The Deep Ocean: Creatures, Trenches & Unexplored Mysteries

Question 1

What is the name of the deepest known point in Earth's oceans, located in the Mariana Trench?

Accepted Answer

Challenger Deep

Answer

Hadal Abyss

Answer

Mariana Pit

Answer

Vityaz Depth

Question 2

Approximately what percentage of the Earth's ocean floor has been mapped in high resolution — comparable to how we've mapped the Moon and Mars?

Accepted Answer

About 20–25%

Answer

About 50%

Answer

About 80%

Answer

About 5%

Question 3

Which deep-sea creature was identified in research by 2016 as having the largest eyes of any animal on Earth?

Accepted Answer

The colossal squid (Mesonychoteuthis hamiltoni), with eyes up to 27 cm in diameter

Answer

The giant squid (Architeuthis dux)

Answer

The oarfish (Regalecus glesne)

Answer

The giant isopod (Bathynomus giganteus)

Question 4

Approximately what percentage of deep-sea creatures can produce their own light through bioluminescence?

Accepted Answer

About 76%

Answer

About 10%

Answer

About 30%

Answer

About 99%

Question 5

Which jellyfish species, found in the deep ocean, has been called the 'immortal jellyfish' because it can revert to its juvenile state when stressed or old?

Accepted Answer

Turritopsis dohrnii

Answer

Aurelia aurita

Answer

Physalia physalis

Answer

Pelagia noctiluca

Question 6

In 1977, scientists made a landmark discovery at underwater hydrothermal vents on the ocean floor. What was so extraordinary about this ecosystem?

Accepted Answer

Life thrived there without sunlight, using chemosynthesis instead of photosynthesis

Answer

Life was found surviving at 200°C under extraordinary pressure

Answer

Organisms appeared to be hundreds of millions of years old, preserved by cold water

Answer

The vents produced oxygen from seawater, suggesting early Earth had subsurface oxygen

Question 7

The water pressure at the bottom of Challenger Deep (the deepest point of the ocean) is approximately how many times greater than atmospheric pressure at sea level?

Accepted Answer

About 1,100 times — roughly 1,100 bar or 16,000 psi

Answer

About 100 times

Answer

About 5,000 times

Answer

About 50 times

Question 8

In 1960, who became the first humans to reach the bottom of Challenger Deep in the submersible Trieste?

Accepted Answer

Don Walsh (US Navy) and Jacques Piccard (Swiss oceanographer)

Answer

Jacques Cousteau and Frédéric Dumas

Answer

Robert Ballard and Jean-Louis Michel

Answer

Sylvia Earle and Graham Hawkes

Question 9

The barreleye fish (Macropinna microstoma) has remarkable transparent barrel-shaped eyes that it can rotate to point straight upward. What can it see when its eyes face upward?

Accepted Answer

The silhouettes of prey (fish and crustaceans) swimming above it against the faint light from the ocean surface

Answer

Bioluminescent signals from potential mates hovering directly above

Answer

Predators approaching from the direction of the ocean surface before they can dive

Answer

Stars and the Moon through the water column, used for navigation

Question 10

The Greenland shark (Somniosus microcephalus), found in the deep, cold waters of the North Atlantic, has been dated to be how old?

Accepted Answer

Over 400 years old — making it the longest-lived vertebrate on Earth

Answer

Over 100 years old

Answer

Over 200 years old

Answer

Over 50 years old

Question 11

The blobfish (Psychrolutes marcidus) looks dramatically different when brought to the surface than it does in its natural deep-sea habitat. Why?

Accepted Answer

At depth it looks like a normal fish — at the surface, pressure loss makes its body decompress into a blob

Answer

Blobfish develop their jelly-like texture only in the weeks before death

Answer

Bright camera lights cause their skin to swell and distort

Answer

Blobfish are blob-shaped naturally, but the effect was exaggerated by the camera lens

Question 12

Osedax, the 'zombie worm,' was discovered on whale-fall ecosystems (carcasses that sink to the ocean floor). What do these worms eat?

