Nyamuragira Volcano Erupts فوران آتشفشا ن " نیاموراجیرا " در جمهوری کنگو "

On November 6, 2011, after more than a year of relative peace, the Nyamuragira volcano in the Democratic Republic of Congo surged to life. Lava has erupted spectacularly from a fissure low on one of the volcano's flanks and spilled northward, away from populated areas. Nyamuragira is a shield volcano and one of Africa's most active.

For more than a week, cloud cover mostly obscured the view from space until the Advanced Land Imager on NASA’s EO-1 satellite captured images on November 12, 2011. This false-color view combines shortwave infrared, near infrared, and green light. Fresh lava is bright red, an indication that it was active at the time the satellite flew overhead. Billowing, blue-tinged steam clouds rise above the superheated fissure and lava-bathed landscape. In the full-size, wider view (available by link just below the image), the lava lake at nearby Nyiragongo volcano (to the south) glows red through the cloud cover.

A blogger and ranger from Virgunga National Park wrote:

...We hiked a bit further until we came to a section where the vegetation ended and the ground was covered in small pebbles of weightless lava gravel. The thundering roar of the volcano was incredible and the heat of the 100-meter column of lava clearly tangible...The eruption site is truly amazing. It’s located on a flat area, but the sides have been building up around the crack over the last week...The lava has a low silica content resulting in lava with a low viscosity (very fluid), which in turn results in the amazing lava fountain.

Ground-based video of the eruption is available here from the Virunga National Park. Wider satellite views of the landscape around the eruption on November 8 and November 16 are available online through the LANCE/EOSDIS MODIS Rapid Response Team.

1.   References

2.   Global Volcanism Program (2011, November 8) Nyamuragira. Accessed November 16, 2011.

3.   Gorilla.CD Blog (2011, November 13) New Overnight Trek to Nyamulagira Volcano Eruption Site. Accessed November 16, 2011.

4.   Klimetti, Erik (2011) Eruptions Blog: Nyamuragira. Accessed November 16, 2011.

Polynya off the Antarctic Coast ویژگی زمستانی در قطب که به شکل گرفتن دریای یخ می انجامد

Winter conditions in the Arctic and Antarctic lead to the formation of sea ice. But in some places where sea ice should occur, open water appears instead. Persistent areas of open water amidst sea ice are known as polynyas. Often the result of the upwelling of warm ocean water, polynyas can also result from winds.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this natural-color image of a polynya off the coast of Antarctica, near Ross Island and McMurdo Station on November 16, 2011. The polynya was likely caused by katabatic winds, which derive their name from the Greek term for “descent.” The winds blow off Antarctica’s high interior toward the ocean and can attain hurricane strength—up to 200 miles (320 kilometers) per hour.

Strong winds have pushed sea ice away from the coast in this image, but not uniformly. Ross Island and the mountains to the west block some winds, so sea ice lingers near those landforms. Along the lower-elevation area east of Ross Island, winds clear the ice from a large stretch of ocean. North of the polynya, sea ice shows varying degrees of thickness, perhaps the result of alternating windy and calm spells.

Polynyas, ice shelves, and sea ice were prime targets for IceBridge, a NASA mission that uses airplanes equipped with radar and lidar to develop a three-dimensional view of Antarctic ice. The 2011 Antarctic campaign concluded on November 20. You can learn more about the mission in IceBridge: Building a record of Earth’s changing ice, one flight at a time.

1.   References

2.   All about Sea Ice. Polynyas. National Snow and Ice Data Center. Accessed November 21, 2011.

3.   Antarctica: The End of the Earth. Unequaled extremes. PBS Nature. Accessed November 21, 2011.

Suguta Valley, Kenya دره ی " سوگوتا " ، یکی از خشگ ترین مناطق در کشور کنیا

The Suguta Valley is one of the driest places in Kenya, and may be one of the driest places near Earth's Equator. The remote location limits field studies, but data indicate that annual precipitation is less than 300 millimeters (12 inches) a year, while evaporation ranges from 3,000 to 4,000 millimeters (120 to 160 inches). And yet, as recently as 8,000 years ago, this arid valley was a vast lake.

