Skip navigation.

olelog

What on earth

Posts tagged with "geology"

Alps Growing or Shrinking?

Friday, 6. November 2009, 16:36:48

A couple of months ago I wrote about a new hypothesis by Egholm et al. according to which the maximal mountain height correlate closely with climate-controlled gradients in snowline altitude rather than with tectonic activity. In Denmark this hypothesis seems to have lead to a heavy discussion about the uplift/erosion history of the Norwegian mountains between geologists at the University of Århus versus geologists at the University of Copenhagen, and I am looking forward to hear more about this dispute at the Nordic Geological Winter Meeting in Oslo in January.



But how about the Alps? A paper in the latest volume of the science magazine "Tectonophysics" (No. 474, S.236-249) seems now to prove that today's uplifting of the Alps is driven by strong climatic variations. The formation of the Alps through the collision of the two continents Africa and Europe began about 55 million years ago. By now the Alps are shrinking just as quickly in height, as they are growing. Due to the erosional work of glaciers and rivers about exactly the same amount of material is eroded from the Alps as added by uplifting.

Swiss geodesists, who have been measuring the Alps with highest accuracy for decades, have observed, that the Alp summits, as compared to low land, rise up to one millimetre per year. Over millions of years a considerable height would have to result. Researchers from the GFZ German Research Centre for Geosciences have calculated that the mountains eroded concurrently at almost exactly the same speed.

Though the Alps are constantly rising, it is no longer the plate forces but the strong climatic variations since the beginning of the so-called quaternary glacial before approximately 2.5 million years, to which mountain slopes in particular have been reacting so sensitively. To-days rise is attributed to the melting of Alpine glaciers.

Well, today it is probably just a question of isostasy, i.e. gravitational equilibrium between the earth's lithosphere and asthenosphere, meaning that the Alps "float" at an elevation which depends on their thickness and density. The burning question is, why the Alps stopped “growing”, where they did, during their collision phase. Was this only a question of isostasy or was the “snowline effect” at work?





Academics

No comments

Largest Alpine Karst Area In Scandinavia

Thursday, 5. November 2009, 10:37:26

,

The Norwegian Glomfjellet hosts the largest alpine karst area in Scandinavia. The Glomfjell karst consists of some 200 km² metacarbonates containing bands of relatively pure calcite marble (’grey marble’) interbedded with mica schist and less purer, micaeous marble (’yellow marble’).

The karst topography includes caves, dolines, bogazes, and karren.

It is planned to be a “Verneområde” (Area of Conservation) and is in this context described in an article at the Norwegian Geoportalen. Now, although the article is written in Norwegian it contains some really nice pictures of karst and other geologic features in the area for everybody to enjoy - just scroll downwards. So DO click here.

Latitude and longitude 66° 47' 8.95" N 14° 12' 8.04" E

Note:
A bogaz is a type of formation in which the rock (usually limestone) was eaten away along a joint to form a long, narrow cleft or ravine. They often have steep, almost vertical sides. This is exactly the same thing as a grike, except bigger. Boğaz is Turkish for throat.
Karren are furrows or channels formed on the surface of soluble bedrock by dissolution of a portion of the rock. (Also known as lapies.)

In Norwegian:




Academics

No comments

Franz Josef Land (in the Arctic)

Wednesday, 4. November 2009, 20:07:28

, ,

Few people know where Franz Josef Land is, or have ever heard of it. Except for a few Russian army border guards, Franz Josef Land is totally uninhabited. It has no native inhabitants. This is not because the area is small - Its 191 islands have a total area of 16,134 km². It is however situated far up north in the Arctic - and was furthermore completely closed to visitors for roughly 60 years until 1991. It is the most northerly group of islands associated with Eurasia and the Eurasian continental plate. Gakkel Ridge further north is normally seen as on the border zone between The Eurasian and the North American plate.

The situation may change now that the sea ice in the Arctic is melting and icebreakers in a few years perhaps no longer may be needed to reach the islands (Most of the Russian icebreakers in the area are - as far as I know - nuclear icebreakers). Since 2005 cruises are organised from Murmansk.