Accepted Answer

Whale bones — they dissolve the bone with acid-secreting tissue and feed on the lipids inside

Answer

They feed on the soft whale tissue that other scavengers have left behind on the bones

Answer

They eat the bacteria that colonise whale carcasses on the ocean floor

Answer

They consume the mineral-rich sediment that whale carcasses stir up when they land on the ocean floor

Question 13

The anglerfish is famous for its bioluminescent lure. Based on all species studied so far, which anglerfish carry it?

Accepted Answer

Only the females — males are tiny parasites that permanently fuse to the female's body

Answer

Both males and females, though females have a larger lure

Answer

Only juvenile anglerfish — adults lose the lure once they reach maturity

Answer

Only males — they use the lure to attract females, not prey

Question 14

The Dumbo octopus (Grimpoteuthis) gets its nickname from which distinctive feature?

Accepted Answer

Ear-like fins on either side of its head that it flaps to swim — resembling Dumbo the elephant's ears

Answer

Its unusually large eyes that are disproportionate to its body size, like cartoon eyes

Answer

Its pink colouration and round body shape that resembles the cartoon elephant

Answer

Its ability to inflate itself, giving it a round shape similar to a cartoon character

Question 15

What is the 'hadal zone' — the deepest layer of the ocean?

Accepted Answer

Ocean depths below 6,000 metres — primarily found in ocean trenches like the Mariana Trench

Answer

The zone below 1,000 metres where sunlight cannot penetrate at all

Answer

The area of the ocean floor that is completely unmapped and unexplored

Answer

The layer of water between 200 and 1,000 metres known as the twilight zone

Question 16

In a 2023 scientific expedition to seamount ridges off Chile's coast, researchers made what remarkable discovery?

Accepted Answer

More than 100 previously unknown species in a single expedition, including corals, sea urchins, and glass sponges

Answer

A complete new hydrothermal vent field producing previously unknown mineral compounds

Answer

A deep-sea ecosystem containing bacteria over 1 million years old

Answer

Evidence of a submerged prehistoric human settlement dating to 12,000 years ago

Question 17

The dragonfish (Malacosteus niger) produces far-red light invisible to nearly all other deep-sea animals. How does this help it hunt?

Accepted Answer

It illuminates prey with light they cannot see — a private spotlight invisible to its victims

Answer

It signals other dragonfish at close range without attracting predators

Answer

Far-red light penetrates deep-water sediment better than visible light

Answer

It detects body heat from nearby fish to navigate in total darkness

Question 18

Hydrothermal vents on the ocean floor can expel superheated water reaching temperatures above 400°C (750°F). Why doesn't this water boil?

Accepted Answer

Extreme ocean-floor pressure raises water's boiling point far above 400°C

Answer

Dissolved minerals raise the boiling point beyond what fresh water can reach

Answer

The water reaches 400°C only briefly before being cooled by the surrounding ocean

Answer

Vent water enters a supercritical state that cannot undergo normal phase changes

Question 19

The Mariana Trench's Challenger Deep is approximately 11 km deep. How does this compare to the height of Mount Everest?

Accepted Answer

Challenger Deep (about 11 km) is roughly 2 km deeper than Mount Everest is tall (8.8 km)

Answer

They are approximately equal — both measure about 8–9 km

Answer

Mount Everest is taller than Challenger Deep is deep

Answer

Challenger Deep is more than twice the height of Mount Everest

Question 20

What percentage of the ocean remains unexplored, according to NOAA (National Oceanic and Atmospheric Administration)?

Accepted Answer

More than 80%

Answer

About 50%

Answer

About 20%

Answer

About 95%

The Deep Ocean: Creatures, Trenches & Unexplored Mysteries

What is the name of the deepest known point in Earth's oceans, located in the Mariana Trench?

Publisher

The Deep Ocean: Creatures, Trenches & Unexplored Mysteries