deepest place in Earth's crust
What is a trench?
third largest ocean
What is the Indian Ocean?
this voyage marks the beginning of modern oceanography
What is the HMS Challenger expedition?
item J

What is a trench?
What is oceanography?
flattest regions on Earth
What are the abyssal plains?
largest ocean; contains more than half of Earth's global ocean water
What is the Pacific?
DAILY DOUBLE
a class of submersible that remains connected to a research ship when in use

What is a bathysphere?
item A
What is the continental shelf?
covers more than 2/3 of Earth's surface
What is the global ocean?
flat-topped seamount
What is a guyot?
extends from Antarctica's coast to the 60 degree S latitude
What is the Southern Ocean?
used in sonar to measure depth of the ocean floor
What are sound waves?
item F

What is abyssal plain?
the unique quality of the mid ocean ridge at Iceland

What is it rises above sea level (above the surface of the ocean)?
a seamount that rises above sea level (ocean's surface)
What is an island?
the second-largest ocean
What is the Atlantic Ocean?
these underwater vessels (manned, unmanned, autonomous, and tethered) enable oceanographers to perform tasks on the ocean floow
What is a submersible?
item G

What is a mid ocean ridge?
where most mid ocean ridges form 
What are fracture zones?
reason why an atoll eventually becomes a guyot
What is wave erosion?
the smallest ocean
What is the Arctic Ocean?
name two types of research tools used by scientists to study the deep ocean
What are research vessels, bathyscaphes, bathyspheres, ROVs, and sonar?
item B
What is the continental slope?
A large body of saline (salt) water that may be surrounded by land
What is a sea?