Discoveries on the 90 East Ridge
Posted by: Dr. Will Sager
Monday, July 9, 2007
4:00 PM Indian Ocean
Cool discoveries
The seamount at site NER2 gave us some surprises. We expected this seamount to be much like the others to the north in Ninetyeast Ridge or elsewhere around the oceans and have a dome-like shape.
As our multibeam bathymetry map below shows, that is not the case.
This seamount is highly irregular and has several peaks and troughs on its summit.
Moreover, many of the troughs, and many high and low points and escarpments all have trends that are nearly west-east or slightly a bit north of west-east. What’s that about? The seismic data show that the volcanic basement beneath the sediment is broken and faulted. The faults show up most on north-south lines, meaning they are oriented more-or-less east west.
It looks like the NER2 seamount has been chopped up by faulting. The fact that the faults are not all exactly parallel suggests that maybe there was more than one episode. We think that some of the faulting may have been original, i.e., the faults were formed at the time the seamount formed. This bit of the Ninetyeast Ridge may have been very close to the west-east spreading ridge that was creating the Indian and Antarctic plates about 50 or 60 million years ago.
But some of the faults may be more recent. Several scientists (including S. Krishna and D. Gopala Rao, who are on board with us) have noticed that the Indian plate has been breaking up for the past 7 million years or so in the Central Indian Basin to the west and that the faults extend right up to Ninetyeast Ridge. It looks like these faults may cut into and through the ridge here. The trend that is slightly north of east is the trend of those faults to the west.
To get the story straight, we will have to process and interpret the seismic profiles to go with the bathymetry, but it looks like we have some good evidence here.
JULY
7/30 - Final day at sea: on the way into Singapore
7/26 - A Day in the Life of a Teacher at Sea
7/18 - Checking our Position (Latitude) with a Sextant
7/16 - Monsoon Blues in the Indian Ocean
7/15 - WAVES, Rough Weather, but an exciting day... WHALES
7/11 - Not the Best Day for Science at Sea
7/9 - Discoveries on the 90 East Ridge
7/5 - Closer to Home, Life Here Onboard
7/2 - Ocean Careers: Texas to Russia
JUNE
6/30 - Easy Cruising Day: Now in the Southeast Trade Winds
6/27 - We Crossed the Equator Today, Heading South.
6/21 - Night Time Fun in the Indian Ocean
6/20 - Transit Gale in the Indian Ocean
6/17 - Arrived in Phuket, Thailand (finally)
