olelog

In Gulf Stream born 3 million years ago? I wrote about what happened at the Panama isthmus about 3 million years ago.

But how was the situation in what is now Central America before then? Mainly based upon sedimentology Kirby et al. try to get a better grip on the last 30 million years in an open access article in PLoS ONE: Lower Miocene Stratigraphy along the Panama Canal and Its Bearing on the Central American Peninsula.

Here is the opening paragraph from their introduction:

The palaeogeography of Central America has changed profoundly over the past 30 million years (m.y.), from a volcanic arc separated from South America by a wide seaway, to an isthmus that connected North and South America by 3 Ma. The formation of the Isthmus of Panama was important because it allowed the mixing of terrestrial faunas between the two continents, as well as physically separating a once continuous marine province into separate and distinct Pacific and Caribbean communities. The formation of the Isthmus of Panama also ultimately led to profound changes in global climate by strengthening the Gulf Stream and thermohaline downwelling in the North Atlantic.

The palaeogeographic nature of southern Central America before the isthmus has been much disputed. Much of the discussion relates to the relative and absolute timing of some of the sediment formations along the Panama Canal (see the paper for this discussion).

As part of the Central American volcanic arc, the Panama microplate formed through subduction of various oceanic plates during the Cretaceous (145 to 65 million years ago) and Cenozoic (65 million years ago to the present). This microplate lies between the Cocos and Nazca plates to the south, the Caribbean plate to the north and the South American plate to the east. See tectonic map below.



A short-lived strait - the Culebra Strait - may have existed across the Panama Canal Basin sometime between 21 and 19 million years ago (on the first map in this post light grey represents the outline of tectonic plates containing continental or volcanic-arc crust. Dark grey represents land above sea level). The earliest evidence for a terrestrial connection between Panama (but NOT South America) and North America is 19 million years ago. After that the authors found no evidence for the disruption of the southern Central America peninsula until 6 million years ago, when there is evidence for a short-lived strait across the Panama Canal Basin. The existence of a peninsula for much of the Miocene (about 23 to 5 million years ago) has implications for our understanding of the tectonic, climatic, oceanographic and biogeographic history related to the formation of the Isthmus of Panama.

* http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002791
* http://www.physorg.com/news136614198.html
* http://www.terradaily.com/reports/Isthmus_Of_Panama_Formed_As_Result_Of_Plate_Tectonics_999.html

In Mudslide Buries Geysers I reported about a large landslide that destroyed much of the Geyser Valley in Kamchatka.
For those of you who are not quite sure where Kamchatka is - here is a situation map (centered on the North Pole).

The Valley of the Geysers in Kamchatka is considered one of the great natural wonders of the world. It is the second largest concentration of geysers in the world. The 6 km long basin has approximately ninety geysers and many hot springs. On 3 June 2007 the Valley of Geysers was seriously damaged by a landslide. Here are some photos taken a year later - in July 2008.


The slide dumped millions of m³ of mud and rocks on the valley. One of the landslide's tongues came close to tourist camp buildings in the Geyser Valley. Part of the household buildings were destroyed, while three main houses (hostel, scientist's house and ranger's house) did not suffer. The landslide stopped few meters from the hostel. The photo shows the rim of the landslide a few meters from a house that escaped from being destroyed. Practically the only way of getting to the valley is by helicopter.

The landslide is well covered by text (Russian + English), maps and photos here.


Boardwalk through the valley. The Valley of the Geysers 6,700 km from Moscow, was only discovered in 1941. It was opened to tourists 50 years later, that is only about 17 years ago.


A couple of mud pots. There are many mud pots, both small and large. A mudpot, mud pool or paint pot is a sort of hot spring or fumarole consisting of a pool of usually bubbling mud. Water rises to the surface at a spot where the soil is rich in volcanic ash, clay and other fine particulates. The thickness of the mud usually changes along with seasonal changes in the water table. The mud takes the form of a viscous, often bubbling, slurry. As the boiling mud is often squirted over the brims of the mudpot, a sort of mini-volcano of mud starts to build up. Although mudpots are often called "mud volcanoes", true mud volcanoes are very different in nature. The mud is generally of white to greyish color, but is sometimes stained with reddish or pink spots from iron compounds. When the slurry is particularly colorful, the feature is then called a "paint pot". The slopes of the mud pots in this photo have beautiful mud cracks. Mud cracks form when muddy sediment dries up. They have a characteristic polygonal shape. They are also called desiccation cracks (desiccation is the state of extreme dryness, or the process of extreme drying).

