Oceanus Magazine
Back to Woods Hole Oceanographic Institution's Homepage

Images: Indian Ocean's Atlantis Bank Yields Deep-Earth Insight

Five-meter bathymetric map of Atlantis Bank created by WHOI scientist Maurice Tivey from the James Clark Ross echo sounding tracks in collaboration with the other scientists on the cruise. The extraordinary high-resolution map shows the very top of Atlantis Bank with the wave cut platform and the precipitous sea cliffs to either side. One can see old headlands and seastacks in the image, as well as the great arcuate fossil lagoon on the west side where oolitic limestones were dredged.

Lithologic column compiled by JOIDES Resolution scientists showing the varia-bility of lithologies downhole and the gradation from predominantly oxide-rich gabbros at the top to olivine-rich gabbros at the bottom. The figure was constructed by using a running average of the different lithologic units drilled (almost 1,000 in all).

Author Henry Dick standing next to the Canadian ROV ROPOS on site in the Indian Ocean.

Drilling results for the two most successful hard-rock holes in the ocean crust: Hole 735B penetrated the lower ocean crust formed beneath the Southwest Indian Ridge and Hole 504B the upper ocean crust formed at the Costa Rica Rift in the eastern Pacific. Note that while Hole 504B is deeper, it took nearly four times as long to drill, and only 18 percent of the rock drilled was recovered while some 87 percent of the rock drilled was recovered from Hole 735B.

Highly productive drilling on Atlantis Bank in the Indian Ocean gave scientists a surprising new look at the lower ocean crust.

Hypothetical model for the unroofing and uplift of Atlantis Bank to sea level from beneath the Southwest Indian Ridge from the Scientific Results Volume of the Ocean Drilling Program (Leg 118). Once uplifted, the island then submerged as the ocean crust on which it sat cooled and sank over the last 10 million years.