EARTH: Thinking outside the rocks in the search for ancient earthquakes

The eyewitness accounts, written in columns from right to left, top to bottom, testify that there was no warning of the tsunami, no shaking to drive villagers to high ground before the wave hit, drowning rice paddies and swamping a castle moat. The entries, written by merchants, peasants and samurai, all clearly mark the time and date: just after midnight on Wednesday, Jan. 27, 1700.

For centuries, it was unclear why no shaking preceded the Japanese tsunami of 1700. Now, researchers know that it’s because the tsunami was set off by an earthquake clear across the Pacific. By noting the height of the waves described in the accounts and working backward from the moment the tsunami struck, modern-day researchers detailed the magnitude and timing of the causative event: a massive magnitude-9.0 earthquake that demolished villages along North America’s Pacific Northwest coast about 9 p.m. on Tuesday, Jan. 26, 1700.

As EARTH details in its September feature, “Thinking Outside the Rocks in the Search for Ancient Earthquakes,” modern-day scientists are getting creative in the search for information about past quakes.

Read more about how researchers are turning to old newspaper articles and photographs, folklore, petroglyphs, crumpled buildings and toppled monuments – and how learning about past quakes can help seismologists to assess future seismic risk – and read other stories on topics such as what scientists are learning from the dust from the Twin Towers’ collapse on 9/11 that might help them determine how it affects people’s health; how clean rivers are actually creating a problem with “rock snot”; and how CAT scans may help us find oil and gas in the September issue. And be sure to check out the travelogue about Nova Scotia’s ancient rocks.

Climate in the past million years determined greatly by dust in the Southern Ocean

A group of scientists led by researchers from the Universitat Autònoma de Barcelona (UAB) and the Swiss Federal Institute of Technology (ETH Zürich) has quantified dust and iron fluxes deposited in the Antarctic Ocean during the past 4 million years. The research study published in Nature evidences the close relation between the maximum contributions of dust to this ocean and climate changes occurring in the most intense glaciation periods of the Pleistocene period, some 1.25 million years ago. Data confirms the role of iron in the increase in phytoplankton levels during glacial periods, intensifying the function of this ocean as a CO2 sink.

Dust, formed by particles of soil, plants, etc. affects the climate by altering the energetic balance of the atmosphere and provides iron and other micronutrients necessary to marine organisms. Scientists considered that dust fluxes deposited by the wind into the Antarctic Ocean increased during glacial periods and that iron fertilization may have stimulated marine productivity, contributing significantly to the CO2 reduction in the atmosphere during the most recent Pleistocene glacial periods (in the past 800,000 years). However, the magnitude of these effects and their role in the evolution of the climate system had remained unclear.

Records of the period studied in this research work – the longest and most detailed up to date on the Southern Ocean – reveal a sharp increase in dust and iron inputs during the Climate Transition of the Middle Pleistocene Epoch (1,250,000 years ago) in which fluxes tripled. This transition marked a global climate change with the beginning of glacial periods lasting 100,000 years, in comparison to the gradual intensification of glacial cycles occurring in the three million years immediately before, when periods lasted 41,000 years.

For the first time results show the close connection between the highest levels of dust deposited in the Antarctic Ocean and the lowest concentrations of CO2 in the atmosphere, which gave way to the appearance of the deep glaciations typical of Earth’s recent history. The study indicates that the dust most probably played a key role in fertilizing microscopic algae of the Southern Ocean, emphasizing its role as a CO2 sink. These microorganisms grow uptaking the CO2 found in the atmosphere and when they die they sink releasing carbon into the depths of the ocean.

For Antoni Rosell Mele, ICREA researcher at the Institute of Environmental Science and Technology of UAB, and Alfredo Martínez Garcia, currently researcher at EHT Zürich who earned his PhD at UAB, the research carried out offers new clues on the causes behind the most intense glaciations of the Pleistocene Epoch, particularly on how interactions between dust with oceanic biology influence CO2 and the climate. It also allows scientists to understand how future changes in atmospheric circulation and the superficial biology of oceans can make the Antarctic Ocean change the efficiency with which it captures and removes carbon dioxide from the atmosphere.

There are in fact initiatives to fertilize the Southern Ocean with iron with the purpose of reproducing the natural process observed during glaciations and reduce today’s levels of CO2 in the atmosphere. It is an issue which has generated much controversy. “Although our data indicates that this process occurred naturally during glacial periods, we must take into account that ocean circulation was completely different to what it is now, and this made the role of iron fertilisation more efficient in capturing carbon dioxide from the atmosphere. There are also several unknown aspects of what could happen to marine ecosystems if iron were artificially added in large quantities, and therefore its commercial application continues to be unviable at the moment”, researchers conclude.

The geophysicist’s guide to striking it rich

Prospecting – the search for valuable reserves such as gold, diamond and natural gas – isn’t just a matter of luck. It’s about knowing where to look. Now researchers at Tel Aviv University have modernized the hit-or-miss search with cutting-edge technology that scans the earth for signs of lucrative resources that could lurk beneath our feet.

Combining a number of surveying techniques for the first time, Prof. Lev Eppelbaum of TAU’s Department of Geophysics and Planetary Sciences at the Raymond and Beverly Sackler Faculty of Exact Sciences and Dr. Youri Katz of TAU’s Department of Zoology at the George S. Wise Faculty of Life Sciences have carried out a more accurate and in-depth land survey of Israel and the surrounding Mediterranean area than ever before. Their findings pinpoint the most likely places to find reservoirs of natural gas and oil.

Fifteen years in the making, their technique, which recently appeared in the journal Positioning, can be applied to any region in the world to more accurately identify possible riches below – before the costs of drilling or mining are incurred.

From buyers to producers

To create detailed structural-tectonic maps of Israel and the surrounding areas, Prof. Eppelbaum and Dr. Katz carried out an integrated survey using a variety of geophysical tools, including advanced analysis of magnetic, gravity, and temperature fields; utilization of seismic, magnetotelluric, and satellite imaging; and numerous well sections and outcropping studies. All of these results were integrated with plate tectonics reconstructions.

Perhaps the most valuable results of their study, the researchers say, are a series of prospective maps which identify specific areas where geological-geophysical teams are most likely to be successful in the search for natural gas and oil. Such information is not only of critical economic importance to Israel, but will also diversify oil and gas options for consumers worldwide.

Just off the shore of Haifa, a northern city along Israel’s coastline, there is believed to be a five hundred billion cubic meter area of gas reserve, Prof. Eppelbaum says. The survey indicates that a few tens of kilometers away, there may be another reserve that would significantly increase the current estimated amount of gas, he notes.

His predictions for additional oil reserves in deep water zones increase the estimated total of gas reserves by 200-300%. “Israel could have a future as a gas country – one that can produce oil and gas and sell it to the rest of the world,” Prof. Eppelbaum predicts.

A well-rounded approach

Prof. Eppelbaum says that the research was inspired by Prof. Zvi Ben-Avraham of the Department of Geophysics and Planetary Sciences, who was the first to apply the theory of plate tectonics to Israel and the Eastern Mediterranean. His findings provide a deeper understanding of the geophysical conditions in the region.

Warning that many researchers specialize too narrowly in a specific field or method, Prof. Eppelbaum stresses that the interdisciplinary approach of the Tel Aviv University team had a direct impact on the success of the study. An integrated approach puts critical information firmly in the grasp of today’s scientists – and those “prospecting” for a brighter tomorrow. </