July 11, 2018
A River Ran Through It
Originally published April 15, 2009
image by Damian Peach, Barbados
In the past I have compared the Alpine Valley to the Red Sea because both are long with relatively straight and steep sides. But the Sea is 2300 km long, nearly 15 times the size of the 166 km long Valley, so do they have any significant similarities? The Red Sea formed by the slight doming and then stretching and fracturing of eastern Africa and Arabia. The crust was ruptured completely and an ocean floor spreading center formed, with eruptions filling the space that openned up as the shores were pushed apart. We don't know exactly how the Alpine Valley formed, but we do know that, unlike the Red Sea, it is not part of a global system of plate tectonics. The radial alignment of the Valley with the center of the Imbrium Basin powerfully suggests the the Valley formed is response to stresses generated by the basin-forming impact. Because the Valley cuts through Imbrium ejecta and is not filled with it, the Valley must have formed after the impact. Was the floor of the Valley produced by limited doming and pulling apart, like the Red Sea? Or did the crust simply drop down, and is it somewhere under the Valley floor's lava covering? We don't know. Finally, the sinuous rille running down the center of the floor was presumably the source of the lava, but it is peculiar that the rille is so well centered within the floor.
May 25, 2007, Approx 23:00 UTC. 14" scope at F42 in green light with the Moon 74º above the horizon.
Rükl plate 4
Yesterday's LPOD: Beginning To See the Unseen
Tomorrow's LPOD: Landscape of Treasures