Research Cruise

Breakfast

• Sausage and egg sandwiches
• Oatmeal

Lunch

• Hamburgers
• Veggie burgers
• Chunky tomato soup
• French fries
• Salad bar

Dinner

• Flank steak
• Rice pilaf
• Pita and hummus
• String beans
• Penne pasta
• Salad bar
• Ice cream

Weather

Winds NW at 22 knots, swell 10-16 feet

Position

S 41° 31.64′  E 152° 50.76′

We finished up our dive at Cascade yesterday, and are now heading Northeast for fairer weather and some deeper waters!  Cascade is a fascinating feature.  It is incredibly large,  ~10 km wide by ~22 km long, and the top is almost completely flat.  It is then completely different from any other seamount we’ve visited so far  – all others have been relatively small and with a very distinct summit.  There is only one way a seamount like Cascade could have been formed, and that’s if it was once exposed above sea level.  This process is commonplace in the South Pacific – in fact, it is the same process that allows atolls and barrier reefs to form.  Darwin was the first to put these seemingly disparate land formations together in The Voyage of the Beagle: 

“As the barrier-reef slowly sinks down, the corals will go on vigorously growing upwards; but as the island sinks, the water will gain inch by in on the shore – the separate mountains first forming separate islands within one great reef – and finally, the last and highest pinnacle disappearing.  The instant this takes place, a perfect atoll is formed…If , instead or and island, we had taken the shore of a continent fringed with reefs, and had imagined it to have subsided, a great straight barrier, like that of Australia or New Caledonia…would evidently have been the result.” 

In Cascade’s case, the surrounding barrier reef continued to grow on top of the shrinking island.  The reef, of course, grows flat near the surface of the water, so as the island subsided, a flat rock layer slowly built around the subsiding peak until it was completely submerged, and completely flat.  Consider an atoll that continues to submerge until even the surrounding islets are underwater.  Thus, Cascade was once a formidable island, that, as it subsided, was overgown by a coral mass.  Now, its wide, flat summit lies submerged 500 meters under the sea surface – Pretty incredible!  This type of feature is known as a “guyot”.  Compared to the other features in the area, such as the Southern Hills or the other smaller seamounts we’ve visited, Cascade is absolutely huge – there is no way the smaller features would have been exposed so much to the atmosphere.  Instead, they are pockmarks similar to those seen around Cascade’s perimeter – “acne,” as Jess calls them.  Most seamounts are formed when the crust passes over hot spots in the magma, causing uprising in some cases above sealevel, like many islands that dot the South Pacific. 

Unfortunately, the HD camera feed cut out fairly early on in our dive on Cascade, so we had to rely on the digital camera to look around – it made us realize how spoiled we were with the crystal-clear quality of HD!  It seems that the fiber optic cable that transmits the HD camera feed to the ship was severed; fortunately it wasn’t the cable that transmits Jason’s controls!  We were able to replace the cable once Jason was recovered, and we should have the video feed back for our next dive. 

Speaking of which, we’re now about a day and a half’s steam Northeast of Cascade, in an attempt to escape a particularly nasty low-pressure system descending on the area.  We’re going to try to get some deeper dives in up here, maybe down to 3,500 meters, to extend our fossil coral depth histogram.  Unfortunately, the weather is not particularly Jason-friendly up here either – although the chop and winds are down, the swell is too big for a launch, and doesn’t really seem to be decreasing any time soon.  In the meantime, we’re doing some CTD casts and catching up on coral-cleaning and other activities…I’m looking to post more HD photos shortly from other dives, so check back soon for those!

This entry was posted on Tuesday, January 6th, 2009 at 9:08 pm by Adam Subhas and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.