olelog

Julia (The Ethical Palaeontologist) has already commented on the Science article Molecular Phylogenetics of Mastodon and Tyrannosaurus rex here and here.

There is not much meat on the article itself, it is just one single page, so it may be no surprise, that the media add lots of feathers. Never the less I found the article quite interesting because of the method used to confirm the relationship between dinosaurs and birds.

Evidence of close evolutionary relationships among birds and non-avian dinosaurs have been accumulating for a long time. See a.o. my post on the Archaeopteryx - probably the most famous fossil, and considered an important link between dinosaurs and birds.

In 2005 it became known that a group of dinosaur researchers had discovered soft tissues in fossil Tyrannosaurus rex bone unearthed in 2003 by Jack Horner in the Hell Creek Formation in Montana, USA. As the bone was 68 million years old it is surprising to have found still elastic soft tissues looking like blood vessels and cells. We are not talking Jurassic park and no DNA could be analysed. By using mass spectrometry protein sequenced from collagen were however detected. Collagen is a protein that is the basic building block of connective tissues.

Phylogenetics is the classification of organisms based on how closely they are related in terms of evolutionary differences - or in other words the construction of a (phylogenetic) tree structure, a diagram that represent the evolutionary tree of life. A tree of life for the 22 organisms compared in the study is shown in figure 1 of the article. For those of you who do not have access to Science I can refer to this account - NB in Norwegian - of the article, where the figure is shown. Please do note that this tree does not indicate that chicken “descended from the fearsome Tyrannosaurus rex” as mentioned in the heading of Sun here, but merely that Tyrannosaurus, Ostrich (Struthio) and Chicken (Gallus gallus) are related (within the taxon Archosauria). I have redrawn the Archosauria bit from the figure.

A serious problem with using molecular methods, be it on DNA or collagen, is that the samples are extremely easily contaminated (from other organisms, including living species). Furthermore fossil material is destroyed by the analysis, and the analysis is expensive. Of course nondestructive examination of unique fossils are preferred if possible.

Molecular palaeontology in the modern sense probably began with a report by Abelson in 1956 of the recovery of proteinaceous components of fossils. As technology expanded and increased in accuracy, sensitivity, and reliability, new analytical methods began to be applied to fossil material. A piece on the future of molecular paleontology by Mary Highby Schweitzer is found here.

• http://www.livescience.com//animals/080424-dino-birds.html
• http://www.msnbc.msn.com/id/24297066/
• http://www.eurekalert.org/pub_releases/2008-04/hu-mac041808.php
• http://www.thesun.co.uk/sol/homepage/news/article1087903.ece
• http://palaeo-electronica.org/2002_2/editor/r_and_p.htm

The greatest earthquakes occur in subduction zones, where one tectonic plate is sliding beneath another. Virtually all of the big earthquakes, the ones of magnitude eight or nine or above, happen at sea. The largest earthquake ever recorded is no exception to this rule.

The epicentre of the Great Chilean Earthquake of 22 May 1960 was about 160 km off the coast of Chile in the Peru-Chile Trench (39.5° S, 74.5° W) with a focal depth of 33 km. Two days later, on 24 May 1960, Cordón Caulle, a fissure vents system located in the Chilean Lake District, erupted, sending ash and steam as high as 6 km.

At the Peru-Chile trench the Nazca Plate is subducted beneath the South American Plate. In the area hit by the earthquake the dip of the subduction zone is about 30° and the subduction gives rise to an arc of still active volcanoes.

Buildings fell all along the Chilean coast from Conception to the southern end of Isla Chilor. The towns of Valdivia and Puerto Montt were devastated. (The earthquake is also known as the 1960 Valdivia earthquake / Gran terremoto de Valdivia).

The earthquake set off huge landslides and sent rocks and boulders tumbling down the mountain sides. The land around the city of Puerto Montt sank and coastal areas were flooded. Rivers had their courses changed and landslides created new lakes. Many of the landslides occurred in the Chilean Lake District from Lago Villarica to Lago Todos los Santos.

The earthquake set off huge tsunamis which radiated out from the epicentre, travelling at speed of up to 350 km/h, the Chilean coast was devastated by a 25 (or was it 12 ?) m high tsunami which arrived 10 to 15 minutes after the quake. Remains of houses were carried inland as much as 3 km. There was also severe damage in the Philippines, Hawaii and the japan.

Over 2000 people died and 3000 were injured. 2 million people became homeless. There were not extremely large numbers of victims, for such an earthquake, because the population was alerted on that something was going to happen by previous shakes and underground noise.

Map of some of the places mentioned and the most important volcanoes in the district. In 2005 we made our way from Puerto Montt to San Carlos de Barriloche in Argentina through the Chilean Lake District (bus, boat, bus, boat, bus) - as many tourists do. Under way I photographed the following volcanoes: Osorno (famous for its Fujiyama look), Puntiagudo ("Volcán Puntiagudo" (Spanish for "Sharp-pointed Volcano") is a stratovolcano with a prominent 2,493 m high sharp-pointed summit that results from glacial dissection and gets its name from this feature), and Tronador. See the 3 photos below.