The archipelago is dominated by Jurassic to Tertiary basalts, but there are also late Triassic and Jurassic sediments lying in near horizontal strata. Fossil tree trunks show that the climate here was warmer in the Mesozoic. The basalt layer above the Jurassic sediments is up to 500 m thick and part of a Large Igneous Province (LIP) formed in the Cretaceous, and called the High Arctic Large Igneous Province (HALIP). This is a major Late Cretaceous large igneous province located in the Arctic. It includes the Ellesmere Island Volcanics, Strand Fiord Formation, Alpha Ridge, Franz Josef Land and Svalbard. These areas were closer to each other in the Cretaceous - since then the spreading ridge (Gakkel Ridge) has brought them further apart. A multitude of tectonic fault lines has broken the archipelago into many relatively small islands.

The age of the HALIP volcanic rocks is rather uncertain, but a long period of magmatism between ca. 136 and 80 million years ago has been suggested for the whole LIP.

From 15 June 2009 the archipelago became part of the newly established Russkaya Arktika National Park.







Academics

2 comments

Dinosaurs died out, but what about Insects?

Thursday, 29. October 2009, 10:11:16

,

The Cretaceous–Paleogene extinction event, which occurred approximately 65 million years ago, was a large-scale mass extinction of animal and plant species in a geologically short period of time. The most famous victims were the dinosaurs. More than half of the species that lived in the sea died out at this time - including ammonites and rudists.

What happened to the insects?

Gunnar Ries at Amphibol commented in a post of 28 October 2009 some of the different causes used to explain the extinction event. His post is in German. This post drew my attention (thank you!) to a publication by a team of biologists form Bonn in the Proceedings of the Royal Society.

Previous studies of insect-damaged fossil leaves in the US Western Interior showed major plant and insect herbivore (plant feeding) extinction at the Cretaceous–Palaeogene boundary. The Bonn team studied leaf fossils from the middle Palaeocene Menat site, France, which has the oldest well-preserved leaf assemblage from the Palaeocene of Europe, to test the generality of the observed Palaeocene US pattern. Apparently the insects were harder hit in the US than in Europe, and where it took about 10 million years for the insect fauna in the US to recover, Europe did in half that time, namely only 5 million years.

The diversity and complexity of plant–insect interactions at Menat suggest that the net effects of the Cretaceous–Paleogene extinction were less at this greater distance from the Chicxulub, Mexico, impact site. Along with the available data from other regions, the study seems to show that the end-of-Cretaceous event did not cause a uniform, long-lasting depression of global terrestrial ecosystems. Rather, it gave rise to varying regional patterns of ecological collapse and recovery that appear to have been strongly influenced by distance from the Chicxulub structure.

This does not end the discussion, but seems to back up the Chicxulub hypothesis. Who makes the next goal?

Reference:
Wappler et al.
No post-Cretaceous ecosystem depression in European forests? Rich insect-feeding damage on diverse middle Palaeocene plants, Menat, France
Published online before print September 23, 2009
doi: 10.1098/rspb.2009.1255

Unfortunately NOT open access !

The Palaeocene Epoch is a geologic epoch that lasted from around 65 to around 56 million years ago.
The Palaeogene Period (that began around 65 and ended around 23 million years ago) on the other hand comprises the Palaeocene, Eocene and Oligocene





Academics

No comments

Bulletin of the Geological Society of Denmark now Open Access

Monday, 26. October 2009, 14:45:45

,

Good news from the Geological Society of Denmark (DGF). All papers published on the DGF website will now be Open Access for free download. The pages will be updated in the coming weeks.

The Bulletin of the Geological Society of Denmark is a peer-reviewed journal written in English. The Bulletin publishes contributions of international interest in all fields of geological interest, with a natural emphasis on results of new work on material from Denmark, The Faroes and Greenland.



Academics

No comments

Unnatural Global Warming

Monday, 26. October 2009, 08:45:09

,

Is the current climate change simply a natural variation like others that have occurred throughout geologic time. Some people still believe it, but more and more evidence points to human beings being (at the very least partly) responsible. The current global warming is in other words not natural. There is an abbreviation for the phenomenon - AGW (anthropogenic global warming).

