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December 2005[edit]

Plate tectonics is a theory of geology developed to explain the phenomenon of continental drift, and is currently the theory accepted by the vast majority of scientists working in this area. In the theory of plate tectonics the outermost part of the Earth's interior is made up of two layers, the outer lithosphere and the inner asthenosphere.

The lithosphere essentially "floats" on the asthenosphere and is broken-up into ten major plates. These plates (and the more numerous minor plates) move in relation to one another at one of three types of plate boundaries: convergent (two plates push against one another), divergent (two plates move away from each other), and transform (two plates slide past one another).

Plate tectonic theory arose out of two separate geological observations: continental drift, noticed in the early 20th century, and seafloor spreading, noticed in the 1960s. The theory itself was developed during the late 1960s and has since almost universally been accepted by scientists and has revolutionized the Earth sciences (akin to the development of the periodic table for chemistry, the discovery of the genetic code for genetics, or evolution in biology).


January 2005[edit]

Clepsydra Geyser in Yellowstone

A geyser is a type of hot spring that erupts periodically, ejecting a column of hot water and steam into the air. The name geyser comes from Geysir, the name of an erupting spring at Haukadalur, Iceland; that name, in turn, comes from the Icelandic verb gjósa, "to gush".

The formation of geysers requires a favourable hydrogeology which exists in only a few places on Earth, and so they are fairly rare phenomena. About 1000 exist worldwide, with about half of these in Yellowstone National Park, USA (Glennon, J.A. 2005). Geyser eruptive activity may change or cease due to ongoing mineral deposition within the geyser plumbing, exchange of functions with nearby hot springs, earthquake influences, and human intervention (Bryan, T.S. 1995).

Erupting fountains of liquefied nitrogen have been observed on Neptune's moon Triton. These phenomena are also often referred to as geysers. On Triton, the geysers appear to be driven by solar heating instead of geothermal energy. The nitrogen, liquefied by a kind of greenhouse effect, may erupt to heights of 8 km.



Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years

An ice age is a period of long-term downturn in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers ("glaciation"). Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this definition we are still in an ice age (because the Greenland and Antarctic ice sheets still exist). More colloquially, when speaking of the last few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and Eurasian continents: in this sense, the last ice age ended about 10,000 years ago. This article will use the term ice age in the former, glaciological, sense; and use the term 'glacial periods' for colder periods during ice ages and 'interglacial' for the warmer periods.

During the last few million years, there have been many glacial periods, occurring initially at 40,000-year frequency but more recently at 100,000-year frequencies. There have been four major ice ages in the further past.


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December 2005[edit]

Structure of the Earth

January 2006[edit]


The rest of 2006[edit]

Receding glacier-en.svg
Receding glacier landscape

Retired Sections[edit]

Did you know[edit]

December 2005[edit]




November 25, 2005: Researchers in Antarctica have found that icebergs "sing". Unlike singing sand dunes, iceberg "songs" are not audible to humans. It is believed that the iceberg sounds are due to water flowing through crevasses inside it. The flow of water is caused when an iceberg hits the sea floor, slowing down; the water inside continues moving, building up water pressure, getting the iceberg walls to vibrate. This would produce regularly spaced tremors, resulting in the oscillating "songs".

November 24, 2005: A record ice-core reveals information of the Earth's atmosphere, showing correlations between greenhouse gases and temperature changes. This ice-core, taken by the European Project for Ice Coring in Antarctica is 3270 metres long.


January 20, 2006: Rocky debris on Mars has been found to be caused by glacier activity. Article on CBC News

January 15, 2006: The Chesapeake Bay Impact Crater Deep Drilling Project was completed successfully. A 1.77km (1.1 miles) core was taken within the crater, being one of the most complete cores ever taken from an impact structure. Article on ScienceDaily

January 14, 2006: Augustine Volcano erupts, exploding three times. Article on Aljazeera.net

January 13, 2006: Plants have been found to contribute significant amounts of methane to the Earth's atmosphere. Article on Geotimes

January 4, 2006: "Global warming millions of years ago put seas in a spin: The circulation of the deep oceans reversed abruptly some 55 million years ago, according to a study of fossilized sea creatures. This rings alarm bells about today's climate change, because the reversal coincided with a period of global warming driven by greenhouse gases." Article on Nature News

March 18, 2006: Ocean warming has been found to result in stronger hurricanes. Article on Nature News

March 12, 2006: The University of Arizona and the California Institute of Technology are in the process of creating tricorders to identify gemstones. Eurek!Alert article

March 9, 2006: Cassini discovers geysers of water on Enceladus. NASA Press Release

March 2, 2006: Neighbouring vortices are found to suck energy from each other, not have a smaller one fuel a larger one, like previously thought. Article on ScienceNOW