• http://earthquake.usgs.gov/regional/world/events/1960_05_22.php
• http://en.wikipedia.org/wiki/Great_Chilean_Earthquake
• http://www.gochile.cl/html/ChileValdivia/Chile-Valdivia-Terremoto.asp
• http://www.geophys.washington.edu/tsunami/general/historic/chilean60.html
• http://www.usgs.gov/faq/list_faq_by_category/get_answer.asp?id=154





Notes:
The volcano Puyehue is often cited as the volcano that erupted on 24 May, but actually it was the nearby fissure volcano Cordón Caulle. Although Cordón Caulle is sometimes listed as part of Puyehue volcano, it is tectonically and magmatically distinct from Puyehue. No historical eruptions are known from Puyehue, and eruptions in 1921-22 and 1960 listed in some sources actually occurred at Cordón Caulle volcano located to the Northwest.

As far as I know the epicentre of the main quake was at 39.5° S, 74.5° W - some maps however show it inland (including the USGS map). Well of course there were more than one shock, but even then?

Can earthquakes trigger volcanic eruptions? The volcanic eruption 2 days after the 1960 Chilean earthquake has been taken as evidence, but that could still be a coincidence, and the question is still debated. That volcanoes, on the other hand, can cause earthquakes, is well known.

What I wanted to stress here is the role of subduction zones for important natural hazards like earthquakes, volcanoes, tsunamis and landslides.

Much has been written about the impact from volcanic eruptions on climate change (cooling) and sea level changes. Less has been said about the impact from global warming and sea level rise on volcanism.

Sea level rise can reactivate volcanoes situated near sea level. Alaska's Pavlof volcano erupts every winter when (local) sea levels are higher - well just about 30 centimetres. Thirteen of sixteen magmatic eruptions of Pavlof Volcano in nine of the years from 1973 to 1998 have occurred between 9 September and 29 December. A significant correlation exists between the eruptions and yearly nontidal variations in sea level and may result from ocean loading. (See this abstract). The melting of polar ice sheets from global warming and the resulting stress placed on the earth's crust from rising sea levels will cause more magma and increase volcanic eruptions on a global scale in the years to come.

Carolina Pagli of the University of Leeds, UK, and Freysteinn Sigmundsson of the University of Iceland in Reykjavik calculated how shrinkage of the Icelandic ice cap Vatnajökull affects what is happening below ground. Their findings will shortly be published in Geophysical Research Letters.

Pagli, C., and F. Sigmundsson (2008), Will present day glacier retreat increase volcanic activity? Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajokull ice cap, Iceland, Geophys. Res. Lett., doi:10.1029/2008GL033510, in press.

When ice disappears, the added weight it forced upon the crust below it disappears as well. As a result this is increasing the rate at which the rocks under the ice sheet melt into magma. Iceland is home to several active volcanoes that exist underneath the ice, including Gjàlp, home of the last big eruption in 1996, and 58 years earlier in 1938. But according to Pagli and Sigmundsson the extra magma produced over the past century and more could reduce that time down to a gap of 30 years between each eruption. Volcanoes in Antarctica and Alaska will be at risk of similar increased volcanic activity. The shifting stresses could even cause eruptions in unexpected places.

And now that I am talking about Icelandic volcanoes - according to Iceland Review Online a giant volcano has recently been discovered off Reykjanes peninsula, Southwest Iceland, almost as large as the peninsula itself, and expected to erupt at any time. In the centre of the volcano there is a caldera measuring ten kilometres in diameter.

Since the volcano is at a depth of 1,500 metres eruptions would not have any effect on Iceland, except perhaps causing earthquakes (and tsunamis?). The volcano’s discovery is considered significant because it was believed it couldn’t exist in that area. Such large volcanoes are not supposed to be located on oceanic ridges. They are always drifting apart and that prevents a volcano from being created, so the volcano’s existence really came as a surprise.

• http://www.dailygalaxy.com/my_weblog/2008/04/will-a-warmer-w.html#more
• http://environment.newscientist.com/channel/earth/mg19826515.100-melting-ice-caps-may-trigger-more-volcanic-eruptions.html
• http://www.abc.net.au/news/stories/2007/09/14/2033161.htm?section=justin
• http://environment.newscientist.com/channel/earth/climate-change/mg19626324.600-volcanoes-give-sea-level-a-temporary-boost.html
• http://www.abc.net.au/science/news/stories/2005/1494475.htm

Googling the combination “euxinic conditions” gave me 2060 hits, and the combination “euxinic sediments” 875 hits, so the term is obviously used, and it has been in use in geology at least since 1930.

Euxinic literally means ‘pertaining to the Black Sea’. The word euxinic comes from the old Roman (and ultimately from the Greek) name for the Black Sea (the Romans called it the Euxine Sea, Pontus Euxinus). So, before I go on, let us have a look at the conditions in the Black Sea.

