GEOGRAPHY

2010-08-03T21:41:00.000-07:00

Breakthrough Achieved in Explaining Why Tectonic Plates Move the Way They Do.

A team of researchers including Scripps Institution of Oceanography, UC San Diego geophysicist Dave Stegman has developed a new theory to explain the global motions of tectonic plates on the earth's surface.Read full topic....click here

(The sinking of the Farallon plate beneath the North American continent over 30 million years created the geologic feature known as the Basin and Range Province, an area of the western United States that encompasses much of Nevada, seen here in a topographic model. (Credit: Mike Sandiford/University of Melbourne)

2010-08-03T21:34:00.000-07:00

Key Compound of Ozone Destruction Detected; Scientists Disprove Doubts in Ozone Hole Chemistry

ScienceDaily (July 22, 2010) — For the first time, Karlsruhe Institute of Technology (KIT) scientists have successfully measured in the ozone layer the chlorine compound ClOOCl, which plays an important role in stratospheric ozone depletion. The doubts in the established models of polar ozone chemistry expressed by American researchers based on laboratory measurements are disproved by these new atmospheric observations. The established role played by chlorine compounds in atmospheric ozone chemistry is in fact confirmed by KIT's atmospheric measurements.Read more....click here

Acid rain

2010-08-03T21:27:00.000-07:00

Acid rain is a rain or any other form of precipitation that is unusually acidic, i.e. elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals, and infrastructure through the process of wet deposition. Acid rain is caused by emissions of compounds of ammonium,carbon, nitrogen, and sulfur which react with the water molecules in the atmosphere to produce acids. Governments have made efforts since the 1970s to reduce the production of sulfur dioxide into theatmosphere with positive results. However, it can also be caused naturally by the splitting of nitrogen compounds by the energy produced by lightning strikes, or the release of sulfur dioxide into the atmosphere by volcano eruptions.

Geographic information systems

Main article: Geographic information system

Geographic information systems (GIS) deal with the storage of information about the Earth for automatic retrieval by a computer, in an accurate manner appropriate to the information's purpose. In addition to all of the other subdisciplines of geography, GIS specialists must understand computer science and database systems. GIS has revolutionized the field of cartography; nearly all mapmaking is now done with the assistance of some form of GIS software. GIS also refers to the science of using GIS software and GIS techniques to represent, analyze and predict spatial relationships. In this context, GIS stands for Geographic Information Science.

[edit]Remote sensing

Main article: Remote sensing

Remote sensing is the science of obtaining information about Earth features from measurements made at a distance. Remotely sensed data comes in many forms such as satellite imagery, aerial photography and data obtained from hand-held sensors. Geographers increasingly use remotely sensed data to obtain information about the Earth's land surface, ocean and atmosphere because it: a) supplies objective information at a variety of spatial scales (local to global), b) provides a synoptic view of the area of interest, c) allows access to distant and/or inaccessible sites, d) provides spectral information outside the visible portion of theelectromagnetic spectrum, and e) facilitates studies of how features/areas change over time. Remotely sensed data may be analyzed either independently of, or in conjunction with, other digital data layers (e.g., in a Geographic Information System).

Notable geographers

2010-08-02T07:50:00.000-07:00

Main article: List of geographers

The Geographer by Johannes Vermeer

Eratosthenes (276BC - 194BC) - calculated the size of the Earth.
Ptolemy (c.90–c.168) - compiled Greek and Roman knowledge into the book Geographia.
Al Idrisi (Arabic: أبو عبد الله محمد الإدريسي‎; Latin: Dreses) (1100–1165/66) - author of Nuzhatul Mushtaq.
Gerardus Mercator (1512–1594) - innovative cartographer produced the mercator projection
Alexander von Humboldt (1769–1859) - Considered Father of modern geography, published the Kosmos and founder of the sub-field biogeography.
Carl Ritter (1779–1859) - Considered Father of modern geography. Occupied the first chair of geography at Berlin University.
Arnold Henry Guyot (1807–1884) - noted the structure of glaciers and advanced understanding in glacier motion, especially in fast ice flow.
William Morris Davis (1850–1934) - father of American geography and developer of the cycle of erosion.
Paul Vidal de la Blache (1845–1918) - founder of the French school of geopolitics and wrote the principles of human geography.
Sir Halford John Mackinder (1861–1947) - Co-founder of the LSE, Geographical Association
Carl O. Sauer (1889–1975) - Prominent cultural geographer
Walter Christaller (1893–1969) - human geographer and inventor of Central place theory.
Yi-Fu Tuan (1930-) - Chinese-American scholar credited with starting Humanistic Geography as a discipline.
David Harvey (1935-) - Marxist geographer and author of theories on spatial and urban geography, winner of the Vautrin Lud Prize.
Edward Soja (born 1941) - Noted for his work on regional development, planning and governance along with coining the terms Synekism and Postmetropolis.
Michael Frank Goodchild (1944-) - prominent GIS scholar and winner of the RGS founder's medal in 2003.
Doreen Massey (1944-) - Key scholar in the space and places of globalization and its pluralities, winner of the Vautrin Lud Prize.
Nigel Thrift (1949-) - originator of non-representational theory.

