DIASTROPHISM

Reporter:Janelyn P. AlejandroMariemhel Alforte

DIASTROPHISM

• a general term that refers to deformation of the Earth's crust, and more specifically to folding and faulting.

• Diastrophism can be considered part of geotectonics.

• Diastrophism comes from the Greek word meaning a twisting.

• It is also associated with volcanic features.

The evidence of earth movements

• Mount Robson, in the Canadian Rockies towers more than 13000 feet above the present sea level. Yet fossils of marine animals, such as shark’s teeth, are found in the topmost rock layers. Such fossils indicate that these layers were pushed up from under the waters of the ocean.

World's Wickedest City, Port Royal (Jamaica)

One of the advantages of marine or nautical archeology is that, in many instances, catastrophic events send a ship or its cargo to the bottom, freezing a moment in time. A catastrophe that has helped nautical archeologists was the earthquake that destroyed part of thecity of Port Royal, Jamaica. Once known as the "Wickedest City on Earth" for its sheer concentration of pirates, prostitutes and rum, Port Royal is now famous for another reason: "It is the only sunk city in the New World," according to Donny L. Hamilton.

Port Royal began its watery journey to the Academy Awards of nautical archeology on the morning of June 7, 1692, when, in a matter of minutes, a massive earthquake sent nearly 33 acres of the city -- buildings, streets, houses, and their contents and occupants -- careening into Kingston Harbor. Today, that underwater metropolis encompasses roughly 13 acres, at depths ranging from a few inches to 40 feet.

In 1981, the Nautical Archaeology Program of Texas A&M University, in cooperation with the Institute of Nautical Archaeology (INA) and the Jamaica National Heritage Trust (JNHT), began underwater archaeological investigations of the submerged portion of the 17th-century town ofPort Royal, Jamaica. Present evidence indicates that while the areas of Port Royal that lay along the edge of the harbor slid and jumbled as they sank, destroying most of the archaeological context, the area investigated by TAMU / INA, located some distance from the harbor, sank vertically, with minimal horizontal disturbance.

In contrast to many archaeological sites, the investigation of Port Royal yielded much more than simply trash and discarded items. An unusually large amount of perishable, organic artifacts were recovered, preserved in the oxygen-depleted underwater environment. Together with the vast treasury of complimentary historical documents, the underwater excavations ofPort Royal have allowed for a detailed reconstruction of everyday life in an English colonial port city of the late 17th century.

Cleopatra's Palace in Alexandria (Egypt)

Off the shores of Alexandria, the city of Alexander the Great, lies what is believed to be the ruins of the royal quarters of Cleopatra. A team of marine archaeologists led by Frenchman Franck Goddio made excavations on this ancient city from where Cleopatra, the last queen of the Ptolemies, ruled Egypt. Historians believe this site was submerged by earthquakes and tidal waves more than 1,600 years ago.

The excavations concentrated on the submerged island of Antirhodus. Cleopatra is said to have had a palace there. Other discoveries include a well-preserved shipwreck and red granite columns with Greek inscriptions. Two statues were also found and were lifted out of the harbour. One was a priest of the goddess Isis; the other a sphinx whose face is said to represent Cleopatra's father, King Ptolemy XII. The artifacts were returned to their silent, because the Egyptian Government says it wants to leave most of them in place to create an underwater museum.

The submerged temples of Mahabalipuram (India)

According to popular belief, the famous Shore Temple at Mahabalipuram wasn't a single temple, but the last of a series of seven temples, six of which had submerged. New finds suggest that there may be some truth to the story. A major discovery of submerged ruins was made in April of 2002 offshore of Mahabalipuram in Tamil Nadu, South India. The discovery, at depths of 5 to 7 meters (15 to 21 feet) was made by a joint team from the Dorset based Scientific Exploration Society (SES) and marine archaeologists from India's National Institute of Oceanography (NIO). Investigations at each of the locations revealed stone masonry, remains of walls, square rock cut remains, scattered square and rectangular stone blocks and a big platform with steps leading to it. All these lay amidst the locally occurring geological formations of rocks.

Based on what at first sight appears to be a lion figure at location four, the ruins were inferred to be part of a temple complex. The Pallava dynasty, which ruled the region during the 7th century AD, was known to have constructed many such rock-cut, structural temples in Mahabalipuram and Kanchipuram.

The reasons for the submergence of the ruins are remain unclear.

Jima (Japonia)

Situated 68 miles beyond the east coast of Taiwan, Yonaguni Islands are a remarkable place for its rugged and mountainous coastlines. The special attraction is the submerged ruins located in the southern coast of Yonaguni: a superb 100×50x25 meters man-made artifact out of solid rock slabs stands erect at right angles. Its is estimated to be around 8000 years old, which is remarkably early for the kind of technology that has been used for carving it. Different theories exist about the possible identities of this structure.

While some say these ruins are the remnants of the missing Continent of Mu, other archeologists attribute them to be the outcome of unexplained geological processes, although, when you see the finely designed hallways and staircases, this ‘natural phenomenon' idea will appear sheer out of place.

The megalith was discovered quite accidentally by a sport diver in 1995 when he had strayed beyond the permissible limit off the Okinawa shore. The interesting thing about this massive stone building is that it had arches made of beautifully fitted stone blocks bearing resemblance with the building architectural style of the Inca civilization. Debates were rife aboutthe ruins being associated with the prehistoric Motherland of Civilization. Surveying the ruins minutely takes time and skill because of the rough oceanic

Earth movements may described according to the direction of motion:

• Uplift -either a local or a widespread rising of the crust.

• Subsidence-occurs when the earth’s crust sinks.

• Thrust -is a horizontal motion of the crust, by which large masses

of rock slide against one another into new positions.

CAUSES OF DIASTROPHISM

Theory of IsostasyThe mechanism

whereby areas of the crust rise or subside until the mass of their topography is buoyantly supported or compensated by the thickness of crust below, which "floats" on the denser mantle. The theory that continents and mountains are supported by low-density crustal "roots."

The Contraction Theoryaccording to the

contraction theory the earth is gradually shrinking. This may be true either because it is cooling, or because great pressures squeeze parts of it into a smaller volume, causing an increase in density. Because of this shrinking, the interior is always becoming a little too small for the exterior. This “misfit” would bring about a continual tendency toward readjustment. Gravity draws the crust, being rigid, cannot just settle down upon the smaller interior as an unruffled layer. Thus it undergoes thrusting and buckling. The stronger and heavier blocks of the crust sink. At the same time, the weaker strata to form the great mountain ranges.