You find basic informations about the hot vents of the deep sea, the earth´s structure, the geology of the sea floor, the life and the exploration of the deep sea, the technology and the tools for deep sea research in the brochure “Expedition to the deep“ (Expedition in die Tiefen der Ozeane, only in German)

Here is a download for the pdf

Blue planet

Our Earth is a warm planet. On its orbit around the sun, it circles through the icy outer space. At the earth’s heart is the super hot, solid inner core (temperatures are ranging between 4000-5000° Celsius (7200-9000° Fahrenheit). The mantle encases the core. The mantle has the same temperature as the core, but it is viscous like thick honey. Only the outer mantle and the Earth crust are solid- they get cooled by the low temperatures of the outer space.

Looking at the Earth from outer space, you can see that the Earth is a blue planet. Water covers 71% of the surface, the remaining 29% are land. Have a look at a world map and you will see the 5 great continents Eurasia, America, Africa, Australia and Antarctica as well the 3 big oceans the Pacific, the Atlantic and the Indian Ocean.



Constantly moving

The viscous mantle moves in the inside of the Earth and drives the shifting of the tectonic plates at the Earth’s surface. There are thick continental plates, thin oceanic plates and continental-oceanic plates. The latter ones are partly thin and covered by the sea and partly thick and protruding from the sea.


some plates collide with each other. When this happens the heavier plate slides under and melts on in the mantle again. (convergent boundaries)


other plates move apart. The gaps in the crust are filled up with material of the mantle. This happens in form of volcanic eruptions. (divergent boundaries)

plates can also slide part each other. Jerky earthquakes happen there because there is a lot of friction at this boundaries. (transform boundaries)

You can easily recognize, that the tectonic plates are of complete different shape than the continents and the oceans.



The long list of various tectonic plates (large, small and "tiny“ plates)

Large plates:

Eurasian Plate

African Plate

North American Plate

South American Plate

Indo-Australian Plate

Pacific Plate

Antarctic Plate


Small plates:

Arabian Plate

Cocos Plate

Nazca Plate

Carribean Plate

Scotia Plate

Filipino Plate

3 things to keep in mind

1. Turn off the light

Most areas of the oceans are very deep. At depths where light can no longer reach, the deep sea begins. This is the largest habitat on earth. Depending on the quantity of small-suspended substances, light can maximally penetrate into a depth of 1000 meters. At greater depths it is pitch dark.

2. Dress warm

The predominant part of these water masses is very cold, just 2° Celsius (35,6 ° Fahrenheit). Only the Mediterranean Sea and the Red Sea stay warm up to depth of 2000 meters.

3. The pressure increases and increases

Because of the weight of the overlaying water, there is high pressure present in the depths of the oceans. At sea level we have a pressure of 1 bar. The pressure in the water increases for 1 bar per 10 meters depth. While gases get compressed, liquids and solids stay practically the same size. An example: A gas filled balloon shrinks to half of its size in 10 meters water depth. In 20 meters it has just a quarter of its surface volume. What do you think? How will it look in 1000 meters?

No light- no plants

Plants, algae and some bacteria can produce their own food. The process they are using is called photosynthesis. They just need water; the gas CO2 and they need light. They have green pigments called chlorophyll, which they need to catch the light (the photons). With the light as energy source they synthesize sugar and starch, which the organisms can turn into energy or into proteins and fat. This kind of metabolism is called autotrophic and this is the way these organisms can grow and proliferate.

Animals have to eat food produced by others, because they cannot make it themselves; they are heterotrophic. There are also some protozoa and bacteria, who are heterotrophic and therefore need aliment.

The food, which is available in the deep sea, is entirely made in the upper, shallow water column and on land. Only there is light and only there plants, algae and bacteria can run photosynthesis. The single big exceptions are the hot vents! At this sites food is produced abundantly. We will explain how this works 4 pages further.

The bulk of food for deep-sea organisms is floating slowly down in form of small particulate material. We call this process pelagic rain. Everybody down there is longingly awaiting it. But the pelagic rain does not only consist of food. There are also very tiny stones raining down and accumulate in the deep-sea silts since millions and millions of years. Wood and other parts of plant as well as big dead animals like corpses of fish and whales are also sinking down. Still, since just little food is reaching the deep sea, only few animals can live there. They can look very really creepy, though most of them are tiny little critters. Formerly it was thought, that there are just few different species living in the deep-sea environment. Today we know that it is completely different. There are many, many species of bacteria, protozoa and animals living there. The biodiversity (the species richness) is as high as in a tropical forest or a corral reef. Scientists are still puzzled why it is like this.