In a paper, titled "Recent Changes in a Remote Arctic Lake are Unique Within the Past 200,000 Years", sediments retrieved by University at Buffalo geologists from a remote Arctic lake show that recent variations are unlike those that have been seen during previous warming episodes. The environmental transformations going on in the Arctic are dramatic.

The 20th century is the only period during the past 200,000 years in which aquatic indicators reflect increased warming, despite the declining effect of slow changes in the tilt of the Earth's axis which, under natural conditions, would lead to climatic cooling.

Reference:
Recent Changes in a Remote Arctic Lake are Unique Within the Past 200,000 Years
by Axford et al.
Proceedings of the National Academy of Sciences
Published online before print October 19, 2009
doi: 10.1073/pnas.0907094106
(requires a subscription or payment of US$10.00)





Academics

No comments

Greenland and Oil

Saturday, 24. October 2009, 14:54:00

, ,

So-called self-government began in Greenland on 21 June 2009. Greenland wants, fair enough, more independence to explore its own natural resources. On the other hand it needs to exploit the same natural resources to “buy” more independence. Is this a vicious circle?

Roughly 76 percent of the voters in a referendum in 2008 wanted greater self-rule; on June 21 2009, they got it. But as part of that self-rule deal, Denmark will end up reducing its annual subsidy to Greenland—about €7.300 per person, representing about 60 percent of the island’s budget. Hence the high hopes for oil revenue. Some estimates, including those of the U.S. Geological Survey, suggest Greenland’s coastal waters could hold anywhere from 16 billion to 47 billion barrels of oil, or 800,000 barrels for every man, woman, and child.

The race has begun. 13 oil firms have been pre-qualified for the first license round for 14 enormous blocks in the Baffin Bay area off the west coast of Greenland. A second round is planned for 2012.

The water depths are typically 300-400 metres, not particularly deep by today’s standards, but the wells are still expected to cost about 67 million € a time, and drilling is likely to be confined to the summer months. After all it is still a bit dark, cold and rough in the Arctic winters.

Where will the money go? and what will the impact be on the pristine environment?



In Danish:




Academics

No comments

Algae Key To Mass Extinctions?

Friday, 23. October 2009, 13:10:25

, ,

There are lots of hypotheses about what causes mass extinctions, one more fanciful than the other. Two ideas taken more seriously are volcanoes and cosmic impacts. Now a new hypothesis suggests algae may be the killer behind the world's great fauna annihilations.

The idea was introduced in "Hypothesis for the role of toxin-producing algae in Phanerozoic mass extinctions based on evidence from the geologic record and modern environments" , a paper published in the March 2009 issue of the peer-reviewed journal Environmental Geosciences, and also presented in a talk on 19 October 2009, at the annual meeting of the Geological Society of American in Portland, Oregon, USA. (The full paper by Castle and Rodgers from March can be downloaded from this Clemson University site).

Castle and Rodgers have spent two years analyzing data from ancient stromatolite structures finding evidence that blue-green algae, which produce poisons and deplete oxygen, were present in sufficient quantities to kill off untold numbers of plants and animals living on land or in the sea. The geologic record demonstrates a pronounced increase in abundance and environmental range of algae, including stromatolitic cyanobacterial mats, coincident with the first four of the five major Phanerozoic (the last 545 million years) mass extinctions. During these past events of algal expansion, population decline of animals could have been caused by effects of algal blooms, including algal-produced toxins, at a scale sufficient to generate a fossil record of mass extinction.


Mass extinctions have often been attributed to climate changes, sea level, volcanic activity, and asteroids. Castle and Rodgers claim that these causes are contributors, but algae were the mass killer.

Environmental changes such as climatic warming, sea level fluctuation, and increased nutrient supply may have promoted algal blooms over vast expanses of marine to freshwater environments. and indeed, in my humble opinion toxic algae may just be another contributor together with other factors leading to (too) harsh environmental conditions.