• http://www.ewpnet.co.uk/kamchatka/geyser.htm
• http://www.kamchatka.org.ru/geysers.html
• http://spanishflyer.livejournal.com/7519.html
• http://news.bbc.co.uk/2/hi/europe/6723567.stm

The concentration of oxygen in the Earth's atmosphere rose from negligible levels 3000 million years ago to about 21% in today. This increase is thought to have occurred in six steps, 2650, 2450, 1800, 600, 300 and 40 million years ago, with a possible seventh event identified at 1200 million years ago.

According to an article by Campbell and Allen published online 27 July 2008 in Nature Geoscience the timing of the steps suggests that they coincided with the formation of supercontinents (and supermountains). This might mean that the basic driver behind the increase of oxygen in the atmosphere is plate tectonics.

How could the forming of supercontinents and increase in atmospheric oxygen be connected?
The continent to continent collisions required to form supercontinents produce enormous mountain ranges. These mountains then erode quickly, flushing nutrients such as iron and phosphorous into the oceans. This fertilisation in turn boosts the numbers of (photosynthetic) oxygen-producing algae and cyanobacteria in the oceans. Enhanced sedimentation during these periods promoted the burial of a high fraction of organic carbon, thus preventing reaction with free oxygen This subsequent burial of organic carbon along with the mountain sediments would have sustained the increased oxygen levels.

Other scientists have already shown that the formation and erosion of the Himalayas led to increases in atmospheric oxygen.

Reference:
Campbell and Allen, Formation of supercontinents linked to increases in atmospheric oxygen, Nature Geoscience, 27 July 2008 | doi:10.1038/ngeo259

• http://www.nature.com/ngeo/journal/v1/n8/abs/ngeo259.html
• http://sciencenow.sciencemag.org/cgi/content/full/2008/729/2?rss=1
• http://www.abc.net.au/science/articles/2008/07/28/2316318.htm

Emission to the atmosphere of greenhouse gases, mainly resulting from combustion of fossil fuels, is considered a major player in global warming. Carbon dioxide (CO₂) is the main greenhouse gas, accounting for around 65%. Carbon capture and storage (CCS) is an approach to mitigate global warming by capturing carbon dioxide (CO₂) from large point sources such as fossil fuel power plants and storing it instead of releasing it into the atmosphere.

Since 1996 the Norwegian oil and gas company Statoil has been injecting 1 million ton CO₂ per year into a salt water containing sand layer, called the Utsira formation, which lies 1 km below the bottom of the North sea. Other countries in Northern Europe have very advanced plans (some under construction) to store CO₂ in terrestrial reservoirs, typically consisting of sand or sandstone (aquifers) sealed by an overlying layer of clay or other impermeable rock.

There are, however, concerns about putting large amounts of CO₂ into the ground. You don’t want any leakage so that it seeps up to atmosphere, which is missing the point by the injection. In the case of deep ocean storage, there is a risk of greatly increasing the problem of ocean acidification, a problem that also stems from the excess of carbon dioxide already in the atmosphere and oceans. (So far there has been no leakage from the Norwegian Sleipner project).

It would be better if the CO₂ through chemical reactions were bound in minerals. E.g. a reaction between calcium (Ca) and CO₂ to form (stable) calcium carbonate (CaCO₃).

According to a paper published online (and with open access!) deep-sea basalt offers a unique environment for CO₂ storage (or CO₂ sequestration as it is often called). The paper by Goldberg et al. is titled Carbon dioxide sequestration in deep-sea basalt (PNAS of 22 July 2008, vol. 105. no. 29). Oceanic crust is mainly composed of basalt (welling up at mid-ocean ridges), which means that vast volumes of seawater-filled pore space are available. Within deep-sea basalt aquifers, the injected CO₂ mixes with seawater and reacts with basalt, both of which are rich in elements with which the carbon dioxide can react. The release of Ca² and Mg² ions from basalt will form stable carbonate minerals as reaction products.