What is a stratigraphic column?

2010-08-02T07:41:00.000-07:00

This is going to be a long answer, so pull up a chair and get comfortable. While it's fun to look at the earth and try to figure out what has happened in a particular place, one of the most important things that geologists do is to attempt to combine these bits of local information into a regional model of earth history. This is much tougher, but in the long run well worth the effort.
Several steps/processes are involved in any attempt to unravel earth history. It all starts with the rocks.
Lithology is the study of bedrock: the rocks which occur in a specific location. While this obviously includes igneous and metamorphic rocks, sedimentary rocks are very important for several reasons: many of the classical laws of geology relate to the accumulation of sediments, and the formation of sedimentary rocks; and they may contain fossils which aid in determining how old they are. Therefore sedimentary rocks can also help in our understanding of both sequence and timing.
As fate would have it, the earth works in a completely different time frame than we do, and all earth processes don't even work at the same speed. Two of the main processes which have different timing are the tectonic forces which build the mountains, and the surface processes which tear them down and transport the sediments to low energy environments where they are deposited. This often results in thick piles of similar sediments which accumulate before there is a fundamental change in the area's depositional environment. Changes in sea level provide a great example. The distribution of sediment on the seafloor is directly related to the amount of energy in the water, and the energy is directly related to the depth of the water and the distance to the beach. In general, the earth deposits big stuff (sand and gravel) near the beach, with silt and clay piling up farther offshore. As the land rises and falls in response to tectonic forces, the higher energy shore zone (the sandy beach) changes location, moving "offshore" or "onshore" in response to the resulting fluctuations in sea level. But the sand is coming in faster than the tectonic processes are causing the sea level changes, so it's common to get a thick pile of sand before water depth changes and something different is deposited. Geologists group together similar lithologies, and call these larger sedimentary sequences formations. There are some fairly simple rules on how formations are named, mostly related to where they are located and what's in them. For example, if it's all the same stuff it might be called the "Lyons Sandstone," or the "Benton Shale." If, on the other hand, there are several different lithologies within the formation, we need to use more general terminology such as the "Morrison Formation," which contains siltstone, sandstone, and limestone.
After geologists study the lithologies in a particular area and group them into formations, the next step is to work out the stratigraphy. Determining the local stratigraphy obviously requires an understanding of the rocks, but it also deals with the relationships between the rocks: the sequence and timing of events are now extremely important. So now it's time to throw in all the other stuff: faults and folds, dikes, unconformities, age relationships, and other complexities which tend to further complicate the issue. The stratigraphic information can be presented in several ways. One of the most useful is the stratigraphic column: a graphical representation of the stratigraphy of a particular area. For regional studies, geologists will study the stratigraphy of as many separate areas as they can, prepare a stratigraphic column for each, and combine them in an attempt to understand the regional geologic history of the area.

EARTH'S INTERNAL STRUCTURE

2010-08-02T07:21:00.000-07:00

Five billion years ago the Earth was formed in a massive conglomeration and bombardment of meteorites and comets. The immense amount of heat energy released by the high-velocity bombardment melted the entire planet, and it is still cooling off today. Denser materials like iron (Fe) from the meteroites sank into the core of the Earth, while lighter silicates (Si), other oxygen (O) compounds, and water from comets rose near the surface.

(J. Louie) The earth is divided into four main layers: the inner core, outer core, mantle, and crust. The core is composed mostly of iron (Fe) and is so hot that the outer core is molten, with about 10% sulphur (S). The inner core is under such extreme pressure that it remains solid. Most of the Earth's mass is in the mantle, which is composed of iron (Fe), magnesium (Mg), aluminum (Al), silicon (Si), and oxygen (O) silicate compounds. At over 1000 degrees C, the mantle is solid but can deform slowly in a plastic manner. The crust is much thinner than any of the other layers, and is composed of the least dense calcium (Ca) and sodium (Na) aluminum-silicate minerals. Being relatively cold, the crust is rocky and brittle, so it can fracture in earthquakes.

Exploring the Earth's Core

How was the Earth's core dicovered? Recordings of seismic waves from earthquakes gave the first clue. Seismic waves will bend and reflect at the interfaces between different materials, just like the prism below refracts and scatters light waves at its faces.

(original image from the Exploratorium; used by permission)In addition, the two types of seismic wave behave differently, depending on the material. Compressional P waves will travel and refract through both fluid and solid materials. Shear S waves, however, cannot travel through fluids like air or water. Fluids cannot support the side-to-side particle motion that makes S waves.

(J. Louie) Seismologists noticed that records from an earthquake made around the world changed radically once the event was more than a certain distance away, about 105 degrees in terms of the angle between the earthquake and the seismograph at the center of the earth. After 105 degrees the waves disappeared almost completely, at least until the slow surface waves would arrive from over the horizon. The area beyond 105 degrees distance forms a shadow zone. At larger distances, some P waves would arrive, but still no S waves. The Earth has to have a molten, fluid core to explain the lack of S waves in the shadow zone, and the bending of P waves to form their shadow zone.