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We are in Mrs. Hood’s kindergarten class studying the ocean. We just went on a pretend dive in Alvin with Sarah Little and we have some questions.

1. What kind of animals are down there?
2. Do you ever see active volcanoes?
3. Have you ever seen any big or interesting fish?

We will look forward to hearing from you.
From Kathleen

Hi Kathleen:
Thanks for your questions. Here are some answers.

1. We see different types of animals on the seafloor. When we are exploring areas away from the mid-ocean ridge we see brittle starfish, crinoids, sea urchins, rat tail fish, and sea cucumbers (holothurians). One of the students on board, Ben Wigham is a specialist in holothurians and I’ll append some information on these slimy creatures at the end of this message.
2. We don’t see “active” volcanoes on the seafloor, but we know they are there! Only a handful of submarine eruptions on the mid-ocean ridge have been documented and studied in detail. The first one was studied with Alvin in 1991 on the East Pacific Rise near 9° 50’N. The other ones have mostly been on the Juan de Fuca Ridge, part of the mid-ocean ridge system off Washington State. Those were detected with the US Navy SOSUS array (look in the “Hot Topics” section of the website for more information on underwater acoustics and detecting earthquakes and eruptions).
3. Once, when diving in a submersible off Hawaii I saw a 20 foot long shark at about 800 meters depth. It was VERY impressive. I think it was attracted by the sub’s lights, I’m glad it didn’t think we were lunch!

Thanks for your questions and keep Diving and Discovering with us.
Best Regards,
Dan Fornari

Holothurians - the “Sea-Cucumbers”
By Ben Wigham:

Holothurians are members of a group of invertebrate animals called the Echinoderms, which includes the starfish, sea urchins, and brittle stars. Unlike their close relatives, holothurians have no arms or spines, and their bodies are flattened. The animal is “stretched”, increasing the distance between its mouth, giving it its characteristic “cucumber-like” shape.

All holothurians have a circle of tentacles surrounding their mouth, which they can use to collect food. Shallow-water species often stretch out their tentacles to collect plankton or other food particles form the water column. Other holothurians, especially those found in the deep sea, use their tentacles to sweep-up the sediment or delicately pick at food particles on the seafloor.

Holothurians move about by using tube feet located on their underside. They have a specialized “plumbing” system which allows them to move water in and out of their tube feet to make them move. Their tube feet also have suckers on the end to help them grip.

Holothurians are very common animals in the deep sea. They are one of the few groups of animal which can be found in the deepest parts of the oceans where their soft bodies help them to cope with the increased water pressure. There are currently over 400 recorded species of deep-sea holothurian, which can be found in water deeper than 400m. Deep-sea species have many strange body forms that are well adapted to their way of life. Some of the animals collected in the North Atlantic Ocean have long tube feet, to help them move over the soft muddy sediments, and some hardly move at all, preferring to live in a burrow. Others don’t really look like cucumbers at all; they may have big buoyant tails or be flattened like a pancake. Some holothurians can even swim!

When we look at photographs and video of the deep-sea floor, such as those taken by Argo II, we don’t always see the holothurians, but we often see the tracks they leave behind. As the holothurian moves across the seafloor it leaves a trail in the sediment. These tracks show up clearly on the video because, when the holothurian moves, it disturbs the top-layer of the sediment, often changing its color.

hi there, dive and discover!

First of all, you have a great site. but anyway, i have a question: how do you carry enough oxygen? we are doing a project in school where our team builds an underwater ocean lab. we would be staying there for about a year. we are not allowed to go to the surface to get anything, so how do you get oxygen? this is for homework, so i would appreciate an answer ASAP!!!!!!

From Madeleine Webb, age 11, Atlanta GA

Hi Madeleine:
Thanks for your question. During expeditions 1 and 2 of Dive and Discover, we used Alvin for our research. On this expedition we don’t go, physically, to the bottom of the ocean; we use the DSL-120 sonar and Argo mapping systems to show us the seafloor.

When we dive in Alvin, it carries its own oxygen bottles and the oxygen is slowly metered out into the personnel sphere. There are also CO2 (carbon dioxide) scrubbers, which remove the CO2 that we breathe out by using different chemicals that bind up the CO2 and take it out of the air. So for a SeaLab, you will need both a supply of oxygen, either that is made using water (a molecule which has 1 oxygen atom for each 2 hydrogen atoms), or that is bottled. You'll also need some type of system that “scrubs” the CO2 out of the air so that it does not accumulate as that can give you headaches and hurt you if you breathe enough of it.
Hope this information helps you with your homework. Keep studying hard, and Diving and Discovering with us.

Best Regards,
Dan Fornari

Hi, are you running any longer summer expeditions lasting from July - September as one of us is an Ocean Science student in England.
From Nikki White

Hi Nikki:
Thanks for checking out the Dive and Discover website. After this current expedition we are planning another one early next year, in 2001, that will explore for hydrothermal vents in the Indian Ocean near 24deg South Latitude. We will keep the website up and running, and will be adding some additional information modules, in the coming months.

Keep checking back and Diving and Discovering with us.
Best Regards,
Dan Fornari

Good People:

When Mt. St. Helens exploded, it literally blew the top of the mountain many miles high and even more miles wide, turning former rock to dust in the process. Assuming such events also occur below the sea, do they ever explode with such force as to penetrate through the sea to the surface and up into the atmosphere? If so, it would be an awesome sight. On the other hand, given the enormous weight of seawater, are such exploding forces insufficient to penetrate through to the surface? What do you think?
Pete Minges, 4/10/00
Cincinnati, Ohio

Dear Peter:
Thanks for your question. You are correct that the pressure of the water above the mid-ocean ridge axis, and the submarine volcanoes there, keeps them from blowing their tops. Also, the type of lava that is erupted is pretty fluid, like what erupts in Hawaii- a basaltic lava, which usually does not erupt explosively, like Mt. St. Helens. One main reason why basaltic lavas erupt less explosively is that they have less silica (SiO2) in them, usually about 48-53 weight percent, compared to rocks (called dacites and rhyolites) from volcanoes that explode which have more silica in them- often greater than 60 weight percent. The less silica in the magma cause it to be more fluid because there are fewer silicon dioxide molecules to make strong bonds with other atoms in the magma.

One other factor is that basalts don’t have much gas in them, while rocks that erupt in explosive volcanoes have more gas.

Hope this answers your question. Thanks for Diving and Discovering with us.
Best Regards,
Dan Fornari