Old Is Gold

Nabro volcano

Since the beginning of the recent eruption, a dense plume of water vapor, gas, and ash has concealed the summit of the Nabro volcano. New images from June 29 finally provided a nearly unimpeded view of the summit, where lava flowed out of the erupting vent and down the slope of the volcano.

Located in the East African nation of Eritrea, Nabro began its eruption explosively on June 12, 2011. The powerful eruption sent plumes of ash streaming over North Africa and the Middle East, and pumped vast quantities of sulfur dioxide into the atmosphere. The ash halted flights in East Africa for a time. The eruption killed seven people, said the Eritrean government, and other reports indicate that thousands were affected in both Eritrea and Ethiopia, though news from the region is sparse.

More recently, the volcano has eased into a quieter, lava-oozing phase, as shown in these images from the Advanced Land Imager (ALI) on the Earth Observing-1 (EO-1) satellite. The top image shows the volcano in visible and infrared light (shortwave infrared, near infrared, and green). The hot lava glows orange-red, fading to black as it cools. The long flow on the west side of the volcano is mottled with black, a sign that the surface is cooling. The lava to the east and south of the vent appears to be newer, since little of it has cooled. It is possible that the cooling lava in the western flow diverted the fresh lava to the south and east.

The lower image provides a natural color view of the volcano. A small, slightly brown plume rises from the vent, and ash blackens the ground to the west and south.

Throughout the eruption, satellite images have been nearly the only source of new information about activity at the volcano. Detailed images like this one provide insight into how erupting lava is behaving. For example, volcanologist Erik Klemetti used previous images from ALI to estimate how quickly the lava is moving and to guess at how thick (viscous) the lava is.

Since the beginning of the recent eruption, a dense plume of water vapor, gas, and ash has concealed the summit of the Nabro volcano. New images from June 29 finally provided a nearly unimpeded view of the summit, where lava flowed out of the erupting vent and down the slope of the volcano.

Located in the East African nation of Eritrea, Nabro began its eruption explosively on June 12, 2011. The powerful eruption sent plumes of ash streaming over North Africa and the Middle East, and pumped vast quantities of sulfur dioxide into the atmosphere. The ash halted flights in East Africa for a time. The eruption killed seven people, said the Eritrean government, and other reports indicate that thousands were affected in both Eritrea and Ethiopia, though news from the region is sparse.

More recently, the volcano has eased into a quieter, lava-oozing phase, as shown in these images from the Advanced Land Imager (ALI) on the Earth Observing-1 (EO-1) satellite. The top image shows the volcano in visible and infrared light (shortwave infrared, near infrared, and green). The hot lava glows orange-red, fading to black as it cools. The long flow on the west side of the volcano is mottled with black, a sign that the surface is cooling. The lava to the east and south of the vent appears to be newer, since little of it has cooled. It is possible that the cooling lava in the western flow diverted the fresh lava to the south and east.

The lower image provides a natural color view of the volcano. A small, slightly brown plume rises from the vent, and ash blackens the ground to the west and south.

Throughout the eruption, satellite images have been nearly the only source of new information about activity at the volcano. Detailed images like this one provide insight into how erupting lava is behaving. For example, volcanologist Erik Klemetti used previous images from ALI to estimate how quickly the lava is moving and to guess at how thick (viscous) the lava is.

The Nabro volcano has not erupted in recorded human history, but lava flows near the volcano are relatively recent geologically. Nabro is part of the very active East African Rift, where three tectonic plates are pulling away from each other. As the Earth’s crust thins in the region, volcanoes rise in weak spots.

1. References

2. BBC News. (2011, June 15). Eritrea volcano: Ash disrupts air travel in East Africa. Accessed June 30, 2011.
3. BBC News. (2011, June 20). Eitrea volcano ash hits Ethiopia villages. Accessed June 30, 2011.
4. Eruptions. (2011, June 29). Nabro. Accessed June 30, 2011.
5. Global Volcanism Program. (2011, June 28). Nabro weekly reports. Smithsonian and U.S. Geological Survey. Accessed June 30, 2011.
6. Sudan Tribune. (2011, June 23). Eritrean opposition asks for international support as volcano kills seven. Accessed June 30, 2011.

NASA Earth Observatory image by Robert Simmon, using EO-1 ALI data. Caption by Holli Riebeek.

i copy it from NASA website..

Get Together 2 July,2011

Some photos of Get Together,2 july, 2011.

GEOLOGY

Geology (from the Greek γῆ, gê, "earth" and λόγος, logos, "study") is the science that comprises the study of the solid Earth and the processes by which it is shaped and changed. Geology provides primary evidence for plate tectonics, the history of life and evolution, and past climates. In modern times, geology is commercially important for mineral and hydrocarbon exploration and for evaluating water resources; is publicly important for the prediction and understanding of natural hazards, the remediation of environmental problems, and for providing insights into past climate change; plays an essential role in geotechnical engineering; and is a major academic discipline.

The study of the physical material of the Earth dates back at least to ancient Greece when Theophrastus (372-287 BC) wrote the work Peri Lithon (On Stones). In the Roman period, Pliny the Elder wrote in detail of the many minerals and metals then in practical use, and correctly noted the origin of amber.

Some modern scholars, such as Fielding H. Garrison, are of the opinion that modern geology began in the medieval Islamic world. Abu al-Rayhan al-Biruni (973–1048 AD) was one of the earliest Muslim geologists, whose works included the earliest writings on the geology of India, hypothesizing that the Indian subcontinent was once a sea. Islamic Scholar Ibn Sina (Avicenna, 981–1037) proposed detailed explanations for the formation of mountains, the origin of earthquakes, and other topics central to modern Geology, which provided an essential foundation for the later development of the science. In China, the polymath Shen Kua (1031–1095) formulated a hypothesis for the process of land formation: based on his observation of fossil animal shells in a geological stratum in a mountain hundreds of miles from the ocean, he inferred that the land was formed by erosion of the mountains and by deposition of silt.

Nicolas Steno (1638–1686) is credited with the law of superposition, the principle of original horizontality, and the principle of lateral continuity: three defining principles of stratigraphy.

The word geology was first used by Jean-André Deluc in 1778 and introduced as a fixed term by Horace-Bénédict de Saussure in 1779. The word is derived from the Greek γῆ, gê, meaning "earth" and λόγος, logos, meaning "speech".

William Smith (1769–1839) drew some of the first geological maps and began the process of ordering rock strata (layers) by examining the fossils contained in them.

James Hutton is often viewed as the first modern geologist. In 1785 he presented a paper entitled Theory of the Earth to the Royal Society of Edinburgh. In his paper, he explained his theory that the Earth must be much older than had previously been supposed in order to allow enough time for mountains to be eroded and for sediments to form new rocks at the bottom of the sea, which in turn were raised up to become dry land. Hutton published a two-volume version of his ideas in 1795 (Vol. 1, Vol. 2).

Followers of Hutton were known as Plutonists because they believed that some rocks were formed by vulcanism which is the deposition of lava from volcanoes, as opposed to the Neptunists, who believed that all rocks had settled out of a large ocean whose level gradually dropped over time.

Sir Charles Lyell first published his famous book, Principles of Geology, in 1830. The book, which influenced the thought of Charles Darwin, successfully promoted the doctrine of uniformitarianism. This theory states that slow geological processes have occurred throughout the Earth's history and are still occurring today. In contrast, catastrophism is the theory that Earth's features formed in single, catastrophic events and remained unchanged thereafter. Though Hutton believed in uniformitarianism, the idea was not widely accepted at the time.