Chapter 9.2 - Sea-Floor Spreading Flashcards
🔑What forms long chains of mountains that rise up from the ocean floor?
Mid-ocean ridges
A device that uses sound waves to measure the distance to an object
Sonar
They found that mid-ocean ridges continually add new material to the ocean floor. They called this process _________.
Sea-floor spreading
🔑What spreading adds more crust to the ocean floor, also at the same time older strips of rock move outward from either side of the ridge?
Sea-floor spreading
Where does this evidence come from?
Scientists found rocks shaped like pillows, that only form when molten material hardens quickly after erupting under water.
Evidence from Ocean-Floor material
Scientists found that the seams formed mountains ranges that ran along the middle of some ocean floors. Scientist called these mountain ranges ________.
Mid-ocean ridges
Where is this evidence from?
Scientists drilled into the ocean floor to obtain rock samples. They found that the farther away from the ridge of rock samples taken, the older the rock was. The youngest rocks were always found at center of the ridges.
Evidence from drilling samples
Eventually the ocean floor plunges into deep underwater canyons. These canyons are called ________.
Deep-ocean trenches
🔑 Part of the ocean floor sinks back into the mantle at ___________.
Deep-ocean trenches
The process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle again is called ___________.
Subduction
_______and________ often work together.
Sea-floor spreading, subduction
The process of subduction and sea-floor spreading can change the size and shape of the ocean. Because of these processes the ocean floor is renewed about every __________ years.
200 million
The sizes of Earth’s oceans are determined by how _____ new crust is the being created at mid-ocean ridges and how ____ old-crust is being swallowed up at deep-ocean trenches.
Fast
