, will certainly have to be re­ Thero (/971). knowledge, however, the original idea of 6. Doumas, C. (ed. ) Thera undthe/legean World. 1, ( 1978). 2, evaluated. Whether a Mycenaean invasion the direct physical destruction of Crete by (1 980). and conquest of Crete happened during the 7. Watkins, N. D. et al. Nature 211, 122 (1 978). of one of the most catastrophic volcanic phenomena has become more and 8. Keller, J. Theraand the Aegean World l , (1 980). aftermath more questionable5,6 • 9. Vitaliano, C. J . & Vit aliano. D. B. Am. J. Archeology 18. volcanic eruptions known in the 19 (1974). Mediterranean will only be revealed by JOrg Keller is in the Geophysical Laboratory, 10. Vitaliano, C . J . & Vitalia no, D. B. Thera andthe Aegean Carnegie Institution of Washington. World. I, (1978). continuing research , D tX l28-0X J6/ 80/ 440779-02$0I .00 © 1980Macmilla nJournals lld