Daily Update: Knorr Seamount
23 deg 52.6S
Longitude: 69 deg 35.8E
Wind Direction: S
Wind Speed: 12 Knots
Sea State 3
Swell(s) Height: 6 Foot
Sea Temperature: 78°F (25.9°C)
Barometric Pressure: 1016.0 MB
Visibility: 16+ Nautical Miles
By Amy Nevala
Just after midnight yesterday, Geologists Susan Humphris and Dan
Fornari lowered the sixth dredge of this expedition over Knorrs side
near 24° 30S latitude. From a map they made of
the Central Indian Ridge rift valley (click
here for a map of the ridge axis), they saw hints of
a giant underwater mountain called a seamount. They concluded
it was likely a volcano. (Click
here to see the 3-D image of Knorr Seamount).
their dredge descended through the blue-black of the Indian Ocean,
they were eager to see what rocks they would collect from the
seamount. Seamounts are not always volcanoes, but in this case,
Susan and Dans volcanic suspicions were correct.
This is super-fresh glass, said Dan as he pulled shiny black basalt
rocks from the dredge. The glass forms on the seafloor when hot lava spurting
from deep with the Earth meets the icy ocean water. It was the proof that Susan
and Dan needed that this large seamount was indeed an active volcano.
The Central Indian Ridge is part of the global mid-ocean
ridge system, a nearly continuous 46,000 mile-long chain of mountains,
mostly located on the seafloor. While it is not unusual to find
a volcano on the mid-ocean ridge, they are generally not as big.
The seamount has a long triangular shape, with a 24-mile length
(40 km), an 11-mile width (18 km) and a height of 4,264 feet (1300
For an hour, Dan and Susan dragged the dredge, connected
by a steel wire to a winch on the ship, across the seamounts summit. At one point, the dredge bit or
snagged on rock outcrops, causing violent tugs on the winch and tension up to
nearly 10,000 pounds.
Oops, theres a good bite. Theres another bite, uh-oh· I
think youre hung up, said Susan to Dan, who was controlling the winch.
Eventually he cleared the snags and after an hour-long return transit, the shiny
glass rocks landed on the deck with a thump.
Weve got some great preliminary data and have an excellent bathymetric
base map to start making a story of how this feature was created, said
Dan. Weve decided to name it Knorr Seamount in honor
of this great ship and its crew.
Scientists on board are excited by evidence of young
volcanism on the seamounts
summit. Plume Team members Bob Collier, Marv Lilley, and Darryl Green all have
a sparkle in their eyes knowing that they will do a CTD cast on the seamounts
summit later tonight to see if there are any indications of hydrothermal activity.
Where theres fire theres smoke, said Dan. Fresh
lava usually means you have a good heat source that can drive hydrothermal systems.
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