Sea Floor Spreading

What is Seafloor Spreading? Seafloor spreading is the process by which new oceanic lithosphere is created as older materials are pushed away. Wegener’s Theory of Continental Drift was finally confirmed by evidence supporting the idea of seafloor spreading.

How does new seafloor form? There are cracks, or rifts, in the Earth’s crust. These cracks/rifts are known as mid-ocean ridges. At the center of a mid ocean ridge is a rift valley At these cracks magma rises from inside the Earth to fill the rift. This process continually adds new material to the ocean floor.

What is the Mid-Atlantic Ridge? There is a chain of submerged mountains running through the center of the Atlantic Ocean. This chain is the Mid-Atlantic Ridge.

What evidence is there for Seafloor Spreading? Evidence of seafloor spreading: rock that makes up the ocean floor lies in a pattern of magnetized “stripes” Rock near a rift is younger than rock farther away http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_seafloorspreading.html

Why doesn’t the Earth get bigger? If seafloor spreading is constantly creating new oceanic lithosphere why doesn’t the Earth get bigger? Subduction!

What happens at a subduction zone? Oceanic crust is thinner but denser than continental crust causing it to subduct under the continental crust when plates converge.