Seafloor Spreading

What is a magnetometer?

• A device that can detect small changes in magnetic fields

• An imaginary line on a map that shows points that have the same age

• Happens when the flow in the outer core changes, and Earth's magnetic field changes direction

• Is the study of the history of earth's magnetic fields

What is Seafloor Spreading

• It describes what the ocean looks like

• How volcanoes are made

• The theory that explains how new oceanic crust is formed at ocean ridges, and destroyed at deep sea trenches

• Where the continents used to be placed

The youngest rocks on the ocean floor are located...

• near continents

• at mid-ocean ridges

• far from mid-ocean ridges

• near Asia

Seafloor spreading occurs because

• new material is being added to the asthenosphere

• earthquakes break apart the ocean floor

• sediments accumulate at the area of spreading

• molten material beneath Earth's crust rises to the surface

The magnetic pattern of ocean-floor rocks on one side of an ocean ridge is

• a mirror image of that of the other side

• younger than on the other side

• much different from the magnetic pattern found in rocks on land

• at right angles to the ocean ridge

A vast, underwater mountain chain is called

• ocean ridge

• oceanic crust

• deep-sea trench

• ocean floor sediment

In sea-floor spreading, molten material rises from the mantle and erupts

• deep sea treches

• oceanic crust

• ocean floor

• along mid-ocean ridges

Mid-ocean ridges are found

• on land

• in all of Earth's oceans.

• in the ring of fire

• on volcanoes

How did scientists discover that rocks farther away from the mid-ocean ridge were older than those near it?

• by mapping rocks on the sea floor using sonar

• by observing eruptions of molten material on the sea floor

• my measuring how fast sea-floor spreading occurs

• by determining the age of rock samples obtained by drilling on the sea floor

The process by which the ocean floor sinks beneath an deep-ocean trench and back into the mantle is known as

• conduction

• convection

• continental drift

• subduction