18 Feb '12, 11pm

Guam [image] #NASA

Guam has two seasons: wet (June to December) and dry (January to June), and ALI acquired this image during the transition from wet to dry. The fate of that rainwater has a lot to do with whether it lands in the northern or southern part of the island. In southern Guam, volcanic rock predominates, but in northern Guam, limestone overlies volcanic rock. Limestone is porous—so porous, in fact, that practically all the water in northern Guam infiltrates the rock. After percolating through the limestone, water in northern Guam becomes part of the groundwater system. Guam’s rivers are confined to the southern part of the island, where less porous volcanic rock enables water to collect on the surface.

Full article: http://earthobservatory.nasa.gov/IOTD/view.php?id=77189&s...

Tweets

Guam: Fields, forests, military bases, and sett...

earthobservatory.nasa.gov 18 Feb '12, 11pm

On December 30, 2011, cloud-free skies presented NASA’s Earth Observing-1 (EO-1) satellite with this unobstructed view of ...

Guam: Fields, forests, military bases, and sett...

earthobservatory.nasa.gov 18 Feb '12, 11pm

On December 30, 2011, cloud-free skies presented NASA’s Earth Observing-1 (EO-1) satellite with this unobstructed view of ...

Steam and Ash Plume over Tinakula Island : Imag...

earthobservatory.nasa.gov 18 Feb '12, 8pm

Tinakula is a small, volcanic island in the South Pacific, located about 2,300 kilometers (1,400 miles) northeast of Brisb...

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earthobservatory.nasa.gov 19 Feb '12, 11pm

Lake Fitri is an endorheic or “terminal” lake in the southern Sahara Desert. Deserts get so little rainfall that the river...

Lake Fitri, Chad: In the desert, a lake shows a...

earthobservatory.nasa.gov 19 Feb '12, 11pm

Lake Fitri is an endorheic or “terminal” lake in the southern Sahara Desert. Deserts get so little rainfall that the river...

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earthobservatory.nasa.gov 12 Feb '12, 11pm

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Steam and Ash Plume over Tinakula Island: After...

earthobservatory.nasa.gov 17 Feb '12, 11pm

Tinakula is a small, volcanic island in the South Pacific, located about 2,300 kilometers (1,400 miles) northeast of Brisb...

The Eddy and the Plankton [image] #NASA

earthobservatory.nasa.gov 10 Feb '12, 11pm

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earthobservatory.nasa.gov 20 Feb '12, 11pm

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earthobservatory.nasa.gov 11 Feb '12, 11pm

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The Amery Ice Shelf has a loose tooth : nasa Im...

earthobservatory.nasa.gov 11 Feb '12, 11pm

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earthobservatory.nasa.gov 09 Feb '12, 11pm

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earthobservatory.nasa.gov 05 Feb '12, 11pm

The Balearic Islands are an archipelago located in the Mediterranean Sea to the southwest of Spain. Catalan—the native ton...

Cold Snap Across Europe [image] #NASA

earthobservatory.nasa.gov 09 Feb '12, 11pm

Rare snowstorms in Rome and Tripoli and mounting death tolls from exposure were among the consequences of a severe cold sn...

Rhodes, Greece : Image of the Day #NASA

earthobservatory.nasa.gov 05 Feb '12, 3pm

Rhodes (also Rodos) is the biggest island in the Greek Dodecanese chain, which lies in the southeastern Aegean Sea. Rhodes...