card
183

seafloor

OLogy Series
place
card
183

seafloor

OLogy Series
place

The seafloor covers more than half of the Earth's surface. Most of the seafloor consists of the flat, expansive abyssal plain. But the landscape is very different where cracks in the seafloor allow molten rock to well up from below. In these volcanic areas, there are hot-water vents, giant mountain ranges, and deep trenches. Communities of bizarre organisms feast on dead animals that fall from above.

Creatures of the Deep
Deep under the ocean's surface, jets of hot water gush from rifts in the seafloor. These deep sea vents, called hydrothermal vents, spring up on the ocean floor almost every day. Some shoot out hot clear fluid. Others spout water that is black with minerals. The water in some hydrothermal vents is hotter than 370 degrees Centigrade -- hotter than molten lead. Yet a number of bizarre animals thrive on the heat and minerals at these vents. Unlike most life on Earth, which depends on energy from the Sun, this food chain depends on the energy from chemicals. Specially adapted bacteria thrive on chemicals that would be toxic to most other animals on Earth. In turn, these bacteria provide energy for the entire community of vent animals. Some animals, like the giant tubeworms and giant white clams, get their nutrition from the bacteria living inside their bodies.

With the discovery that deep sea animals live without sunlight, scientists believe it is possible that:

the first life on Earth may have originated at the deep seafloor

there could be life elsewhere in the Universe

both A and B

Are you right?

Correct!

The first life on Earth may have originated on the deep seafloor, protected from the cosmic rays that bombarded Earth billions of years ago. It is also possible that life is found elsewhere in the Universe, such as in the warm, wet places beneath the surface of Mars.

Most seafloor dwellers survive on "sea snow." Sea snow refers to falling particles of:

food dropped by humans on the ocean's surface

dead plants and animals, and animal waste

the ice that forms in cold waters

Are you right?

Correct!

Sea snow consists of particles of dead plants, animals, and animal waste that fall from above. Crabs, snails, and sea stars (starfish) scavenge sea snow off the surface of the seafloor.

The deepest trenches of the ocean floor are about as deep as the Grand Canyon.

Fact
or
Fiction
?

Fiction

The deepest trenches of the ocean floor are more than six times as deep as the Grand Canyon. Some drop as much as 11 kilometers (7 miles) below sea level.

The sparse ecosystem of the deep seafloor has little diversity compared to a tropical rain forest.

Fact
or
Fiction
?

Fiction

With more than 200,000 species living in its distinct habitats, the seafloor is now compared to such diverse ecosystems as the rain forest.

Definition: the vast landscape of the ocean bottom
Characteristics: expansive plains, mountains, trenches, ridges, and hydrothermal vents
Where: in all the oceans of the Earth
Inhabitants: over 200,000 mud-dwelling animals, most of which are tiny one-celled organisms
Significance: one of the most diverse ecosystems on Earth

Image credits: courtesy of NOAA, Ocean Explorer, Alvin.