Lab 4-3: Sea-Floor Spreading Pages 155 – 158 Vocab • Sea-Floor Spreading: – Ocean crust is created at a divergent boundary as plates pull apart and molten material rises from deep within the Earth. • Mid-Ocean Ridge: – Boundary between two plates where new crust is created. • Rift Valley: – Valley between diverging plates. • Seamount: – Underwater mountain • Continental Shelf: – An undersea extension of a continent which can stretch for many miles out to sea. What prominent sea floor feature Is found in the central Atlantic Ocean? • The Mid-Atlantic Ridge What feature is found at a distance of 4,100 kilometers on the ocean bottom profile you constructed? • An island (it’s above 0!) What motion of the sea floor is responsible for the formation of the Mid-Atlantic Ridge’s rift valley? • The ocean crust is moving in opposite directions (diverging). As distance from the Mid-Atlantic Ridge increases, what change in the age of the sea floor is observed? • Rocks get older as you move away from the ridge. How old are the oldest rocks of the Atlantic sea floor? • Jurassic / 142 – 206 million years old Skip #6 ☺ Describe the features of the North Atlantic Ocean bottom that are forming due to sea floor spreading. • The Mid-Atlantic Ridge with a rift valley.