Download Sea Floor Spreading NOTES 2016

NAME: __________________________________________
CLASS PERIOD: 2
3 4 5 6
SEA FLOOR SPREADING
Sea-floor ____________ is a process that continually adds new material to the ocean floor. It is the process by
which new oceanic lithosphere forms as magma rises toward the surface and solidifies.
Spreading Process
1. Starts at the __________________
2. Molten material rises from the _____________ and erupts.
3. The molten material then ____________________
4. Pushes ___________ rock to both sides of the ridge.
5. The molten material ___________
6. Forms a strip of solid rock in the center of the ridge.
7. More molten material splits apart the strip of solid rock.
8. _______________ it aside.
9. The process starts over again.
Evidence of Sea Floor Spreading
1. Magnetic _____________: Throughout Earth’s history, the north and south magnetic poles have
changed places many times. When the poles change places, the __________ of Earth’s magnetic poles
changes

____________ rock at mid-ocean ridges contains tiny mineral grains of ________. These minerals
align with Earth’s magnetic field. When molten rock cools, the minerals solidify in place and record
information about the polarity of the Earth during a certain period of time.

If the magnetic field changes, the grains will align in the ___________ direction.
2. Mid-Ocean Ridge: The longest chain of ______________ in the world

Discovered using a __________ which is a device that bounces sound waves off underwater objects,
and then records the echoes of these sound waves.

Curves along the sea floor, extending into _______ of the Earth’s oceans.

If seafloor spreading DID NOT occur, the ocean floor would be ___________.
NAME: __________________________________________
CLASS PERIOD: 2 3 4 5 6
3. Rocks shaped like ________ that can only form if molten material hardens quickly after erupting under
water have been found in the central valley of the mid-ocean ridge.
4. Scientists took samples of rocks for testing. Rocks ________ away from the ridge were older than the
ones __________ to the ridge.

If seafloor spreading DID NOT occur, all of the oceanic crust would be the __________________
_______________.
Does the ocean floor just continue to get bigger and bigger? NO!
 The ocean floor sinks beneath deep underwater canyons called
deep-ocean ___________________
 Where there are trenches, _______________________
takes place.
 Subduction is the process by which the ocean floor
_______________________beneath a deep-ocean trench
and back into the mantle.
Fun Facts
 These processes cause the ocean floor to be renewed about every ____________________ years.
 The __________________________ Ocean is shrinking – the trenches are swallowing more ocean crust
than the mid-ocean ridge is producing.
 The _______________________ Ocean is expanding – in most places the oceanic crust is attached to
the continental crust.
Which two boundary types balance each other?
A _______________________ boundary, which ________________ new crust, and a ___________________
boundary, which ___________________crust.