by Suvojit Bagchi
BBC News, Delhi
Last December's tsunami altered the landscape in India's Andaman and Nicobar archipelago, scientists say.
Chunks of coral reefs and mangroves have disappeared
A survey of satellite photographs by India's National Institute of Ocean Technology (NIOT) shows new land masses in the north-west of the islands.
Meanwhile, land has caved-in and chunks of coral reefs and mangroves have almost completely vanished in south-eastern part of Nicobar islands.
At least 200,000 people died in the 26 December Indian Ocean tsunami.
Several thousand of those were in India's Andaman and Nicobar Islands and in Tamil Nadu on the Indian mainland.
Anup Kumar Dhar, a scientist involved in the survey, gave details of the new land masses to the BBC.
"Between landfall and north Andaman island, one can see new land masses about 100 sq metres in size," he said.
But in the south-eastern Nicobar and Nancowry group of islands, land had sunk by 90cm to 1.5m resulting in the coral reefs and mangroves almost completely disappearing, Mr Dhar said.
Samir Acharya, the founder of Port Blair based Society for Andaman and Nicobar Ecology (SANE) told the BBC, they had also recorded some land movements in the archipelago's capital, Port Blair.
"In some areas of Port Blair land mass had caved in after the tsunami by about 90cm and now it has reversed back by another 10cm," he said.
In order to monitor both big and small land movements, SANE has recently installed a tiltmeter in Coriaghat region of Port Blair.
The tiltmeter is a 300m long pipe filled with water - buried in about one metre of water with sensors attached to holes on the pipe - to record land movement.
The data is then digitised and fed into a computer.
Monitoring land movements is important to see whether the collapsed land masses will reverse or continue to sink further which would alter the area's landscape, scientists say.
The National Science Foundation (NSF) in the United States and the Indian Institute of Astrophysics (IIA) have collaborated with SANE for this project.
The project aims to install another six tiltmeters in the region over the next few years.