|
|
|
马上注册，结交更多好友，享用更多功能，让你轻松玩转社区。
您需要 登录 才可以下载或查看，没有帐号？FreeOZ用户注册
x
FROM: http://www.sciam.com/article.cfm?id=birth-of-an-ocean
Ghostly salt deposits near Afdera volcano testify to ancientinundations in Ethiopia's Afar region. In the past 200,000 years theRed Sea flooded Afar's lowlands at least three times; the salt stayedbehind as the seawater evaporated. One day the ersatz seascape willlikely become the real thing.
- Africa is splittingapart at the seams—literally. From the southern tip of the Red Seasouthward through Eritrea, Ethiopia, Kenya, Tanzania and Mozambique,the continent is coming unstitched along a zone called the EastAfrican Rift.
- Like a shirtsleeve tearing under a bulgingbicep, the earth’s crust rips apart as molten rock from deep downpushes up on the solid surface and stretches it thin—sometimes to itsbreaking point. Each new slit widens as lava fills the gap from below.
- Thisspectacular geologic unraveling, already under way for millions ofyears, will be complete when saltwater from the Red Sea floods themassive gash. Ten million years from now the entire rift may besubmerged.
In northeastern Ethiopia one of the earth’s driest deserts is making way for a new ocean. This region of the African continent, known to geologists as the Afar Depression,is pulling apart in two directions—a process that is gradually thinningthe earth’s rocky outer skin. The continental crust under Afar is amere 20 kilometers from top to bottom, less than half its originalthickness, and parts of the area are over 100 meters below sea level.Low hills to the east are all that stops the Red Sea from encroaching.
Such proximity to the planet’s scorching interior has transformedthe region into a dynamic landscape of earthquakes, volcanoes andhydrothermal fields—making Afar a veritable paradise for people, likeme, eager to understand those processes. Yet few outsiders, scientistsincluded, have ever set foot in Afar. Daytime temperatures soar to 48degrees Celsius (118 degrees Fahrenheit) in the summer, and no rainfalls for much of the year. But I knew I faced more than treacherousgeology and climate.Nasty geopolitical struggles—namely, war between Ethiopia andneighboring Eritrea—combine with those natural hardships to make Afarutterly inhospitable.
Geologists predict another million years of the land stretching andsinking, combined with a massive deluge from the Red Sea, could putAfar at the bottom of a new ocean. For now, this incipient seabed is adesolate landscape where lava stifles vegetation, hellish heat makesacid boil, devilish formations emit toxic fumes, and the salty legacyof ancient Red Sea floods provides nomadic tribes of Afar with aprecious export.
Click here to view this photo essay as a slide show |
|
发表于 6-10-2008 19:28:35
收藏
赞
踩
楼主
