The Hellenic Navy (HN) (Greek: Πολεμικό Ναυτικό, Polemikó Naftikó, abbreviated ΠΝ) is the naval force of Greece, part of the Greek Armed Forces. The modern Greek navy has its roots in the naval forces of various Aegean Islands, which fought in the Greek War of Independence. During the periods of monarchy (1833–1924 and 1936–1973) it was known as the Royal Navy (Βασιλικόν Ναυτικόν, Vasilikón Naftikón, abbreviated ΒΝ).The total displacement of all the navy's vessels is approximately 150,000 tons.The motto of the Hellenic Navy is "Μέγα το της Θαλάσσης Κράτος" from Thucydides' account of Pericles' oration on the eve of the Peloponnesian War. This has been roughly translated as "Great is the country that controls the sea". The Hellenic Navy's emblem consists of an anchor in front of a crossed Christian cross and trident, with the cross symbolizing Greek Orthodoxy, and the trident symbolizing Poseidon, the god of the sea in Greek mythology. Pericles' words are written across the top of the emblem. "The navy, as it represents a necessary weapon for Greece, should only be created for war and aim to victory."...............The Hellenic Merchant Marine refers to the Merchant Marine of Greece, engaged in commerce and transportation of goods and services universally. It consists of the merchant vessels owned by Greek civilians, flying either the Greek flag or a flag of convenience. Greece is a maritime nation by tradition, as shipping is arguably the oldest form of occupation of the Greeks and a key element of Greek economic activity since the ancient times. Nowadays, Greece has the largest merchant fleet in the world, which is the second largest contributor to the national economy after tourism and forms the backbone of world shipping. The Greek fleet flies a variety of flags, however some Greek shipowners gradually return to Greece following the changes to the legislative framework governing their operations and the improvement of infrastructure.Blogger Tips and Tricks
This is a bilingual blog in English and / or Greek and you can translate any post to any language by pressing on the appropriate flag....Note that there is provided below a scrolling text with the 30 recent posts...Αυτό είναι ένα δίγλωσσο blog στα Αγγλικά η/και στα Ελληνικά και μπορείτε να μεταφράσετε οποιοδήποτε ποστ σε οποιαδήποτε γλώσσα κάνοντας κλικ στη σχετική σημαία. Σημειωτέον ότι παρακάτω παρέχεται και ένα κινούμενο κείμενο με τα 30 πρόσφατα ποστς....This is a bilingual blog in English and / or Greek and you can translate any post to any language by pressing on the appropriate flag....Note that there is provided below a scrolling text with the 30 recent posts...Αυτό είναι ένα δίγλωσσο blog στα Αγγλικά η/και στα Ελληνικά και μπορείτε να μεταφράσετε οποιοδήποτε ποστ σε οποιαδήποτε γλώσσα κάνοντας κλικ στη σχετική σημαία. Σημειωτέον ότι παρακάτω παρέχεται και ένα κινούμενο κείμενο με τα 30 πρόσφατα ποστς.........

Friday, August 14, 2009

Sahara Desert, Aorounga Impact Crater [ 326 ]

Earth Observatory
Aorounga Impact Crater, Chad
Posted August 10, 2009

Aorounga Impact Crater, Chad

Aorounga Impact Crater is located in the Sahara Desert, in north-central Chad, and is one of the best-preserved impact structures in the world. The crater is thought to be middle or upper Devonian to lower Mississippian (approximately 345–370 million years old) based on the age of the sedimentary rocks deformed by the impact. Spaceborne Imaging Radar (SIR) data collected in 1994 suggests that Aorounga is one of a set of three craters formed by the same impact event. The other two suggested impact structures are buried by sand deposits.

The concentric ring structure of the Aorounga crater—renamed Aorounga South in the multiple-crater interpretation of SIR data—is clearly visible in this detailed astronaut photograph. The central highland, or peak, of the crater is surrounded by a small sand-filled trough; this in turn is surrounded by a larger circular trough. Linear rock ridges alternating with light orange sand deposits cross the image from upper left to lower right; these are called yardangs by geomorphologists. Yardangs form by wind erosion of exposed rock layers in a unidirectional wind field. The wind blows from the northeast at Aorounga, and sand dunes formed between the yardangs are actively migrating to the southwest.

Astronaut photograph ISS020-E-26195 was acquired on July 25, 2009, with a Nikon D3 digital camera fitted with an 800 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 20 crew. The image in this article has been cropped and enhanced to improve contrast. Lens artifacts have been removed. The International Space Station Program supports the laboratory to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public, and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by William L. Stefanov, NASA-JSC.

Instrument:
ISS - Digital Camera
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