Hawaii Teacher on Board
Dredging

By Naidah Gamurot

Oct. 24, 1998. When I awoke this morning, I found out we were about 36 km (~20 miles) off shore. The swells are higher out here and the boat's swaying more than it has in several days. The sun is out and the skies are clear.

Today we were dredging at the northeasternmost tip of the Puna Ridge. The water here is over 5,000 km (about 3 miles) deep. The dredges haven't been bringing up a lot of rocks, but the ones that come up are good samples.

Many of the samples were picritic, these particular samples having about 30% olivine crystals in the basalt. Olivine is a (usually) green glassy-looking mineral common to Hawaiian basalts (black lava rock).

Our watch was also involved in a deep water dredge. We went down to around 4700 meters (about2.5 miles down). At 55 m/minute (and a few occasional stops) it took the metal net about 1 hour and 45 to reach the bottom. We spent 43 minutes dredging the bottom, and another hour and a half to retrieve the net.

The dredge set up is very heavy. It takes several people to secure it safely to the deck.

After the net is back onboard, we retrieved the samples, rinsed, dried, and labeled them.

And the dredging continues…