Important mechanisms for trapping CO₂ injected within deep-sea basalt further include
i) blanketing deep-sea sediments, which form a low-permeability stratigraphic barrier impeding vertical fluid migration;
ii) the formation of CO₂ hydrate, which is denser and less soluble than liquid CO₂ in sea-water of 2°C;
iii) gravitational trapping at water depths of at least 2,700 m, where injected CO₂ is denser than typical seawater, causing it to sink.
All three of these mechanisms are simultaneously available within ocean crust, providing independent protective barriers that could safely isolate the oceans, oceanic ecosystems,
and the atmosphere from leakage of CO₂ escaping from deep-sea basalt aquifers.

The deep-sea basalt region of the Juan de Fuca Plate off the coast of Oregon and Washington is suggested as CO₂ storage region for US. Here an area of 68,000 km2 has water depths of at least 2,700 m and a covering sediment thickness of at least 200 m. The total storage capacity for injected CO2 in this area is 208 gigaton of carbon.

• http://www.pnas.org/content/105/29/9920.abstract
• http://environmentalresearchweb.org/cws/article/futures/35017

A small fact sheet in pdf format about the Norweian Sleipner project and the Utsira fomation can be downloaded from:
http://www.bellona.org/factsheets/1191928198.67

See also my post on Carbon Dioxide Storage

Arizona geology has a recent post on geologic sequestration of CO2 here.

The formation of the Isthmus of Panama may be one of the most important geologic events in the last 60 million years. Even though only a small sliver of land relative to the sizes of continents, the Isthmus of Panama had an enormous impact on Earth's climate and its environment. By shutting down the flow of water between the two oceans, the land bridge re-routed ocean currents in both the Atlantic and Pacific Oceans. Atlantic currents were forced northward, and eventually settled into a new current pattern, namely the Gulf Stream. With warm Caribbean waters flowing toward the northeast Atlantic, the climate of northwestern Europe grew warmer. (Winters there would be as much as 10°C colder in winter without the transport of heat from the Gulf Stream.) The Atlantic, no longer mingling with the Pacific, grew saltier. Each of these changes helped establish the global ocean circulation pattern in place today.

Before the present-day isthmus was created a significant body of water (referred to as the Central American Seaway^*)) separated the continents of North and South America. Beneath the surface, two plates of the Earth's crust were slowly colliding, forcing the Pacific Plate to slide under the Caribbean Plate. The pressure and heat caused by this collision led to the formation of underwater volcanoes, some of which grew large enough to form islands as early as 15 million years ago. Eventually the volcanic activity formed a thin strip of land linking the Americas and separating the Pacific and Atlantic oceans. So far it was believed that the isthmus finally had formed between North and South America about 3 million years ago - but is that so?


Engineers digging to widen the Panama Canal have uncovered more than 500 fossils from animals that lived before the land bridge linked North and South America. By comparing the Panama discoveries to fossil records from each continent, palaeontologists hope to determine where the individual animals came from. Volcanic debris embedded in the same layer of rock as the fossils will help pinpoint the time when the animal was found on either side of the land bridge. Determining exactly when this closure happened could be key to understanding the link between major changes in ocean currents and our climate, providing insight into the impact of global warming. Was the closure linked to the start of the ice age is one of the questions.

• http://www.msnbc.msn.com/id/25726314/

*)
The Central American Seaway, also called the Panamanic Seaway or Inter-American Seaway formed in the Mesozoic (200-154 million years ago) during the separation of the Pangaean supercontinent.

See also my post on Ocean (and atmospheric) circulation.



PS: In 2004 Oceanus posted a great article on line titled How the Isthmus of Panama Put Ice in the Arctic with more in depth information.

PS of 11 August 2008:
See also my continuation at http://my.opera.com/nielsol/blog/2008/08/11/panama