Like
some fantastical land conjured by a storyteller, Ethiopia’s Danakil Depression
(or Afar Depression) exhibits some uncommon wonders: lava that burns blue,
bright yellow hot springs, and lakes of bubbling mud. These otherworldly
oddities are all manifestations of a tectonic process called continental
rifting. In other words, the Earth is pulling apart at the seams here.
In
northeastern Africa, the Arabian, Somali, and Nubian (or African) plates are
separating, thinning Earth’s crust as they pull apart. The Danakil Depression
lies between the Danakil Alps (east) and the Ethiopian Plateau (west), which
were once joined until the rifting process tore them apart. The land surface is
slowly sinking, and Danakil Depression will someday fill with water as a new
ocean or great lake is born. But for now, the region is full of other
interesting liquids.
Acquired
on June 27, 2014, the Landsat 8 image above shows a few of the diverse and
compelling features of the Danakil Depression. Chief among them is Gada Ale,
the northernmost volcano in the Erta Ale volcanic range. Gada Ale is a
287-meter (942-foot) stratovolcano built of lava and ash, and it has a crater
lake full of boiling mud and sulfurous gases. Basalt lava from the volcano
paints the surrounding terrain a dark hue, with the youngest flows being the
darkest colors in the satellite image.
Just
southwest of Gada Ale, a 2-kilometer-wide salt dome has pushed ancient lava
flows up to heights of 100 meters (330 feet). North of Gada Ale, a salt lake
(Lake Karum) lies 116 meters (380 feet) below sea level. To the south lies the
Catherine Volcano, a 120-meter (400-foot) circular shield surrounded by a tuff
ring (an amalgamation of volcanic ash). With gently sloping sides of basaltic
lava, the volcano has been dated at less than one million years old. In the
center of that tuff ring is a small, salty lake fed by thermal springs.
The
Afar people have survived in this unforgiving region for at least 2,000 years,
mining and selling the plain’s abundant salt, which was once used as currency
in Ethiopia. The harsh desert also has created an ideal exposure for the
tectonic rifting—a process that often occurs on the recesses of the ocean
seafloor or elsewhere on land where younger sedimentary rocks obscure the
geologic record.
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