Schematic profiles illustrating the influence of climate-induced sea level change on algal growth. (A) Sea level is low, shelves are narrow, and water temperatures are less favorable for algal growth during periods of cool global climate. (B) During periods of warm global climate, sea level is high resulting in extensive areas of shallow marine and coastal environments favourable for algal growth. Warm water temperatures promote the growth of algal blooms, domal and columnal stromatolites, and stromatolitic mats, which increases the potential for toxin production and release.





Academics

No comments

Large Igneous Provinces used for Plate Reconstructions

Thursday, 22. October 2009, 08:53:01

, ,

Palaegeography is mainly a question of Where was What When. As to the “When”, dating of rocks is of course extremely important. Because of recent advances in the recovery and U-Pb dating (uranium-lead dating) of baddeleyite (a rare zirconium oxide mineral) it is now possible to obtain precise ages for the vast majority of the short duration, huge volume, igneous events, known as Large Igneous Provinces (LIPs) that are widespread on all the ~50 main possible 'puzzle pieces' of the Earth's past plates.

Deccan Traps and Siberian Traps are famous examples of such LIPs, because of their possible role in mass extinctions.

Paleocontinental reconstructions are critical to providing a tectonic context for major ore deposits. They are also important to understanding the full context of sedimentary basins. More broadly, robust paleocontinental reconstructions and the recognition of supercontinents through time are essential for inter-block tracing of all geological and structural features of the lithosphere, including their deep mantle roots, and for providing a paleogeographic framework for assessing Earth’s geodynamic evolution and climatic variations through time.

Precisely dated units can be assembled into a LIP 'barcode' (like a supermarket barcode) that characterizes each 'puzzle piece'. By matching these 'barcodes' and using LIP units (particularly their dyke swarms) as piercing points, it is possible to compare and reconstruct the dispersed component pieces into past supercontinents.


Global barcode of LIPs through time. Abbreviations: NA, North America; SA, South America; EU, Europe; AF, Africa; AS, Asia; Au, Australia; PA, Pacific Ocean. Modified after Ernst et al. (2005).





Academics

No comments

Holocene Meteorite Impacts in Bavaria - or rather NOT ?

Wednesday, 21. October 2009, 09:32:32

,

Robert Huber has started a new geoblog to focus on the impact mania currently going on in Bavaria - Chiemgau Impact ? It is (unfortunately for some of you) in German.

What is all the fuss about. I think that Wikipedia puts it quite well:

“Chiemgau impact crater refers to Lake Tüttensee, supposedly created by a Holocene meteorite impact near Lake Chiemsee and the foothills of the Alps in southeast Germany. The findings of a team of hobby-Archaeologists, calling themselves the CIRT (Chiemgau impact research team), has brought some controversy to the Geology and Archaeology community in Germany, but isn't accepted beyond the CIRT team today. The coordinates of Lake Tüttensee are 47°50′48″N 12°34′05″E / 47.846667°N 12.568056°E / 47.846667; 12.568056 (Lake Tüttensee). According to the hypothesis, the strewn field comprises more than 80 individual craters with diameters exceeding 3 m spread over an area of roughly 60 km x 30 km. After the discovery of the Chiemgau strewn field, much work has been done by the CIRT on the Lake Tüttensee crater and its surroundings comprising geological field work, geophysical measurements and petrographic analyses. The lake is 400 m in diameter and 17 m deep encircled by an 8 m high rim of approximately 500 m in diameter. According to radiocarbon data and archeological finds, the impact is dated to 500 BC by the CIRT.”



On October 16, 2004, the journal Astronomy published an online article entitled “Did the Celts see a comet impact in 200 B.C.?“. A special website is dedicated to the event.

