Earthquake Journal Entry
Quakes Changed Island Coastline (May 5, 2005)
False-color infrared satellite picture of coastline of the island of Nias near Suamtra shows line of coral that is now exposed. NASA GSFC.
New satellite pictures show Indonesia's violent earthquakes of December 26th and March 28th changed the coastline of the island of Nias, found 80 miles (125 kilometers) west of Sumatra.
The island's southern coast was uplifted by the quakes, exposing coral reefs that were under water before. In the infrared satellite picture to the right, sea grasses covering the coral reef are red and bare ground is blue-gray.
A United States Geological Survey (USGS) study of the effects of the quakes showed that the crust around Nias was uplifted up to 8 feet (2.5 meters). The uplift happened as the Australian plate subducted or dove under the Sunda plate along the Sunda Trench.
Over hundreds of years, stress builds up along the rock layers at the boundary between the two plates. The recent quakes released much of the stress and sent powerful waves pulsing through the ground. Around the island of Nias, the energy release thrust the Sunda plate upwards and raised the landscape. Along other sections of coastlines around Sumatra, the plate sank and the sea moved inland.
