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Drilling the Mid-Atlantic Ridge

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Artemis
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« on: April 15, 2007, 01:36:10 am »

Cruise diary


Day 18: Thursday 22 March
Sampling area: TOBI survey
Position at midnight: 13o38N, 44 o 57W

 

Michelle writes:

Since the re-deployment of TOBI operations have been running smoothly.  We have now had the opportunity to look through the first half of our survey and have produced some useful images.  Below is a bathymetric (depth) map of our study area, made by combining the results from several previous surveys conducted by other groups, together with some views of the seafloor derived from our TOBI sidescan data which we have “draped” over the 3-D topography using a specialised software  package called “Fledermaus®”.  See the captions beneath each image for more information about what they are each showing.

Don’t forget our crew profiles at the bottom of the page - today meet Mick our Scientific Systems Manager and Kev our mechnical technician...

 


An “aerial” view of part of our study area.  This is on the Mid-Atlantic Ridge at 14ºSA, looking south.  Warm colours are shallow, cool colours deep. The Mid-Atlantic Ridge’s “median valley” winds through the image from north to south, and marks the boundary between the separating African (left) and (North American (right) tectonic plates.  The “Marathon” transform fault lies in the E-W valley seen in the far distance, about 100 km away.  Images like this are built up from a number of surveys using multi-beam echo-sounders and displayed using special computer software called “Fledermaus®”.




A 3-D view of a large lava flow (centre), about 2 km wide and 5 km long, near the axis of the Mid-Atlantic Ridge.  A gullied, partly eroded fault scarp can be seen on the right.  The light- to mid-grey zone in the centre of the image is the lava flow, filling the floor of the basin below the fault scarp.  The far side of the basin is marked by another fault scarp seen in the distance at top left.  The eruption vent for the flow may be at the small volcano marked by the bright patch, with dark crater in centre, at left of centre foreground.
 


A 3-D view of a fault scarp on seafloor about 1 million years old.  The top of the scarp is probably made of volcanic rocks.  These have been eroded leaving a series of narrow ridges and gullies runn ing down the face of the scarp.  The dark grey area in the right foreground is sediment which has covered the original volcanic seafloor.  Lighter grey at the foot of the scarp represents a fan of material eroded from the scarp. This is very similar to the  erosional topography seen at large escarpments on land.   Scarps such as these represent the pervasive faulting that breaks up newly formed ocean crust.  The scarp is aboput 200 m high and foreground view is about 500 m wide.



A 3-D view of a fault scarp on seafloor about 1 million years old.  The top of the scarp is probably made of volcanic rocks.  These have been eroded leaving a series of narrow ridges and gullies runn ing down the face of the scarp.  The dark grey area in the centre foreground is sediment which has covered the original volcanic seafloor. Scarps such as these represent the pervasive faulting that breaks up newly formed ocean crust.  Scarp is aboput 200 m high and foreground view is about 800 m wide.



A 3-D view of a fault scarp on seafloor about 1 million years old.  The top of the scarp is probably made of volcanic rocks.  These have been eroded leaving a series of narrow ridges and gullies runn ing down the face of the scarp.  The dark grey area to the left is sediment which has covered the original volcanic seafloor. Bright material at the foot of the upper scarp material eroded from the scarp. This is very similar to the  erosional topography seen at large escarpments on land.   Scarps such as these represent the pervasive faulting that breaks up newly formed ocean crust.  The scarp is aboput 200 m high and foreground view is about 500 m wide. 



A 3-D view of hundreds of small volcanoes building up an “axial volcanic riudge” in the centre of the Mid-Atlantic Ridge’s median valley.  These volcanoes are formed from pillow lavas erupted up fissures that mark the precise boundary between the separating tectonic plates.  Most of the volcanoes in this view are 200 m to 500 m in diameter and about 20 m to 50 m high.


http://www.noc.soton.ac.uk/gg/classroom@sea/JC007/diary/diary_22-03.html
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