A paper on The Chiemgau Impact: An Extraordinary Case Study for the Question of Holocene Meteorite Impacts and their Cultural Implication by Rappenglück et al. was published in Volume 409 of Cosmology Across Cultures (page 338) with the following abstract:

”Did in the Holocene meteorite impacts of a size capable to affect human cultures happen at all and – if the answer is “yes” – which cultural implications did they have? Since a few years this question is fiercely and con- troversially discussed. The Chiemgau meteorite impact event may provide an important contribution to the discussion. This event stroke south-east Germany very probably in the 1st millennium BC and left a field of about 80 craters. In comparison to other Holocene impacts it provides extraordinary data by the extension of its crater field, the size of the biggest crater, the variety of secondary effects, the direct embedding of the impact layer in an archaeological stratigraphy, and the comparably good dating. The recently known data are introduced and discussed with regard to the question of cultural effects of Holocene impacts.“



Further article: Rappenglück, B. and Rappenglück, M., 2006: Does the myth of Phaethon reflect an impact? – Revising the fall of Phaethon and considering a possible relation to the Chiemgau Impact. - Mediterranean Archaeology and Archaeometry 6/3 (2006), 101-109.

In Germany the discussion goes on - especially in the media. So far the evidence seems extremely doubtful, but that doesn’t necessarily make it less interesting. And at least it has raised local interest in geology.




Academics

No comments

1 2 3 4 5 ... 22 Next »

Showing posts 1 - 10 of 215.

Download Opera, the fastest and most secure browser
November 2009
M T W T F S S
October 2009December 2009
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30

Oles sider

About.com Geology

  • On Ophiolites

    Some friends of mine got it into their heads that they wanted to visit an ophiolite. As a reader of John McPhee's geology books, I thought "of course, what could be more distinctively Californian?" But as I researched and visited likely field sites and did some reading, the subject grew more and mor ...

  • Wrestling with Rocks

    Yesterday I visited the Del Puerto Ophiolite, in preparation for a small field trip I'm planning later this month. Every time I go in the field I return amazed at the energy and insight of geologic mappers. Even though I followed a good field-trip guide, I found it difficult to discern everything on ...

  • How Long Do Aftershocks Last?

    The classroom treatment of aftershocks is fairly simple: An earthquake hits, and then a series of aftershocks occurs that is well summarized by three mathematical expressions called the Gutenberg-Richter relation, Bath's law and Omori's law. The first two relate the aftershocks to the mainshock in t ...

  • Peridotite: A New Gallery

    After a slow drive last month through the eastern Klamath Mountains, with many stops to take pictures and examine rocks, I now consider myself well acquainted with peridotite. That can be hard to do, because peridotite is almost all deep in the mantle and lower oceanic crust. And most of the peridot ...

  • What's a Geopark?

    I've cared about geoparks for several years, so I made sure to attend a session on geoparks at the Geological Society of America meeting, on 19 October. The most important news to me was that the National Park Service is collaborating with the GSA on a formal proposal for establishing geoparks in th ...

Jordnært (på dansk)

Geoblogosphere

"allgeo" via Chris

  • The Perspective of Time

    Leaf ghosts in the Vancouver morning rain I was in Portland, Oregon earlier this week, presenting a paper at the Coastal and Estuarine Research Federation meeting. This big conference attracted people who study all aspects of modern coasts, with a particular focus on human-caused environmental chang ...

  • Geotagging Test - Notice TEST ONLY !

    With static google maps geotagging now has become possible on this blog, where I cannot use JavaScript. So far it seems to work OK, but I still have to experiment a bit. Any helpful suggestions are of course welcome :idea:

  • AZGS presentation to Ad Hoc Committee on Mining Re ...

    We got confirmation that I'm scheduled to make a presentation to the Arizona Legislature's Ad Hoc Committee on Mining Regulations at their next meeting on Monday, Nov 16. The agenda should be released this coming Tuesday. The Committee is looking at ways to increase investment in mining in Ariz ...

  • Daily Geology Photos – November 8

    A summary of photos posted on flickr today, tagged with “ geology .” Displayed below are 35 geology-related photos were added to flickr today. ...

  • 10th anniversary of Kartchner Caverns State Park

    Arizona State Parks is celebrating the 10th anniversary of the opening of Kartchner Caverns to the public. Tours and lectures and going on all day yesterday and today. [ right, construction of the main entrance to the cave a decade ago. Credit, Arizona State Parks ]

Blog catalogs and directories