Our volcano

There are gigantic volcanic mountain ranges, pervading the oceans like veins. Did (do) you know, that this volcanic range is the earth’s longest one? It has a length of 56.000 km. The volcano we are going to visit is located at the East Pacific Rise at 9° 50´ N latitude and 104° 17´ longitude. Have a look at the world map to see where it is.

When plates move apart, the mantle and its magma chambers come close to the surface. During a volcanic eruption molten rock, or magma, gushes out through the crack from beneath the crust. These cracks are called dykes. The diameter of dykes can range from just a few inches to two meters.

As soon as magma bursts out onto the surface, it is called lava. Molten rock, once hardened at the surface is called volcanic rock. The most common type of volcanic rock is the firm, black basalt. Lava forming basalt is the most liquid rock. It has the highest temperature and therefore has the highest flow velocity during an eruption. The greatest part of the ocean floor consists out of basalt. Sands and silts cover it most of the time. Sometimes this layer is just a few millimeters thick; sometimes its size can be hundreds of meters. Bare basalts can be found only at active volcanic sites. Depending on the amount, the velocity and the type of the emerging lava, different types of formations, like lava columns or pillow lava, occur. Pillow lava often features a hyaline (glassy), smooth surface, the black volcanic glass called obsidian.


Attention: volcanic eruption!

A long expected volcanic eruption has finally taken place. For some years scientists predicted that the volcanoes in the source field of the pacific ridge at 9 ° N would become active. At sometime during the spring 2006 this prediction was dramatically proved correct. The lava buried important scientific instruments, which collected data for long-term observations. This loss was actually the reason that drew the scientist’s attention to the eruption. Supported by the US National Science Foundation, scientists got on their way in May 2006. They had just a few days to take pictures of the fresh lava in 2500 meters water depth and to conduct important measurements.

Volcanoes before the eruption

The collected information was passed on to the world public and led to an expedition in June 2006 with the submersible Alvin on board of the Atlantis. Though they had only few dives, scientists were able to observe the impacts of a massive volcanic eruption for the first time. The long known caldera (crater) has completely changed its appearance. Old, and familiar, hot and warm hydrothermal vents were gone and new had emerged from the earth’s crust at other sites. All of the former life was destroyed. Just a few vagile (free to move) organisms, like crabs, were to be found.



The 4 signs of a volcanic eruption in the sea

When magma (the molten rock) moves in the earth’s crust, liquids from there can be extruded into the sea bottom. This fluid consists of various chemicals, but also of microbes living in the crust. Because the fluid is so different to the seawater it can change the ambient water above the sea floor.

1. The seawater can be warmer than the usual 2° Celsius

2. The chemical composition of the seawater can change

3. The seawater can carry more particles than on average

4. Specific microbes know from the earth’s crust can be found in the seawater

In the future all this collected information will help us to learn and understand when and how volcanoes occur. We will have a better insight into the role they play in the genesis of the ocean floor as well as for the animal community of this unique habitat. Our expedition to this volcano in October 2006 will be the first longtime one. We plan to have 16 dives, which give us the opportunity to study in particular the settlement of animals after a volcanic eruption.



Hot and poisonous- deep - sea vents

Hot vents occur where there are volcanoes

Seawater (1) infiltrates deep down into the earth’s crust through cracks and fissures (2) and gets extremely heated (3). Metals and hydrogen sulfide get dissolved out of the rock. The thermal fluid rises and gushes out of the rock as hot vent (4). The thermal fluid with its temperature up to 350°Celsius (662° Fahrenheit) mixes with the cold seawater (5). Gypsum and metal sulfides, like iron sulfide (pyrite or fool’s gold) precipitate (forms into particles). Chimneys and „smoke“ (the gushing thermal fluid with black precipitations) are generated.

Hydrogen sulfide in vents

The gas hydrogen sulfide is poisonous for most creatures, including human beings. Our scent detects this poison even at very low concentrations and warns us. It smells like rotten eggs.











                               Hot vents Chimney with black "smoke“                                           A piece of a chimney


When the thermal fluid already mixes with seawater in the earth’s crust, warm thermal fluid pours out of the basalt. Most of the animals of hydrothermal vents live here.


