Doctor Who: Geologizing with the Tenth Doctor.

Doctor Who logo. © British Broadcasting Corporation.

Doctor Who. © British Broadcasting Corporation.


On November 23, 1963 the first chapter of Doctor Who was broadcast on BBC, with William Hartnell (1908-1975) as The Doctor, a male humanoid alien, the last living Time Lord from the planet Gallifrey. For fifty years – including a gap of sixteen years – the Doctor has embodied the human desire for knowledge and adventure. Doctor Who operates in the fantastic genre where ordinary objects turn extraordinaire, like the legendary TARDIS, a police telephone box, which is a time machine and a spacecraft.

Many authors had wrote about the science of Doctor Who focusing in the physic of time travel, but there’s a side less explored, the geology of Doctor Who. In “The Fires of Pompeii”, the tenth Doctor played by David Tennant and his companion, Donna Noble, travel to Pompeii one day before the eruption of Mount Vesuvius in AD 79. The story revolves around a big moral dilemma: Must the Doctor explode the volcano and sacrifice the city of Pompeii in order to save millions from being converted into Pyroville hybrids? The Doctor’s answer is yes. The volcanic eruption is a “fixed point in time”, and the Doctor cannot save the city of the devastation.
Donna asked the Doctor to save a family. After a brief hesitation, He decided to save the family of Lucius Caecilius – played by Peter Capaldi, the next Doctor – from the horrible destruction caused by the Mount Vesubio.

The Fires of Pompeii.

The Fires of Pompeii.

A real witness of the eruption was Pliny the Younger. Like the Doctor, he observed the eruption from Cape Misenum at a distance of about 20 km from the volcano. His letters are considered the first vivid description of an explosive eruption. He wrote: ”Meanwhile from many points on Mount Vesuvius, wide sheets of flame and soaring fires were blazing, their brightness and visibility increased by the darkness of night”. These letters are so intense that you can feel his anguish: “ Now it was the first hour of daylight, but the light was still weak and uncertain.”

Mount Vesuvius is a stratovolcano, consisting of an external truncated cone, the extinct Mt. Somma,  a smaller cone represented by Vesuvius. For this reason, the volcano is also called Somma-Vesuvio. It was formed by the collision of two tectonic plates, the African and the Eurasian. When Mount Vesuvius erupted in 79 AD released deadly cloud of ash and molten rocks, and lasted eight days, burying and destroying the cities of Pompeya, Herculaneum and Stabiae.

Mount Vesuvius as seen from Pompeii. From Wikimedia Commons

Mount Vesuvius as seen from Pompeii. From Wikimedia Commons

Vesuvius has erupted around three dozen times, since 79 AD. For instance, in 172 AD, Galenus  wrote that ”the matter in it (Vesuvius) is still burning”. Since the great eruption of 1631 to the eruption in 1944,  Vesuvius is almost always in activity with only brief periods of quiescence not exceeding seven years.
Today, volcanic eruptions that send large columns of ash and gas into the stratosphere, like that of the Phillipines’ Mount Pinatubo in 1991, are classified by geologists as Plinian eruptions.

References:

Alison Cooley,  Pompeii, Duckworth Archaeological Histories.   London:  Duckworth, 2003.

Links:

The Fires of Pompeii – Fact File, http://www.bbc.co.uk/doctorwho/s4/episodes/?episode=s4_02&action=factfile

Advertisements

The origin of modern phytoplankton.

plankton

A single valve of the diatom Thalassiosira pacifica, the coccolithophore Scyphospahaera apsteinii and a pair of phycomas of Pterosperma moebii. (From Falkowski 2004)

The term “phytoplankton” derives from Greek roots: φψτος (phytos) –related to plants – and πλαγκτον (plankton) meaning a “wanderer” or a “drifter”. It was coined by Christian Gottfried Ehrenberg in 1897 and describes a diverse, polyphyletic group of mostly single-celled photosynthetic organisms that drift with the currents in marine and fresh waters.

The evolutionary history of eukaryotic phytoplankton has been studied through morphological fossils and molecular biomarkers such as lipids or nucleic acids. Organic walled fossils  made by eukaryotic phytoplankton occur in rocks as old as 1.6 to 1.8 billion years, but their morphological diversity is low and their phylogenetic relationships obscure.

The acritarchs were dominant forms of eukaryotic phytoplankton during the NeoProterozoic and the Paleozoic. These forms diversified markedly, in parallel with the Cambrian and Ordovician radiations of marine invertebrates. The group began to decline in the Late Devonian. And of course, the End-Permian mass extinction marked a major transition in ocean ecosystem structure.

plankton

Geologic range and relative diversity of eukaryotic phytoplankton. From Martin 2012.

Diatoms, dinoflagellates and coccolithophores, appeared in the geologic record during the Mesozoic. The radiation of this modern eukaryotic phytoplankton is paralleled with a long-term increase in sea level with and expansion of flooded continental shelf area.

These taxa have been grouped under the informal heading of “red” algal lineages primarily on the basis of their chlorophyll-c plastids. The shift from green to red phytoplankton lineages may have actually begun during the late Paleozoic.

Trace elements were important in defining the evolutionary trajectory of these groups of phytoplankton. While green algae need higher concentrations of iron, zinc and copper, red forms need higher amounts of manganese, cobalt and cadmium. Geologic evidence indicates that oxygen levels in the Mesozoic were much higher and that helped the micronutrients used by the red phytoplankton to remain dissolved in the oceans and available for uptake.

Diatoms living between crystals of annual sea ice in McMurdo Sound, Antarctica. From Wikimedia Commons.

Diatoms living between crystals of annual sea ice in McMurdo Sound, Antarctica. From Wikimedia Commons.

But, changes in the availability of macronutrients, such as phosphorus, also contributed significantly to the success of these groups. The patterns of diversity in the fossil records of dinoflagellates and coccolithophorids are roughly concordant, but differs with that of diatoms. This reflect different ecological strategies. In contrast to dinoflagellates and coccolithophores, diatoms have evolved a nutrient storage vacuole that can retain sufficiently high concentrations of nitrate and phosphate such that a cell can undergo several divisions without the need for external macronutrients.

Human activities are altering ocean conditions at a speed unsurpassed in our Earth’s history. In modern oceans, the coccolithophores and other calcifying phytoplankton that live in surface waters may be devastated by the acidification, which reduces the availability of minerals needed to make and maintain their shells.
As the oceans warm, they may also become increasingly stratified, impeding upwelling and circulation. In such conditions, dinoflagellates could increase the frequency and surface area covered by toxic blooms in coastal habitats.

References:

Martin, R. E. and Quigg, A. 2012 Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere. Geosciences. Special Issue on Paleontology and Geo/Biological Evolution. 2:130-146.

Falkowski PG, Katz ME, Knoll AH, Quigg A, Raven JA, Schofield O, Taylor FJ., The evolution of modern eukaryotic phytoplankton, Science. 2004 Jul 16; 305(5682):354-60