On January 10, 2011, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of the north end of the Suguta Valley, including Logipi Lake, which seasonally fills just a small portion of the valley. Derived from Shuttle Radar Topography Mission (SRTM) data, the white line around the valley in the top image approximates the Lake Suguta shoreline when water levels were at their highest.

The Suguta Valley floor is relatively flat and stands at an elevation about 300 meters (1,000 feet) above sea level. The surrounding land rises to 1,000 meters (3,000 feet) east and west of the valley, and high-elevation, volcaniccinder cones dot the rim. By studying ancient sediments, fossil remains, and occasional artifacts from the high-elevation sites, geologists have pieced together the history of a lake that rose and fell multiple times over the past 18,000 years.

Two high-elevation sites, known to the researchers as SANC and NAMC, occur along the northern margin of Suguta Valley and are shown in the close-up image (bottom). These cinder cones are part of a broad volcanic complex between the Suguta Valley and Lake Turkana to the north. During a protracted period when Lake Suguta was overflowing into Lake Turkana, wave action carved notches and terraces into these fossil shorelines.

Lake Suguta, which once filled today’s dry valley, reached its maximum height several times in the past 13,000 years. The sprawling lake was influenced by the African Humid Period. Estimated to have lasted from 14,800 to 5,500 years ago, the period was marked by recurring swings of water levels in the tropics. Near Lake Suguta, conditions were wetter than today. Starting about 8,000 years ago, however, the lake level dropped dramatically, falling from 570 meters (1,870 feet) to about 320 meters (1,050 feet) above sea level.

Falling water levels are not the only changes at Lake Suguta over the past several millennia. The lake valley lies within the East African Rift System, where tectonic plates are moving away from each other. As a result, tectonic activity in this region has deformed the shorelines of the ancient lake.

1.   References

2.   Garcin, Y., Junginger, A., Melnick, D., Olago, D.O., Strecker, M.R., Trauth, M.H. (2009). Late Pleistocene–Holocene rise and collapse of Lake Suguta, northern Kenya Rift. Quaternary Science Reviews. 28(9–10), 911–925.

Earthquakes occur at 'subduction zones زمینلرزه در مناطق فرورانده رخ می دهد

Earthquakes occur at 'subduction zones,' such as the one west of Indonesia, when one tectonic plate is forced under another--or subducts. Instead of sliding across one another smoothly, the plates stick, and energy builds up until they finally slip or 'rupture', releasing that stored energy as an earthquake. These earthquakes can generate tsunamis when the seafloor moves up or down rapidly. Sean Gulick, a geophysicist from the University of Texas at Austin joined an international research team to try to figure out why there were two quakes in 2004 and 2005, and what made them so different. The scientists used seismic instruments to study layers of sediment beneath the seafloor with sound waves. The researchers found that the fault surface where the two tectonic plates meet, called a décollement, has different properties in the two earthquake rupture regions

Afghanistan Dust Storm توفان درافغا نستا ن

A dense cloud of dust swept across southern Afghanistan and Pakistan on December 20, 2011. When the Moderate Resolution Imaging Spectroradiometer (MODIS) took this image from the Terra satellite at 10:45 a.m., the dust was largely hemmed in by the Makran and Sulaiman Ranges in Pakistan with only a few wisps reaching south over the Arabian Sea. By the time Aqua MODIS flew over just three hours later, the storm had reached the coast. The dust storm continued on December 21.

The storm is being propelled by strong winds from the north. The winds picked up dust from dry lakebeds in the Hamun wetlands, on the border between Afghanistan and Iran. Concentrated plumes of dust rise from the pale wetlands to become a more diffuse cloud in the south and east. Dry lakebeds and wetlands are among the most common sources of dust in the world.

Dust storms can happen any time of the year in Afghanistan. On average, Afghanistan experiences blowing dust one to two days per month in the winter and six days per month at the height of the summer. Zabon, an Iranian city located near the border in the Hamun wetlands, reports 81 dust storms per year.