                                         Giant tubeworms                                                                               Mussels

The invention of hot vents

There are a lot of different types of bacteria in hot and warm vents. Many of them can produce food by a process called chemosynthesis. They use, for example, the toxic hydrogen sulphide of the vent fluid and the oxygen of the ambient seawater to oxidize the sulphide. At the same time the oxygen gets reduced during this reaction. A lot of energy yields from this process. This energy is used to turn inorganic carbon dioxide into organic carbon, which is their food. The principle is the same one as with the plants’ photosynthesis, but bacteria utilize the energy of chemical compounds rather than the sun’s energy.

The animals of hydrothermal vents

There are not many animals which manage to live at the hydrothermal vents. Of those that do, most are very specialized. They do not only withstand the temperature fluctuations, but also dispose of the toxic hydrogen sulfide in various ways.



Up to date approximately 550 animal species living at hydrothermal vents have been discovered. We find much fewer species at our source field at 9 °N- or rather we found fewer until recently. At the moment it looks quite barren. Never fear, as we know, such hydrothermal vents are settled relative quickly. Soon, we will see which species are already there.



Here are some animals from 9 Degrees N:


Scientific name: Thalassomonhystera fisheri

Phylum: nematode

Class: marine nematodes

Size: 0,7mm (=700µm)

Characteristics: tiny oral cavity

Home: Pacific

Info: Nematodes belong to the so-called Meiofauna (animals which are smaller than 1 mm); feeds on bacteria; lives in tubeworm and mussel aggregations; between 10 and 100 individuals in 10 cm2


Pompeii worm

Scientific name: Alvinella pompejana

Phylum: annelid

Class: bristle worms

Size: 17 cm

Characteristics: lives in a tube

Home: Pacific

Info: lives in symbiosis with bacteria; lives in tubes and whirls cooler sea water to itself; still, this animals are the „hottest“ animals of the world; scientists measured temperatures up to 80° Celsius (176° Fahrenheit) near its gills


Hydrothermal vent octopus

Scientific name: Vulcanoctopus hydrothermalis

Phylum: mollusc

Class: cephalopod

Size: 23 cm

Characteristics: no ink sack

Home: Pacific

Info: predator


Hydrothermal vent eelpout

Scientific name: Thermarces cerebus

Phylum: vertebrate

Class: fish

Size: 37 cm

Characteristics: sluggish

Home: Pacific

Info: Predator, feeds on small invertebrates


Giant tubeworm

Scientific name: Riftia pachyptila

Phylum: annelid

Class: bristle worms

Size: 1,5 m

Characteristics: lives in a tube (which can be more than 2 m long)

Home: Pacific

Info: lives in symbiosis with bacteria, which live inside the worm; has no mouth and digestive tract


Vent mussel - the homeowner

Scientific name: Bathymodiolus thermophilus

Phylum: mollusc

Class: mussel

Size: 20 cm

Characteristics: lives in symbiosis with bacteria and a bristle worm

Home: Pacific

Info: Bacteria live in the gills; one to two bristle worms live as lodger within the mussel’s shell and its mantle cavity


Bristle worm - the lodger

Scientific name: Branchipolynoe symmytila

Phylum: annelid

Class: bristle worms

Size: 5 cm

Characteristics: lives in Bathymodiolus thermophylus

Home: Pacific

Info: Nibbles at the mussel’s gills and lives from litter in the mantle cavity



Scientific name: Neolepas zevinae

Phylum: arthropoda

Class: crustacea

Size: 6 cm

Characteristics: hermaphrodites (they are female and male at the same time)

Home: Pacific

Info: Filter feeder; the feet are reshaped to filter the food out of the water column


Vent crab

Scientific name: Bythograea thermydron

Phylum: arthropoda

Class: crustacea

Size: 6 cm

Characteristics: reduced eyes

Home: Pacific

Info: Predators and scavenger; nibbles sometimes at the tentacles of the giant tube worm; likes to climb the chimneys and walks through the hot, black fluid which blackens the white carapace

Transparent limpet

Scientific name: Eulepetopsis vitrea

Phylum: mollusc

Class: limpets

Size: 1.5 cm

Characteristics: transparent shell

Home: Pacific

Info: Grazers, scrapes biofilm from the basalt or tubes with its radula