Science Spot Physical Science

This is the new home of my physical science news column originally to be found on PSIgate as Spotlight and then as Hot Topics on the Intute site. There’s everything from the 2002-2010 archive providing a snapshot of cutting edge science during that period in Archaeology, Astronomy, Chemistry, Earth Sciences, Environment, Geology, Physics and more.

Although Spotlight and its successor Hot Topics have now been deprecated, this site is not purely an inactive archive, a cobWeb site, but will be updated periodically, especially if readers are keen to see new content.

Please let me know if you’d like to offer a guest blog post or if you spot a missing page or other error.


David Bradley Science Writer

Scrubbing up knowledge of submarine volcanoes

A study of the shape of pumice from three adjacent submarine lava dome volcanoes in the western Pacific reveal that explosive volatility driven by the movement of molten magma is lower in deeper water. The shape of pumice stones, which are formed by expansion of magmatic volatiles as the magma rises to the sea surface, is different depending on the water depth and so can be a useful indicator of the evolution and eruption of underwater volcanoes.

Sharon Allen of the ARC Centre of Excellence in Ore Deposits and the School of Earth Sciences, at the University of Tasmania, Hobart, Australia and colleagues Richard Fiske of the Smithsonian Institution, Washington, DC, and Yoshihiko Tamura of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), in Yokosuka Japan, used sampling and observations collected by a remotely operated vehicle of the three adjacent submarine lava dome volcanoes of the Sumisu, Izu-Bonin arc in the Western Pacific.

Domes of the volcanic complex have summits at ocean depths of 1100, 600, 245, and 95 metres and are mantled with pumice that is chemically identical but size, distribution, and surface texture varies enormously across the volcanic range.

Sharon Allen
Sharon Allen

According to a report in the May issue of the journal Geology, pumice generated from lava domes at water depths of more than 500 metres formed as a thick carapace on dense rock whereas at water depths less than 500 m pumice is blasted out. At shallower than 500 metre depths, the pumice occurs as an apron of blocky giant and smaller rough-textured clasts (rock fragments) enclosed by quenched margins and pockmarked by coarse [centimetre-sized] vesicles, a rock fragment within which is trapped a bubble of gas, the team explains.

The study shows that an increase in hydrostatic pressures over a range of 12 megapascals [120 times atmospheric pressure] reduces volatile-driven explosivity of the dome-forming eruptions the team says, it does not affect the formation of rocky “bubbles, the vesicles. “We conclude that metre-size, highly vesicular pumice is diagnostic of subaqueous dome eruptions in water depths of at least 1300 metres, and its morphology can be used to distinguish between explosive and effusive origins,” they conclude.


Geology, 2010, 38(5), 391-394.
Sharon Allen homepage

Black gold

An estimated 513 billion barrels of “technically recoverable” heavy oil lie in Venezuela’s Orinoco Oil Belt, a 50,000 square kilometre region in the East Venezuela Basin Province.

Worldwide consumption of petroleum was 85.4 million barrels per day in 2008. The three largest consuming countries were United States with 19.5 million barrels per day, China with 7.9 million barrels per day, and Japan with 4.8 million barrels per day. So the Venezuelan heavy oil represents a potential supply that could last a decade at the current rate of consumption.

The United States Geological Survey (USGS) has carried out the first assessment that identifies how much oil might be technically recoverable using currently technology and standard industry practices. According to USGS Energy Resources Program Coordinator Brenda Pierce, this part of the world has one of the world’s largest recoverable oil accumulations. The USGS’s report is part of its program directed at estimating the technically recoverable oil and gas resources of priority petroleum basins worldwide. This is the largest accumulation ever assessed by the USGS.

“Knowing the potential for extractable resources from this tremendous oil accumulation, and others like it, is critical to our understanding of the global petroleum potential and informing policy and decision makers,” explains Pierce. “Accumulations like this one were previously very difficult to produce, but advances in technology and new understandings in geology allow us to assess how much is now technically recoverable.”

USGS team member and a co-author of the report, Christopher Schenk explains further: “Heavy oil is a type of oil that is very thick and therefore does not flow very easily. As a result, specialized production and refining processes are needed to generate petroleum products, but it is still oil and can generate many of the same products as other types of oil.”

The estimated petroleum resources in the Orinoco Oil Belt, range from 380 to 652 billion barrels of oil (at a 95 and 5 percent chance of occurrence, respectively). Schenk says that the estimates are based on a rate of oil recovery of between 40 and 45 percent.

Orinoco (Credit: USGS)
Credit: USGS


However, others are sceptical that these oil reserves are economically or environmentally viable. Venezuelan oil geologist Gustavo Coronel told the Associated Press that he doubted the recovery rate could be much higher than 25 percent given the nature of the crude oil. More intriguing is that the USGS announcement seems to have been timed to coincide with an international auction for drilling rights in the Orinoco Belt which took place on 28th January, with results to be announced on 10th February.

Moreover, there are no little energy and environmental costs to be considered in recovering heavy crude oil as it is not necessarily as easy to extract as conventional crude oil. Moreover, the existence of such reserves while perhaps saving us from short-term oil shortages does not address the issues of carbon emissions and potential climate change.


USGS Assessment

Energy Resources Program

Auction news

Crude claims

AP report