Blowing dust poses a hazard to transportation, as low visibility closes roads and airports. This particular storm prevented British Prime Minister David Cameron from visiting a British military base because the runway was closed for low visibility.

1.   References

2.   National Climate Data Center. (2008, August 20). Climate of Afghanistan. National Oceanic and Atmospheric Administration. Accessed December 21, 2011.

3.   Prospero, J, Ginoux, P., Torres, O., Nicholson, S.E., and Gill, T.E. (2002, February). Environmental characterization of global sources of atmospheric soil dust identified with the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) absorbing aerosol product. Reviews of Geophysics, 40 (1).

4.   Watt, N. (2011, December 20). Dust storm forces Cameron to abandon visit to Cam Bastion in Afghanistan. The Guardian. Accessed December 21, 2011.

NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC. Caption by Holli Riebeek.

Instrument: 

Terra - MODIS

توفان در افغانستان

گرد و غبار از بستر خشک دریاچه ی هامون بر خاست ، و ابری ضخیم را در جنوب و خاور افغانستان در آسمان گسترد .

توفان گرد و غبار در هر زمانی در افغانستان بر می خیزد . شواهد نشان از یک یا دو روز توفانی در ماه در فصل زمستان ، و شش روز در  گرمترین روز های تابستان است .

شهر زابل در کناره ی دریاچه ی خشک هامون ، بر پایه ی گزارش ها، هر سا له حدود هشتاد و یک روز  توفانی است .

Volcanic Activity in the Red Sea فوران آتشفشان در دریای سرخ

1. 

An eruption occurred in the Red Sea in December 2011. According to news reports, fishermen witnessed lava fountains reaching up to 30 meters (90 feet) tall on December 19. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites observed plumes on December 20 and December 22.Meanwhile, the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite detected elevated levels of sulfur dioxide,further indicating an eruption.

The activity in the Red Sea included more than an eruption. By December 23, 2011, what looked like a new island appeared in the region. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured these high-resolution, natural-color images on December 23, 2011 (top), and October 24, 2007 (bottom). The image from December 2011 shows an apparent island where there had previously been an unbroken water surface. A thick plume rises from the island, dark near the bottom and light near the top, perhaps a mixture of volcanic ash and water vapor.

The volcanic activity occurred along the Zubair Group, a collection of small islands off the west coast of Yemen. Running in a roughly northwest-southeast line, the islands poke above the sea surface, rising from a shield volcano.This region is part of the Red Sea Rift where the African and Arabian tectonic plates pull apart and new ocean crust regularly forms.

1.   References

2.   Bauwens, J. (2011, December 22). Eruption in the Zubair Archipelago, in the southern Red Sea. Accessed December 27, 2011.

3.   Gass, I.G., Mallick, D.I.J., Cox, K.G. (1973). Volcanic islands of the Red Sea. Journal of the Geological Society, 129(3), 275–309.

4.   Global Volcanism Program. (2011, December 20). Weekly volcanic report, 14 December–20 December 2011.Smithsonian Institution. Accessed December 27, 2011.

5.   Global Volcanism Program. Zubair Group. Smithsonian Institution. Accessed December 27, 2011.

6.   Klemetti, E. (2011, December 19). Potential eruption off the coast of Yemen. Eruptions. Accessed December 27, 2011.

7.   U.S. Geological Survey, National Park Service. (1999, January 14). Divergent plate boundaries. Accessed December 27, 2011.

8.   Volcano Discovery. (2011, December 21). Volcanic eruption in the Red Sea (Yemen) reported. Accessed December 27, 2011.

فوران آتشفشان در دریای سرخ

فعالیت آتشفشانی در راستای " مجموعه ی زبیر " ، که جزایر کوچکی است در ساحل باختر ی " یمن "، در خطی شمال باختر – جنوب خاور ، چهره گشود . این برجستگی ، بخشی از " بلندی های پنهان در آب، در جایی است که ورقه های زمین ساختی " آفریقا " و " عربستان " از هم دور می شوند تا اقیانوسی نو، شکل گیرد .