Seafloor Spreading Assessment

New seafloor material is formed at places in Earth’s crust where –

• rock is broken into pieces as tectonic plates push against one another.

• one tectonic plate slides beneath another and is forced downward.

• lava flow from volcanic eruptions builds up over many thousands of years.

• magma rises into the spaces where tectonic plates pull away from one another.

Tags

NGSS.MS-ESS2-3

Which of the following provides evidence that the continents on tectonic plates have moved away from each other in the past?

• The composition and thickness of rock layers varies at different depths.

• The frequency of volcanic activity is higher at edges of tectonic plates.

• Ocean currents can be disrupted near boundaries between tectonic plates.

• Fossils of the same plants and animals are found on widely separated continents.

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NGSS.MS-ESS2-3

Part of the recycling of seafloor material includes its destruction. This happens -

• through weathering and erosion of exposed rock layers.

• as a result of violent and frequent volcanic activity.

• at trenches where rock material is subducted.

• when elements in rock are rearranged chemically.

When looking at the shape of the continental shelves that surround South America and Africa, it can be observed that the continental shelves fit together.

This observation is used to support the idea that –

• the continental shelves of these two continents are made of the same type of rock material.

• the tectonic plates beneath these continents are roughly the same age.

• these continents were joined in the past and have moved apart since that time.

• the material that makes up these two continental shelves comes from sediments eroded from the continents.

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NGSS.MS-ESS2-3

NGSS.MS-ESS2-2

Examining rocks that form on either side of the Mid-Atlantic Ridge provides evidence that supports the theory of Plate Tectonics.

These rocks provide evidence of plate movement because, as we look at rocks farther and farther from the ridge, the rocks –

• have higher iron content.

• are made up of smaller particles.

• become thicker and thicker.

• are consistently older.

Tags

NGSS.MS-ESS2-3

Which type of tectonic plate movement results in the formation of mid-ocean ridges? Explain

Examining rocks that form on either side of the Mid-Atlantic Ridge provides evidence of plate movement that supports the theory of plate tectonics.

How does the age of the rocks closer to the ridge compare to the age of the rocks that are farther from the ridge?

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NGSS.MS-ESS2-3

Every few hundred thousand years, the magnetic poles of Earth reverse. Rocks that contain iron provide a record of both normal and reversed magnetic poles. The diagram below shows the pattern of normal and reversed magnetic poles as recorded in the rocks on either side of the Mid-Atlantic Ridge.

How does this show evidence of seafloor spreading?

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NGSS.MS-ESS2-3