Download 1.4 Sea-floor Spreading

Sea-floor Spreading
Section 1.4
Mid-Ocean Ridges
In the mid 1900’s scientists discovered that the
ocean floor is not flat.
• huge mountains
• deep trenches.
• like a zipper or baseball stitching
Mid-ocean ridge
At the mid-ocean ridge new Earth crust is added.
https://www.youtube.com/watch?v=MmMX83diwl0
Sea-floor spreading
The sea floor spreads outward like a conveyor
belt.
Video
Sea-floor spreading
• The sea floor spreads apart along both sides
of the mid-ocean ridge.
https://www.youtube.com/watch?v=oXYAdzmwQsc
https://www.youtube.com/watch?v=MmMX83diwl0
Evidence for Sea-floor spreading
• Molten Material - pillow like features that only form
when molten material cools quickly
VIDEO
Evidence for Sea-floor spreading
Magnetic Stripes – When rocks form they freeze the
magnetic orientation. The ocean surface is striped
at regular intervals of opposite magnetism.
http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Divergent/Mid-Atlantic-Ridge
Evidence for Sea-floor spreading
• Core samples
– Further away you get from the mid-ocean ridge
the older the rocks become.
Subduction at Trenches
Subduction - Process where ocean floor sinks beneath a
continental crust.
Deep ocean trenches are formed where oceanic crust
meets the continental crust.