The waters of the Black Sea are strongly stratified with an upper oxidised layer and a lower anoxic layer. Freshwater (green arrow) flows into the sea from rivers like the Danube, Dniester, Dniepr and Don. Sea-water (blue arrow) flows into the Black Sea from the Mediterranean via the street of Bosporus. Because of the different salinities and densities, the freshwater and sea-water mixing is limited to the uppermost 100-150m. The mixing between surface water and bottom water is strongly restricted, and the whole bottom water is exchanged only once in a 1000 years. Oxygen is needed for rotting of organic matter, so under anoxic conditions organic matter doesn't rot. As a result black, organic rich, sediments accumulate on the bottom. The Black Sea has got its name because such black sediments make the sea water dark. Unlike the Mediterranean, where visibility extends down to a depth of about 30 meters, visibility reaches only as far as about 5 meters in the Black Sea.

Rotting is a bacterial process, and occurs under aerobic conditions, aerobic means occurring only in the presence of oxygen. You also have bacterial activity under anaerobic conditions, that is it occurs in the absence of oxygen. During anaerobic conditions at the bottom of the Black Sea sulphate reducing bacteria strip the oxygen from sulphate and dump hydrogen sulphide (H₂S) as a waste product (a sulphate ion consists of a central sulphur atom surrounded by four equivalent oxygen atoms). Some of the hydrogen sulphide may react with iron to form pyrite (FeS). Increase of pyrite in the sediments is an indication of the activity of sulphate-reducers.

So the term euxinic has to do with an environment of restricted circulation and stagnant or anaerobic conditions. Euxinic conditions are at the same time both anoxic, anaerobic and sulphidic. Euxinic conditions may lead to deposition of euxinic sediments like sapropel. Now there is another nice foreign word. Sapropel (a contraction of the ancient Greek words sapros and pelos, meaning putrefaction and mud, respectively) is a term used in marine geology to describe dark-coloured sediments (mud, slime, or ooze) that are rich in organic matter. Organic carbon concentrations in sapropels commonly exceed 2% in weight.

I have checked the indexes of a few textbooks on oceanography and marine geology. They seem to do quite nicely without using the term euxinic. I have to know the term however to be able to read some of those $@^§* scientific papers!

Papers such as this one:
Euxinia as the cause of the end-permian mass extinction: Evidence from sulfur isotope chemostratigraphy
• http://gsa.confex.com/gsa/2005ESP/finalprogram/abstract_88807.htm
Relevant for my post a few days ago on How to kill 95% of all life?.
Oh ah, and yes, I forgot to say at the start: Google gave me 3,340 results for euxinia! - euxinia means euxinic anoxic conditions.

Euxenite, on the other hand, has nothing to do with euxinia, but is a lustrous, blackish-brown rare-earth mineral consisting primarily of cerium, erbium, titanium, uranium, and yttrium.

Words, words, words.



PS of 30 March 2008
Kim over at All of My Faults Are Stress-Related has started a discussion on possibly unnecessary or outmoded geology terms in the post Geology terms overdue for retirement?.

Ken Amor of Oxford University believes that a large meteorite (at least 500 meters in diameter) hit Northwest Scotland in the Precambrian about 1.2 billion years ago near the Scottish town of Ullapool. A report of the research, 'A Precambrian proximal ejecta blanket from Scotland' is published in the journal Geology.

Previously it was thought that unusual rock formations in the area had been formed by volcanic activity. But, the team lead by Amor found evidence buried in a layer of rock which they now believe is the ejected material thrown out during the formation of a meteorite crater. Ejected material from the huge meteorite strike is scattered over an area about 50 kilometres across, roughly centred on the northern town of Ullapool. The actual meteorite crater is thought to lie within the immediate vicinity, buried under younger rocks.

In the rocks they found the characteristic signature of meteoritic material, which has high levels of the key element iridium, normally only found in low concentrations in surface rocks on Earth. They found more evidence when they examined the rocks under a microscope; tell-tale microscopic parallel fractures that also imply a meteorite strike. Shocked quartz and biotite provide evidence for high-pressure shock metamorphism, while chromium isotope values and elevated abundances of platinum group metals and siderophile elements indicate addition of meteoritic material. The ejecta blanket reaches more than 20 m in thickness. Field observations suggest that the deposit was emplaced as a single fluidized flow that formed as a result of an impact into water-saturated sediments.

So far it is the largest meteorite strike known in the British Isles. There are about 174 known impact craters or their remnants on Earth.

This is the most spectacular evidence for a meteorite impact within the British Isles found to date.

• http://www.gsajournals.org/perlserv/?request=get-abstract&doi=10.1130%2FG24454A.1
• http://www.abdn.ac.uk/mediareleases/release.php?id=1275
• http://news.bbc.co.uk/2/hi/science/nature/7314329.stm
• http://news.softpedia.com/news/UK-039-s-Biggest-Meteorite-Impact-Discovered-81720.shtml
• http://www.inform.kz/showarticle.php?lang=eng&id=162214




PS of 30 March 2008
Hypocentre has some images here.