Red Sea Rifting and Exposure of The Arabian-Nubian Shield
The Arabian-Nubian Shield is representative of the continental crust that underlies NE Africa, SW Asia, and Arabia. Geophysical studies inform us that ANS crust is about 40–45 km thick, typical for continental crust elsewhere. Geologists are interested to study this crust because it provides an outstanding opportunity to learn how continental crust forms. Elsewhere in Arabia and NE Africa the crust is buried beneath kilometers of younger, Phanerozoic sediments and can only be reached by scientific drilling.
Glaciers scoured this land during one of the Neoproterozoic Snowball earth episodes (~630 Ma) and the remarkable Arabian-Nubian peneplain is overlain by the greatest sand sheet on Earth, the Cambro-Ordovician Siq/Saq sands. This is exposed in spectacular cliffs like the site of Petra in Jordan. The Arabian sandstones are overlain by thick deposits of younger sediments that dip and thicken eastwards into the Persian Gulf. These sands are missing in most of Egypt and Sudan, instead the ANS is overlain by the late Mesozoic Nubian sandstones. All of these sediments were peeled off by erosion to expose the ANS, and much of this sand was reworked by desert winds to make great sand dunes in western Egypt and the Ar Rub al Khali (Empty Quarter) of Arabia.
The embryonic ocean called the Red Sea has slowly widened by rifting over the past 25 million years. Rifting typically causes uplift of its margins, or 'rift shoulders', and the covering sediments were removed by erosion as the Red Sea widened, allowing us to examine the basement geology of this region. This examination is favored also by the desert climate of the region - there is no soil, little vegetation, and few cities or roads to obscure the geology.
Read more about this topic: Arabian-Nubian Shield
Famous quotes containing the words red, sea and/or shield:
“Billboards, billboards, drink this, eat that, use all manner of things, everyone, the best, the cheapest, the purest and most satisfying of all their available counterparts. Red lights flicker on every horizon, airplanes beware; cars flash by, more lights. Workers repair the gas main. Signs, signs, lights, lights, streets, streets.”
—Neal Cassady (1926–1968)
“O you singers solitary, singing by yourself, projecting me,
O solitary me listening, never more shall I cease perpetuating you
Never more shall I escape, never more the reverberations,
Never more the cries of unsatisfied love be absent from me,
Never again leave me to be the peaceful child I was before what
there in the night,
By the sea under the yellow and sagging moon,
The messenger there aroused, the fire, the sweet hell within,
The unknown want, the destiny of me.”
—Walt Whitman (1819–1892)
“Vice is its own reward. It is virtue which, if it is to be marketed with consumer appeal, must carry Green Shield stamps.”
—Quentin Crisp (b. 1908)